FUNGOID DISEASES OF AGRICULTURAL PLANTS J.ERIKSSON THE LIBRARY THE UNIVERSITY OF BRITISH COLUMBIA Gift S.G. Fushtey U.B.C. LIBRARIES FUNGOID DISEASES OF AGRICULTURAL PLANTS /!^6//fJ^ ^ l< FUNGOID DISEASES OF AGRICULTURAL PLANTS BY JAKOB ERIKSSON, Fil.Dr. PROFESSOR AND DIRECTOR OF THE BOTANICAL DIVISION OF THE SWEDISH CENTRAL STATION FOR AGRICULTURAL EXPERIMENTS, STOCKHOLM : MEMBER ROYAL ACADEMIES OF SCIENCE, STOCKHOLIVI, COPENHAGEN, AND ROME : CORRESPONDING MEMBER ROYAL SOCIETIES OF AGRICULTURE, VIENNA AND BRUNN ; HON. MEMBER ROYAL HORTICULTURAL SOCIETY, LONDON, ETC. 117 ILLUSTRATIONS, OF WHICHy^i\RE COLOURED- ^jflwv* ^-''^^ TRANSLATED FROM THE SWEDISH BY A N ^J^^^^OLANDERZ^ LONDON BAILLIERE, TINDALL AND COX 8, HENRIETTA STREET, COVENT GARDEN igi2 ^ IS/,. Digitized by tine Internet Arciiive in 2010 with funding from University of British Columbia Library http://www.archive.org/details/fungoiddiseaseofOOerik PREFACE TO ENGLISH EDITION The increased facilities of intercourse between different countries which characterise modern civilization have proved an important factor in the diffusion of plant-diseases. The organisms associated with these diseases, which do untold damage by diminishing the world's supplies of food and fodder, pay scant respect to such human devices as tariff zones and political frontiers. But if the organisms in question be disquietingly cosmopolitan, the workers whose energies are devoted to the study of their life-histories, to the control of their activities, and to the mitigation of the evil con- sequences they induce, are also, fortunately, cosmopolitan. Novi/here is the solidarity of science more benignly manifested, and nothing connected with the amenities of human intercourse is more satis- factory than the neighbourliness with which these workers in every land place the results of their labours at the disposal of countries other than their own. A more pleasing instance of this neighbourly feeling than the preparation of an edition, for the use of English cultivators, of Professor Eriksson's popular treatise on the diseases of plants due vi PREFACE TO ENGLISH EDITION to fungi, could hardly be conceived. By no one will this digest of his wide knowledge, ripe judgment, and practical experience be more heartily welcomed than by his fellow-workers in the same field in the United Kingdom. D. PRAIN. Royal Gardens, Kew, Apyil, 1912. AUTHOR'S PREFACE Nowadays we frequently hear the complaint that the diseases of our cultivated plants become year by year more numerous and more disastrous. It is alleged that new diseases are constantly turning up which have never before been seen or heard of. It is also said that parasitic fungi, which hitherto have proved quite harmless, have changed their nature, and become most destructive. Is this really the case, or is it not ? Some hold this opinion to be erroneous, and claim that the state is the same as before, but that greater attention and the strict investigation which now are given to this study bring the matter more before the public eye, and also result in the discoveries of hitherto unnoticed diseases. This explanation can hardly be gainsaid. In most civilized countries there is now a diligent survey and a close inspection of the health of cultivated plants, and this attention must result in a detection of diseases that have been previously unnoticed. But, on the other hand, there are many cases that cannot be placed summarily in this category, And this refers especially to a great number of the fungoid diseases. It is, after all, an incontestable fact that fresh fungoid diseases have recently appeared and are gaining a footing in various countries. How is this to be explained ? Several causes work simultaneously to this end. The inclination in our time for specialisation, even with regard to agriculture, inasmuch as only one or a few species are cultivated in large masses, helps to make the plants more susceptible. This mass-culture of varieties and sorts generates new characteristics in viii PREFACE the individual plants, and some of these new forms will then be more susceptible to diseases and become a source of disease for the whole plantation. But another important fact must be placed side by side with this. The law of evolution is known and accepted as a truth in the scientific world. Formerly it was thought that hundreds and even thousands of years were required for this evolution. But to-day we are certain that new forms can be brought forth through impul- sive new formation — " mutation " — and these forms can vary from the parent stock in one or more characteristics. Why could not this natural law be applied also to the extensive dominion of the parasitic fungi ? And why could not these new forms of fungi possess qualities that would enable them to avail themselves of the nourishment offered through the new races of host-plants brought about by the mass-cultivation ? This is quite possible, and recent experiments and observations tend to prove this supposition. Beside these two purely scientific explanations, we have the practical one of the easy communication of our days, by means of which contagious matter can be readily spread from one district, country or continent, to another. The combined effects of these circumstances render the research and the prevention of fungoid diseases a matter of international impor- tance. In this work is given a general review of all important fungoid diseases that attack agricultural plants in the countries of Northern Europe, and also of available means for combating with or prevent- ing the said diseases. More than 200 different diseases are treated. In this work are included not only diseases which have established themselves in the above-mentioned countries, but also those that have been noticed in other countries. With the quick communica- tions of our days and the unceasing transactions between different countries, both in export and import, it does not take long before diseases spread to places where they previously have been unknown. In order to render it easier to detect different diseases, illustrations are attached. We have in each case named the authors from whose PREFACE IX works the illustrations have been borrowed. Our own are marked : " The Author." As the primary object of this book is to be a practical guide for planters, to enable them to recognize, prevent, and battle with the diseases, historical and literary facts generally have been omitted. The celebrated phytopathologist, Mr. George Massee, of the Royal Gardens, Kew, has done me the honour of reading over the English manuscript with a view to checking the technical terms throughout. For this act of kindness I wish to express to him my most hearty ^^^"^^^^ THE AUTHOR. EXPERIMENTALFALTET, STOCKHOLM. CONTENTS CHAl'TER PAGE INTRODUCTION ------ xiii I. BACTERIA SCHIZOMYCETES • - - - I II. SLIME MOULDS MYXOMYCETES - - - - l8 III. CHYTRIDIACE^ - - - - - "25 IV. DOWNY MILDEWS PERONOSPORACE/E - - - ^2 V. SMUTS — USTILAGINACE^ - - - - "44 VI. RUSTS UREDINACE^ - - - - 63 VII. CLAVARIACE^ - - - - - - 90 VIII. MILDEWS — ERYSIPHACE^ - - - - "92 IX. PERISPORIACE^ - - - - " " 97 X. SPH.^RIACE^ - - - - - - 99 XI. NECTRIACE.E - - . - . 121 XII. DOTHIDEACE.E ..---. i^I XIII. PEZIZACE^ ------ 1^3 XIV. HELVELLACE^ ..-_-. 1^2 XV. SPH^ROPSIDE^ .---.. 1^2 XVI. HYPHOMYCETES ------ 151 XVII. UNEXPLORED DISEASES - - . - - 168 XVIII. GENERAL PROTECTIVE MEASURES AGAINST THE DISEASES I78 APPENDIX ---..-- 187 INDEX --...--. 206 LIST (3F ILLUSTRATIONS FICi ^AGE FIG I'AGE I. Bacteria 2 33- Loose Smut of Wheat 5^ 2. Potato-Tuber Bacteriosis 3 34- Loose Smut of Barley 54 3- Potato Ring Bacteriosis 6 35- Covered Smut of Barley 56 4- Potato-Stalk Bacteriosis 7 36. Loose Smut of Oats - 57 5- Potato-Stalk Bacteriosis 8 37- Covered Smut of Oats 59 6. Bacillus phytophtliorus 8 38- Ustilago perennans - 59 7- Brown-Bacteriosis in White 39- Smut of Giant MeaJow- Cabbage 10 Grass 61 8. Brown-Bacteriosis in Turnip II 40. Stalk Smut of Rye - 61 9- Turnip Wart-Bacteriosis 12 41. Mj-coplasm and its Transtbr- lO. Beet Mucous-Bacteriosis 14 mation into a Mycelium - 66 II. Beet Wart-Bacteriosis 14 42. Black Rust of Oat - 69 12. Beet Yellow-Disease - X5 43- Barberry Cluster-Cup 71 13- Beet Germ-Bacteriosis 16 44. Brown Rust of Rye - 74 14. Club-Root Disease 19 45- Crown Rust of Oats - 76 15- Cabbage Club-Root - 20 46. Puccinia Arrhenatheri 77 16. Potato Corky- Scab - 22 47- Yellow Rust of Wheat 80 17- Spumaria alba on Grass 23 48. Yellow Rust of Wheat 81 18. Potato Black-Scab - 26 49. Brown Rust of Wheat 82 19. Potato Black-Scab - 27 50. Dwarf Rust of Barley 83 20. Flax Root-Blight 28 51- Pea Rust 86 21. Flax Root-Blight 29 52. Beet Rust 88 22. Crown-Gall of Lucerne 30 53- T y p h u 1 a g r a m i n u m of 23- Mycelium, Vegetative and Wheat-Sprout 91 Frugiferous - 32 54- Tvphula Trifolii 91 24. Germ Blight in Beet - 34 55- Mildew of Wheat 94 25- Pythium Bar3-anum - 34 56. Mildew of Clover 95 26. Potato Blight - 35 57- Root-Rot 97 27- Potato Blight - 35 5«- Straw-Breaker 100 28. Beet Mould - 40 59- Black Pricks of Corn-Straw - 102 29. Blight on Peas 41 60. Black vSpot of Rape - 103 30- Blight on Lucerne 42 61. Black Spot of Turnip-Leaf - 104 31- White Rust of Rape - 43 62. Sooty Mould of Beet - 105 32. Stinking Smut of Wheat 46 63. Stripe-Disease of Barley 106 LIST OF ILLUSTRATIONS FIG. PAGE FIG. I'AGE 64. Stripe-Disease of Barley 107 94- Pea-Pod Spot 149 65- Spot-Disease of Barley 108 95- Grass Leaf-Spot of Wheat - 66. Helmiiithosporium Avenae Sprout 150 of Oats 109 96. Clover-Stem Rot 152 67. Dry Spot of Potato- Leaf III 97- Mucous Mould of Barley - 153 68. Potato Dry Scab 112 98. M3-celium in the Seed of 69. Wheat-Ear Fungus - 113 Bearded Darnel 154 70. Straw-Blight - 114 99. Vessel Brand of Pulses 155 71- Blight of Wheat 115 100. Cells from a Pea -Stem, 72. Blight of Rye - 116 diseased by Vessel Brand, 73- Blight of Rye - 117 with jNIycelium and Rest- 74- Gre}- Spot of Oats 118 ing Spores - 156 75- Potato Winter- Rot - 122 lOI. Brown Rot of Potato 157 76. Snow INIould - 124 102. Oospora cretacea 159 77- Reed Mace Fungus of Timo- 103. Ramularia Betae 160 tln- Grass 125 104. Cercospora concors 161 78. Ergot Disease of Rje 127 105. Cercospora beticola 162 79- Ergots of Grasses 129 106. Root Felt Disease of 80. Phyllachora graminis 131 Clover 164 Si. Phyllachora Trifolii - 131 107. Root Felt Disease - 165 82. Stem Mould of Rape 134 108. Rhizoctonia Solani - 166 S3- Root-Crop Rot of Fodder 109. Heart Rot of Sugar-Beet - 168 Beet - . - - 135 no. Heart Rot of Fodder-Beet - 169 84. Root-Crop Rot of Carrot 136 III. Phoma Betse - 170 85. Root-Crop Rot 137 112. Leaf- Roll Disease of Potato 172 86. Clover-Sclerote 139 113- Mosaic Disease of Tobacco - 176 87. Clover Leaf Spot 141 114. Appel and Gassners Ap- 88. Mitrula Sclerotiorum 142 paratus for Steeping the 89. Phyllosticta Tabaci - 143 Sowing-Seed 181 90. Carrot Disease 145 115- Preparation of Bordeaux 91. Cabbage Canker 146 Mixture 184 92. Cabbage Canker 147 116. Knapsack Spra3-er - 1S5 93- Phoma Hennebergii of 117. Spray Cart with Ten- Wheat-Ears - 148 Branched Sprayer 186 INTRODUCTION The Structure and Life of Fungi. Fungi form a large group of their own in the vegetable world. In appearance they differ — like algae and lichens — from the higher, more developed plants in that they do not show any difference between root, stem, and leaves. The whole body of a fungus con- sists simply of a thalliis of varying shape and structure. In their inner nature and their mode of living the fungi differ from all other groups of plants by the absence of chlorophyl, the lack of v/hich renders it impossible for them to directly absorb and assimilate inorganic things, such as carbonic acid, water, nitric acid, and ammonia, and with them form organic compositions. They are destined to obtain their nourishment, ready prepared, from other organic bodies, either living or dead. Fungi which obtain their food from living animals or plants are called parasitic fungi ; those that live upon remains of either animals or plants are called saprophytic fungi. The difference between them is, how- ever, not very distinct. There are some fungi which appear some- times under one of these types, sometimes under the other. That part of the body of the fungus which accumulates and distributes the nourishing matter is called the vegetative system. This is, as a rule, a spawn [mycelium) consisting of articulated and ramified filamentous tubes (Mycomycetes). In the simplest forms of fungi this spawn is reduced to a single filamentous tube, usually without articulation (Phycomycetes), or it is replaced by an irregularly shaped mucous body — a Plasmodium {Myxomycetcs) — or it may be missing altogether (Schizomycetes). xiii xiv INTRODUCTION When the spawn has reached a certain degree of development the fructifying system of the fungus appears, and produces breeding organs — germ cells (Conidia), or spores. The conidia ger- minate at once. The spores are various in structure and different in nature. With regard to their shape, they vary, being ball- or egg-shaped, club-like, thread-formed, or semicircular. In structure they are one-celled up to many-celled. On the surface they are either smooth or shrivelled, or have warts, hair, or bristle. Some of them germinate as soon as they arrive at maturity {summer spores) ; others require a certain resting period before they grow {resting, or winter spores). Synopsis of the Different Groups of Fung-i. In this work only such parasitic fungi will be noticed that obtain their nourishment from agricultural plants. These fungi can be divided into the following groups : I. Spurious Fungi, which have no filamentous tubes. 1. Sehizomycetes. 2. Myxomycetes. II. Genuine Fungi, which have a spawn of filamentous tubes. (i.) Simpler fungi {Phycomycetes), the spawn of which consists of one single, mostly inarticulate, but often nmch ramified, filamentous tube. 3. Chytridiaceae. 4. Peronosporaceae. (ii.) Higher fungi {Mycomycetes), whose spawn consists of numerous filamentous articulated tubes. {a) Basidiomycetes. 5. Ustilag-inaceae. .6 Uredinaceae. 7. Clavariacese. INTRODUCTION (b) Ascus fungi {Ascomycetes). 8. Erysiphaceae. 9. Perisporiaceae. 10. Sphseriaceae. 11. Nectriaceae. 12. Dothideaceae. 13. Pezizaceae. 14. Helvellaceae {c) Imperfect Fungi. 15. Sphasropsideae. 16. Hyphomycetes. (a) Melancojiiecs. {3) Tuhevculariacea^ (y) MiicedinecE. (5) Deinatiec^. (e) R]iizoctoni2(E. FUNGOID DISEASES OF AGRICULTURAL PLANTS CHAPTER I BACTERIA— SCHIZOMYCETES Bacteria are the smallest and morphologically the simplest amongst organized beings. When aggregated in millions they appear to the naked eye only as the finest sediment, whether in liquid putrefaction or in the tissues of diseased animals or plants. Each individual consists of only a single cell. It, however, frequently happens that several cells are in process of forming colonies, and it is an accumulation of these colonies or congeries that constitutes the sediment referred to. They can be defined only under high powers of the microscope. The shape of bacteria is variable, as seen in the four forms on p. 2 — viz., the spherical, the rod-like, the spiral, and the flagellate. It is particularly the spherical and the rod-like that are active in the origin of plant diseases. Bacteria increase, as a rule, by fission. The two cells may either begin an independent existence, if separated, or otherwise together develop thread-like, tabular, or cube-like colonies. Bacteria are frequently provided with one or more vibratile organs, which serve as a locomotive power. However, there has been noticed in the case of many bacteria an increase, not only by fission, but also by spores. The spores are thick- walled, and originate inside the cells of the bacteria. This development of spores appears especially to take place when the nourishment is scanty, and as a sequel the FUNGOID DISEASES OF PLANTS vegetative process abates. These spores might be styled " resting spores." They possess great resistance against outside influence. It is a long-known fact that bacteria are the agents not only in putrefaction and fermentation, but also m infectious and contagious diseases, both in man and beast. But that they are also the cause of plant diseases is known \^ \ \ / b from the observations, experiments, and re- searches of the last few decades. And every year our know- ledge is increased by the discovery of some additional disease of the same kind, known under the name of Bactci'iosis. This new science is undecided as to whether bacteria are actual parasites which originate the prevailing sickness in the plant, or if they may have the pre- viously diseased and decaying vegetation. In the following pages an account will be given of several of the most important and most thoroughly in\estigated forms of bacteriosis. Fig. 1. — Bacteria (Highly Magnified). (From W. ^Migula and E. Warming.) a. Spherical; h. rod-like, or bacilliform; c, spiral; possibly rf, flagellate. ^ , / settled on Potato-Tuber Bacteriosis. {Bacillus amylobacter and B. solaniperda.) This disease appears in the autumn at the time when potatoes are taken up from the ground. In the first stage it appears as brown spots within the tubers, either as several small spots scattered inside the tuber, or as one large spot in the \ ery centre. If the BA CTERIA —SCHIZOMYCETES soil is clayey, the season rainy, and the potatoes are stowed away in consequence in a damp condition, then the rot will spread all over the tuber. Not only the walls of the cells, but also the starch granules dissolve, until the whole inside of the tuber consists of a fetid, thick matter, more or less covered by the yet unaltered skin. The potato is now said to be " wet-rotten." Should it, on the contrary, happen that the weather is very dry and the soil of a sandy character, the drainage there- fore being good, then the progress of putrefaction will cease. The tuber dries and gets hard, and in- side there develop many little vacua, lined with a white layer of starchy material. In this case the potato is said to be "dry-rotten." The starch in such a potato can be used for technical purposes, such as dextrine and other similar products. It was thought for some time that wet-rot, as well as dry-rot, was caused by the potato mould [Phytophthora Fig. 2. — Potato - Tuber BaCteriosis [c, Highly Magnified), (a and b, FromjE. Rostrup ; c, FROM C. Wehmer.) a and b. Sections of diseased potato-tubers ; c, part of the slimy matter, with two different bacteria : one of them {Bacillus amylobactcr) pointed towards the ends, the other [B. solaniperda) with straight-cut ends. 4 FUNGOID DISEASES OF PLANTS iiifestans), and it was considered that the brown spots produced by this fungus on the surface of mature potatoes were a previous stage of both forms of rot. Finally, an agreement has been arrived at that this is not the case, but that wet-rot, as well as dry-rot, is developed solely through bacteria. But so far the question as to which bacteria produce these two rots is not fully solved. Scientists have arrived at different results. It is now, however, generally believed to be the Bacillus amylohacter (also named Aviylohacter navicula, or Clostridium hityricum), and B. solaniperda, both bacilliform bacteria. A point of contention has been whether the bacteria can of them- selves develop disease in a perfectly sound potato, or if they can only complete a destruction introduced through some other agent. It appears as if both these can take place. In some instances bacteria may attack a perfectly sound potato, if it be injured in some way, so as to give them an entrance ; but especially with regard to B. solaniperda the potato can be infected without any visible defect on the surface. The power of resistance against these various attacks is variable with different sorts of potatoes. The most susceptible are the early food potatoes, while the late fodder and factory potatoes have the greatest resistance. Protective Measures. — (i) Never use anything but perfectly sound seed. (2) Select for larger crops only such varieties as have been proved in the district most capable of resistance. (3) Grow potatoes only in such soil as is high placed, well drained, and mixed with sandy material. (4) Take care that the soil which is cultivated be rich in potassium and phosphate, as an abundance of these has proved to increase the resistance against rot, while, on the other hand, strong lime manuring produces the opposite effect. (5) The potatoes must needs be quite dry when put away for winter supply, and the place where they are laid up should be dry and well ventilated. BA CTERIA —SCHIZOMYCETES Potato Ring"-BactePiOSiS. {Bacillus Solanaceanm.) Occasionally it happens that a few weeks after the potatoes have been planted, several of the seeds do not sprout. If you then dig at the vacant place, you will find the seed-tuber perfectly sound in appearance, but the sprouts are fading away, and also the abnormally richly developed roots. Other plants reach beyond the ground, but soon acquire a sickly and dwarfed appearance, with a glassy stem and petty leaves. Finally, the growth of the plants is suspended altogether. Several other plants continue to grow in seemingly good state until summer-time, when their hearts become transparently brown-spotted, and wither away prematurely. These last-mentioned specimens yield almost a satisfactory crop. This disease, also named " Potato Wilt-Bacillose," is generated by bacteria, especially Bacillus Solanaceavuin, which follow the fibro- vascular system of the whole plant, and originate black spots. If the case be only a slight one, there appears on the section a sickly- looking ring towards the surface of the potato. In more serious cases the whole inside turns dark. Frequently no sign of disturb- ance can be noticed on the skin. It is particularly through slightly infected tubers that the disease is maintained year by year. If a tuber of such quality be planted, the plant itself will become more or less diseased. The disease will spread to sound potatoes through some defect on their surface, thus making an opening for the bacteria. This disease has sometimes proved very disastrous. In the year 1905 in one district of Germany 60 to 70 per cent, of the crop was destroyed — in fact, there were fields so badly attacked that it was deemed futile to attempt to gather the crop. Protective Measures. — (i) Use for seed, only strictly sound potatoes. An investigation should be made in such a manner, that the potatoes be cleft and placed in the air with the cloven sides upwards. If in an hour or two there appear black pricks and spots on the surfaces, it indicates the existence of the disease, and these specimens should 6 FUNGOID DISEASES OF PLANTS be rejected as seed-tubers. (2) If possible, whole and not divided tubers should be used for planting. If, however, it is desirable to Fig. 3. — Potato Ring-Bacteriosis — Bacillus Solanacearum. (From O. Appel.) a. Plant spired from a ring-diseased potato ; b, a slightly, and c, a seriously, ring-diseased potato in section. use divided tubers, then the division should take place a couple of days previously, in order that there may accumulate on the cleft sides a cork layer that will prevent the entrance of the bacteria. BACTERIA- SCHIZOMYCETES (3) Examine during the summer the potato-fields, and destroy thoroughly both stalks and tubers of all prematurely withered specimens as soon as they are suspected of propagating the disease. Fig. 4. — Potato-Stalk Bacteriosis — Bacillus melanogenes and Others. (a, From O. Appel ; b, the Author.) a, A whole plant, diseased ; b, the lower part of a diseased stalk. Potato-Stalk Bacteriosis. {Bacillus melanogenes, and others.) This disease, also called " Black Stalk-rot," becomes conspicuous in the potato-fields early in the summer through the way in which the leaves turn yellow and cease growing, while the heart-leaves turn slightly upwards. Simultaneously that part of the stalk which is in the ground gets black and withers away, and shrinks narrower than the upper stalk. Often only a single sprout of the plant may FUNGOID DISEASES OF PLANTS thus be affected. If the weather is wet the black part of the stem will appear to be slimy, and bacteria are to be found in the vascular system of the stalk proper. Towards the end of June plants of this description appear amongst the healthy ones. By this time no tubers have begun to form, and within a week the plant dies. With regard to those plants which become affected later in the season, and in consequence have formed tubers, the infection will shortly reach them. The inside of these tubers turns black and -J^Tf *'»• ^M'-^>' Fig. 5. — -Potato-Stalk Bacteriosis. (From O. Appel.) Vascular tissue, with two vessels leading the bacteria upwards from the bottom part of a diseased stalk. Fig. 6.- — Bacillus phvtophthorus (Highly Magnified). (From O. Appel.) begins to rot. Slightly affected tubers, used afterwards as seed, develop sickly offspring. From one country and another reports are obtained giving different opinions as to the bacteria that originate the complaint : Bacillus caiilivorns (France), B. atroseptiais (Holland), B. phytophthorus (Germany), B. solanisaprns (Canada), and B. melanogenes (Ireland). This disease was first noticed and investigated in France, where it was called "Gangrene de la tige." This took place about the year 1890. In Germany it goes by the name of " Schwarzbeinigkeit." BACTERIA— SCHIZOMYCETES 9 Both these names could appropriately be translated into English as " Black Leg." In Sweden it appeared in igo8 and igog, and spread over numerous fields in \arious provinces. Protective Measl-res. — (i) Use sound seed. (2) Use in prefer- ence undivided potatoes for seed. (3) Do not cultivate potatoes in soil where during previous years sickly plants have grown. (4) Avoid nitrogenous fertilizing. (5) Examine the potato-fields frequently during the summer, and pull up and destroy at once all sickly plants, thus preventing the ailment from spreading to sound plants in the same field. Potato Brown-Bacteriosis. This name might apply to another sort of stalk-bacteriosis, which appears later in the summer, and for the first time was noticed and described in France during igoi. It was there called " Brunissure," and was observed in England somewhat later. The leaves turn yellow prematurely. The stalks become thin and wither from the lower part. The ring of vessels develops yellowish-brown spots, with suppurating yellow slime both in stalk and tubers. The disease is originated through B. solanincola. Cabbag'e Brown-BaCteriOSiS. {Psendomonas campestris.) This disease, usually called "Black Cabbage-rot," attacks different sorts of cabbage, especially white cabbage and cauliflower, but also Swedish turnip, turnip, rape, and others. In the white cabbage it usually appears first at the edge of the leaves as a brownish-black veiny mesh, and passes from there into the leaf-stalks and stalk proper. In the Swedish turnip and the turnip it reaches the root. Bacteria evidently gain an entrance either through the water- pores at the edge of the leaves, or else through some wound some- where on the surface of the plant. They accumulate in the vessel- strings, that in a cross-cut section appear as brownish-black pricks, distinguishable to the unaided vision. The bacteria continue their work of destruction with the crop stored up for the winter. Even the most solid and perfect cabbage lo FUNGOID DISEASES OF PLANTS tops are then affected, until the whole heart is transformed into a soft, spongy, black-spotted lump. In turnips the disease manifests itself in somewhat different forms. It sometimes appears in the shape of dark stripes arranged radially ; at other times, again, these stripes are longitudinal, in both cases inside the turnip, while the surface appears Fig. 7. — Brown-Bacteriosis in White Cabbage — Pseudomonas cam- pcstris {d, Magnified), {a, b, c, From E. Rostrup ; d, from E. F. Smith.) a, A cabbage-leaf, in which a part of the veiny mesh is blackened by bacteria ; b, section of a leaf-stalk, with vessel-strings black-spotted by bacteria ; c, part of a cabbage-stalk, with black-spotted scars after the diseased leaves have dropped off ; d, section of a vessel-string filled with bacteria. comparatively clean. Finally, the whole inside turns into a slimy, fetid mass. With regard to their shape, the diseased turnips differ from the sound only in this respect, that they do not acquire the ordinary broad, spherical or flat shape, but grow long and thin, almost like BACTERIA— SCHIZOMYCETES -■if' ■ Fig. 8. — Brown-Bacteriosis in Turnip. (The Author.) a 'Section of turnip lengthwise, with two longitudinal diseased strings or '■ stripes ; b, a similar turnip cut across the root ; c, a cross-cut turnip (from another locality) with only radial diseased strings. FUNGOID DISEASES OF PLANTS carrots. The disease is brought on through a bacillus called Pseiidomonas campestris. Occasionally the disease appears visible on the outside of the root in the shape of an abundance of wart-like outgrowths of the size of a pea along both of the two longitudinal depressed furrows on the surface of the root. In the inside of the root you will then find corresponding longitudinal strings or stripes. This form can be styled " Turnip Wart-Bacteriosis." Cabbage Bacteriosis was first in- vestigated and described in the United States of America in the year 1895. At the present time it is said to be very prevalent in that coun- try, usually under the name "brown-rot," or "black- rot." In Europe it has turned up many times dur- ing recent years, as in Hol- land ; France, "Nervation noire "' ; Switzerland ; Ger- many, "Schwarze Faulniss"'; and Denmark. Quite lately it has been noticed in Sweden, in the year 1906 on white cabbage and turnip, and 1907 on turnip. Protective Measures. — (i) Pinch off and destroy all leaves that are attacked, and if the disease has already reached the inside of the plant it should be destroyed altogether, (2) Do not let diseased Fig. 9. -Turnip Wart-Bacteriosis. (TiiK Author.) BACTERIA— SCHIZOMYCETES 13 fragments of plants lie about the field during the winter. (3) Do not gather seed from infected fields. (4) Seed, which you suspect, should before sowing be soaked in a mixture of sublimate (i in 1,000) for fifteen minutes, or in a mixture of formalin (i in 200) for twenty minutes. (5) For two to three years no cabbage should be culti- vated in a field that has been infected. (6) Keep the field cleared of charlock and other Crucifera?, as these also might have been infected, thus retaining the bacteria in the field. Besides these, there have been reported the following new forms of Bacteriosis of cabbage : White-Rot of Turnip, noticed in England in 1900, with leaves turning yellow and dropping off — first the outside leaves and then the younger ; the diseased parts of the roots are greyish-white ; finally the whole root becomes putrid and offensive ; the disease originates through Pscudomonas desfnictaiis. Bacteriosis of White Cabbage, noticed in Germany in 1902, and beginning in the younger stalks and in the central nerves of the leaves, the diseased parts dissolving into an offensive pulp. The disease is provoked through a species of Pseudomonas, which has lodged between the cells. Bacteriosis of Cauliflower and other sorts of cabbage, caused by B. oleracecs, and discovered in Canada in 1901, and also by B. brassiccevorus, noticed in France in 1905. Beet Mucous-Bacteriosis. Of this there are several sorts. One of them — " Beet gummosis," " Bacteriose gummosis," or " Gummose bacillaire" — indicates its existence in such manner that the vessel-strings in the root first turn reddish-brown, then black. When cut longitudinally, there appear dark stripes, running lengthwise. If the section be made transversely, dark rings appear. Finally the whole interior dis- solves into a glutinous or molasses-like slime. This disease has 14 FUNGOID DISEASES OF PLANTS been noticed in many places in Europe, especially in Austria, Germany, Belgium, and Denmark. It is caused through sev'cral different forms of bacteria : B. Beta, B. lacerans, B. Bussei, and others. 4 1 3 ^ -!^M ml if- -''J Fig. io. — Beet Mucous-Bacteriosis — Bacillus Betes and Others. (From P. Sorauer.) a, Longitudinal section ; b, transverse section. Fig. 1 1 . — Beet Wart-Bacteriosis — Bacterium scabiegemim. (From F. C. VON Faber.) BACTERIA— SCH I ZOMYCETES 15 ""V Beet Wart-Bacteriosis. This " Pustelschorf " appears as small black warts on the surface of the root, sometimes with a crater- like concavity in the centre of the wart. In sugar-beets the warts often together form vertical swellings. In fodder-beets the warts appear mostly on the lower part of the root. The disease rarely penetrates deeper into the substance. In many cases the wound-spots heal and the warts drop off. In no case has there been found any general putre- faction. The disease has been noticed in Northern and Central Germany, and in the United States of America. It is caused by Bac- terhim scabiegenum . Beet Yellow-Disease. The " Yellowing of beet leaves " or "Jaunisse" manifests itself on the leaves, first the outside leaves in the bunch, then the inner. The leaf-stalk shows alternately light yellow and dark green spots. It assumes a kind of mosaic appear- ance, best seen if the leaf is held towards the daylight. From the fig. 12.— Beet Yellow-Dise.^se leaf-stalk the disease goes into the —Bacillus iabif.cans. (The " .\UTHOR.) plant-Stalk, which turns into a „_ Early stage, with mosaic- glassy transparency, first in the chequered leaf ; b. later form, with a withered leaf and the upper part, thence lower down. leaf -stalk transparently glassy. i6 FUNGOID DISEASES OF PLANTS The leaf feels sticky and soon dies. If the beets bloom, the same sickly manifestations appear in the flowers. Should the attack be severe, it will arrest the growth of the root. The disease was observed for the first time in the North of France in i8g6. In South Sweden its existence was proved in the beginning of August, 1909. It is brought on by B. tabificans. Beet Germ-Bac- teriosis. This attacks with more or less disastrous results the tiny sprouts when they protrude from the seed. In severe cases these are totally destroyed. The disease is especially studied and mentioned in Hungary. It is principally caused by B. my CO ides. Fig. 13. — Beet Germ-Bacteriosis — Bacillus mycoides. (From G. I.inhart.) a, Seed-bundle, with protrudingdiseased sprouts ; b, a diseased young germinating plant. Californian Beet-Pest. The "Beet-pest" has been noticed in Cali- fornia since 1899. The leaves become small, yellowish -brown, finally black; the root dwarfed, not larger than a radish, with plenty of root-strings. The interior of the root shows dark concentric rings. From the vessels penetrates a dark juice, which turns black in the air. Protective Measures. — (i) Pull up and destroy plants imme- diately they get diseased. (2) Do not let diseased remnants lie in the field over the winter. (3) Be careful that soil from an infected field is not carried by means of vehicles, implements, dray-animals and other things to the field that is intended for next year's beet-crop. (4) Do not allow the remains of diseased beets to get mixed with BACTERIA— SCHIZOMYCETES 17 the manure. (5) Do not take seed from beets grown in soil that was infected. (6) In a field that produced diseased beets, no beets should be planted for at least three years. Amongst other diseases of agricultural plants considered to originate from bacteria may be mentioned : Seed Bacteriosis. — The diseased seeds, of a rosy hue, develop poorly, become shrivelled and sometimes even hollow. The disease has, since 1878, been occasionally noticed on wheat in France, and also in Denmark. It is caused by Micrococcus Tvitici. In Sweden, a similar disease has been noticed on two-row barley. Lupin Bacteriosis. — Young plants develop first yellow and then brown spots on the leaves, and shortly wither. It was noticed in 1899 in Hungary, and is caused by B. elegans. Carrot Bacteriosis, or " Soft-rot of Carrot." — The carrots are attacked by a soft -rot while stored up for the winter, usually starting at the crown, and quickly proceeding downwards. The affected part becomes mellow and brown. This disease acquired a malignant type in 1897 and 1898 in Vermont, U.S.A. It has been proved to spread to many other plants, as turnip, rutabaga, radish, salsify, parsnip, onion, celery, tomato, and others. It is caused by B. cavatovoyiis. Tobacco Bacteriosis. — Of this there are several kinds. One of them, " Chancre bacterien," forms on the stem and on the principal nerves of the leaves in long, groove-like, dark spots, and may cause the death of the plant. The disease is caused by B. idviiginosus, and is widely distributed in France. — Another disease, " ]\Ialadie des taches blanches," forms on the leaves small, irregularly shaped, at first pale green, then white and dried spots. It is caused by B. macn- licola, and, like the previous one, is widely spread in France. — A third one, " Granville tobacco-wilt," is prevalent in North Carolina, Florida, Georgia, U.S.A. The leaves become dry, bend down, and die. The layer of wood in the stem turns black and dies. The disease is thought to be caused by B. Solanaceaynm (see previous account of Potato Ring-Bacteriosis). CHAPTER II SLIME MOULDS-MYXOMYCETES These fungi, which are of a very low order, do not consist of real cells or filamentous tubes, but have only a naked mucous body {Plasmodium), lacking in clearly defined outlines. When maturity is reached, the plasmodium is transformed into a large number of spherical spores. When a spore germinates, there dev'elops a roaming body {niyxamoeha), which is continually changing its shape and progresses by creeping movements. The mucous bodies take their sustenance from the substance — either dead or alive — upon which they grow, and often many of them collect into one large mucous mass. Most of the slime moulds live upon a dead substance, such as decayed wood, rotten stumps of trees, withered leaves, and so forth : and then it frequently happens that they further extend to living plants or to parts of them. Thus they can do damage by depriving them of light and air. The saprophytically existing forms possess as a rule minute fruit bodies (cndospores), with a wall formed from dried mucus, and an inside mesh of fine threads. A few of the slime moulds appear as parasites on living plants. In their case the common covering round the spores is missing. The spores are contained in the cells of the plant that support them. Cabbage Club-Root. {Plasmodiophom Brassica:.) The history of this disease can be traced back to the year 1736, when it was spoken of in England ; but not until 1820 was it con- 18 SLIME MOULDS— MY XOMYCETES 19 sidered as a harmful destroyer from an economical point of view. After that time it is described as bad in many lands. This disease thrives not only on the different varieties of Brassica oleracea in our kitchen gardens — viz., white cabbage, cauliflower, nettle-cabbage, brussels-sprouts, etc., but also on other cabbage- like plants, such as Swedish turnip {B. Napus) and turnip [B. Rapa). -i \ i\ a b Fig. 14. — -Club-Root Disease — PlasmodiopJwra Brassiccp. (The Author.) a, In a turnip ; b, kohlrabi. Further, it has been noticed on numerous other plants of the Cruciferai' family, cultivated as well as wild — viz., Capsella Bursa pastoris, Cheiranthus Cheivi, Erysimum cheivanthoides, Hespevis matronalis, Iberis umbellata, Matthiola incana, Raphanus Raphanistrum, R. sativus^ Sinapis alba, S. avvensis, Thlaspi arvejtse, and others ; and quite lately in France, although only once, in water-melon, celery, and sorrel. The disease manifests itself in the cabbage and turnip fields during 20 FUNGOID DISEASES OF PLANTS the summer in such a way that sundry plants cease growing and die away. If the roots of these plants are examined, they will be found covered with nodose swellings much varied in size and shape. The /~~ ^-^^ /^' Fig. 15. — Cabbage Club-Root. (From M. Woronin.) a, Section of a diseased root ; h, cells from the root-tumours, with mucous bodies ; c, cell, with spores ; d, spores ; e, germinating spores ; /, swarming bodies. root appears thus very much distorted. Until the end of the summer these tumours keep white and hard ; late in autumn they rot, and become a dark, fetid mass. If one of these tumours be examined under a microscope during SLIME MOULDS— MYXOMYCETES 21 summer-time, it will be seen that several of the cells are more or less filled with a colourless mass of fine granular particles. If high magnifying is applied, it will be seen that these granules consist of mucous bodies enclosed in the interior of the cells. These bodies belong to the fungus of the club-root disease {Plasmodiophora Brassiccd) . They pass through several stages of development. At first they are separated from each other, but later on float together into a common plasmodium, which more or less fills up the whole cell. Finally, the whole plasmodium resolves itself into numerous spherical thick-walled spores. When the diseased roots decay in autumn these spores become free in the surrounding soil. They remain unaltered during the winter, but in the spring they retain the power of germination. From the spore the mucous substance exudes, forming a movable swarming body of a protean nature and constantly changing shape. If such a swarming body strikes upon a young root-string of a susceptible plant, it will force its way into it. The root is then infected. Soil which has been infected retains the infection three years for certain — -most likely five years, and possibly longer. This disease will be carried from a sickly to a sound field by means of agricultural implements, the hoofs of dray animals, and the footgear of men. It is not proved that any considerable dis- tribution is caused through manure from live stock having fed on diseased roots, except in those cases when remains of the fodder, which possibly have been left in the manger, get into the manure. In certain cases it seems as if the disease is propagated with the seed. Thus it happened in 1903, on an estate in Sweden, that the disease appeared only with turnips raised from fresh seed, while plants of the old stock were sound all over the field. The disease varies in its ravages in different years and soils. Fields on a low level promote it ; chalky soil resists it. Protective Measures. — (i) If it be the first year that the disease appears in the place, then pull up and remove early in the summer, before the root has begun to rot, every one of the sickly plants and every string-root. (2) If possible, do not cultivate for a period of 22 FUNGOID DISEASES OF PLANTS four to six years any kind of cabbage in a field that previously has produced a diseased crop, but plant instead other vegetables, as potatoes, peas, clover, straw-seed, etc., and take care that the soil meanwhile is kept perfectly clear from weeds of the genera Sinapis, Thlaspi, Capsella, Erysirmtrn, and others, on which the fungus can find its sustenance. (3) If it should be imperative within a year or two to again plant cabbage in sickly soil, then mix with the earth a year and a half, or at least half a year previous to the planting, an abundant supply of finely ground chalk, and not less than 2 tons fr Fig. 16. — Potato Corky-Scab — Spongospora scabies. (From T. Johnson.) a, A whole potato; b, potato (cross-section) ; c, fungi-carrying cells close below the potato skin. slaked lime, or 4 tons carbonate of lime per acre. Kainite has also been used with success; about 15 cwt. per acre, sprinkled around in the spring. (4) Be careful to prevent the spread of disease from infected to sound earth through implements, hoofs of animals, and footgear of the agricultural workers. (5) Do not use any earth in hotbeds for cabbage that is not perfectly free from suspicion of infection, and cleanse carefully all the frames used for the purpose. Examine also every plant before planting out, lest there should be some indication of tumours on the root. (6) If slightly diseased roots are to be used as fodder, then care should be SLIME MOULDS— MY XOMYCETES taken that no remains of these get mixed with the manure ; the best way would be to boil the roots before feeding the stock with them. (7) If it be preferable not to use any sickly roots for fodder, then the diseased roots should be absolutely got rid of by burning or otherwise, but by no means mixed with heaps of dung or compost. Potato Corky-Scab. {Spongospom scabies.) This disease manifests itself in the shape of small concave spots with turned-up edges all over the skin of the tuber. If the soil be comparatively dry, a healing layer of cork forms beneath the sickly spots, and the disease stops. But in very moist earth no such healing process takes place. The fungus penetrates deeper and deeper into the potato, and the cavities continue to increase in size. The cells in the sickly parts of the tuber contain the fungus which provokes the disease {Spongospora scabies) in its different stages of development. At first it appears as a number of spherical plasma bodies, then as one single Plasmodium, in shape somewhat like a bunch of grapes ; and, finally, as a mass of number- less spores. The disease is reported from Norway, Ire- land, and England. Especially in Ireland is it said to be widely spread, and is there considered as seriously destructive. It has also appeared in isolated localities in Germany, and was noticed in the autumn of 1908 in the western part of Sweden.^ Protective Measures. — (i) Do not use diseased potatoes for planting. (2) If this cannot be avoided, then the diseased potatoes, as ' ]'>y the name of scab several other diseases of potatoes are known, although they have no connection with the one just described. These are caused by different condi- tions of the soil, through manure, or by artificial fertilizing. Fig. 17. — Spumaria ALBA ON Grass. (The Author.) 24 FUNGOID DISEASES OF PLANTS well as those that have a sound appearance, but are gathered from aninfected field, should be steeped before planting in a 2 per cent. Bordeaux mixture or sulphate of copper. The steeping should last about twelve to eighteen hours. (3) For at least three years no potatoes should be planted in an infected field. As indirectly injurious, slime moulds on grass lawns may be mentioned : Physarum Cinereum appeared on pastures in Sweden in 1905. The straws were covered by a mucous mass, and soon acquired a greyish-white hue, which finally turned black. There appeared a kind of black dust, together with greyish-white remains of cracked skin. The fungus arrested the development of the straw. Spumaria alba appeared in the same place during the following years, also on grasses, and took the shape of large, snowy-white or grey-black mucous masses, especially on the root-stumps left after the hay had been cut. CHAPTER III CHYTRIDIACE^E The fungi of this class are the most inferior of the fungi that, as a rule, are provided with mycelmm. The mycelium, when such exists, is, at the beginning at any rate, without partition walls. Every new individual fungus originates from a spore, which settles upon one of the cells of the host ; whereupon it penetrates into the cell, and there completes its development. Most of these fungi are aquatic, and exist as parasites upon alga^. Only a few settle as parasites on plants of a higher order. Potato Black-Scab. {Chysophlyctis endobioiica.) This disease, also called" Wart Disease," " Cauliflower Disease," " Canker Fungus," and " Potato Rosette," appears as warty, uneven growths on the new tubers, which develop when the potato is flowering. Sometimes these warts are also on the sprouts that develop the new tubers, or else on other parts of the stem and on the roots. As a rule these growths reach the size of a walnut, or even larger. In very serious cases the whole thing finally looks like a huge, irregular mass of tumours. These growths, which at first are white, later on acquire a dark brown or black colour. If the sick potatoes are stored up in a damp state, then they will soon all rot away. This disease is caused by a fungus — usually named Chvysophlyctis eiidobiotica—vjhich lives within the potato cells, especially in the parts nearest the skin. In every diseased cell is a plasmodium, which by degrees is transformed either into one to three spore- cases of yellowish-brown colour, each containing a vast number of 26 FUNGOID DISEASES OF PLANTS vibratile spores, that are agents for the spread of the fungus during the time of vegetation, or else into one single thick-walled resting spore, that retains the fungus alive until another year. Fig. 1 8. — Potato ]3lack-Scab — Chrysophlyctis endobiotica. {a and c. From O. Appel ; b, FROM T. Johnson.) a, The underground parts of a sick plant ; b and c, diseased. potato-tubers. The resting spores might settle in the surrounding earth, thus infecting the same ; or if slightly infected potatoes are used for planting, these spores will mix with them. Soil that is infected can CHYTRIDIACEM 27 retain the infecting power for six to eight years. The attack of the disease is more or less severe, all depending upon different sorts of potatoes. In England the following kinds have proved to possess a great power of resistance : " Snowdrop," " Main Crop," " Lang- worthy," " What's Wanted," and " Conquest." The disease was noticed for the first time \n Hungary in 1896. Since 1900 it has become prevalent in England, where it has spread to an alarming extent. Lately it has manifested itself in Scotland and Ireland, and in two districts in Germany; during igo8 in the Rhine provinces and Westphalia, and in 1909 in Silesia and Newfoundland. Fig. ig. -Potato Black-Scab, {a, c, and d, From T. Johnson ; b, from K. SCHILBERSZKY.) a, Section of a part of a tuber, with resting sporangia (slightly magnified) ; b, tissue with resting sporangia (highly magnified) ; c, a mature resting sporangium ; d, swarming spores. Recently the opinion has been pronounced that the disease, which has turned up in the United Kingdom, is not quite identical with the one observed in Hungary in 1896, and the fungus has been given a different name — viz., Synchytvium Solani {S. endohiotica). Protective Measures.— (i) Totally destroy at once all diseased plants, and do not use potatoes taken from infected fields for seed, even if they have a sound appearance. (2) For a period of four to five years no potatoes should be planted in a field that yielded a sickly crop, although even only a small percentage. (3) Isolate a field that yielded a diseased crop, lest earth should be brought from it by means of implements, people, and animals, and mixed with 28 FUNGOID DISEASES OF PLANTS good soil. (4) If you are bound to use potatoes for planting that you suspect are diseased, or if you must use a field that is infected, you should prepare the soil with gas-lime, 4 to 5 tons per acre ; and the potatoes that are to be planted should be sprinkled with sulphur dust, 4 to 5 pounds per ton. (5) It is best not to cultivate potatoes at all in an infected field, but to use it for some other Fig. 20. -Flax Root-Blight — Asterocystis radicis. b, FROM v.. DUCOMET.) (a. From E. Marchal; Plants in an early stage of the disease, the tops of the stems relaxed and drooping ; b, the top of a branch of the root, with fungi in the cells. vegetable, after you have previously arrested the infection in the following way : dress the soil in the month of March or April with 2 pounds of gas-lime to each square yard, and plough this down to a depth of 3 inches ; or mix in the month of May sulphur powder with the earth (4 ounces per square yard). (6) If potatoes, suspected as diseased, are to be used for fodder, great care should be exercised that no fragments of them find their way into the manure CHYTRIDIACE^ or remain in the mangers, thus making sources of infection. best to boil such potatoes before using them as fodder. 29 It is Flax Root-Blight. {Asferocystis radicis.) This disease appears in the early summer in sundry spots in the flax-fields. The lower leaves of the affected plants become yellow. The stem gets slack, with a relaxing and drooping top ; the ultimate root-strings become glassy and brittle. If the weather be rainy or the soil damp, the disease will quickly disseminate over the entire field. The fungus that causes this disease {Astei-o cystis radicis) is located in the outer cells of the fine root-strings. It penetrates there while the roots are very young, and forces an entrance above the point of the root. This is easiest done from the thirteenth to the eighteenth day after sowing the flax. After the plants have reached their twenty-fifth day they are free from danger. The fungus goes from cell to cell. In the diseased cell the plasma body, which seems to embrace the plasma of both the cell and the fungus, looks like a sediment, sometimes filling the entire cavity of the cell. By degrees the plasma body is transformed into one or more masses of swarming spores, which gain an exit through an opening in the wall of the cell. The fungus subsists from year to year with resting spores, one or more in each cell. It can also live in the roots of other plants, such as cabbage, turnip, radish, lucerne, lettuce, onion, and others. This disease is known in Holland by the name of " Brulure," and is also prevalent in Belgium and France, and has been noticed in Germany and Ireland. /(/ Fig. 21. — Flax Root- Blight. (From E. Marchal.) a, Cells from the ex- terior parenchyma of the root, with fun- goid bodies in the cells, in an early stage of develop- ment ; b, cells with resting spores. 30 FUNGOID DISEASES OF PLANTS No other protecting remedy is known for this disease than to avoid for a period of seven to ten years the cultivation of flax in a diseased field. It has also been advised to pull up and burn every plant that shows an indication of the disease. Amongst others belonging to the group of the Chytridiaceae fungi may be mentioned : Urophlyctis leproidea, or " Beetroot Tumour," which forms large tumours on the root of the beet either at its top or its middle part. a b Fig. 22. — Crown-Gall of Lucerne — rllrophlyctis Alfalfce. (From G. Korff.) a, Root of lucerne with tumours ; b, section of the tumour, showing cavities filled with resting spores. These tumours have a short stem, and are irregularly intersected. When you examine them, they show dark pricks on the surfaces. The disease has been noticed in Algeria, France, and once in Sweden (1900) and in England (1905). Urophlyctis Alfalfse, or "Crown-Gall of Lucerne," causes in lucerne coral-shaped tumours on the neck of the root about the size of a pea. The disease was first seen in America, then in Switzerland, Italy, Alsace, England, and Bavaria. CHYTRIDIACEm 31 Olpidium Brassieae, or " Seedling Cabbage Disease," attacks tiny cabbage-plants in the spring, especially if they grow crowded and are kept very moist. The disease manifests itself in such manner that the head of the root gets black and breaks, when, in con- sequence, the plants wither away. 0. Nicotianae. — Possibly a variety of the previous one. It attacks young tobacco-plants. 0. Trifolii, which causes blister-like swellings on white clover. PyPOCtonum sphaericum, which kills wheat-plants, thus spread- ing yellow, dead patches over the fields ; it is noticed in France. CHAPTER IV DOWNY MILDEWS— PERONOSPORACEiE These fungi are nearly all parasites. They possess a well-developed and richly ramified system of spawn {mycelium). The vegetative Fig. 23. — Mycelium, Vegetative and Frugiferous. «, Intersection of a diseased leaf, with vegetative mycelium inside the leaf and frugiferous outside ; h, vegetative mycelium thread, with short, globular haustoria (after Cystopus) ; c, a similar one, with long, ramified haustoria (after Peronospora). (nutritive) part of the mycelium extends as a mesh within the host plant between the cells, and penetrates by means of small side 32 DOWNY MILDEWS— PERONOSPORACE^ 33 branches (haustoria) into the cells. The fructificative (spore- producing) part of the mycelium appears outside the host plant as a grey mould. Examined through a microscope, this mould is seen to consist of numerous erect aerial threads or filaments, often repeatedly bifurcated, which bear egg-shaped breeding-cells, by which the fungus propagates during the period of growing. As a rule, the germination takes place in such a way that the contents subdivide into a number of swarm spores, which are liberated one by one, and extend a germinating tube or filament. Occasionally the breeding-cell sends out undivided one tube or filament, in that case acting as a conidimn. For the continuance of the fungus until the coming year there are provided thick-walled resting spores, which later in the season develop within the affected cell-tissue, but frequently not before the same has begun to decay ; these do not germinate until the winter is gone. The attack of the fungus has usually this effect, that the cell-tissue very soon dies. In some cases, however, only a distortion takes place, while the host plant loses the power of producing ordinary blossoms or to yield ripe fruit. Seedling" Blight. {Fythium Bavyanum.) This fungus thrives in wet earth, especially in hotbeds, and proceeds from the soil to young plant germs, on which it especially attacks that part of the stalk which is under the seed-leaves (cotyledons). The plants become soft, bend down, and die. For this reason the disease has also been named " damping-off of seedlings." In moist air there grow out short fungus threads through the epidermis, and these cast off spherical spore-cases, the contents of which are diffused as a blister, and resolve eventually into numerous swarm spores. These spores are capable of im- mediate germination. The resting spores, intended to last through the winter, develop later in the decaying tissue, and remain in the ground. The fungus attacks plant germs belonging to many different varieties of plants, such as beet, barley, peas, lupin, clover, cabbage, spurry, sinapis, asparagus, stock, and others. Recently it 3 34 FUNGOID DISEASES OF PLANTS is spoken of— especially in Germany— as a parasite on beet-plants. Sometimes it will attack older portions of plants, as potato-tubers and stalks, heads of asparagus, etc. Protective Measures.— (i) Mix into the upper layer of the earth in hotbeds, where plants are germinated, fine sand or coal dust, and keep them sufficiently moist and warm during the early stage, while Fig. 24. — Germ Blight in Beet — Pythium Baryanum. (From W. BUSSE.) a. Diseased plants; b, sound plant (at the same age) . Fig. 25. — Pythium Baryanum. (From E. Rostrup.) a, A filamentous tube, with two spore - cases ; 6, a spore - case ready to develop swarm spores ; c, a resting spore. the Stalk beneath the cotyledons still keeps on growing. (2) If the disease appeared in a hotbed during the previous year, then new soil should be brought and all frames and glasses thoroughly cleansed. (3) If there be reason to suspect that the beet-seed contains any infection, then the seed-bunches should be kept moist for two to three days, and then steeped for two hours in a solution of sulphate of copper to a strength of i per cent, to 2 per cent, before they are sown. DOWNY MILDEWS— PERONOSPORACEjE 35 Potato Bligrht. {Phytophthora infestans.) This is the best known of all the different diseases to which the potato-plant is subject, and is generally referred to as " Potato Disease." It shows its presence by the appearance of large dark spots on the leaves during the time the plant is blooming or shortly Fig. 26. — Potato Blight — Phv- Fig. 27. — Potato Blight. (From tophthova infestans. (From "E. E. Rostrup.) Rostrup.) a, Two branches of a filamentous tube protruding from a cleaving, and carrjang breeding-cells ; b, a breeding -cell germinating with sprout ; c, two similar ones, just ready to discharge swarm spores : d, a swarm spore ; e, a germinating swarm spore. after. The spots increase daily both in quantity and size. Soon all the leaves wither away and the stalks are almost bare. Meanwhile a fetid and rotten smell emanates from the potato-field. When examining a diseased spot on a leaf you will find the lower 36 FUNGOID DISEASES OF PLANTS side covered with a dirty grey stuff or blight. At first this bhght is evenly distributed over the whole spot, but as the spot gets older its centre, which was first diseased, dies, and as there now remains no nutrition for the fungus, the blight disappears from the centre, and is conspicuous only at the edges. This dirt-grey blight is composed of hanging, ramified, colourless fungoid threads, which bear numerous egg-shaped breeding-cells. While germinating they act as a rule like spore-cases (sporangia) — i.e., their contents arrange themselves into a varying number of four to sixteen separated plasma bodies, that pass out through an opening at one end of the spore-case. These bodies are provided with two fine vibratile cilia, which give them a gyratory or vibrating motion. After about half an hour this movement stops, the cilia drop off, and the spores begin to germinate. Sometimes it may, however, happen that the breeding - cells, which are cast off from the ramified mycelium threads, directly sprout a germ-tube, thus acting as an ordinary spore or conidium. The extension of the disease over the potato-field depends to a considerable degree upon the state of the weather at the first outbreak of the disease and after. If the weather be damp, especially foggy, the disease will spread very rapidly — within one to two weeks the whole field is black. But if the weather be quite dry at this period, the propagation is tardy, and may even stop altogether, at any rate for some time. It has occasionally happened that potatoes planted in hotbeds in January or February have shown the disease by the middle of April, just when the tubers were forming, and within a few days the plants have withered away. When the leaves have thus died all over a potato-field, it will not be long before the new tubers begin to show ominous spots, especially those nearest to the surface of the earth. These are mostly of a brown colour, and penetrate more or less deeply into the potato. The way in which the disease reaches the tubers has generally been considered to be through the breeding-cells, which have dropped on the ground and have been washed down into the DOWNY MILDEWS— PERONOSPORACE^ 37 soil by the rain. It is true enough that such a surmise has been estabHshed by several experiments undertaken in 1880 and later on, both in Denmark and England. In these experiments spores were strained through layers of sand of various depths. It has also been tried with success to protect the tubers against serious attacks of the fungus by means of mounds arranged high round each plant. Against this simple explanation of the dispersion of the disease we have several experiments of a later date. At these trials it proved next to futile to render a sound potato sickly by means of diseased leaves. And in those cases where disease developed, it proved to be not potato blight, but dry-rot, a disease which, as previously described, is caused by bacteria. If these latter results should be further confirmed, there remains no other way of explaining the access of the disease into the tubers than to accept the conjecture that it reached the tubers in the same manner as it came to the leaves. But, then, how does the disease first get into the leaves ? This question is as yet unsolved, and so is also another query : In what way does the fungus of potato blight hibernate ? Several different hypotheses have been brought forward, but none of them have been definitely proved. The only thing we are sure of in regard to this fungus is, that it does not show a natural stage with resting spores as most of the other downy mildews do. At least, so far, all researches in the open for such a stage have proved futile. The year 1845 is generally considered as the first year of the appearance of the disease in Europe, when an account was given of the fungus and its scientific name settled. The same year it was prevalent over a considerable portion of the Continent as a very destructive pest. The extraordinarily rapid spread of the disease has been considered as arising from the weather conditions during the summer and autumn of that year. But a quite satisfactory explanation of the phenomenon has scarcely been found. Equally remarkable and unexplained is the sudden appearance of this pest in North America. 38 FUNGOID DISEASES OF PLANTS Experience has proved that various kinds of potatoes are more or less severely attacked by the disease. This observation has been of service as a protection against the disease. But all the vicissitudes which a planter is subject to in this respect are fairly well known. Even if certain sorts of potatoes have once shown resistance, it by no means follows that they always will do so. On the other hand, it is not merely this point that has to be considered by the potato planters, but also other qualifications, such as rapid growth, prolific nature, taste, degree of starch, and so forth. A sort that still keeps its good record is the old, well-known " Magnum bonum." As valuable new sorts might be mentioned " Konigin Carola " (early food potato), "Up-to-date" (somewhat early food potato), and " Marcker " (rather late factory potato). The same fungus has also been noticed in several other plants more or less related to the potato, such as Solannni etuherosiim, S. caripense, S. stolonifevmn, S. utile, S. Maglia, S. verviicosian, S. Dul- camara, S. laciniatnm, S. mavginatuni, S. tiihcvosiim x utile, S.Lycopevsi- cuni, Anthocercis viscosa. Petunia liyhvida, Schizanthus Gvahami, Datura Metel, and others. For some time it was thought that the same fungus was the origin of the two diseases which late in the autumn affect the potato, and are commonly known as "wet-rot" and "dry-rot." But we have previously learnt that these diseases are caused by bacteria. Protective Measures. — (i) Use only sound seed. Potatoes gathered from a diseased field crop should not be used for planting, even if they look comparatively sound. We have every reason to believe that it is by means of slightly diseased tubers and by the living germs concealed in them that the disease is retained from one year to another. (2) Select a field, the soil of which is appropriate for culture. The best would be in a dry locality with well drained sandy soil or clay strongly mixed with sand. (3) Select such kinds of potatoes as will have the greatest resistance, and let this selection be guided by previous experience gained in the locality. (4) Avoid cultivating potatoes year after year in the same soil. (5) Do not DOWNY MILDEW— PERONOSPORACEjE 39 fertilize the Tield with manure from the farmyard, especially fresh manure, immediately before planting the potatoes. (6) Bank up the potatoes high. In that case the earth should be piled so high that the topmost tubers are 9 centimetres (about 3^- inches) down, if in sandy soil, and 10 to 13 centimetres (4 to 5 inches) if the soil consists of clay. This arrangement with mounds requires a wider distance between the rows than the customary one — viz., on sandy soil 80 centimetres (about 2 J feet), and on harder soil 95 centimetres (about 3 feet). (7) Sprinkle the field at the time the spots first begin to appear (or one week in advance in accordance with experience from previous years) with some fungoid-killing fluid, as, say, i per cent. Bordeaux mixture, and sprinkle it again after three to four weeks. During normal years it has proved best in Southern Sweden — and the case might most likely be the same in Southern England — to sprinkle early potatoes for the first time during the first half of July, and medium early and late potatoes during the latter half of the same month. The effect of such a sprinkling will be that the leaves remain green about one to five weeks longer than they otherwise would, and also that not only the number of sound tubers will increase, but the total weight of the whole crop will be higher. (8) Do not take the potatoes up from the ground too early, while the surrounding atmosphere is still filled with infectious germs from withering leaves and stalks, which as yet are not quite dead. (9) Store the potatoes in a dry condition, thus preventing the outbreak of disease during winter. Beet Mould. {Psvomspora Schachtii.) Both fodder and sugar beets are subject to this disease. While young, the diseased leaves are pale, with curled and rolled-back edges. When older, they are pulpy and swollen, and covered on the under side with an ashy-coloured or yellowish mould. This grey mould consists of repeatedly branched or forked fun- goid threads or filaments, which at the points bear egg-shaped breeding-cells, the source of the disease. The attacked leaves die prematurely. In old withered leaves there occasionally develop 40 FUNGOID DISEASES OF PLANTS resting spores, which are thick-walled and hibernate. Sometimes rotten spots appear on the roots. It is alleged that the fungus can exist from one year until the next as a sterile thread-mesh in the top of hibernating seed-beets. This disease is known in Denmark, Germany, and France, and occasionally is very destructive, as was the case in Saxony in 1894. Fig. 28. — Beet Mould — Perojiospora Schachtii. (From E. Rostrup.) a, The top of a beet-plant (reduced size) with the edges rolled backwards ; b, re- peatedly forked or bifurcated fungoid threads or filaments, with breeding- cells. Protective Measures. — (i) Do not take seed-beets from a dis- eased field. (2) Try early to sprinkle the infected beet-tields with a 2 to 3 per cent. Bordeaux mixture. Among other downy moulds injurious to agricultural plants can he mentioned : Peronospora Viciae on peas, fitch or vetch, and other plants related to them. It forms grey-violet blight patches close to DOWNY MILDEWS— PERONOSPORACEM 41 each other, or also one continuous blight over the under side of the leaves. This blight consists of repeatedly branched or bifur- cated threads, giving off breeding-cells at the points. Within the diseased leaf-tissue the hibernating resting spores are developing. It frequently happens that the harvest of fitch or vetch, etc., is greatly reduced through this attack, P. trifolioruni on both cultivated and wild clover, and on several other related leguminous plants, such as lucerne, lotus, and others. It produces larger or smaller pale patches on the leaves, which have often the shape of broad, cross-going tapes. The patches are on the under side of the leaves, covered by a grey or pale - lilac coloured mould, with almost globular breeding-cells on the tops of the filaments. Its ravages are worst on lucerne, especially if this has come from America. It has been noticed as a practi- cally different degree of dis- ease from different seed, even although the plants have grown side by side. This fact would indicate that the disease is spread by means of the seed. Resting spores are developed quite sparsely and have been noticed in the tissue of the stipule. P. parasitica on turnip, Swedish turnip, rape, sinapis, and other both cultivated and wild cruciferous plants. The fungus forms white, flour-like coverings on stem, leaves, and the blooming sprout. Often the attacked parts become quite distorted. P. obovata on spurry ; the leaves turn mouldy. Fig. 29. Blight on Peas — Perono- spora Vici(B. (From E. Rostrup.) 42 FUNGOID DISEASES OF PLANTS The under side of Plasmopara nivea on carrot and parsnip, the leaves is covered by a snoviry-white mould. Protective Measures against Several of these Diseases. — (i) Do not plant in earth which has produced a sickly harvest for several years the same kinds of plants, neither any related to them that might be susceptible to the disease. (2) Do not use seed from Fig. 30. — Blight on Lucerne — Pcroiospova tyifoliorum. (From E. Rostrup.) a, A leaf of lucerne with pale blight patches ; b, a forked thread with breeding- cells ; c, a breeding-cell ; d, a resting spore. diseased plants. (3) If possible, try and sprinkle the field in the early summer with 2 to 3 per cent. Bordeaux mixture. Cabbagre White Rust. {Cystopus candidus.) This fungus, known as " White Rust," differs from the previously described downy moulds in that the fertile filaments of the mycelium do not become conspicuous outside, but are hidden under the cuticle, the latter being of a shining white appearance. In this case they are short, undivided, crowded threads, which at their tops bear breeding-cells arranged moniliformly, or like bead-strings. Finally, however, the epidermis breaks, and the white spore meal becomes free. Inside the diseased tissue there develop hibernating spores. DOWNY MILDEWS— PERONOSPORACEM 43 Such a'white rust (C. candidus) is prevalent on a number of wild cruciferous plants, as CapseUa, Thlaspi, Sinapis, and others, and also Fig. 31.— White Rust of B.^v^-Cystopus candidus. (From O. Kirchner and H. BOLTSHAUSER.) a, Immature fruit with fungoid swellings : h, two fungoid swellings, one of them broken ; c, fungoid tubes with breedmg-cells. occasionally on cultivated plants related to them, as cabbage, Swedish turnip, turnip, rape, and others. However, this disease rarely causes any considerable loss to agricultural plants. CHAPTER V SMUTS— USTILAGINACE^ These fungi — often named Bunt — are genuine parasites, which expand their tiny mycelium for some time through the whole plant without hindering its normal development to any visible extent. They reach up to the blooming stalk, where the formation of the spores takes place, and a thorough devastation sets in. The spores appear as a brownish-black mass of dust in long stripes on the stalks and blades of the leaves, or they wholly occupy the generative organs of the plant. The spores are spherical, and provided with a thick wall, which often has wart or mesh-formed protuberances. As a rule the spores appear separated from each other ; occasionally a few may be seen together. They either germinate at once, or they act as hibernating spores, in which case they are said to retain their power of germination as long as ten years. When the spores germinate, there appears either a germ thread, that at once penetrates into the host plant (if the germination has taken place on the surface of the plant), where immediately a spawn is formed, or otherwise there develops a short and thick tube formation (basidium), which bears spores (basidic spores). If the germination takes place in a specially prepared nourishing fluid, as fertilizing extract, or the like, then a rich formation of bud-cells, similar to yeast fungi, will develop. As long as nourishment is available, this formation can go on indefinitely. From such cultiva- tion infection can be brought on very tiny parts of a plant which is susceptible to the disease. 44 SMUTS— USTILAGINACE/E 45 Stinking- Smut. {Tilktia.) The spores are simple, warty, and seldom smooth on the surface. At germination they develop a short basidium, which at its summit has a ring of thread-like basidic spores, often united at their middle part in pairs, and either give off germinating threads, or produce bud-cells, which germinate. Stinking" Smut of Wheat. {Tilktia caries and T. levis.) This smut, also called " Stinking Bunt," does not indicate its existence when first attacking wheat-plants. These appear to be healthy until the time comes when the seed begins to ripen. At this time the diseased plants become ominously conspicuous through their dilated ears and their shorter and thicker corns. As a rule every ear in a plant and every corn in an ear are diseased. Only occasionally sound and sickly corns are found in the same ear. At maturity the affected corns are grey outside, while inside they are filled with a brownish-black mass of dust. They have a fetid smell, peculiar, penetrating, and disagreeable; hence the disease is called "Stinking Smut." This disease is brought about by either one of the two fungi : TiUetia Tvitici and T. levis. The former has warty spores, the other has spores with a smooth surface. It is principally T. Tvitici that is the offender. The husk of the smut-corns does not break of its own accord, but these corns are brought together with the sound ones into the granary. At the threshing they are more or less crushed, and the black spore dust gets free. Spores then fasten easily on the healthy corns, especially on the hair pencil at the summit. Infected wheat gets a blackish-grey colour and smells badly, as well as the fiour prepared from it. By means of infected corn the disease is propagated to next year's crop. When the wheat-corn grows, then the smut-spores grow on its husk. These form a short tube, which has at one end a ring of long, narrow spores, that either directly, or through separate bud- 46 FUNGOID DISEASES OF PLANTS cells, send germinating tubes into the young wheat sprigs. Such infection is called "germ infection." If the fungus once gains an entrance into the tender plant, then it will spread through the Fig. 32. — Stinking Smot of Wheat — Tilletia Caries, (a and b, The Author.) a, Smut-ear of unbearded wheat ; h, smut-ear of bearded wheat ; c, two smut- corns, one whole and the other cross-cut ; rf, three spores ; e, spore that has germinated. entire plant down to the ovule, within which it develops its dust-like mass of spores. The spores retain their germinating power for years. Different sorts of wheat, especially spring wheat, are susceptible SM UTS— USTILA GIN A CE^ 47 in another way. But even in the same sort the effect of the attack can vary during different years. Of special importance in this respect are the chmatic conditions at the sowing and subsequently. A low temperature at this time will delay the germination of the wheat, thereby prolonging the period under which it is exposed to infection. Hence a late sowing of autumn wheat and an early sowing of spring wheat promotes the ravages of the disease. It has sometimes been feared that smutty wheat, given as fodder to the stock, may also convey disorder. But to judge from experi- ments with horses, cattle, pigs, hens, and pigeons, this is not the case. Neither has any lowering in the general condition of health taken place, nor have any sickly formations been found in their inner organs. Protective Measures. — i. Take the grain for soimng from a field where no disease has appeared during the year. Should this pro^'e to be impossible, the following precautions might be observed : 2. Wash the Sowing-Grain. — If the sowing-seed is mixed with smut-corns, they must be separated by pouring the grain slowly into a vessel containing water, and thoroughly stirred. The smut- corns float, and are skimmed off. 3. Swamp the Sowing-Grain. — Since, even m spite of the washing, there are always to be found smut-spores on the corns, especially at the top, it will be safest to swamp the grain. Several methods may be chosen : {a) Steeping in a Solution of Copper Vitriol. — Half a kilogramme of copper vitriol is dissolved in 100 litres of water, or say about I pound to 20 gallons. The vitriol is put in a cloth bag, which is kept in the water until all is dissolved. The solution is then stirred up carefully, and the wheat poured in in such quantity that the fluid is about 4 or 5 inches above the wheat. The seed is stirred repeatedly. After twelve to fourteen hours the fluid is poured off and the grain poured out on the floor of the granary, that previously has been washed with a similar solution. Then the seed is sprinkled with a lime solution prepared from i kilogramme of slack lime and 100 litres of water, or say about 2 pounds to 20 gallons. Finally, the 48 FUNGOID DISEASES OF PLANTS seed is spread to dry. As soon as sufficiently dried, it is sown. The sacks in which the grain is transported should previously have been soaked for at least twelve hours in 2 per cent, vitriol solution. (b) Cvysiallising or Candying ivith Bordeaux Mixture. — In a vessel 2 kilogrammes of copper vitriol (copper sulphate) is dissolved in 50 litres of water, or say about 4 pounds to 10 gallons. In another vessel lime-wash is prepared in such a way that 2 kilogrammes of new burnt lime (stone lime) is so moistened with water that it becomes a white powder. To this 50 litres of water is added to the solution and well stirred. Both the solutions are then mixed together in equal strength. The Bordeaux mixture prepared in this way should have a pretty blue colour, turn red litmus-paper blue, and deposit a blue precipitate at the bottom. In this solution a wicker-basket, lined inside with coarse linen, is submerged. Then the grain is poured into the basket, stirred up a few times, while the smut-corns and spores that are floating up to the surface are being skimmed off. After ten to fifteen minutes the basket is taken up and the grain spread out to dry. By such procedure the corns get candied with a thin crust ; this will remain on them when they are sown, and will at the germination act as a spore-killer (fungicide).^ {c) Steeping in a Formalin Solution. — In a 36 to 40 per cent, water solution of formalin \ to \ litre is mixed with 100 litres of water (say, \ pint to i pint to 20 gallons). Into this solution the seed is poured, all that floats up to the surface being skimmed off, while it is stirred repeatedly. It is then left to stand for half to one hour ; then the fluid is poured off, and the seed spread to dry. For such a steeping on a large scale there is constructed a special apparatus — " Dehne's Disinfection Apparatus." This is, however, applicable only for seed that is free from whole smut-corns. With this apparatus one can sodden 1,000 kilogrammes, or about i ton of seed, in half an hour, 1 The disadvantage in using copper vitriol is that the power of germination will he somewhat diminished, especially if the seed be machine-threshed. Another trouble is that if there be any seed left over after sowing, such cannot be used for foodstuff, as it is poisonous. SMUTS— USTILAGINACE.^ 49 (d) Ceres Treatment. — The Ceres powder contains as fungicide principally sulphurated potash, and also substances calculated to promote a rapid germination of the corn and a quick development of the germ-plant. The powder is dissolved in cold water, i kilo- gramme powder to 350 kilogrammes seed, say about 2 pounds to 7 cwt. The grain-heap is sprinkled repeatedly with the solution, stirred up thoroughly, and allowed to remain thus soaked from ten to twelve hours ; then it is spread out thinly to dry. The Ceres treatment does not exterminate the disease altogether ; it only has a diminishing effect. If it is adhered to for several years, the per- centage of the disease will be reduced year by year, until finally there is not much of it left. Seed treated with Ceres should not be sown sooner than two to three days after the treatment. (e) Warm-Water Treatment. — Under this treatment the seed is sub- merged in water of about 56° C, after having first been placed in a lined wicker basket or in coarse sacks. Should the temperature sink at the submersion, then warm water should carefully be poured in until the temperature of the water in the vessel is the required one. As an alternative, before the submersion, dip the basket or the bags containing the seed repeatedly in water of 40^ to 45° C. The seed is kept submerged in the 56° water for about ten to fifteen minutes, and is then spread out to dry quickly in the air. (/) Treatment ivith Warm Air. — Then the seed is exposed for a quarter to half an hour to air of 60° to 65° C, and this sort of treat- ment has latterly been tried with success. For this treatment a special apparatus is required for drying. Such an apparatus, named " Selecta," has been introduced into the market by the firm, Select Grain Machine Company, Berlin, W. 35.^ Amongst the different methods of soddening, the warm-water treatment is now considered the best and most reliable one. As, however, its proper procedure requires more time and labour than planters in general feel inclined to bestow upon it, various means have been adopted in different countries to render ■"■ Seed treated with formalin, warm water, or warm air, can be used lor other purposes, if all is not needed for sowing. 4 50 FUNGOID DISEASES OF PLANTS the method more practicable. In Denmark several dairies have been induced to do the work for payment, as these establishments have easy access to warm water, necessary vessels, and so forth, and also have a working staff accustomed to work with the use of the thermometer. In Germany there have been constructed various apparatus, as " Arnim-Schlagentin's," by means of which the seed is passed through warm water ; and " Appel and Gassner's," in which the warm water is passed through the seed. With the latter, 50 hectolitres (equal to 135 to 140 bushels) of seed can be sodden in one day. 4. Take care lest the threshing-machine bring infection, as it might previously have been used for infected seed. Among other forms of " stinking smut,'' that destroy grasses by filling them with a greyish-brown dust-mass, may here be mentioned : Tilletia Secalis, on rye, noticed in Germany, Austria, and Italy ; T. Lolii, on rye-grass {Lolmm), in Germany and Denmark ; T. deci- piens, on Agrostis, in Germany, Denmark, and Sweden ; T. Holci, on soft-grass (Helens), in Belgium and Denmark. Other forms belonging to this sort develop their masses of spores in long wound-stripes on the straws and leaves of grasses. Such a one is T. striSBformis, which attacks a great number of different grasses, as Poa, Holcus, Festiica, and others. This disease is known in most of the European countries. Loose Smut. (Ustilago.) The spores are simple, either warty or smooth. At germination there is formed a short basidium, which divides into joints, each one developing a basidium spore. The spores are seldom directly germinating. Loose Smut of Wheat. (Ustilago Tritici.) In contrast to the stinking smut, the loose smut becomes con- spicuous as soon as the wheat begins to form ears, and the corn husk that covers the dust-mass cracks immediately, when the spores SMUTS— USTILAGINACE^ 51 are scattered by the wind. Soon there will remain of the whole ear nothing but the bare rachis, partly black by means of smut-spores that remain at the joints. The disease is caused by a special fungus, Ustilago Tvitici. For a long time it was thought that the same fungus brought on the loose smut disease on wheat, barley, and oats ; recent researches, however, have proved that this is not the case, but that the loose smut of different seed belongs especially to each one of them, and does not infect the others. The spores of the loose smut are globular and unicellular, with small warts on the surface. They can germinate at once, but do not retain their power of germination longer than a few weeks ; consequently they cannot infect sound corn in the same way as the spores of the stinking smut. The spores of the loose smut diffuse simultaneously with the blooming of the wheat. The spores stick to the viscid stigmas of the pistil, and germinate there quite readily, just like pollen, and send their germ-tubes right through the style down to the developing seed, thus bringing on the infection. This form of infection is called " blooming infection." A seed-rudiment infected in this way does not show the infection during the first stages of development. It grows and ripens just like any ordinary wheat-corn, and cannot in the cleansed stock of grain be picked out from the sound ones, although the infected corns do not seem to equal the average size of the sound corns ; but in the next crop the latent disease becomes conspicuous. If the infected seed is sown, then the plants become sick with the smut. The ears on the formation of the corn are filled with a black mass, which is at once scattered by the wind, and continually provokes fresh infection. The conditions of the weather during the period of blooming will influence the dispersion of the loose smut. If heavy rain showers occur when the smut-ears are about to let out the black mass of spores, then a number of the spores — possibly most of them — reach the ground and germinate there, thus never reaching the styles of the blossoms ; but if the weather be dry and 52 FUNGOID DISEASES OF PLANTS calm during the blooming period, then the blossoms are subjected to infection. As long as the corn is dry, the fungus that has infected it is in a V-^ ri^ Fig. 33. — Loose Smut of Wheat — Ustilago Tritici. (a. The Author.) a. Three smut-ears ; one of them has lost both smut-corns and awns, and the wind has left only the bare ear-stalk ; b, spores, before and after germina- tion ; c, style of a blossom infected with smut. stage of perfect rest, and can in no way be influenced from without ; but if the corn be kept for several hours in lukewarm water, then SMUTS— USTILAGINACE^ 53 the fungus changes into a stage of germination, and becoming influenced by higher temperatures, is in consequence open for treatment with warm water or warm air. When the wheat ultimately ripens, there is hardly any dust of this sort of smut ; but even if it were there, it could not penetrate into the ripe, sound corn. Consequently a plant grown from such a corn is sound, as this sort of smut cannot produce germ infection. Protective Measures. — (i) Do not take sowing-seed from a field where during the blooming period loose smut has been prevalent, as presumably many blossoms have been infected, and seed of such blossoms produces smut-plants in the following crop. (2) If the sowing-seed comes from an infected field, or belongs to a kind of seed that is known to be easily susceptible to the disease, then sodden the sowing-seed with warm water or use warm air in the following manner : Steep the sowing-seed first in lukewarm water of a temperature of 20" to 30^^ C. for four to six hours, and submerge it in warm water of 50° to 54° C. for twenty minutes, or expose it to warm air of 55° to 60*' C. for thirty minutes. The percentage of the disease has thus in numerous experiments sunk to next to nothing. (3) Try to prevent the infection during the blooming period. On smaller experimental plots this can be done by closely inspecting the wheat day by day during the formation of the ears, and pulling up by the root and burning every plant that is setting smut-ear. This is continued until it is certain that every plant has produced at least one ear. In the same way the private planter can also procure a sound wheat stock if he reserve in his plantation a special little experimental field far away from the rest of the wheat-fields. In this the weeding out of the diseased plants can be done, and, by taking special care during the period of the first formation of the ears, he may finally reach his goal, and be in possession of a perfectly sound sowing-seed for all his fields. 54 FUNGOID DISEASES OF PLANTS Loose Smut of Barley. (Ustilago nuda.) This smut corresponds with the loose smut of wheat ; it appears when the barley is forming the ears and beginning to bloom. The Fig. 34. — Loose Smot of Barley — Ustilago nuda. (The Author.) Three smut-ears, the third having only the rachis left, the wind having carried off awns and smut-corns. dust-m.ass is at once scattered by the wind. Several spores are thus brought into the blossoms of sound ears. Some of them stick to the young stigmas of the pistils. There they germinate, sending germ- SM UTS— U ST I LA GIN A CEM 5 5 tubes down to the developing seed, which thus gets infected. The seed of the infected blossom develops like an ordinary corn-seed, but the infection is latent, and next year a diseased plant will develop from this previously infected corn. This disease is caused by a fungus named Ustilago nuda. The spores are globular, with a warty wall. At their germination they develop a long, jointed, and ramified germinating filament that infects the pistil. Some sorts of barley are more susceptible to this disease than others, and this is evidently owing to the difference that the pistil of one sort is less protected from infection than is the case with another sort. In the southern part of Sweden the populace evince great preference for the " Hannchen " barley, but this is very susceptible to the disease. If the weather be dry during the bloom- ing period, then the spores can float about, while strong showers of rain wash them down to the ground, where they can cause no harm. Protective Measures. — The same as for loose smut of wheat. Covered Smut of Barley. (Ustilago Hovdei.) It is only lately that we have learned to distinguish between two different sorts of smut of barley. The covered smut differs in many important ways from the loose smut. Barley ears affected by covered smut are during the blooming period not very much unlike the sound ones. But a few weeks later the smut-ears catch the eye through their darker hue ; their tiny ears are distorted into a broad, swollen, tripartite formation, the middle tooth corresponding to the middle corn and the side teeth with the side blossoms. The husk that covers the smut remains as a silver-grey pellicle, quite perfect until the barley ripens, only showing a few unim- portant cracks. Thus no infection of the blossoms takes place, as the spores do not spread while the barley stands on its root. The covered smut-ears are brought with the sound into the granary, and break only at the threshing. The spore-stuflf is then spread to the sound corns, and, should the same still remain fit for germination when this barley is sown, then the germinating sprout becomes 56 FUNGOID DISEASES OF PLANTS infected, and the growing plant produces smut-ears. In this case the germination infection takes place in this way. The disease is caused by a special smut, named Ustilago Hordei, with larger and more edged spores than those of the previously described smut ; their cell walls are smooth. When the spores germinate, they develop a short germ fila- ment that bears bud-cells. Protective Measures. — The same as against stink- ing smut of wheat. Of 36 per cent, formalin, there is taken I kilogramme to 225 litres of water — say about 2 pounds to 45 gallons — and the steep- ing should last for ten to fif- teen minutes, after which the seed is left untouched in a heap for seven to eight hours. Sulphate of copper reduces the power of germination. Loose Smut of Oats. [Ustilago Avencc.) This, the more common of the two sorts of smut to which oats are subject, ap- pears like the loose smut of wheat and barley. As soon as the oats begin to form ears the smut becomes conspicuous. The attacked ears are narrower than the sound ones, and the bristles are less dilated. Sometimes all the small ears in a panicle are afiFected, but it might also happen that sound ones are mixed with them, especially at the top. Fig. 35. — Covered Smut of Barley — Ustilago Hordei. (The Author.) SMUTS— USriLAGINA CEAi 57 Those of the spikelets that are entirely destroyed are of a globular shape, forming one homogeneous mass of dust. Other spikelets that are only partly attacked retain their natural shape better, and only their lower part is filled with smut. When the smut-ears first appear, the husk of the corn is more or less cracked, and the smut is ready to diffuse. This diffusion lasts in their case longer than with wheat and barley — viz., from the com- mencement of the blooming until the period of ripening. By harvest - time the wind has carried off most of the spores. In spite of the early dispersion of spores, it appears in this case that a blooming infection seldom, if ever, takes place. The disease is infecting the plant during the blooming per- iod in such a way that spores settle in the open oat blossom, outside the seed-rudiment, and are retained there during the growth of the seed between this and the tightly closing husks. Later on the disease also spreads through spores that have stuck outside the growing oat-corn. This disease is caused by Ustilago Avencc, which has globular spores with a warty surface. When these germinate they usually develop Fig. 36. — Loose Smut of Oats — Usti- lago Aveiite. (The Author.) Three smut panicles, from one of which the wind has carried off the awns as well as the smut-corns ; only the stalk of the panicle is left. 58 FUNGOID DISEASES OF PLANTS a short germ sprout, from the top of which, as well as from the joints, bud-cells fall off, and in their turn germinate and infect the tender plant. The germination of the spores thrives best when the weather is warm and the sowing takes place in the spring. The spores retain their power of germination for a long time, certainly for several years. All infection with this fungus is germ infection. It is not unusual for 30 per cent, of the crop to be lost through this smut — in fact, cases are known where the destruction has been as high as 60 per cent. And very seldom is an oat-field quite free from it. Thus it is wise to beware even of a slight attack, as this, under conditions that might be favourable to the development of the ailment, may lead to a great destruction the following year. Different sorts of oat are susceptible in different degrees. In Canada (Guelph, Ontario) there is an early sort of oat — " Early Ripe " — that is almost immune. The loose smut of oats depends greatly upon climatic conditions. Dry and calm weather during the blooming period is auspicious for the spores while getting into the blooms, and damp, warm weather at the time of sowing promotes the infection of the sprouting corn. Both of these conditions in conjunction may bring about a serious outbreak of the disease. This explains the variations of crops in different years. Protective Measures. — The same as for stinking smut on wheat and covered smut on barley. The washing of the sowing-seed is in this case futile, as the moisture would not reach those spores that are closed up between the husk and the kernel of the oat-corn, where they penetrated during the blooming period. Of the different methods of steeping, that with sulphate of copper should not be adhered to, as the ger- minating power of the oat would thereby be considerably checked. If formalin solution is used, then 36 per cent, formalin should be taken in the proportion of i kilogramme to 300 litres of water (say about 2 pounds to 60 gallons), and the steeping last for ten minutes, after which the seed is left untouched in the heap for seven to eight hours. SMUTS— USTILAGINACE.E 59 Covered Smut of Oats. {Ustilago KolUri.) The oat panicles, which are affected by this smut, show at first nothing different from the sound ones, neither with regard to the § ! / Fig. 37. — Covered Smut of Oats— Ustilago Kolleri. (From O. Appel.) Fig. 38. — Ustilago perennans. (The Author.) panicles themselves nor to the spikelets. Later on, towards the time for ripening, the black mass of spores becomes conspicuous when showing through the husk of the corn. The husk keeps 6o FUNGOID DISEASES OF PLANTS whole, at any rate until the ripening time ; then when the grain is threshed the spores are let loose and stick to sound oat-corns. If they are let alone upon these, then the infection will be conveyed to the tender germ-plant. This disease comes from a smut-fungus, called Ustilago Kolleri, or U. levis, different from the previous one in that the spores are on an average somewhat larger, more edged, and smoother on the surface. They germinate in the same manner as the loose smut on oats. Protective Measures. — The same as for the loose smut of oats. Amongst other forms belonging to this sort of smut-fungi, which attack and destroy the fruits of grasses, may be noticed : UstilagfO perennans on Avena elatiov, which is thought to hibernate in the rhizome of the host plant, and renders the fodder poisonous to cattle ; U. bromivora on brome-grass {Bvoimis arvensis, B. mollis, and others) ; both of them, especially the second one, are not uncommon. Beside these there exist several forms of loose smut, which develop their spores on leaves and stems of different grasses. One of these, Ustilag'O longfissima, forms on the leaves of Glycevia aqiiatica long, parallel, open stripes, filled with spores of an olive-coloured hue. The attacked sprouts as a rule develop no ears. Cattle eating fresh sprouts that are smutty, become ill, and may even die. Several such cases occurred in 1899 in the southern part of Sweden. On one estate twenty-four cows became ill. The symptoms of the sickness set in about one hour after the fresh grass had been consumed, and appeared as diarrhoea, stiffness, and a lowering of the temperature of the body. Most of them gradually recovered, but after that they never touched the grass. On another estate in the same locality three cows became ill in the same way, and so severe was the attack that the animals had to be killed. It is only the fresh grass that shows these poisonous qualities. When dried it is evidently harmless. Another form, U. grandis, brings on swellings of the thickness of a finger on the topmost joint of the stem of reed, Phragmites communis ; these swellings are filled with a black mass of dust. The affected stems do not develop any ears. SM UTS— USTILA GIN A CE^ 6i Fig. 39. — Smut of Giant Meadow-Grass — Usti- lago loiigissima. (The Author.) Fig. 40.— Stalk Smut of RYR—Uvocystis occulta, (a, The Author.) a. Smutty straws ; b. spore-balls not germi- nated ; c, a germinating spore-ball. Stalk Smut. {Uvocystis.) The spores, numbering about ten, are joined into spore-balls or clusters, with one or more larger and darker spores in the centre 62 FUNGOID DISEASES OF PLANTS and several smaller and lighter spores outside. At the germination there grows out from each one of the inside spores a basidium, having at the top a crown of spool-formed spores. Stalk Smut of Rye. {Urocystis occulta.) The spore masses originate on the stem and leaves of rye in long, parallel stripes, at first covered by the cuticle of the organ and of a lead-grey colour. Finally the epidermis breaks, and the black spore-stuff becomes visible. The diseased straws are more or less distorted and stunted in their growth. Usually there is no ear- formation, or else the ears are empty. Generally every straw in the plant is affected. In sporadic cases the disease has infected wheat. The disease is not of a very frequent occurrence. Usually it is limited to sundry specimens in the field. In Denmark cases are known where it has caused a reduction in the crop of 50 per cent. At the threshing of such rye the air is filled with spore-dust to such an extent that the labourers are subject to nausea. Protective Measures. — The same as against stinking smut on wheat. CHAPTER \I RUSTS-UREDINACE/E These fungi are, like the moulds and smut - fungi, veritable parasites. They develop their mycelium as a mesh of fungoid threads inside the host plant between the chlorophyl cells. Inside the cells the mycelium, as a rule, sends only short side-branches, sucking warts, or suckers. Sometimes there is found, also inside the cells, a largely ramified mycelium. The cells are not at once destroyed by the fungus, but retain their natural shape for some time. Gradually they are, however, pressed together by the constantly growing mycelium, and all the parts of the cells — viz., their walls, chlorophyl bodies, and so forth — are overcome and consumed by the fungus. Finally there is formed a homogeneous hymcnium, from which proceed long strings which bear spores. Then the cuticle of the host plant breaks, and an open wound appears, filled with a yellow or brown mass of dust. Sometimes the epidermis remains unbroken over the stuff like a transparent film. The rust fungi have usually several forms of spores. In the summer there develop summer spores {uredospovcs). These are yellow, or yellowish-red, unicellular, and warty or prickly on the sur- face (see Fig. 42, b and c). They can, as a rule, germinate at once. The germinating filaments penetrate the stomata of the infected organ and bring on fresh sores within a week or two. During the course of the summer several such generations of spores may germinate. From the same mycelium there will later on in the summer and in the autumn come forth autumn and winter spores (teleutospores). 63 64 FUNGOID DISEASES OF PLANTS These are brown or black, both unicellular and many-celled, with thicker walls (see Fig. 42, e). Occasionally they germinate at once, but in most cases they are hibernating spores, and do not grow before the following spring. The germination of these spores takes place in such manner that from each compartment of the spore there grows out a short hasidimn (see Fig. 42, /), which is divided or jointed, and from each one of these joints a basidium spore (sporidium) is separated and carried away by the wind. Should this spore reach a growing leaf, or any other part of a plant that is susceptible to this fungus, then the spore will penetrate its epidermis by means of a germ-thread, and thus get access to the inside of the organ, later on becoming evident by rust sores on the surface. This invasion may be either on the same host species where the spores have bred, or on a plant closely related thereto, or on a plant that is far apart from them. In the latter case the fungus is said to be " host-changing" {heteyoccious), in the two former cases "non- host-changing " {ajttcecioiis). That stage of the fungus which originates at its change of host plant, differs considerably from the previously described stages of summer spores and winter spores. It is called the "cluster-cup stage" {/Ecidium, see Fig. 43), and embraces, as a rule, two different stages of development. One of these forms is called spevjiiogonia, and consists of very small flask-like formations arranged in groups, which are sunk in the leaf. These little vessels contain a large number of thin rod-like spevmatia. The other form, which often appears on the opposite side of the leaf, consists also of small groups of closely crowded cups, having reflexed or turned-out ragged edges (see Fig. 43, h), or else bare spore-heaps {Cc^oma), The aecidiospores are arranged in bead-like or moniliform rows. These spores, as a rule, are able to germinate at once, and produce, within eight to ten days, sores with summer spores, if they strike upon a susceptible host plant or a corresponding uredo-carrying species. However, all rust fungi do not possess all these kinds of spores ; frequently one or more of them may be missing. RUSTS— UREDINACEM 65 The most important of the spore-form are the teleutospores. because the fungus usually hibernates with them. From these spores the systematic arrangement of the rust fungi is made and the genera named. The different species are, however, called after the host plant. Some of the rusts can live on several species of host plants that are related to each other {Jietevofaguons), but others are confined for their sustenance to only one species {isofaguous). By the " specialising "' of the parasitismus is meant the fact that within the very same species of fungus can be discerned several different biological races, "specialised forms," in their appearance quite like one another, the differences being confined to their inner nature, and manifested in the circumstance that each of these forms lives on its own — either one or more — -species of host plants. In those cases where it has proved insufficient to explain by means of hibernating spores the reappearance of the disease the following year, it has been said to depend upon a hibernating mycelium resting in the stalk or in the rhizoma of the host plant, or also upon hibernating uredospores. The truth of the former supposition is hardly gainsaid. But different opinions exist with regard to the hibernating uredo stage being a link in the life-history of the rust fungi. It is surely a fact that there are occasionally found, sometimes in one, sometimes in another, kind of rust, sundry hibernating uredospores, that are able to germinate. And as these are found towards the spring — in March, April, and May — it seems that a fresh outbreak of the disease during the summer might originate from them, but this is by no means proved. A critical survey of the known observations is opposed to such a supposition. From all the extensive investigations, which have been carried on during the last fifteen years with regard to the nature and development of the rust fungi on seed, it appears as if in these fungi there should be distinguished — -beside the well-known vegetative mycelium stage — another vegetative stage, when the fungus exists in the cells of the host plant as a formless plasma body, a sort 5 66 FUNGOID DISEASES OF PLANTS oi Plasmodium^ symbiotically fused with the protoplasm of the cells, and forming together with these a mycoplasnt. The mycoplasm- FiG. 41. — Mycoplasm and its Transformation into a Mycelium. (The Author.) a, Leaf-cells of a germinating plant of autumn wheat, forty four days after sowing, partly containing mycoplasm ; vipl, in dormant stage ; k, nucleus ; hi, chlorophyl corn ; h, leaf-cell of autumn rye-plant, one to two weeks before the summer outbreak of the brown rust on rye, the diseased nucleus en- larged ; c, leaf-cell of a similar plant, from the neighbourhood of the point wliere the first uredo sores broke forth, the mycoplasm being in the stage of maturing, the nucleus in a state of dissolution, and miniature nucleoli forming in the plasm ; d, leaf-cells of oat-plant, from the neighbourhood of the point where the first uredo sores broke forth, the mycoplasm penetrating into the place between the cells, where it forms a mycelium ; e, young stage of a mycelium with conspicuous separating walls. carrying cell presents otherwise a normal appearance, with nucleus, chlorophyl bodies, and so forth. There cannot be recorded any RUSTS— UREDINACE^ 67 parasitical fungoid life that would waste away the host plant. We may surmise that the fungus in this way can exist in most of the chlorophyl-carrying cells, up to the ears and bloom, in all sorts of seed that are especially suitable for the fungus, or, as it is expressed, are in a higher degree susceptible. The period during which the fungus exists in this latent state varies in different cases. From four to five weeks, it might last for as many months and even for some years. This is the dormant stage of the mycoplasm. Sooner or later, at a certain period of the life of the host plant, at a certain season, and with favourable environment or circumstances (soil, moisture, warmth, light, and so forth) for the development of the fungus, and varying with different sorts of rust, there will commence a new stage in the existence of the mycoplasm — the stage of maturing, when the fungus forces its way out from the symbiotic complex, penetrates the walls of the cell, and develops an intercellular mycelium. This maturing seems to be of short duration : it lasts only for a day or two, or possibly only some hours. As soon as the intercellular mycelium begins to form, it takes generally one week before open rust sores with spore-stuff begin to appear on the surface of the plant. ^ Two-Celled Rust. {Puccinia.) Among the genera of the rust fungi this one contains the greatest number of species. The winter spores are generally bilocular and contained in patches of sores, round or in stripes, either un- covered or occasionally covered by the epidermis of the host plant. Sometimes there may appear one-celled winter spores mingled with the double-celled. 1 Those who wish to learn more about this new doctrine regarding the inherent character of the rust disease, and also about the foundation of this new theory, are referred to the following works upon the subject by the author of this book : " Uber die Mycoplasma-Theorie, ihre Geschichte und ihren Tages- stand " (" Biol. Centralbl.," 1910, p. 618), and " Der Malvenrost, seine Verbrei- tung, Natur und Entwickelungsgeschichte " (Kgl. Sv. Vet.-Akad. Handlingar. vol. xlvii.. No. 2, Stockholm, 191 1). 68 FUNGOID DISEASES OF PLANTS GRAIN RUSTS, (i.) Species that Shift their Host Plants. Black Rust of Cereals. {Pnccinia graminis.) This is the most noticed and best known of all the different species of grain rusts. It not only infests all our cereals — rye, wheat, barley, and oats — but also many grasses. It appears in Central Sweden about the middle or towards the end of July ; a few weeks earlier on the autumn sown plants than on those sown in the spring. It is in the shape of longer or shorter reddish- brown dust-filled sores scattered on the leaves and stalks, especially on the sheaths, but also on ears and panicles. These sores are the stage of the summer spores of the fungus (livedo). The spores are long, covered with prickles, and supplied at the narrower middle part with two opposite germ pores. Exposed to moisture (rain or dew) they will germinate in a few hours. If this germination takes place on a suitable substance, say if spores from oat germinate on a young oat-leaf, then the germ-thread forces its way into this and produces on the maculated spot, within eight to ten days, a group of fresh sores, filled with similar spore-stuff. For the following two to three months generation will follow generation as long as there is any supply of fresh green sprouts. Until a few years ago it was believed that spores from one kind of seed could convey the disease to another, and also that seed could get diseased from different sorts of grasses, and in its turn convey the disease over to them. This idea is, however, erroneous. Within the species of black rust there exist several specialised forms, more or less adapted to their own host plant or plants. As the species appear in Sweden, there can be distinguished the following six forms : (A) Not distinctly fixed (occasionally going over to other forms of grass): (i) f. sp. Tritici on wheat (seldom on rye, barley, and oat). (B) Distinctly iixed (firmly confined to the indicated species) : (2) f. sp. Secalis on rye, barley, and on couch grass (Triticuni vepens), RUSTS— URE DIN ACE^ 69 Elymits ai'cnaritis, Bvonins secalinus, and others ; (3) f. sp. AvenaB on oat and on Avena elatior, Dactylis glomerata, Alopecunis pvatensis, Milium effnsmn, and others ; (4) f . sp. Po3e on Poa comprcssa and P. pvatensis a d f -Black Rust of Oat — Puccinia "niminis. (The Author.) Fig. 42. a. Stem of oat with uredo sores ; b and c, summer spores — one of the spores germinating; d. straw of oat with puccinia sores ; e and/, winter spores — one of the spores germinating ; g, barberry-leaf with cluster-cup rust. (5) f. sp. Airse on Aira ccsspitosa and A. hottnica ; (6) f. sp. AgTOStis on Agrostis canina and A. stolonifcra. An oat-plant infected with black rust can thus in its turn infect ^o FUNGOID DISEASES OF PLANTS only oat, but not wheat, rye, barley, and so forth. In different countries, however, the specialising of a fungus species may take place in different ways. Thus, as an example, the black rust form of barley is in Sweden the same as that of rye, but in North America the same as that of wheat. About two weeks after the first appearance of the summer spore stage, generally the end of July or the beginning of August, the winter spore stage {Puccinid) begms to show itself. This forms long streaks of sores, filled with a black dust-mass, hence the name " black rust." The winter spores are bilocular and thick-walled, narrowing off towards the top. After a natural hibernation in the open, where they have been exposed during the winter to air and wind, these spores are able to germinate the next spring. But if the spores during the winter have been protected, either by cold or warm surroundings, or if they have been in a grain stack, then they can by no means be induced to germinate. Rusty straw that has been laid either in the granary or in a stack can thus be considered as harm- less in respect to next year's crop. The hibernating spores, which have been free in light and air, have their greatest germinating power in the spring, in April or May. This declines towards the summer, and has generally ceased by the autumn. The power of germination is not exhausted through ploughing down the rusty straw and stubble deeply into the ground. Rusty portions of straw that have been dug down in the middle of October as deeply as 20 to 50 centimetres, or say 8 to 20 inches, have in experiments proved to have still retained the power of germinating when unearthed the next May. Exposed to warm, damp air, the hibernating spore will germinate. Each of its cells sends out a germ-thread, a basidium, which divides itself into several (as a rule four) joints. From these joints basidium spores are borne, and these will, in their turn, germinate. Should this germination take place on the young leaf, or sprout, or fruit of the barberry-shrub {Berhevis vulgaris), or on the young fruit of the Mahonia Aquifolinm, occasionally cultivated in our gardens, then there appears on these the barberry cluster-cup R USTS-^UREDINA CE^ 71 {^cidium Berheridis). On the barberry-leaves the rust spots are almost circular, on the upper side red, with numerous tiny black pricks, these being the openings of the flask-shaped spermogonia embedded in the leaf. On the under side they appear as large yellow patches, with numerous closely-massed open tube- or cup- like ajcidia. In the spermogonia there develop small staff-formed spermatia, whose function is, as yet, not fully known. The fficidium tubes have a ragged, reflexed edge, and they contain numerous fficidium spores arranged in bead-like strings from the bottom. The barberry cluster-cup appears earliest during the last days of Fig. 43.— Barberry Cluster-Cup— .E«rf/«;« Berhcvidis. {b, The Author.) a A barberry-leaf section, showing spermogonia above and jecidia below ; b, patch with cluster-cup from the under side of the leat. June, or the first days of July. The spores germinate somewhat irregularly and capriciously. The germination is promoted to some extent by chilly nights with intervening warm days. If spores from a cluster-cup spot, which has originated through contamination with a rusty oat-straw, should happen to germinate on a young oat- leaf, then there will arise in about eight to ten days a group of sores in the stage of the summer spores of the fungus. The same will happen if the germination has taken place on young leaves of some of the other grasses that are susceptible to the same form of black rust as the oat— viz., cock's-foot grass {Dactylis glomerata), meadow fox-tail {Alopeciivus pratensis), and others. But should it happen that the germination of this cluster-cup form takes place on rye, wheat, barley, and so forth, then no rust sores will appear. In the same way cluster-cup, which originated through contamination 72 FUNGOID DISEASES OF PLANTS from rusty rye- and barley-straws, will provoke rust sores on rye and barley, but not on wheat, oat. and so forth. This difiference of forms just described in the barberry cluster-cup, as to the existence of which we have only recently become aware, has naturally a great influence in regard to the role of the barberry- shrub as an agent in the spread of black rust to the grain-fields. A barberry-shrub that has been infected through rusty oat, cock's- foot grass, or meadow fox-tail can spread rust to an oat-field, but not to rye-, wheat-, or barley-fields. By this the share of the barberry- shrub is rather limited in the occasional devastations of cereals by black rust. This also explains why current opinions differ concern- ing the danger of this shrub. Most persons who have recently devoted themselves to a special study of the rusts of cereals agree now upon this point, that the influence of the barberry-shrub is by no means so important as some time ago it was thought to be, this recent opinion being the result of fresh investigations and discoveries. One of these discoveries, already referred to, is the capricious nature of the spores of the cluster-cup in regard to germination. The cases where germination has succeeded are but few in comparison with those that have failed. Another observation is that the capacity to spread abates wdth the distance from the shrub It remains yet to be proved that any contamination is incurred at a greater distance than 25 to 50 metres (say 75 to 150 feet) from the shrub. It is also now acknow- ledged that the distribution of black rust is in no way proportionate to the greater or lesser existence of the barberry -shrub in a district. On the contrary, it happens that black rust is very destructive in places where neither barberry nor any other carriers of this cluster- cup exist. ^ Neither has it been proved that occasional legislative measures ^ It must specially be pointed out that black rust is destructive to Australian whea to the extent of nearly ;i^i, 000,000 sterling per annum, although the barberry- shrub is not indigenous there, and the imported specimens never show signs of cluster-cup. (See "The Rusts of Australia," by D. McAlpine, Melbourne, 1906, pp. 64, 66 e^ scq. ) RUSTS— UREDIN ACE Ai 73 for the destruction of the barberry-shrub in one locality or another have prevented or reduced the destructiveness of the black rust.^ It is a matter of course that with regard to the black rust the same circumstances that affect other rust fungi, such as the level of the field, the drainage, the physical and chemical conditions of the soil, the fertilizers, the previous crop, the season of sowing, the state of the atmosphere, and so forth, have a material effect upon the more or less malignant nature of the disease. In spite of numerous observations and experiments for the purpose of solving all these interesting problems we are still at a loss to give definite advice to the planter. Only general observations can be furnished. It has not been discovered whether different plants possess in any degree different powers of resistance against this fungus. Protective Measures. — See pp. 84, 85. Brown Rust of Rye. {Puccinia dispersa.) This rust only settles on rye. The time when the summer spores appear is generally the middle of June for rye sown in the autumn, and a few weeks later for rye sown in the spring. Occasionally there may be seen solitary uredo sores in the rye-fields in the autumn about a month after the sowing, and also very early in the spring when the snow has melted away. This proleptic outbreak of the disease terminates of its own accord sooner or later, and is in no direct connection with the principal outbreak in the summer. The uredo sores form on the leaves, generally on the upper side, in small, chocolate-brown, irregularly scattered patches. The spores are globular, and, as a rule, germinate readily. A few weeks after the outbreak of the uredo sores there appear on the under side of the leaves the black groups of the teleutospores, which are covered by the epidermis of the leaf. In this kind of rust these spores are able to germinate the same autumn, as soon as they have reached their full maturity. Should their germination take place on young leaves or other parts of Anchusa avvensis, or ^ See " Die wahie Bedeutung tier Berberitze fiir die Verbreitung des Getreide- rostes," von J. Eriksson, " Illust. Landw. Zeit.," Berlin, May 22, 1907, No. 41 74 FUNGOID DISEASES OF PLANTS A. officinalis, then the cluster-cup {^cidium Anchusa) develops on these. This form of cluster-cup is found frequently in the southernmost part of Sweden and in Denmark during the months of August and Fig. 44. — Brown Rdst of Rye — Piiccinia dispersa. (The Author.) a, Rye-leaf with uredo sores ; b and c, summer spores —one of the spores germinating ; d, rye-leaf with puccinia spots ; e, autumn spore group ; /, autumn spore germinating ; g, branch of Anchusa arvcnsis with cluster-cup. September on two weeds {Anchisa arvensis and A. officinalis) in potato-fields, on the edges of ditches, and so forth ; but in Northern and Central Sweden it is rare. These two weeds are perfectly sound RUSTS— UREDINACE^ 75 in these districts, even in places where rye, seriously affected with brown rust, grows in the vicinity. The spores of the cluster-cup grow readily and quickly. If there are young sprouts or plants of rye close by, these will become con- taminated, and uredo sores appear on them in eight to ten days. With the approach of winter all the upper parts of the Anchusa species fade away — Anchusa arvensis dies altogether — only their seeds remain, and thus also perishes the cluster-cup stage of the rust, which can no more be an agent for a fresh outbreak of brown rust of rye during the following year. Neither does any hibernation of teleutospores take place, as these germinate during the autumn. Add to this that, in spite of careful research, no hibernating uredo stage has been found, either in the shape of spores or of mycelium. Hence the only explanation that remains is that the hibernation of this fungus takes place solely in the shape of a vegetative plasm. Protective Measures. — See pp. 84, 85. Crown Rust of Oats. {Puccinia covonifera.) This kind of rust affects oats amongst the cereals and also several forms of grasses. On oats the uredo stage appears by the end of July or the beginning of August. It forms shorter or longer orange-tinted sores on the leaves and the sheaths. The spores are globular, and germinate easily. A few weeks later the winter-spore stage sets in, as black spots placed in ring form around the uredo sores, covered by the epidermis of the leaves and sheaths. The teleutospores bear at the top a crown of blunt projections or processes, hence the name of " crown rust." They are genuine winter spores, and will not germinate before the following spring, after their natural hibernation. In Northern and Central Sweden this kind of rust is only of subordinate consequence ; it does not even occur every year. In more southerly countries, as in Germany, it is abundant, and seems there to take the place of oat rust instead of the black rust. Should the germination of the winter spores, after their hiberna- tion, take place on a young leaf of Rhamnus cathavtica, then there 76 FUNGOID DISEASES OF PLANTS «'^ d I if will appear within eight to ten days a kind of cluster - cup (JEcidinm Cathavtica:). The spores of this cluster-cup germinate readily, and in their turn give origin to uredo sores on all the (,• iU,, ! species of grass that are susceptible. This sort of rust appears on many other grasses, abundantly on rye-grass ; but the forms on these grasses are individually adapted to them. Of this species we know the fol- owing specialised forms : (i) f. sp. Avenae on oat. (2) f. sp. Alopeeuri on Alo- pecuvns pratensis, to which in sundry cases oat is suscep- tible. (3) f. sp. Festucse on Festuca elatiov and other kinds of Festuca. (4) f. sp. Lolii on English rye-grass {Loliiim pennne) ; in some cdises Festuca elatiov is susceptible to this. (5) f. sp. Glyceriae on Gly- ceria aquatica. (6) f. sp. Ag^- POpyri on Triticiim repens. (7) f. sp. Epigfaei on Calama- gvostis epigeios ; in rare cases oat is susceptible to this Fig. 45. — Crown Rust of Oats — Piiccmia coronifera. (The Author.) a. Oat-leaf with uredo sores ; b, sumriier spore ; c, oat-leaf with puccinia spots ; d and e, winter spores — one of them germinating ; /, leaf of Rhamnus ca- thartica, with cluster-cup. form (8) f. sp. Holci on Holciis lanatus. Protective Measures. — See pp. 84, 85. Another very closely related species of crown rust attacks several grasses; this is P. COPOnata, which develops its cluster-cup on Rhamnus Frangula, and shows the following specialised forms : (i) f. sp. Calamag'POStis on Calamagyostis ayundinacea, and others; in R USTS— U RE DIN A CEJ£ 77 sporadic cases Phalaris ariindinacea is susceptible. (2) f. sp. Phalaridis on Phalaris avundinacea ; only seldom Calamagrostis avundinacea is sus- ceptible. (3) f. sp. Agrostis on Agrostis viilgcms and A. stolonifeva. Of the genus Puccinia the following grass rusts that shift their host plants may be noted : ' ; Mi mmf' Fig. 46. — Puccinia Arrhexatheri. (The Author.) < -O-/ black pycnidia, which have a great number of jointed conidia. This disease was rather malignant in the autumn of 1899 on spring wheat near Stockholm. Ascochyta. The spermogonia appear on stalks and leaves. The conidia are bilocular and colourless. To this genus belong a great number of species, differing one from another essen- tially by their ap- / ©'X pearance on different host plants. Pea-Pod Spot {A scochyta Pisi) causes ' on the leaves, stalks, and fruits, and at times on the seeds, of peas, vetch, lucerne, ^^ ' and others, yellow, brown - edged spots, with small brownish- biack spermogonia in the centre. The disease can occasion a considerable reduc- tion in the pea-crop. Peas taken from diseased plants must not be used as sowing- seed. Other species are A. g'Paminicola, on cereals and grasses ; A. Fagopyri, on buckwheat ; and A. Nicotianae, on tobacco. o ^ d y^ Fig. 94. — Pea-Pod Spot — Ascochyta Pisi. (From O. KiRCHNER AND H. BOLTSHAUSER. ) a, Stipulae, and b, pod with fungus spots ; c, pyc- nidium ; d, conidia. Septoria. Forms belonging to this genus become conspicuous on leaves and stalks. The pycnidia contain long and narrow conidia. These are frequently provided with a row of drops or with cross-walls. I50 FUNGOID DISEASES OF PLANTS This genus also contains many species. Gpass Leaf-Spot on Cereal Sprout {Septovia graminum) produces on leaves of wheat, oat, rye-grass, and A vena elatiov pale spots with small black pricks, •il Fig. 95. — Grass Leaf-Spot of Wheat-Sprout — Septovia graminum. (The Author.) a. Portion of a leaf, with spots of the disease ; b, cross-section of a spot, with a pycnidium ; c, conidia. arranged in rows. Occasionally it causes great destruction of the tiny wheat-sprouts in the early spring. Similar leaf-spots are caused by S. Pastinacse on parsnip, S. Medicagrinis on lucerne, S. silvestris on Lathynts, S. Anthyl- lidiS on lady's-fingers, and S. Spergulse on spurry. CHAPTER XVI HYPHOMYCETES The conidia are not enclosed in special cases, but develop either from a cup- or disc-formed bed (stroma), or from separated, loosely placed filamentous tubes. (a) MELANCONIEiE. The conidia develop from an extended stroma, originally under- neath the epidermis of the host plant, but later on laid bare, through the rupture of the epidermis. Clover Stem-Rott {Gloeosporium caiilivoviim.) This disease — also called "Anthracnose" — was first noticed in America and later on in several places in Europe — viz., Bohemia, Wiirtemberg, Saxony, Brandenburg, and other places. It attacks red clover, and occasionally alsike clover. It forms on stem and leaf-stalks ovate-oblong, light brown spots, hollow in the centre, with a broad, black border. Frequently the leaves that are outside the diseased parts wither away. The conidia-beds develop in these hollows. This disease has sometimes destroyed 25 to 50 per cent, of the harvest. It is worst on American clover. A related form — G. Trifolii — troubles only the leaves. Other species of the same sort are G. graminum, that creates numerous small brown beds of conidia on the leaves of rye-grass, and G. Dactylidis, which causes brown papillae on the top stalks of cock's-foot grass. Both these forms have been noticed in Denmark. 151 152 FUNGOID DISEASES OF PLANTS To the same fungus group belong the following forms : Marssonia Secalis produces on the leaves of rye and barley and on several wild grasses long, greyish-white, brown-edged spots, which on their under side develop conidia-beds. Cryptosporium leptostromi- forme forms spots on the stalks of lupin (yellow and blue), at first pale, and later on brown, upon which long black conidia- beds break out. Plants that are severely attacked soon die, often before they bloom. The fungus can survive on dead lupin-stems on the ground. Hence the cul- tivation of lupin in the diseased soil should be avoided for two to three years. a b P'iG. 96.— Clover Sruu-Ror—Gloeosporium caidivorum. (From O. Kirchner.) a, Red clover plant, with long, dark spots of the disease on the stem ; b, section of stroma, with conidia. (/3) TUBERCULARIACE^. The stroma is from the beginning placed free on the surface of the host plant, and is usually waxy or mucous. HYPHOMYCETES 153 Fusarium. The conidia are spool-formed, slightly bent, usually provided with several traversing walls. The mucous or nappy fungus cover is first colourless, then either yellow, orange, or terra-cotta. Mucous Mould on Cereals. {Fnsarwm avenaceum.) During damp autumn weather there frequently appear fleshy or mucous fungoid formations, either salmon or terra-cotta coloured, on the ears and panicles of cereals and grasses, both on awns and corns. Similar formations are found on the stubble and occa- sionally on the germ-sprouts of cereals. The red cover consists of a thick, felt-like layer of fungus threads, and upon this layer is a ramification of filamentous tubes, turned outwards. These bear one or more ovate-oblong spores, four to six celled, slightly curved, and pointed. The forms which attach them- selves to different cereals and grasses are often described as being each one a specific form : Fusavitim culmorum on wheat and rye, F. Tritici on wheat, F. Hor- dei on barley and oat, F. Lolii on rye-grass, and so on. It is asserted that seed affected by this disease is poisonous, and produces in man and beast the same symptoms as previously mentioned in the case of " Giddy Rye" — viz., dizziness, headache, and so forth. It has even been claimed that a special poison has been extracted which originates through the dissolution of the albumen Fig. 97. — Mucous Mould of Bar- ley— Fusarium avenaceum. (From W. G. Smith.) a, Spiculse and grain of barley with a fungoid cover ; b, portion of the fungoid cover. 154 FUNGOID DISEASES OF PLANTS in the grains. However, experiments on animals \vith seed con - taminated by this fungus have given contradictory results. Some times the animals are affected, sometimes not. Hence nothing positive can be said about it. From rye-grains that have been strongly affected by this fungus during the autumn there appears occasionally in the spring a cup - like fungus, which is very similar to, and even has been considered as synonymous with, a cup fungus named Stvomatinia temulenta, which has sometimes been noticed to sprout in the spring from diseased rye- grains which have been im- pregnated by the mycelium of another fungus, called Endoconidium temiilentiun. To the cup fungus (StPO- matinia temulenta) has also been attributed the sterile mycelium that appears in the seed of bearded darnel [Lolium temiilcntum), close against the glutinous cell - layer. This mycelium has been traced through the whole plant, but no spore-formation has been detected, nor could it be brought forth through culture. This mycelium does not cause any disease to the host plant ; but rather the contrary, as it accumulates nitrogen for the benefit of the plant. Wherever this sort of rye- grass appears, it is more or less accompanied by this fungoid formation. This same sort of mycelium has been found in grass- seed from the tombs of the Pharaohs about four thousand years old. The mycelium renders the seeds of this grass poisonous, as has been known since the days of Virgil, Ovid, and Pliny. In rare cases a similar mycelium-formation has been seen in the Fig. 98. — Mycelium ix the Seed of Bearded Darnel — Lolium tenndentuni. (From P. Guerix.) a, Section of fruit ; the layer of fungus threads (drawn in black) around the grain, below the scale ; b, section of fruit-wall. HYPHOMYCETES 155 seeds of English rye-grass (Loliiim perenne) and also in Lolium linicola. Vessel Brand on Pulses. {Fusarinm vasinfectum.) By the name of Vessel Brand can be called a disease which has been noticed lately on different sorts of pulses, as peas, Wind- a . b Fig. gg.— Vessel Brand of Pulses— F«san'Hw vasinfectum. (From G. SCHIKORRA.) a, Diseased lupin-plant ; h, young plant of Windsor-bean, artificially infected. sor-bean, lupin, and others. The disease becomes conspicuous by the sudden and unexpected withering of the plants. In peas it 156 FUNGOID DISEASES OF PLANTS has been seen to start in the month of May. Sundry young leaves and parts of the stalks become soft and pale ; finally the whole plant withers away. This usually takes place towards the end of June, hence this ailment has been called " the midsummer disease of peas" ("St. Johanniskrankheit "). In the Windsor-bean a similar destruction sets in if the plants have been infected while very young. But if they should be older when exposed to infec- tion, then the parasite cannot break down the main stems, and it is only the leaves that die. With regard to lupin — especially Lupinus angustifoliiis, and also L. pevennis and L. mutabilis, but not L. luteiis — the disease has the same effect, either on young plants, shortly before they bloom, or on older plants which have already formed pods. The main stems remain erect. The disease begins at the neck of the root, in one or more dark, decay- ing stripes, which often reach above the surface of the soil. The con- taminating stuff gains an inlet through sores and fissures caused by external agency, such as the pulling off of branch roots, and so forth. The fungus grows into the tissue of the vessels, and penetrates the whole plant. The vessels become filled with a yellowish mucus. The mycelium extends to the neighbour- ing cells, and develops plenty of These spores retain the live fungus cell-tissue that is penetrated by the mycelium happens to lie bare, then there appears an air-mycelium, which develops conidia, one to two locular, or even more, say three to six locular, by means of which the disease can be spread from plant to plant during the vegetative period. This disease has been noticed especially on peas in Holland Fig. 100. — Cells from a Pea- Stem, DISEASED BY VESSEL Brand, with Mycelium and Resting Spores. (From G. schikorra.) multilocular resting spores, during the winter. If the HYPHOMYCETES 1 57 and Germany, and also on other pulses, as Windsor-bean, lupin, and clover. The form on pea has been considered as a special sort of its own — forma Pisi. It has, however, been found from experi- ments that forms from one parent plant may infect other species. Protective Measures. — (i) Do not use for sowing grains that are slow in germinating. (2) If there should be discovered places in the fields where the infection has gained a footing, then all the diseased plants ought to be taken away and destroyed. (3) Gather and destroy all diseased remains of the harvest. (4) On soil that is badly infected do not cultivate pulses for two to three years. A similar fungoid formation — Fusarium roseum, var. Lupini albi — has been noticed in Germany on pods of Lnpinus angiistifolius. Fig. ioi. — Brown Rot of Potato — Stysanus Stemonites. (a, From J. Reinke AND G. Berthold ; b, from O. Appel and W. F. Bruck,) a, Group of spore-brooms ; h, cell from the skin, with mycelium. F. Betse appears on beets as yellow, mucous, shrivelled e.Kcrescences on the root which otherwise appears sound. The my- celium penetrates inside the root, and occasionally forms papillae. The disease appears on young plants at the beginning of July, when 158 FUNGOID DISEASES OF PLANTS they mostly wither away. It can also cause destruction on seed- beets and on beets in winter storage. F. Brassicse appears in a similar way on rape, turnip, and other such plants. Here may also be mentioned Brown Rot of Potato [Stysanus Stemonites). This parasite lives in the skin of the potato as an intercellular mycelium. From this mycelium extend greyish-black, broom-like processes that bear egg-shaped conidia at their points. The germinating tubes of these can only attack a sound potato- tuber or a potato-sprout when there is a wound by which the tubes can enter. This fungus is especially harmful, as it prepares the way for other more destructive fungi. (y) ]\IUCEDINE/E. The conidia-bearing fungus threads are free, and protrude from the openmgs. The filamentous tubes and conidia are colourless. Oospora cretacea. This disease becomes conspicuous towards crop-time. The surface of the root is then found to be dark and to a large extent covered by a bark, crossed by fissures. Often there is an entangle- ment on the root, usually at the middle, on account of w^hich the disease in Germany is called " Giirtelschorf "; or otherwise there are irregular cavities of various shapes. The disease is caused by several different species of the group Oospora (O. cretacea, 0. vosella, and others), often promoted by the agency of certain worms [Enchytvaeidcw) which bore hollows in the root. The fungi are not able to attack the sound surface of the root, and can gain access only through wounds. The disease is worst after dry or open winters. It is encouraged by a wet and cold spring, or a dry and hot summer. It increases on being fertilized with Chili saltpetre. The disease has appeared in Germany in many places since about the year 1895, being especially malignant during 1899 and 1903 in HYPHOMYCETES 159 It can reduce the district between Aschersleben and Hildesheim the crop by 25 to 50 per cent. Protective Measures. — (i) Avoid contaminating sound fields with diseased soil. (2) Drain swampy fields. (3) Sprinkle the soil with lime. In North America a somewhat similar disease, often called " Beet Scab," attacks the sugar-beet. It is thought to be caused by ^ a 1 Fig. 102. — OosPORA cretacea. (From F. Kruger.) a, Early, and b, later stage of the disease ; c, transverse section of a diseased beet ; d, vegetative filamentous tubes and moniliform spores of the fungus. Oospora Scabies. It begins as small excrescences on the surface of the root. These are at first either separate or in patches. Later on they extend and unite into larger or smaller knots, covered by papillae. The disease is considered to be identical with scab on potatoes, caused by a fungus of the same name. To the same group belong several fungi that form leaf-spots. Ramularia Betas produces on the leaves of beets round, whitish- grey spots, visible on both sides, and surrounded by a brown i6o FUNGOID DISEASES OF PLANTS WUh't border, with white in the middle, owing to fungoid threads and conidia. This disease has occasionally been so malignant in Denmark that almost every leaf in a beet-field has been affected. Similar spots are caused by R. sphseroidea on the leaves of vetch, R. Onobrychidis on the leaves of esparcet, and R. Schulzeri on the leaves of bird's - foot trefoil (Lotus covnictilatus). Nearly related is Ovularia deusta, which forms small, pale spots on the leaves of Lathy vits. These spots have bunches of fungoid threads. -Ramularia Bet.i:. e. rostrup.) (From a, Portion of a leaf with fungoid spots; b, conidia. (S) Dematie^. Fungoid threads that are carrying the conidia stand free. The filamentous tubes and the conidia — at any rate one of them — have coloured, light or dark brown walls ; hence a sooty cover is formed on the afifected parts of the plants. Cereospopa. Fungoid threads and conidia are pale brown, the latter being pointed towards the terminals, and usually ovate-oblong or needle- like, with several cross-walls. Cercospora concors. From the middle of July this fungus causes irregular spots of various sizes on potato-leaves. These spots are at first yellow above, and are somewhat numerous. Beneath they are covered HYPHOMYCETES i6i with a grey - violet nap of fungoid threads which cast conidia. The leaf turns more and more yellow, while at the same time the colour of the spots becomes brownish -black. The conidia on the under side are numerous, short, and blunt ; on the upper rc\ ^ ^ b 1/ c «d Fig. 104, — Cercospora concors. (From G. Lagerheim and G. Wagner.) a, Diseased leaf seen from above ; b, section of a bunch of fungoid threads ; c, short, and d, long conidia. side fewer, longer, ovate - oblong, and somewhat pointed at one end. This disease may reduce the crop considerably, especially as it appears early in the summer. It has been noticed in Sweden in i8g6 and 1902, and also in various other parts of Europe. Protective Measures. — (i) Remove and destroy all old leaves from the diseased potato-field. (2) Do not cultivate potatoes in a field that has yielded a diseased crop until two to three years have elapsed. II 1 62 FUNGOID DISEASES OF PLANTS Cercospora beticola. This disease begins as small, brown, red-brimmed spots, irregu- larly scattered over the blades of the leaves. The brown colour of the spots soon turns into grey, and then black. The spots dry up, and at the same time fissures and holes form over the blade. Fig. 105. — Cercospora beticola. (a. From O. Kirchner and H. Bolts- HADSER ; b AND C, FROM B. M. DdGGAR.) a, Portion of a leaf with disease spots ; b, the conical root-neck of a diseased beet ; c, a mycelium bunch, liberating conidia. Finally, the whole leaf becomes dry and shrivelled. The outside leaves of the rosette first become diseased, then those inside. Meanwhile the plant strives to replace the old withered leaves by developing fresh ones inside the rosette. During this process the neck of the root is elongated and becomes conical, while the lower part grows but little. The disease can also occur on the bloom, if it develops at all, and on the seed-clusters. When the spots attain a grey colour, there may generally be found HYPHOMYCETES 163 in them bunches of fungoid threads belonging to Ccvcospora heticola. From the points of the threads are set free long, narrow, many- jointed conidia that readily germinate and diffuse the disease. The disease attacks sugar-, fodder-, and red-beets. Amongst the last-mentioned, several sorts have more resistance than others. Protective Measures.- — (i) Sprinkle those parts of the field that show signs of the disease with Bordeaux mixture (i per cent.). (2) Do not use diseased beets for seed-beets. Similar leaf-spots are caused by C. Apii on carrot, parsnip, and others, and by C. radiata on lady's-fingers (Anthyllis Viilneyaria). (e) RhIZOCTONIE/E. Fungi belonging to this group form a felt-like, violet or brown mycelium on the surface of roots and other underground parts. The organs of propagation are poorly developed. Root Felt Disease. {Rhizodonia violacea.) This disease — also called "Copper Web" and "Root-Rot" — attacks a great number of plants, especially carrot, beet, clover, and lucerne ; but sometimes also turnip, rape, spurry, and others, and may extend to the roots of trees and shrubs. In the month of June or July the disease appears on clover and lucerne. There appear circular patches over the fields with yellow and withered plants. On the leaves and stalks nothing is to be found that would give a clue to the phenomenon. But if the plants be pulled up by the roots, there is found on these a red felt of fungoid threads. On the carrot- and beet-fields the disease becomes conspicuous later on at crop-time. In sundry places the leaves wither away. In this case also the root is covered by a red fungoid felt. This forms a homogeneous layer round either the upper, middle, or lower part of the root. Those parts of the root that are only slightly or not at all affected develop fairly well and retain their natural colour. The felty parts are often shrunk and narrower than the sound parts. 164 FUNGOID DISEASES OF PLANTS When pulling up the plant, the soil sticks to the fungoid felt, and upon attempting to free the root a part of the fungoid felt falls off as well as some of the root-tissue. When advanced in age, the threads of the fungoid felt contain a red dye - stuff, but the walls are usually colourless. In the felt are embedded numer- ous round, brownish- black dots, similar in appearance to the pyc- nidia of other fungi. These formations never develop any organs of propagation on the liv- ing plant. But the following spring, on the dead root, there may be detected in the dark red fungoid meshes numerous egg- shaped conidia with red contents. Sometimes ramifica- tions of filamentous tubes twine together into irregular bunches, reddish -yellow on the outside, colourless in the middle, and ulti- mately blackish-red — altogether a kind of sclevotia. These formations often separate from the root, mix with the surrounding soil, and become factors in the spread of the disease. From their surface are often separated spool-formed, colourless conidia, either unicellular or bicellular. The mycelium remains alive in the earth from year to year. Fig. 106. — Root Felt Disease of Clover — Rhizoctonia violacea. (From E. Rostrup.) a, Diseased clover-plant ; b, mycelium and pycnidial knots of threads ; c, part of a mycelium (from the root of a species of Rumex) ; d, conidia. HYPHOMYCETES 165 It appears as if the various forms of this fungus, which attack diverse host plants, are biologically different. The form that troubles carrot can only with difficulty be conveyed to leguminous Fig. 107. — Root Felt Disease. (The Author.) u, On carrot ; b, on sugar-beet (infected by contagion from a carrotl ; c, on fodder-beet ; d, on turnip. 1 66 FUNGOID DISEASES OF PLANTS plants, beet, and potatoes ; at any rate, it will not remain long on these plants. Efforts have been made to prove a continuous stage of develop- ment of this fungus, but the result arrived at has been neither certain nor unanimous. At one time it was surmised to belong to TrichosphcBvia circinans (Trematosphcsria c, Leptosphcsria c), at another time to Corticunn vagjtm, and again to a species of the genus Rosellinia . Protective Measures. — (i) At harvest-time carefully separate all roots that show even the slightest sign of disease. (2) During the winter examine repeatedly stored-up roots that have been taken from diseased fields, and destroy everything that is unsound. (3) Do not cultivate in diseased soil the same sort of plants for at least three to four years. (4) Should the disease turn up in the first year's clover or lucerne, then the diseased parts of the field should be dug up and sown with grass-seed, and the extension of the disease should be checked by digging trenches round the affected parts of the field. (5) Choose for the cultivation of different plants such sorts as locally have proved of greatest resistance. (6) Take care that the soil is nutritious and well drained. (7) Do not fertilize with fresh barn manure if the stock has been fed with partly diseased roots. The related fungoid form Rhizoctonia Solani yields small, dark brown papillae on the surface of potato-tubers. These papilla; consist of a compact mass of reddish-brown, thick, jointed fungoid threads, without any sign of propa- gating organs. As a rule the fungus does not penetrate deep into the potato, and the papillae can easily be scraped off. Occasionally it may gain an entrance through insect burrows, and then develop a sort oisclerotia. Fig. 108. — Rhizoctonia Solani. (From E. Ros- TRUP.) HYPHOMYCETES 167 R. fusca forms on the roots of rape and turnip brown, and ultimately almost black, concave papillae, often uniting into crests. The papillae consist of short-jointed, ramified fungoid threads, which are entangled at the joints. This fungus remains only on the surface of the root. CHAPTER XVII UNEXPLORED DISEASES Heart Rot of Beet. This disease — also called " Blight of Beet," " Herzfaule," " Maladie du Cceur," " Pourriture du Cceur " — appears in the month of July a b Fig. 109. — Heart Rot of Sugar-Beet. (The Author.) a, Earlier stage of the disease (in the month of August) ; h, later stage of the disease (in the month of October). 168 UNEXPLORED DISEASES 169 or August, on sundry plants, or on certain parts in the beet-fields. The first indication is that the youngest leaves in the rosette turn black and die. Soon it extends to neighbouring older leaves through their petioles, where often broad, pale cross-stripes appear, and so the disease reaches the blades. Gradually these leaves die off, and the beets by the end of the summer have lost all their original leaves. In their place small leaf-rosettes with stunted leaves frequently develop on the neck of the root. At the same time the disease becomes conspicuous on the root, usually first on the outside of the thickest part. It forms there brown, decaying spots that go more or less deeply into the root. Sometimes the disease stops of its own accord, but the beet becomes inferior to sound speci- mens both with regard to size and sugar - qualities. Generally the beet decays. This disease attacks both sugar- and fodder-beets, and varies in its severity in different years, even in the same locality. It is generally supposed that prolonged drought during the summer, when the leaf grows most abundantly, renders the plants especially susceptible to the disease, an assisting cause also being that the evaporation from the leaves is too great in comparison with the quantity of moisture introduced by the roots. As yet nothing is known with certainty about the original cause of this disease. Some think that it is simply a state of general debility in the beet-plant, brought about by excessive cultivation, and that consequently the fungoid formations that are found on the Fig. 1 10. — Heart Rot of Fodder- Beet. (The Author.) lyo FUNGOID DISEASES OF PLANTS affected beets are only of secondary importance in the work of destruction. But as a rule fungi of one form or another are con- sidered as being the primary cause. Several investigators think it to be Phoina Beta (Ph. sphcevospenna, Phyllostida tahifica), a stage of development of the genus Mycospharella. Other investigators seek to find it in Sporidesiniiim putrefaciens, a form of development of the genus Pleospora, and still others in a bacterium, Bacillus mycoides. Finally^ the opinion has been expressed that the cause of the disease may be a slime mould-fungus, Myxomonas Beta, which at Fig. III. — Phoma Bet^. (From G. Linhart.) a. Cell-tissue with fungoid mycelium • b, pycnidia, one of them extending strings of conidia. first could in the stage of plasma dwell symbiotically with the plasma of the cell — hence something like the previously described mycoplasm, that is, a latent stage of development of certain rust- fungi — and later on develop as a parasite. However, the existence of such a mucous fungus has been disputed. It is possible that the name "Heart Rot" may embrace several separate diseases, each one caused by different agents. The disease can with certainty be traced back to about 1885, when it appeared very malignantly on beet-fields in Brandenburg and Silesia. In the year 1892 it was noticed and described in France, and the year after it appeared very destructively in Germany, in almost every district where beets were cultivated. Simultaneously UNEXPLORED DISEASES 171 it was noticed also in Belgium. In 1907 it appeared in the southern part of Sweden. Now it is scattered all over Europe. Protective Measures. — (i) The earth should be worked deeply, so as to be able to resist the drought. (2) Avoid fertilizers that bring on a too rapid maturing of the beets. (3) Do not sow too early, lest the summer drought aftect the beets during their most critical period. (4) Do not throw leaves of diseased beets amongst the manure. (5) For at least four years no beets should be culti- vated in a field that has yielded a diseased crop. (6) Only seed- beets should be used that have proved of greatest resistance. Leaf-Roll Disease of Potato. Towards the end of July or beginning of iVugust there may be seen on the potato-fields many plants of a peculiar appearance. The leaflets folding over and the edges turning upwards assume a trumpet-like form. Sometimes these plants are scattered over the field, or they are gathered together, forming larger or smaller patches. As the under side of the leaves is turned outwards, its paler colour becomes conspicuous against the dark green hue of the sound plants, and shortly the whole field has a spotted appear- ance. With many sorts of potatoes the rolled-up leaves have a yellowish or reddish tint, especially the nerves on the under side. In the first year of disease, the affected plants yield an almost normal crop of sound tubers, being only somewhat defective in starch. If these tubers are used for seed next year, then the eyes will sprout, but when appearing above the ground the plants become stunted, and the rolling up of the leaves commences earlier than in the first year. Tubers are formed, but they are small, often not larger than hazel-nuts. Sometimes the runners get so short that the tubers are close against the stalk, and none of them attain a normal length. The eyes of these small tubers may send out runners, which form rudimentary tubers. If tubers from the second year of disease are used for seed the following year, then their runners cannot reach above the ground, and they may not have any at all. 172 FUNGOID DISEASES OF PLANTS In the cross-section of the stalk of a diseased potato-plant it will be seen that the vessel-ring is occasionally yellow-tinted. On a thin section of such a stalk may be seen in the yellow ring a fungoid mycelium that upon cultivation brings forth spores, which might Fig. 112. — Leaf-Roll Disease of Potato. (From R. Schaxder.) a, Diseased plant ; b, crop of Magnum Bonum from sound plants (on the left) and from diseased plants (on the right). be classified as belonging to the fungus group Fusavinm. A similar yellowish ring of vessels is occasionally found inside the diseased tuber, especially at that point where the tuber was fixed to the runner. But no mycelium has, as a rule, been found, either in the UNEXPLORED DISEASES 173 vessel-ring of the tuber or in any other of its tissues, a phenomenon which has been explained by the suggestion that the fungus possibly may be only plasma in the tubers, but develops fungoid threads in the runners. In many places doubt has been expressed about the parasitical nature of the disease, as there is no mycelium in the diseased tuber. It is supposed that the disease arises from abnormal and unfavourable conditions of the atmosphere and the soil, in connection with the use of immature seed-potatoes. As a result of these co-operating causes, there may have taken place inside the potato-tuber enzymotical disturbances, hence a disorder which possibly is nothing but a recurrence of the long-know^n " Curl Disease," a malady proved to be only of a temporary nature. In those cases where a fungoid mycelium has been discovered, this should by no means be considered as the origin of the disease, but as something of later growth. But against this hypothesis that the disease is non-parasitical is the experience of the autumn of 1908. It then appeared in numerous thoroughly investigated localities in Germany, Austria- Hungary, Switzerland, Holland, and other countries, and the out- break was not due either to c-imatic or geological causes, and was not due to the use of immature seed-potatoes. As for the theory that the disease is parasitical, it may be observed that the plants which grow from diseased potatoes almost without exception develop the disease, and this occurs even when they have been raised from seed taken from such plants and sterilized ; also there is the fact that the disease can be carried to a previously sound field by means of diseased seed-potatoes. This disease was first noticed in Western Germany, Westphalia, and the Rhine Provinces in 1905, and it has been suggested that this was the effect of an unusually severe and prolonged drought during 1904 and 1905. It soon appeared in other places, and is now known in most European countries. At the beginning of 1908 this disease induced a genuine panic in Germany and the adjacent countries. This was caused by an 174 FUNGOID DISEASES OF PLANTS alarming newspaper article, written by one of Germany's most prominent potato cultivators, which was reproduced by numerous papers, and headed " The Potato-Culture of Europe at Stake." It expressed the fear that in all Germany— with very minor exceptions — there was not to be found one sound potato for seed. The loss for Germany alone was estimated at 600,000 German marks, or ;£f30,ooo, and it was considered desirable that the Government should grant 250,000 marks, or /'i2,50o, for the purpose of an experi- mental station of 500 to 600 hectares, or 125 to 150 acres. These apprehensions proved to be exaggerated. To be sure, the disease appeared in the autumn of 1908 in numerous places in all those European countries where potatoes are cultivated, especially where the industry is carried on extensively, and where the disease once gained a footing there it recurred and attacked all sorts of potatoes. But there were numerous and large districts where it scarcely put in an appearance, and where the crop was an average one. In the year igog the disease appeared in many places in Europe, especially in the south-eastern part of Germany and in Austria- Hungary, and caused greater devastation than in the previous year. For instance, in Bulgaria it spread to such an extent that not a single district was free. And there it happened that different kinds of potato were differently affected, those imported suffering worse than the indigenous. The destruction varied from 10 to 100 per cent. But the very same year several districts in Germany were comparatively free from this disease. This disease has been thoroughly investigated in recent years in Germany and Austria, but as yet the real cause cannot be ascer- tained. It may be that under the name of " Leaf-Roll Disease " are included several different forms of disease, varying both with regard to their economic importance and to their appearance in the development of the leaves, their rolling up, the attachment of the tubers, either with or without stolons, and so forth. Protective Measures. — (i) Use perfectly sound seed-potatoes taken from a field where no disease has occurred. (2) Do not cultivate potatoes on a diseased field for two to three years. (3) If UNEXPLORED DISEASES 175 the disease breaks out in a field, then all affected plants should be pulled up and destroyed ; but if you cannot afford to do this, then they should be labelled, so that their tubers can be separated at the harvest from those taken from sound plants. (4) Take care that no earth from a diseased field is brought by means of people, animals, or utensils to a field intended for next year's potato plantation. A similar, also unexplored, potato disease is reported from Ireland under the name of " Yellowing"," or " YellOW Blig'ht." By the middle of July the plants begin to wither, turn yellow, and die prematurely, and the crop is next to nothing. No parasite has been detected. Good drainage and ordinary care will arrest the disease. Mosaic Disease of Tobacco. During the summer, two to three weeks after the tobacco-plants have been placed out of doors, many become conspicuous by an abnormal appearance. On the leaves are irregular spots of various shades, some of them dark green and not at all transparent, while others are lighter and transparent. When the leaf is held toward the light the formations have a mosaic appearance. The dark green spots grow rapidly and develop into slightly convex excrescences, while the paler spots remain stationary, and the affected plants become stunted in their growth. Sound and diseased plants are mixed together without any order. The disease does not of itself extend from plant to plant, but if a piece of a diseased leaf, or sap pressed from such a leaf, comes into contact with a wound on a leaf or stem of a sound plant, then there will develop within three to six weeks (all depending upon the age of the sound plant) a similar disease, although not in the in- fected organ itself, but on the tender leaves which gradually grow out at the terminals of stem and branches. The poison seems to follow with the circulating sap up to the youngest elements of the tissue, where it first begins its work of destruction. A contamina- tion of this kind can readily take place from plant to plant, when 176 FUNGOID DISEASES OF PLANTS the tobacco-plants are topped in order to check the fructifica- tion. Then the infection takes place by means of the workman's hands or implements. As a rule the side branches of the topped plants get the mosaic disease. The diseased leaves fetch less in the market than sound ones. They cannot be used as covering leaves for cigars, and when used for pipe-tobacco are said to have a strong, unpleasant odour. The disease attacks all sorts of Virginia tobacco {Nicotiana Tahaciun), but does not appear on Enghsh tobacco (N. vnstica). As yet nothing definite is known about the real cause of this disease. Several investigators think that it is caused by bacteria so extremely minute that neither microscope nor culture renders them visible. Other scientists presume the existence of a con- tagious fluid (" contagium vivum fluidum "), which is intimately united with the plasmic cell con- tents, hence a kind of mycoplasm. Others, again, deny the existence of any parasitic origin of the disease, which they surmise is brought about by certain dis- turbances in the ordinary nutrition of the plant. There can be either an over-production of enzymotically originated oxidases and peroxidases, or otherwise a production of toxin caused by some external irritation. These disturbances may arise from high temperature, abundant watering, damp atmosphere, poor nutrition, or injudicious selection of seed-plants, and so forth. - Mosaic Disease of (From D. Iwanovvski.) UNEXPLORED DISEASES 177 This disease has long been known in many countries where tobacco is cultivated, but has not been scientifically studied until about the year 1885 in Holland. Since that time it has been strictly investigated, not only in Holland, but also in France, Russia, North America, and elsewhere. On the tobacco plantations round Stock- holm it has been very serious for many years past. Protective Measures. — (i) Select only sound plants as seed- producers. (2) Keep capsules and seeds in a suitable and dry place, and avoid their being in the neighbourhood of remains of diseased plants. (3) Get sound soil for the hotbeds where the plants are nursed. (4) Drain the field well. (5) Do not use fresh barn-yard manure, but fertilize preferably with kainite and Thomas- phosphate. (6) Top first all plants that suffer with the mosaic disease, then cleanse and disinfect hands and implements before beginning to top the sound plants ; this should be done later on. It often happens that in the same tobacco plantation where mosaic disease exists there appears another spotted disease, sometimes attacking the very same plants that have already been troubled by that complaint. It is called in Germany " Pocken- krankheit." It appears as numerous, often very tiny, brown or white dried-up spots, scattered over the whole blade. Some investigators consider it to be a special disease, others only a sequence to the mosaic disease. 12 CHAPTER XVIII GENERAL PROTECTIVE MEASURES AGAINST THE DISEASES The measures that may be employed to combat plant diseases caused by parasitical fungi are principally of two kinds : either preventive (prophylactic), or curative (therapeutic). With regard to the growing crops of our cornfields, fodder- grounds, and root-crop fields, their close association makes curative measures both tedious and futile ; hence in their case the preven- tive method is the best. The matter is different with garden plants, as each individual tree or shrub can be given curative treatment. I. — -Preventive Measures. I. Sound Seed, taken from Sound Plants. — In certain cases — as, for instance, ergot and brand in seed of cereals and grasses, sclerotia in the seed of clover, beet, turnip, and mustard, and so forth — an ocular examination will be sufficient. The planter himself can undertake this investigation, or he can send samples to the nearest station for seed-control, and obtain a verdict. But in many cases a botanical exaniination will not suffice. The most dangerous diseases may evade microscopical analysis, and although neither spores nor mycelia have been detected, experience has proved that the disease has followed with the sowing-seed. This takes place, for instance, with sowing-seed which carries the disease of loose smut and rust, especially yellow rust, and also with potatoes from plants suffering with bad leaf-roll disease. To 178 GENERAL PROTECTIVE MEASURES 179 be perfectly protected against these diseases, one should be certain that the crop from which the sowing-seed is taken was sound, and in some cases it is not enough to know only about the previous year, as the disease might be latent in the sort for several years until a year occurs with atmospheric conditions that provoke an outbreak. Proofs of this have been obtained through several kinds of wheat which are especially susceptible to yellow rust. The sowing-seed of such wheat, being either shrunk or full-sized, might yield apparently a sound crop of good-looking, well-developed seed- corns, and might do so several years successively. But if there comes a year with atmospheric conditions suitable for the develop- ment of the fungus of yellow rust, then the disease will break out again in a malignant form. In such cases it will be best for the planter himself to examine the crops of preceding years. If this cannot be done, he should procure reliable information concerning previous crops. 2. Selection of such Species of Agricultural Plants as possess Resistance. — It wnll frequently be found that different varieties of the same sort of plants vary wirh regard to their susceptibility to the diseases. This takes place, for instance, with the potatoes against the leaf-mould, and wheat against the yellow rust. The best guide in this respect will be the previous experience gained in the place or its vicinity. In different districts the same sort of plants may be susceptible in a different way. But in other cases it might happen that all the varieties get affected, as is the case with all plants with regard to bacteriosis, and cereals as regards black and brown rust, and so forth. 3. Careful Preparation and Draining of the Field. — It goes without saying that too much moisture as well as too much drought render the plants more susceptible to diseases. Hence every precaution should be taken to avoid everything that might deprive them of their stamina. 4. Fresh Barn-yard Manure should not be used, as it easily might carry infection. 5. Diseased Sprouts, Leaves, Roots, and so forth, should be destroyed, i8o FUNGOID DISEASES OF PLANTS either by burning or being dug down deeply, otherwise they might diffuse the infection. 6. Frequent Inspection of Roots stored up for the Winter. — Everything found to be diseased should be totally destroyed, lest it might in one way or another become a means of diffusion of disease during following seasons. 7. The Parasites might be Starved. — Through letting a longer period pass before the same sort of plants again are culti- vated on the same place, the parasitical fungi will be rendered destitute of nourishment. This is especially effective with root- parasites such as clump-root on cabbage-plants, root-felt disease on carrot, beet, clover, etc. 8. A II Plants carrying the Infection with them should he removed from the Vicinity. — This is especially important with regard to cereals and grasses that may be attacked by the different varieties of cluster-cups which shift their host plants. Such plants as Berhens, Rhamnus, and Anchusa ought not to be allowed nearer than 25 to 50 metres, or 80 to 160 feet, to fields and pastures. Likewise weeds like Tviticnm vepens, Dactylis glomerata, and others that bear rust fungi which infect cereals and fodder grasses should be removed. q. Treating the Sowing-Seed with Fungicides. — This can be done in various ways : (rt) Steeping with copper sulphate solution ; already described in this book (pp. 24, 34, 47). (b) Crystallisation with Bordeaux mixture ; already described in this book (p. 48). (c) Steeping with formalin solution ; already described in this book (pp. 13, 48). (d) Ceres treatment ; already described in this book (p. 49). (e) Steeping with sublimate solution ; already described in this book (pp. 13, 124). (/) Warm -water treatment ; already described in this book (pp. 49, 53, 107). For this purpose there are available several kinds of apparatus. One of these is the " Getreide-Beizapparat," by Appel and GENERAL PROTECTIVE MEASURES i8i Gassner, manufactured by Paul Altmann in BerUn (Luisen- Strasse 47). This one consists of two principal parts : the warm- water cistern and the steeping cylinder. An ordinary wooden vessel in good condition might be used as a warm-water cistern to hold at least twice as much as the steeping cylinder— say 200 litres, or about 40 gallons. Fig 114-Appel and Gassner's Apparatus for Steeping the Sowing-Seed. (From O. Appel.) a, Steeping cylinder with the warm-water cistern above; b, letting out the steeped seed. The steeping apparatus consists of a framework on wheels, and on this the cylinder is hung. Inside this cylinder there are two strainers, one at the bottom and the other 20 centimetres, or 8 inches, below the lid, and is fixed to and removed with it. The space between these two strainers is intended for the seed that is to be treated. The cylinder is supplied with two pipes : one, carrying the water in, enters the cylinder beneath the lower strainer; the other one, leading the water away, extends from the cylinder above the upper strainer. i82 FUNGOID DISEASES OF PLANTS The warm-water cistern is placed high up, about 4 metres, or 13 feet, on any sort of landing, and is connected by means of a tube with the feeding-pipe of the cylinder. The cistern is filled with water that is heated by steam to a temperature of 55° C. If no steam be available, cold and hot water must be mixed in the cistern until the desired temperature is reached. When using the apparatus it should be done in this way : The seed is poured into the cylinder above the lower strainer. Then the upper strainer is fixed to the lid, which is put on. The tap is turned, letting in the warm water. This pours into the cylinder from beneath, and runs out through the waste-pipe at the top. At first it will be found that the temperature of the waste water is considerably lower than it was in the feed-pipe. But it will be found that the temperature of 55° C. is attained by the waste water in two minutes after a volume of water one and a half times as large as the quantity of seed has been used. The feeding- tap is then closed, and the apparatus is let alone about five to ten minutes. To counteract any injurious after-effect of the heating up, cold water is let in the cylinder by means of the same tube. After a few minutes, and as soon as the cylinder water is found to be of the same temperature as the cold water in the feeding-pipe, the tap is again closed and the water allowed to run off. Finally, the lid, together with the top strainer, is lifted up, and the seed is poured from the cylinder, and spread out to dry. The whole process requires only twelve to fifteen minutes, hence there will be time to do four different turns in a single hour. Should the cylinder hold 115 litres, or 23 gallons, of seed, then 50 hectolitres, or 135 bushels, can be treated in one day. II. — Curative Measures. When a disease is to be stamped out over large fields or pastures, it is out of the question to pay special attention to each individual plant, as can be done with shrubs and trees in a garden. The only practical method is to sprinkle the whole field with some fungicide. GENERAL PROTECTIVE MEASURES 183 (a) Powders as Fung-icides. 10. Flowers of Sulphur. — This should be strewn over the diseased plants when the weather is clear, calm, and warm — not colder than 20° C. Then the acid will develop from the sulphur, and kill exterior mycelia — for instance, that of the mildew fungi. The sulphur should be pure and finely ground, then the powder will stick better to the plant. The chemical decomposition is thus promoted and the destruction of the fungi more certain. This method was greatly employed about 1850 in the vineyards of Southern Europe for the destruction of the vine mildew. In recent times this remedy has been superseded by fluids, especially the Bordeaux mixture. This sulphur treatment is also useful against other forms of mildew, as that on peas, and is still the remedy most in use for rose mildew in hothouses. 11. Sulfosteatit is another granulated powder, used in the same way as sulphur. It consists of 10 per cent, copper-vitriol and go per cent, magnesia. The copper-vitriol is the killing substance, and the magnesia causes it to stick to the plants. This remedy was introduced into the market in i8go by the firm Jean Souheur of Antwerp. For the diffusion of fungicide powders there have been constructed several kinds of bellows, some used by hand, others cafried on the back, and, again, others conveyed by carriage. {h) Liquids as Fungicides. About the year 1880 liquid fungicides were to some extent employed in the vineyards of France. Later on they gained a footing in England and North America, and it is mainly through extensive experiments in the latter continent that their value has been recognized and utilized. Particularly potato blight is amenable to this sort of treatment. The most prominent of these fluids is — 12. Bordeaux Mixture. — This preparation, made of sulphate of copper, should not be bought in the form of a powder, but as large blue crystals. For the usual mixture (known as i per cent.), i kilo- gramme, or 2\ pounds, of sulphate of copper should be used. This i84 FUNGOID DISEASES OF PLANTS quantity is placed in a bag of coarse cloth, and submerged in a vessel containing 50 litres, or about 10 gallons, of water. This vessel should be a wooden one, not metal, and for the purpose of stirring up the mixture either wood or glass should be used. It requires about twelve to twenty-four hours to dissolve, depending upon the tem- FiG. 115. — Preparation of Bordeaux Mixture. (From B. T. Gallaway.) I, Vessel for the lime-wash ; 2, vessel for the copper-vitriol solution ; 3, vessel for the mixture. perature of the water. It dissolves more quickly if the bag be moved backwards and forwards in the fluid. At the same time a similar quantity of lime-water is prepared in another vessel. This is done in the following manner : 2^ pounds, or I kilogramme, of quicklime is first slightly sprinkled with water, then gradually diluted until 50 litres, or 10 gallons, of water have been used. It is then strained, and no coarse particles are allowed to remain in the fluid. Both these solutions are now mixed in equal proportions. The liquid thus obtained is called Bordeaux mixture because it was first used in the vineyards surrounding that town. It should be blue in colour (not green), turn red litmus-paper blue, and, when left unstirred in a test-tube, deposit a blue sediment at the bottom. Above this sediment there should be a clear liquid. If it is bluish, GENERAL PROTECTIVE MEASURES 185 then more lime should be added. A little too much hme will not hurt ; but too much copper-vitriol would be harmful, as the acid might burn spots on the plants. Fig. 116.— Knapsack Sprayer. {Benton and Stone, Birmingham.) Before falling the sprayer, the mixture should be stirred up thoroughly, as it is the sediment, and not the liquid, that is effective. Mycelia of fungi are thereby killed and germinating spores are checked. As a result, the spread of the disease is stopped. The 1 86 FUNGOID DISEASES OF PLANTS spraying should take place when the weather is dry. Should a heavy shower occur immediately after the spraying, then it must be done over again, as the rain washes away the mixture. Bordeaux mixture of this sort is said to be of i per cent. Should either weaker or stronger mixture be required, then the ingredients should be increased or decreased in proportion. Freshly-prepared Bordeaux mixture should be used each time the spraying is done, as it loses power. Recently, however, experi- FiG. 117. — Spray Cart with Ten-Branched Sprayer. ments have been successfully carried out with a view to preserving it for longer periods. Sugar has proved to be quite effective. For I hectolitre, or 2| bushels, of rather weak mixture, 10 to 20 grammes of sugar has retained its fungus-killing qualities for a whole year. But for stronger mixtures — say 2 and 3 per cent. — 30 to 50 grammes of sugar should be used for i hectolitre, or 2| bushels, of the mixture. The sugar should be added within twenty-four hours. Amongst other mixtures might be mentioned Burgundy mixture (copper sulphate -f- sodium carbonate), ammoniacal copper carbonate (copper carbonate -f- ammonia), liver of sulphur (potassium sulphide), and so forth. But these have mostly been used for garden plants. APPENDIX TABLE OF THE FUNGOID DISEASES OF AGRICULTURAL PLANTS ARRANGED AFTER THEIR HOST PLANTS I. CEREALS AND GRASSES. Wheat, Triticiim vulgdre. A. On Sprouts. page (a) Web-like mesh over the plants in the spring, when the snow melts : Snow Mould, Nectria graini7iicola {Fiisariuin nivale) -------- 133 (b) Small and hard sclerotia of a reddish-yellow colour on the leaves, while the snow melts : TypJiula grai)iinum - - 90 B. On Ears. {a) Corns filled with a brownish-black fetid mass: Stinking Smut, Tilletia caries and T. Icvis - - - - - 45 {b) Spiculte transformed into a black dust, soon scattered by the wind : Loose Smut, Ustilago Tritid- - - -50 {c) Ears partly, with an entanglement in the middle, empty and black : Dilophia graminis - - - - -112 {d) Seeds of a rosy hue, shrivelled and frequently hollow : Bac- teriosis. Micrococcus Tritici - - - - - 17 {e) Awns covered with brick-coloured mucous blotches : Mucous Mould, Fusariiim avenaccitni - - - - ^53 (/) Awns with brown, black-dotted spots : Phoma Hennebergii - 148 C. On Leaves and Stalks. (a) Pale spots, with small, black pricks, often arranged in rows : Leaf- Spot, Septoria gramiiucin and Ascochyta graini?iicoIa 149, 150 (^) Black prickles on the sheaths and leaves (most conspicuous if they be held against the light) : Black Pricks, Leptospharia Tritici -------- loi 187 i88 FUNGOID DISEASES OF PLANTS TAGE (t) Long, pale stripes, with small, brown dots on leaves and sheaths : Sphccrella exitialis 2iTi6, S. basicola - - - - 119 {d) Straw bent, and finally snapped at the base ; the lowest joint of the straw inside the sheaths brown, sometimes with a black cover of fungus threads : Straw-Breaker, Lepto- spharia culinifraga - - - - - - 99 (e) The lowest joint of the straw inside the sheath and also the roots, with a black cover of fungus threads : Take- All (White- Heads), (?/'/«(?<^o///^^r^w/«/j and O. ^^r^tf/;7(r/z(7/i'/£'i- - 113 D. On all Parts above Ground. {a) Long, reddish-brown, confluent, finally black, dust-filled sore stripes, especially on the sheaths and stalks, but also at times on the outside of the ear-scales : Black Rust, Puccinia grainiiiis - - - , - - - - 68 (d) Short, brown, scattered, dust-filled sores, mostly on the upper side of the leaves ; finally short, black sore groups, covered with the epidermis of the plant, on the under side of the leaves and on the sheaths : Brown Rust, Puccinia iriticina 82 {c) Small, lemon-tinted, dust-filled sores, arranged in stripes, mostly on the upper side of the leaves ; finally stripes of very tiny, black pricks, covered by the epidermis, mostly on the sheaths, sometimes also on the inside of the awns and the wall of the grain : Yellow "Rust, Puccinia g/umarum - 79 (d) Blotches of a grey or white thick felt, with numerous little black dots embedded in the felt : M.ild.evf, Brjsip/ie gra/ziim's - 94 ((f) Greyish-black covering over the whole plant, especially on the ears, sometimes also on the corns, the disease soon stopping the growth of the plant : Blight, Cladosporitcm herbaruvt {Sphcerella Tulastiii) - - - - • - w^ (/) Plant ceasing to grow, leaves turning yellow and withering, seeds becoming shrivelled : Pyrocioiiuni spluericu)!! - - 31 Rye, Secale cercale. A. On Sprouts. ^novf 'M.0UI6., Nectria graminicola. See Wheat, A (<^j) - - 123 B. On Ears. {a) Stinking Smut, Tilletia Secalis, See Wheat, B {a) - - 50 (p) At first the whole of the ear covered by a sticky, sweetish fluid ("honey-dew") ; later on solitary corns developing into long APPENDIX 1 1 PAGE horny sclerotia, white inside and dark violet outside : Ergot Disease, Claviceps purpurea - - - - - 126 (c) Mucous Mould, Fusariwn avctuiceum. See Wheat, B {e) - 153 C. On Leaves and Stalks. (a) Black Pricks, Lcptosphceria Tritici. See Wheat, C {b) - 101 (d) Spharella exit talis and 5. basicola. See Wheat, Q {c) - 119 (c) Leaves with long, greyish-white, brown-edged spots : Mars- sojtia Secalis - - - - - - "^52 {d) Straw -Breaker, Leptosphceria culmifraga. See Wheat, C [d) 99 {c) Take-All (White-Heads), Ophiobolus gramwis and O. herpo- trichoides. See Wheat, C (^) ■ - - - - T13 D. On all Parts above Ground. (a) Straw distorted, with long, lead-grey stripes, filled with a black dust ; ear empty : Stalk Smut, Urocystis occulta - - 61 (^) Black Rust, Puccinia grammis. See Wheat, D (a) - - 68 (c) Brown Rust, Puccinia dispersa. See Wheat, D (^) - - "Ji (d) Yellow Rust, Puccim'a g-lumarum. See Wheat, D (r) - 79 {e) Mildew, Erysiphe gramiuis. See Wheat, D (rtf) - - 94 [f)'&\igla.%, Cladosporiuin herbaru)/!. See Wheat, D (^) - - 115 Barley, Hordeum sativum. A. On Sprouts. Plants pale, slack, bending down, with a brown spot at their lower end: Seedling Blight, /'//////^w ^rtry^jw//;;/ - - - 33 B. On Ears. {a) Loose Smut, Ustilago nuda. See Wheat, B (i^) . - 54 \b) Seeds blackish-grey, filled with a black dust ; the silver-grey pellicle quite perfect, only showing a few cracks : Covered Smut, Ustilago Hordei - - - - - 55 (c) Ergot Disease, Claviceps putpurea. See Rye, B {b) - - 126 {d) Bacteriosis. See Wheat, B i^d) - - - - 17 C. On Leaves and Stalks. (a) Sphcerella exitialis and S. basicola. See Wheat, C (r) - 119 [b) Marssonia Secalis. See Rye, C (f) . - - - 152 (r) Take-All (White- Heads), Ophiobolus graminis and O. herpo- tric/ioides. See Wheat, C 0') - " - ' "3 I90 FUNGOID DISEASES OF PLANTS PAGE {d) Leaves with oblong, dark brown spots ; plants and ears not distorted : Spot Disease, Helminthosporium teres (Pleo- spora trichostoma f. Hordei iiutatitis) - - - - io8 D. On all Parts above Ground. {a, '&\z.z)s.'B^iS,\,^ Piiccmia grajninis. See Wheat, D (^;) - - 68 {b) Yellow Rust, Puccinia glumariun. See Wheat, D (c) - 79 {c) Diminutive yellow, dust-filled sores, especially scattered over the upper surface of the leaves ; finally small, black, covered spots, mostly on the sheaths : Dwarf Rust, Puccinia simplex - - - • - - - 83 (d) Mildew, Erysiphe graininis. See Wheat, D {d) ■ - 94 (e) Leaves at first with yellowish-white, brown-edged stripes, run- ning lengthwise, finally resolving themselves into long threads ; plants distorted, covered with a greyish-black dust ; ears almost empty : Stripe Disease, Hclmiiithosporium grainineian {Pleospora trichostoma/. Hordei erecti) - - 105 (/) Leaves turning yellow, with small brown or black prickles (most conspicuous in the transparent sheath, if this be held against the light) ; plants ripening prematurely, with dis- torted ears : Black Pricks, Lcptosphceria Tiitici. See Wheat, i Avettcc - - - - -no {d) Black Pricks, Lcptosplurria Tritici. See Barley, D (/) - loi {e) Sheaths covered with black prickles ; plants small : LcEsiadia microspora - - - - - - - 119 APPENDIX 191 PAGE On all Parts above Ground. (a) Black Rust, Puccinia gra)ninis. See Wheat, D (^0 - - 69 {b) Brownish-yellow, dust-filled sores of varying lengths, frequently placed in groups, the sore group ultimately encircled by a ring of little black-covered spots : Crown Rust, Puccinia corofiifcra - - - - - - ' 7S (c) Mildew, ErysipJie i^raininis. See Wheat, D (^) - - 94 Timothy Grass, Phleum prateme. {ci) Sores of varying lengths, reddish-brown, finally black, dust- filled, mostly on the sheaths and stalks : Timothy Rust, Puccinia Phlci-pratensis - - - - - §3 {b) Greyish-white, later on golden-brown, cover over the topmost swollen sheath of the straw : Reed Mace, Epichlo'e typhifia 125 {c) QtXQY ^^o\>^ Scolccotrichiaii graininis. See Oats, B ( {d) - - 94 {e) Reed Mace, Epichloe typhina. See Timothy Grass, {b) - 125 APPENDIX 193 Reed Poa Grass, Glyceria aqumtica. PAGE Smut, Ustilago longissima. See Meadow-Grass (a) - - 60 False Oat Grass^ Avena elatior. (a) Loose Smut, Ustilago perennans. See Wheat, B {b) - - 60 ijb) Black Rust, Piiccinia gramitiis. See Wheat, T> {a) - - 68 (f) Pucciiiia Arrhenatheri. See Meadow-Grass (^) - - ']^ {d) Mildew, Erysiphe graini7iis. See Wheat, D {d) - - 94 (e) Dilophia g)'aniinis. See Timothy Grass (^i^) - - - 112 {/) QrXQy-^'pot, ScolecotrichiDii gramitiis. See Oats, B ((5) - 119 (g) Jje&f-^'pot, Sep/oria gramifmm. See Wheat, C (i^?) - - 150 {/i) Ergot Disease, Claviceps purpurea. See Rye, B (<5) - - 126 Yellow Oat Grass, Trisetiwt flavesceiis. Puccinia Triscti. See Meadow-Grass {c) • - - - 84 Bent Grass, Agrostis vulgaris, Fiorin Grass, A. slolo?iifera, and others. {a) Stinking Smut, Tilletia decipiens. See Wheat, B {a) - 50 ((J) Black Rust, Puccinia graminis. See Wheat, D {a) - • 68 [c) Crown Rust, Puccinia coronata. See Cock's-Foot Grass {b) - 76 {d) Dilophia graminis. See Timothy Grass (ysiphe Polygoni - 95 (t-) Leaves with large pale yellow, red-brimmed patches, sprinkled with brown prickles : Phyllosticta Betce - ■ - I44 {/) Leaves with brownish-grey, often red-brimmed, spots on the under side, these being covered with fine grey bunches of fungoid threads : Cercospora beticola - - - - 162 {g) Leaves with round, red-violet spots, which are white in the middle owing to a nap of fungoid threads : Ramularia Behc 159 (Ji) Leaves with brown, dry patches : Sporidcsmium putrefaciens {^Pleospora piitrefacicns) - - - " - 104 C. On Root. (ii) Vessel strings in the root, first reddish-brown, then black; the interior of the root finally dissolved into a glutinous or molasses-like slime ; top of the root black, dead : Mucous Bacteriosis, Bacillus Bettc and others - - - I3 (P) Small black warts on the surface of the root, often together forming vertical swellings : Wart Bacteriosis, Bacterium scabiegenum - - - ' ' ' ' ^ {c) Large, short-stemmed, irregularly intersected, tumour-like excrescences on the upper part of the root : Beetroot Tumour, Uroplilyctis hproidca - - - - 3° {d) Wart-like excrescencesor fissure-like concavities on the surface of the root ; root usually with an entanglement at the middle : Oospora cretacea 2iXid. o'Cci^'!?, - - " " - 158 {e) Decaying spots, with white, afterwards yellow, slimy, shrivelled covering : Fusarium Betce - - - ' - i57 (/) Root Felt Disease, Rhizoctonia violacea. See Potato, A {e) 163 D. On the Whole Plant. (a) Root-Crop Rot, Sckrotinia Libertiaiia. See Potato, B {b) - 135 {b) Leaves small, yellowish-brown, finally black ; root dwarfed, with dark concentric rings in the interior ; from the vessels a suppurating dark juice : Californian Beet-Pest - 16 {c) Small, brown sclerotia on the upper part of the root, and also on and within the stem and branches : Typhula Betce - 9° {d) The youngest leaves in the rosette first brown, then black; root ceasing to grow, finally its surface is covered with con- i9«- FUNGOID DISEASES OF PLANTS PAGE cave blotches or fissures, sprinkled with little dark brown pricks ; ultimately small leaf-rosettes on the neck of the root : Heart Rot - - - - - - i68 Cabbage, Cauliflower, Swedish Turnip, Rutabaga, Rape, Turnip, Brassica oleracca., B. Napus, and B. Rapa^ A. On Seedlings. (a) Seedling Blight, Pythium Baryanum. See Barley, A - 33 {b) Head of the root getting black ; plants breaking down, dead ; Seedling Cabbage Disease, 6'///V//V/;// ^rt^j-j-zVt? - - 31 B. On Stem, Leaves, and Blooming Sprout. (a) The central nerves of the leaves and the younger stalks of white cabbage, dissolving into an offensive pulp : Bacteriosis ofWhite Cabbage, a species of /'j't7/(^/w//w/cii' - - 13 (b) Tops of cauliflower decaying : Bacteriosis of Cauliflower, Bacillus oleraceus and B. brassicccvot'iis - - 13 if) Stem, leaves, and the distorted blooming sprout, with snowy- white, shiny crusts : White Rust, Cystopiis candidiis - 42 {d) Stem, leaves, and the distorted blooming sprout, with white, flour-like coverings : Blight, Peronospora parasitica - 41 (e) Stalk and leaves covered by a white film, with embedded black dots : Mildew, Erysiphe Poly go ni - - - - 95 (/) Stem, leaves, and fruits, with ovate-oblong or round, blackish- brown spots : Black Spot, Sporidesiniuni cxitiosiiin {Lepto- sphcrria Napi) • - - - - - 103 (g-) Stem Mould, Sclcrotinia Fuckelia?ia. See Potato, B (a) - 133 {h) Root-Crop Rot, Sclcrotinia Libertiana. See Potato, B {b) - 135 (z) At first pale green, then white spots on the leaves, with small, dark specks in the middle of the spot : Phyllosticta Brassiccz 144 C. On Root. {a) Roots distorted, with numerous, irregularly formed outgrowths, finally decaying : Ghih-'B.oot, Plas?nodiophora Brassiccr - 18 ip) Root with large, round, reddish-yellow spots, with a slimy covering; finally putrid : Ficsariiim Brassicce - - 158 {c) Root Felt Disease, Khizoctonia violacca. See Potato, A {e) - 163 1 Here are included — in order to avoid repetition — the roots Swedish .Turnip and Turnip, as well as Cabbage and Rape, the injurious fungi of all cruciferous plants being essentially the same. APPENDIX 199 PAGE (^ Root with brown, nappy papillae : Rhizoctonia fusca - - 167 (e) The upper part of the root with discoloured spots, covered with little back dots ; root ultimately rotten ; Dry Rot, Phonia Napobrassiar - - - - - - 148 (/) On growing cabbage-plants, the root just under ground dying ; from the root beyond the dead part plenty of branch-roots growing out ; plants often entirely withering away ; in stored-up cabbage " canker-spots " inside the cabbage- trunk : Canker, Phoma oleracea - - - - 146 D. On the Whole Plant. (a) The central nerves of the leaves and the leaf-stalks with black vessels ; root brown-spotted, with either radial or longi- tudinal black stripes inside it ; root frequently growing long and thin, almost like a carrot : Brown Bacteriosis, Pseudo- monas campestris ..-.-- g ib) Leaves yellow, dropping off; the pulp of the root with greyish- white spots ; root eventually putrid and offensive : White Rot, Pscudonionas destructans - - ■ -13 {c) Leaves and roots with small, first brown, then black, sclerotia, of the size of a cabbage-seed : Typhula gyrans - ■ 91 Carrot, Daucus Carota. A. On Parts above Ground. {a) The under side of the leaves, covered by a thick, snowy-white mildew : Blight, Plasmopara nivea - - - - 41 (b) Leaves with brown spots ; these spots on the under side covered with fine brown mycelium bunches : Cercospora Apii - - - - - - - - 163 (c) Stem Mould, Sclerotinia Fuckelia?ui. See Potato, B {a) - 133 B. On Root. (a) Root with brown spots, the disease starting at the crown and proceeding downwards and inwards ; roots quickly decaying, mostly while stored up for the winter : Bacteriosis, Bacillus caroiP7'onis - - - - - - -17 (fi) Root Felt Disease. Rhizoctonia violacca. See Potato, A {e) - 163 C. UN THE Whole Plant. (a) Root-Crop Rot, Sclerotinia Libertia7ta. See Potato, B {b) - 135 {b) Stem and root, with grey, frequently concave, blotches, sprinkled with small papill;i?, each of these papillre sending FUNGOID DISEASES OF PLANTS PAGE forth a flesh-coloured thread ; no seed obtained from the plant ; the roots stored up for the winter often putrid : Carrot Disease, Phoma RostrupH ' ■ - - - 144 {c) Leaves," and later on also the upper part of the root, with a black covering : Macrosporiuni Dauci - - - iii Parsnip, Pastinaca sativa. (a) Blight, Plasmopara ftivea. See Carrot, A (a) - - 41 {b) Stalk and leaves covered with a loose, white film : Mildew, Erysiphe Heraclci - - - - - * 95 {c) Cercospora Apii. See Carrot, K{b) - - - - 163 (d) Leaves with small, pale spots and Httle black pricks in the centre of the spot : Sepioria Pastinacce - - - 1 50 {e) Numerous, small, flat, crust-like, black spots on the under side of the leaves: Phyllachora Pasti7iacce - ■ - - 12,'2. (/) Bacteriosis, Bacillus ca:-otovorus - - - - 17 Chicory, Cichorium Intybus. {a) Leaves and stalk with small, yellow, sometimes eventually black, dust-filled sores : Rust, Pur.ci7iia Cichorii - - 85 (b) Leaves and stalk covered with a thin, white film, with numerously embedded black pricks : Mildew, Erysiphe Cichoriacearum - - - - - "95 (c) Root-Crop Rot, Sderotinia Libertiana. See Potato, B {b) - 135 III. PULSES. Common Pea, Pisum sativum. Field Pea, P. arve^tse. A. On Seedlings. [Seedling Blight, PytJduin Baryamnn. See Barley, A -2)2) B. On Root. (a) Brownish-black dust all over the surface of the root ; roots shrunk, mellow ; stalks and leaves stunted : Root-Rot, Thiclavia basicola - • - - - "97 (b) Root interwoven with fungoid threads, often red or brown; stalk and leaves turning yellow, dying : Vessel Brand, Fusariuin vasinfcctum - - - - ■ ^55 APPENDIX 20 1 I'AGK C On Parts above Ground. {a) Leaves and stem with small, rusty-brown, finally black, dust- filled sores : Rust, Urotnyces Pisi-sativi - - - 87 {b) Leaves with large, discoloured patches, covered on the under side with a thick grey-violet blight: Blight, Feronospora Vicia ■ - - - ■ ■ - - 40 {c) Mildew, Erysiphe Polygoni. See Beet, B (^/) - - 95 {d) Stem Mould, Sclerotmia Fuckeliana. See Potato, B {a) - 133 {e) Stalks and fruits, at times also seeds, covered with yellow, brown-edged spots : Ascochyta Pisi - - - - '49 (/) The whole plant suddenly turning yellow, covered with a greenish-black dust: C/'^'/^i'/^r/ww /?^r^rtrz^w - - nS Vetch, Vicia sativa, V. villosa, and others, Windsor-Bean, Faba vulgaris. A. On Root. Vessel Brand, Fusarhim vasinfectum. See Common Pea, B {b) 155 B. On Parts above Ground. («) Leaves and stem with rusty-brown, dust-filled sores ; later on with hard, blackish-brown swellings : Rust, Uroviyces Fabce 88 {b) Blight, Perojiospora Vicia. See Common Pea, C [b) - 40 (c) Mildew, Erysiphe Polygoni. See Beet, B (rt') - - 95 {d) Stem Mould, Sclerotinia Fuckeliana. See Potato, B (a\ - 133 (e) Ascochyta Pisi. See Common Pea, C (c) - - - I49 (/) Pale yellow patches on the leaves, sprinkled with brownish- black dots : /"/u'/^J/Zt-Ai /^(?^ensis. {a) Seedling Blight, Pythium Baryamim. See Barley, A - 33 [b) Leaves and stem with reddish-brown, later on black, round, dust-filled sores : Rust, Piicciitia Spergiihv - - - 86 {c) Leaves with pale spots, covered by a fine grey mildew : Blight, Peronospora obovata ■ - - - - -41 {d) Leaves and stalks with pale, later on black, spots ; dying : Sphcerella isariphora and Septoria Spergulce - 119, 150 Buck-Wheat, Fagopyrum esculenium. {a) ^\iQXSi'M.OxCiA.., Sclerotinia Fiickeliana. See Potato, B (/?) - 133 {b) Leaves and stem with large, round, buff-coloured spots, with darker brim and drab-coloured centre : Ascochyta Fagopyri 149 {c) Leaves and stem with pale spots, surrounded by a light red brim : Phyllosticta Polygonofuni - - - - I44 Tobacco, Nicotiana Tabaciini. A. On Seedlings. {a) Stem part rotting, the putrefaction progressing from below : Bacteriosis, Bacillus amylobacter [See Potato, A (a)\ and Olpidiioii l\icotiance - - - -- -2, 31 ib) Root-Rot, Thielavia basicola. See Common Pea, B {a) - 97 {c) Plants, especially seed-leaves, slack, slimy, finally with a black, velvety covering : Altcrnaria tenuis - - - - 112 B. On the Full-grown Plant. {a) The joints of the stem, with long, groove like, dark spots ; plant dying: Stem Bacteriosis, Bacillus ccruginosus 17 {b) Leaves with small, pale, finally white and desiccative patches: 'hQ'dX'StZ,c\QX\0%\s>, Bacillus }nacidicola - - - I7 {c) Leaves and stem with whitish spots; on these spots later on hard, black sclerotia : Sclei'otinia Nicotiance - - 140 {d) Mildew, Erysiphe Polygoni. See Beet, B (rt') - - 95 (e) Leaves with numerous, light, later on white and dried, spots; occasionally with little black dots at the centre : Phyllo- sticta Tabaci • - - - - - - 144 (/) Leaves with brown, dried, irregular spots : Ascocliyta Nico- tiance ■ - - ' - - - " 149 ig) The youngest leaves with irregular spots of various sizes and shades, some of them light and transparent, others dark and not at all transparent ; older leaves battered, frequently distorted: Mosaic Disease - - - - i/S {/i) Leaves with small, brown, or white, finally dried patches : Pox Disease - - - - - - - i75 INDEX ^cidium Bcrberidis,i\ ; CaiharticcE, 76 ; <^raveoltii.<;, 78 ; yiibclhiui, 78 ; Tnssilaginis, 78 Alternaria Solani. in ; tenuis, 112 Ainylobacter navicula, 4 Anthracnose, 151 Ascochyta Fagopyri, 149; graniini- cola, 149; Nicotiancc, 149; Z*/^/, 149 Asterocystis radicis, 29 JBacillus czruginosHS, 17; ainylobac- ter, 2; attosepticus, 8; ^^/f^", 14; brassicesvoriis, 13; Bussei, 14; ra;'f- tovoi'iis, 17; call I ivories, ^\ elegans, 17; lacerans, 14; inaculicola, 17; nielanogenes, -J \ nivcoides, 15; c/t'- racece, 13; phytophthorus, 8; 5"c&- naceariun, 5, 17; solanincola, 9; solaniperda, 2 ; solainsaprus, 8 ; tubificans, 15 Bacteriosis ; on beet : Californian beet-pest, 16; germ, 16; mucous (beet gummosis), 13; wart, 15; yellow, disease (yellowing), 15 on cabbage : brown (brown-rot, black-rot, black cabbage-rot), 9; of cauliflower, 13; of white cabbage, 13; turnip wart, 12; white-rot of turnip, 13 on carrot (soft-rot), 17 on kipin, 17 on potato : brown, 9 ; ring (wilt- bacillose), 5; stalk (black stalk- rot, black-leg), 7 ; tuber, 2 on seed, 17 on tobacco, 17 Bacterium scabicgenuvi, 15 Beet mould, 39 Beetroot tumour, 30 Black-leg, 9, 1 14 prick of cornstraw, loi spot of cabbage, 103 stalk-rot, 7 Blight of beet, 16S of cereals, 115 Botrytis cinerea, 133 Brown-rot, 1 2 spot disease on wheat-ears, 148 Brulure, 29 Brunissure, 9 Bunt in seed (see Smut), 45 Cabbage canker, 146 club-root, 18 white rust, 42 Canker fungus, 25 Carrot disease, 144 Cauliflower disease, 25 Cercospora Apii, 1 63 ; beticola, 162 ; concors, 160; radiata, 163 Chancre bacterien, 17 Chrysophlyctis eiidobiotica, 25 Cladosporiuui herbarimi, 115, 117 Claviceps uiicroccphala, 130; pur- purea, 126 Clostriduim butyricinn, 4 Clover leaf spot, 140 sclerote, 138 stem rot, 151 Coniosporinui, 114 Copper web, 163 Crown-gall of Lucerne, 30 Cryptosporium leptostromiforine, 152 Cystopus candid us, 42 Diachora Onobrychides, 132 Dilophia graininis, 112 Dry rot of rape, 148 spot of potato-leaf, 1 10 DiirrfleckenKrankheit, III Early potato blight, iii Endoeonidiiini teiuulentuni, 154 Epichloc typhina, 125 Epilepsy, 147 Ergot disease, 126 ErysipheCiehoriaccarum, 95; graini- nis, 94 ; Heraclei, 95 ; Polygoni, 95 206 INDEX 207 Falling at the butt, 136 Federbusclisporen-Kranklieit, 1 13 Flax root-blight, 29 Foot-rot, 1 14 Fiisariiun avenaceum, 153 ; Betes, 157 ; BrassiccB, 158 ; ciilmorum, 153 ; Hordei, 149 ; Lolii, 149 ; nivale, 123 ; roscinn, var. Lupini albi, 157 ; Solani, 121; Triiici, 153; vasin- feciiim, 155 Gangrene de la tige, 8 Giddy-rye, 116 Gloeosporiiiin cauUvorum, 151 ; Dacty- lidis, 151 ; graminum, 151 ; 7Vz- /o/zY, 151 Granville tobacco-wilt, 17 Grey spot of oats, 117 Gummose bacillaire, 13 Giirtelshorf, 158 Haughing, 136 Helmintosporios, 108 HeUnintosporium Arenas, no; gra- ntiueum, 105 ; tei'es, 108 Herzfaule, 168 Jaunisse, 15 Lccstadia microspora, 119 Leaf-roll disease of potato, 171 -spot on cereal sprout, 150 Leptosphceria ciirinatis, 166; nilini- fras^a, 99 ; herpotrichoidcs, 99 ; Napi, 103 ; Tritici, loi jSracrosporiiun Daicci, in; sarcina:- forine, 112; Solani, ill Maladie du Cceur, 168 du Pied, 1 14 des taches blanches, 17 Dfarssonia Secalis, 152 Mastigosporiiun album, 1 12 Melavipsora Lini, 89 Micrococcus Tritici, 17 Midsummer di«ease of peas, 156 Mitrula Sclerotioruin, 142 Mosaic disease of toliacco, 175 Mucous mould, 53 ISIyxovionas Betcv, 170 Nectria grauiinicola, 123; Solani, 121 Nervation noire, 12 Olpidiuin Brassiccc, 31 ; NicotiancB, 31 ; Trifolii, 31 Oospora cretacca. Scabies, 159 Ophiobolus graiuiiiis, trichoides, 113 Orrag, 116 Ovularia dcusta, 160 150; rosella, 158; herpo- II- Pea-pod spot, 149 Peronospora obovala, 41 ; parasitica, 41 ; Schachtii, 39; Trifolioruvi, 41 ; VicicF, 40 Phellomyces-Faule, 112 Phoma Betcc, 170; Hennebergii, 148; Napobrassiccr, 148 ; oleracea, 146 ; Rostnipii,\i,\; sphcBrospei'ina, 170 Phyllachora grantinis, 131 ; Pasti- nacce, 132 ; Trifolii, 132 Phyllosticta Be tee, 144 ; BrassiccB, 144 ; FabcB, 144; Mcdicaginis, 144; P; a- tensis, 87 : striatits, 87 ; Trifolii, 89 ; Trifolii-repeiitis, 88 Urophlyctis AlfalfcB, 30; leproidea, 30 Ustilago Avence, 56 ; broviivora, 60 ; grandis, 60; Hordei, 55; Kolleri. 59; longissima, 60; nuda, 54; per- ennans, 60; Tritici, 50 Vessel brand on pulses, 155 Wart disease (potato), 25 Wheat-ear fungus, X12 White-heads, 113 rot of turnip, 13 rust, cabbage, 42 spot, 136 Yellowing or yellow blight, 15 Uaillicrc, Tindall and Cox, 8, Hcniieita street, Covciit Gaiiten, London. 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