Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. ae «4 % oF re i 1 7) Tie = CIRCULAR No. 464 MARCH 1938 UNITED STATES DEPARTMENT OF AGRICULTURE WASHINGTON, D.C. THE GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL’ By A. F. Buresss, principal entomologist, Division of Gypsy Moth and Brown-Tail Moth Control, and W. L. Baker, assistant entomologist, Division of Forest Insect Investigations, Bureau of Entomology and Plant Quarantine CONTENTS : Page Page RhewypsSyeMoOpnes === eee ee ee oe 1 | The brown-tail moth—Continued. History of the pest in the United States____ 1 INative:ecnemies 222 sa een eee see 33 Conditions of infestation in New England.. 5 Introduced parasites and other enemies_____ 33 IP ORIS COT Yee ee eee eee se 6 | Effect of low temperatures__-_---_.----______ 33 Injury caused by the gypsy moth__________ 8 Methodsiof control at eat eae set eo es 33 WOOGRD aN USE ee en ee es ga 9 Recent Controle lontsess eee 3 Wieansiotspread =.) ee itia Leeehie 13 | Organization and status of work against the HnecholiGlimates———=— = SP 14 gypsy moth and the brown-tail moth________ 34 INGLIVOlCNeMieS © acs en eer eo on ye ee ee 15 VA TING os oe ae oe ra Re ee tee 34 Introduced parasites and other enemies______ 15 INeweklampshires]: Gas sae eee eta 35 @ontrolemet hogs asses ee ee ae 16 GTI TG xe a eee ee 35 Recent control work in New England and iViassachusetis=eae = sas 2 hee eee eee ee 35 ING wry ork woodlands: =-25 2-225 2. 23 IRhodewslandis=== 2 ee eee 36 Record of clean-up of outlying colonies______ 23 Connechicu te. eras a eee ee eee 36 Extermination project in New Jersey______-_ 25 ING WSY(Or Koka eee eet eae pons Se 2 ay tens 3 36 Extermination project in Pennsylvania_____ 28 IN CAS CTSC Vissi Sate 8 a le oe 36 HHetbrowal-vallomno thee ete See ee eee EEE 29 IRennSylvariiaeee eee. eee eee eek eee 36 History of the pest in the United States____ 29 Mominioniok@anaday _-—- = i eee 36 STOUR ISL OG Vee oe ee ee Oe eee 31 United States Department of Agriculture... 37 Hoodsplants aaa ee eee eee Per ee 31 Cooperative: workers oh ss setae Seas ees 37 Injury caused by the brown-tail moth______ 32 THE GYPSY MOTH HISTORY OF THE PEST IN THE UNITED STATES In 1869 a number of egg clusters of the gypsy moth (Porthetria dispar Li.) were brought from France to Medford, Mass., by a French mathematician and astronomer, who had the idea that he could cross this insect with silkworm moths and thus develop a hardy race of silk-producing insects. In the course of his rearing experiments some of the eggs were accidentally lost or some of the caterpillars escaped, and he made at that time public acknowledgment of this fact, evidently appreciating the danger. The insect increased slowly at first. After 10 years it seemed to have been noticed by local residents but was believed to be some native caterpillar. Not until the summer of 1889, or 20 years after its introduction, did this insect become so abundant and destructive as to bring it into general public notice. At that time fruit and shade trees were completely defoliated, and the caterpillars, swarming 1This circular supersedes Farmers’ Bulletin 1623, The Gipsy Moth and the Brown-Tail Moth. 35349°—38——1 1 2 CIRCULAR 464, U. S. DEPARTMENT OF AGRICULTURE into the houses, became a very grave nuisance. The situation was so serious that the State of Massachusetts appropriated funds and delegated to the State Department of Agriculture the task of exter- minating this pest. The infested area then covered about 359 square miles, and trees in many towns around Boston were completely defoliated each season fora number of years. As the work continued, more effective methods of treatment were developed and better results were obtained; conse- quently, during the summers of 1898 and 1899 little defoliation could be found in the entire area and few specimens of the moth were located throughout the residential sections. Careful examination indicated that the insect had been exterminated in some of the towns bordering the originally infested area. In February 1900 the legislature ordered the work discontinued because of the popular belief that the danger had passed, in spite of the advice of experts that the insect had not been stamped out. During the next 5 years the insect increased enormously. Many of the towns and cities in the old infested area were overrun with cater- pillars, which completely defoliated trees in many of the residential sections, and thousands of acres of woodland were stripped of leaves during the summer. The situation became so serious and intolerable that in 1905 the State resumed control work. In the meantime the insect had spread far beyond the original limits of infestation, more than 2,224 square miles being involved in Massachusetts as well as many isolated areas in Maine, New Hampshire, and Rhode Island. In 1906 an appropriation was made by Congress, and the Secretary of Agriculture was authorized to take all possible measures, in coopera- tion with the States concerned, to prevent the spread of this pest. The insect had increased to such enormous numbers and had spread so rapidly that the utmost efforts of the Federal and State forces were only able to apply relief measures in the badly infested residential sections and slightly retard the continued spread of the pest. Efforts were made to prevent the shipment of the insect to uninfested localities by inspecting products that were likely to carry it. This phase of the work was greatly strengthened as a result of the enactment of the plant quarantine law by Congress on August 20, 1912. Since October of that year shipments from the infested district have been regulated by Federal quarantine. On account of the continued spread and increasing damage caused by this insect, efforts were constantly being made to develop better means of control. The process of manufacturing lead arsenate, which was first made and used on the gypsy moth work in 1893, was im- proved so that the cost of production was reduced and the product could be more effectively applied. Spraying machinery and equip- ment were developed to a high point of efficiency. The details of field management were constantly improved, following experimental work in carrying on field operations, in order that the greatest possible volume of effective work could be done with the funds available. In spite of the efforts that were made by the Federal Government and all the States concerned, the insect continued to spread. By 1914 it had covered the southern half of New Hampshire and extended as far east as Bangor, Maine. On the west it had crossed the Con- necticut River in Massachusetts and into Vermont. Rhode Island and towns in eastern Connecticut were found to be infested. GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL 3 During the war period conditions were unfavorable for preventing spread. The loss of efficient personnel and the constant turn-over of men, together with extraordinary increase in costs, made progress difficult. By the fall of 1922 scattered colonies were found farther west in Vermont, Massachusetts, and Connecticut, and in New York State near the Massachusetts State line. There was every indication of the continued spread of the insect unless more intensive work was done. To meet this serious situation a conference was held in the office of the commissioner of farms and markets in Albany, November 26, 1922, which was attended by representatives from all the infested States, the Dominion of Canada, and the United States Department of Agriculture.? The entire subject of the prevention of spread of the gypsy moth and its control was discussed, and a resolution was adopted urging that sufficient funds be obtained from the States interested and the Federal Government to continue and strengthen control methods in the infested area, to do necessary scouting for the discovery and destruction of border infestations, to determine the location of the most practical place for a control zone, to take necessary steps to make control therein effective, and to destroy all infestations in and west of said zone. To carry out this project, in April 1923 the State of New York appropriated $150,000 to be administered by the Department of Conservation. Federal funds were also provided for the fiscal year beginning July 1, 1923, to bring about effective cooperation. The plan finally adopted, by the Federal and State authorities, was to locate a zone where clean-up operations to prevent westward spread of this pest would be centered. This barrier zone embraced an area of about 9,000 square miles east of the Hudson River extend- ing from Long Island Sound (excluding Westchester County, N. Y.) to the Canadian border, a distance of more than 250 miles, and rang- ing in width from 25 to 30 miles (fig. 1). This is the shortest and most feasible area in the United States that could be selected to pre- vent Nation-wide spread of the insect. The territory east of this zone was to be treated by the States concerned as far as their funds would permit, and their work was to be supplemented by liberation of imported parasites and other natural enemies of the insect by the Bureau of Entomology. Work in the New York portion of the area was to be financed by the State, with such assistance as could be given by the Bureau after covering the eastern part of the zone in western Vermont, Massachusetts, and Connecticut. _ While much of the extremely rugged country in the Adirondacks in northern New York and the Green Mountains in Vermont was avoided, as well as the Catskills and some of the rougher country west of the Connecticut River in Connecticut, there are areas in this zone, embracing the Berkshire Hills in western Massachusetts and some of the territory directly south and southwest of them in Con- necticut and New York, where the terrain is extremely difficult. In 1924, owing to the number of infestations found in Massa- chusetts and Vermont, and the discovery of a colony at Henrysburg, Quebec, by the inspection force of the Dominion entomologist of Canada, the quarantine line was moved westward from the eastern 2 FELT, E. P., and others. THE GYPSY MOTH, AN IMMINENT MENACE TO THE FOREST AND SHADE TREES OF THE STATE OF NEW YORK. N. Y. State Dept. Farms and Markets Agr. Bull. 148, 58 pp., illus. 1922. 4 CIRCULAR 464, U. 5. DEPARTMENT OF AGRICULTURE boundary of the zone to embrace the entire State of Vermont and additional towns in northwestern Connecticut. A foreign quaran- tine regulating the movement of Christmas trees was made effective covering the southern tier of towns in the Province of Quebec. In 1926, owing to the effectiveness of the clean-up work in the zone and the fact that scouting west of the zone showed no infestation, the area under quarantine lying in the zone was eliminated from quaran- tine. The Canadian quarantine was withdrawn July 1, 1928. LEGEND AREA QUARANTINED FOR GYPSY MOTH 1934. DELIMITS AREA QUARANTINED FOR BROWN-TAIL MOTH 1934. E35 sarrier Zone. AREA REMOVED FROM BARRIER ZONE 1934. PENN, GYPSY MOTH INFESTED AREA. ISOLATED GYPSY MOTH INFESTATIONS IN NJ. AND N.Y. i PLATTSBURG © - © ROCHESTER © SYRACUSE NEW Yo R K ALBANY® © ITHACA SCRANTON ° PENNSYLVANIA © HARRISBURG TRENTON PHILADELPHIA ¢ ! f JERSEY 7 SATLANTIC VA CITY FIGURE 1.—Barrier zone and status of the gypsy moth and brown-tail moth control areas at the end of 1934. Later in 1928 more infestations were found in the Massachusetts and northern Connecticut portions of the barrier zone than during the previous fiscal year. This made the problem far more difficult and emphasized the necessity of carrying on work in the territory east of the zone to facilitate eradication in the zone itself. Since there was also an increase in infestation directly east of the zone, 7 towns in Vermont, 12 in Massachusetts, and 31 in Connecticut, embracing an area of 1,581 square miles, were reclassified from the lightly infested: to the generally infested area. - GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL oO Scouting during the latter half of 1929 and the first half of 1930 showed a further increase in the number of infestations in the barrier zone, and Congress made additional funds available for clean-up work. No provision was made, however, for examination of terri- tory immediately east of the zone to check the increase there. The infestations located in 1929 and 1930 were new ones, as most of those previously discovered had been cleaned up. In 1933, after the passage of the National Industrial Recovery Act, funds were made available and extensive scouting and clean-up work was undertaken between the barrier zone and the Connecticut River. This was extended very materially by personnel from certain Civilian Conservation Corps camps, which were supervised by the gypsy moth organization of the Bureau of Entomology and Plant Quarantine through cooperative arrangements with the Forest Service of the United States Department of Agriculture, the State forest services, and the United States Department of the Interior. The prompt elimination of a few sporadic colonies that had been found just beyond the zone, together with the suitability of the area in the zone for effective clean-up, offers conclusive proof of the feas- ibility of checking westward spread. In 1934 a change in quarantine was made by transferring from the lightly to the generally infested area 74 towns in Maine, 5 in New Hampshire, 2 in Vermont, and 3 in Connecticut. In northern Ver- mont 39 towns were dropped from quarantine. The barrier zone line in northeastern New York was relocated on the New York- Vermont State line, thus eliminating 807 square miles, and a strip of towns in Vermont adjoining the barrier zone on the east, aggregating 604 square miles, was added to the zone. Since July 1935 emergency funds have been made available for gypsy moth work, and more scouting and clean-up work has been carried on than heretofore. This has suppressed the insect in many isolated colonies and improved the condition in the barrier zone and the area adjoining it to the east. CONDITIONS OF INFESTATION IN NEW ENGLAND From the beginning of its gypsy moth work the Bureau of Ento- mology obtained general records of the density of local and general infestations in the territory not covered by the Bureau. Since 1911, however, counts of egg clusters have been taken annually from a series of woodland plots in the eastern portion of the infested area. They are summarized as follows: Egg clusters Egg clusters per acre Year per acre “ar LS Sa A gt a a A era 431) | Oe ee Ronn nee ee est FF ST 110 Ps LASS 3? SESS * ieee oe ee PEPE Les J HR Gal: VOR TOSI fete lit 50 Lis 3 Geek See Oa es eC BYon pale) agile Deke ee ee oe ee ee 61 Lee eS Sa oe a ee STR 2 ee ees 127 Lie 22k toa a es AAO OMe ee ge 303 Te De 2 ee eh NR a i ipl Sel ha eee ee tee Cte 722 Va wee eee Br TAN PAN OS! 2 407 LS iets Se i ry ee Be j4 PeC ayy AUS). ce ee 66 LSU oS ee EM Ses el pe ee SS Sk ey 42 i AD aR aed Scat Tee a a Fee eats Ro tile Oil Ne Si 112 LSet | Ue ils oe eG eS Dots | LO ae ene CVC set 344 Hera pen mene ty); rl) _phiechogh cen 402 | 1934 181 6 CIRCULAR 464, U. S. DEPARTMENT OF AGRICULTURE As the habits and the variable mortality of the gypsy moth and its food-plant limitations cause wide differences in its abundance in various parts of the infested area, it has seemed that the damage done and the possibilities of greatest "future injury could be gaged most accurately by determining the defoliation caused by the species over the area as a whole. The total acreage showing from 25- to 100-per- cent defoliation each year beginning in 1924, when defoliation was less than in any previous year, is as follows: Year Acres defoliated | Year Acres defoliated 19242 Lioisa8 On iS EN S25MOS1. Oe wee I ee erie 204, 720 FIGURE 2.—Life stages of the gypsy moth: A, Female moth; B and F, pupae; C, larvae or caterpillars; D, male moth; E, egg mass. All about three-fourths natural size. The danger of reinfestation of the barrier zone depends largely on the severity of infestation east of the zone. In the last 3 years the areas of defoliation were smaller in eastern Massachusetts and certain sections of southeastern New Hampshire, which comprise most of the older infested territory. In the same years heavy defoliation was noted much farther west in Massachusetts, and in 1934 and 1935 extensive areas of complete defoliation occurred in the Connecticut River Valley and the adjoining territory about 20 miles from the zone. LIFE HISTORY The gypsy moth passes through four stages—the egg, the larva or caterpillar, the pupa, and the adult or moth (fig. 2). There is one generation a year. The times of the year when the different forms may be found in the field are shown in figure 3. ( GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL 7 THE EGGS The female gypsy moth lays from 100 to 800 eggs in a cluster, depending on her size. The average number per cluster is approx- imately 400. In light infestations where the food supply is plentiful clusters are larger than the average, and in heavy infestations where the food supply becomes limited during the late larval stages they are smaller. Each cluster is covered with buff-colored hairs from the body of the female, which no doubt serve as a protection for the eggs during the long interval between oviposition and hatching. Most of the egg clusters are laid in July and hatch the following spring. The hatching date varies from about May 1 in southern New England to May 25 in the extreme northern part. The date of oviposition bears no relation to the date of hatching, as eggs laid in mid-August may hatch at the same time as those laid early in July under the same envi- ronmental conditions. Eggs deposited in warm locations, as on the southern exposure of buildings, may hatch several days earlier than others laid in cool and moist locations. The gypsy moth egg must be exposed to a chillng temperature before it will hatch. Just what this temper- ature is is unknown. Eges that have under- gone this conditioning process will hatch in midwinter in a warm building. The female moth de- ; posits her ego clusters FIGURE ee ees Seat ene ner stages of the on the trunks of trees, on the underside of limbs, under loose bark, in cavities in the trunks or branches, and sometimes on leaves, on ground debris, under stones, and in stone walls. When infested trees are found along stone walls, a large proportion of the eggs are often laid in the wall; but where the ground is free of stones or debris, a large proportion of clusters will be found on the tree trunks. THE LARVAE The newly hatched larvae begin immediately to search for palatable food. In pure stands of favored food this is a simple matter, but as the proportion of favored food in the stand decreases the problem becomes more acute. There is no evidence that such larvae can pick out a favored tree from an unfavored one without examining the foliage. They find the food through random movement. The normal mortality of first-stage larvae is very high. Newly hatched larvae can ordinarily live only about a week without feeding. The re) CIRCULAR 464, U. S. DEPARTMENT OF AGRICULTURE absence of water becomes less of a problem as the larvae increase in size, probably because of the decrease in the ratio between evapo- rative surface and body volume. First-instar larvae move very slowly. They are active only when the temperature is above 60° F. and are more active when the temper- ature is 70° or higher. Gypsy moth larvae that are to become male moths molt five times, and those that are to be females molt six times. The full-grown larva is from 1% to 2% inches long. The head has yellow markings; the body is ale or ‘sooty colored, hairy, and on the dorsum is a double row of five pairs of blue spots followed by a double row of six pairs of red spots. As the larvae grow, the quantity of foliage eaten per day increases tremendously. Approximately 75 percent of all the foliage eaten by larvae having five instars is eaten in the fifth or last instar, and approximately 65 percent of the foliage eaten by larvae living through six instars 1s consumed in the last instar. Con- trol measures against larvae should therefore be applied as soon as possible after the eggs hatch, to protect the foliage from the later instars. THE PUPAE When full grown, the larvae shed their skins and transform to chestnut-brown pupae bearing tufts of yellow hairs. After about 10 days in this stage the adult moths emerge. THE ADULTS The male gypsy moth is dark brown with black wing markings, and is a strong flier. The males usually emerge earlier than the females, and fly near the ground, in a characteristic zigzag manner, in search of female moths. The female moth is nearly white, with black wing markings, and is much larger than the male. Because of the weight of their bodies, the females are incapable of flight, and are usually found beside their empty pupal cases. Here they deposit their eggs, and once this function has been performed they die. Oviposition begins within a day or two after the female emerges from the pupa. The moths do not feed. INJURY CAUSED BY THE GYPSY MOTH It is impossible to state with precision the loss to New England forests due to the ravages of the gypsy moth. The best information compiled from data extending over a long period of years indicates losses of many millions of dollars in tree growth. These losses have been due not only to the direct or indirect killing of the trees but also to the retardation of growth through defoliation. Although far less spectacular than the immediate killing of trees, the second type of loss is more to be feared, for tens of thousands of trees are so affected for every one killed. Most conifers, notably hemlock and white pine, are killed by a single complete defoliation. Most rapid- growing deciduous trees put out a new crop of foliage the same season in which stripping occurs; they are therefore without foliage but a GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL 9 short interval during the growing season, but retardation of growth aud less wood result. Trees that are weakened by defoliation are susceptible to secondary injuries by fungi and bark borers. From 1912 to 1915 heavy mor- tality was noted among oaks that had been defoliated by the gypsy moth, and this was followed by an outbreak of the two-lined chestnut borer (Agrilus bilineatus Weber), whose larvae fed beneath the bark of the weakened trees. During recent years this beetle has not caused noticeable damage, but such a condition might recur without warning. The importance of tree growth in aiding retention of moisture in the soil and preventing erosion, particularly in rugged country, is well recognized. Defoliation encourages evaporation of moisture from the soil during the most critical growing period in the summer, renders such areas more susceptible to forest fires, and undoubtedly diminishes the flow of small streams, some of which furnish the water supply for reservoirs maintained for commercial or city use. The money value of these losses cannot be readily computed. Defoliated or dying trees along roadsides and streets in residential areas are objectionable, and the removal of trees from such locations is a distinct loss to the community and the publicin general. Recrea- tional areas are being used to a greater extent each year, and here the value of trees far outweighs the commercial value of the timber. Ragged foliage and denuded trees, accompanied by crawling cater- pillars, are avoided by the public. Trees in such locations have more of a struggle for existence than trees that grow in natural environ- ment without interference by man, and they therefore require added protection. The increased interest in natural playground develop- ment in New England and New York State seems to warrant more than ordinary expenditures to preserve the trees for their esthetic value alone. Figures 4, 5, and 6 illustrate the results of gypsy moth feeding in various types of stands. FOOD PLANTS Unlike many leaf-eating insects, which confine their feeding to a single species or group of plants, the gypsy moth is a general feeder on trees and shrubs. In fact, in heavy infestations few species of trees are ignored, especially by the larger larvae, and when food is scarce grass and cultivated crops are sometimes eaten. A study of the food plants of the gypsy moth in 1913 ® revealed distinct differences in the preferences of the very small and the larger larvae. The food plants were grouped in four classes, which are given herewith, with a few changes that subsequent observations have justified. This classification can be used as a basis for thinning to eliminate the most favored species and retain and encourage the more valuable and resistant species. It will be noted that class 2 includes most of the conifers, which suffer severely if grown in association with more favored species. Unfortunately, the infested region abounds in class 1 trees either in solid stands or in more or less diluted mixtures. ie MOSHER, F.H. FOOD PLANTS OF THE GIPSY MOTHIN AMERICA. U.S. Dept. Agr. Bull. 250, 39 pp., illus. 1915. 35349°—38——2 CIRCULAR 464, U. S. DEPARTMENT OF AGRICULTURE 10 illed by the gypsy moth. ted and k la defoli ith favored food trees, ture Ww 1X inm ine growing i FIGURE 4.— White p ted by the gypsy moth. la Oak trees defoli RE 5. FIGU GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL Lit. FIGURE 6.—Hemlock growing in mixture with favored species defoliated and killed by the gypsy moth at Orange, Mass., in 1934. 12 CIRCULAR 464, U. S. DEPARTMENT OF AGRICULTURE Cuass 1.—Species that are favored food for the gypsy moth larvae Alder, speckled Oak, rock chestnut Apple Oak, bear Aspen, American ~ Oak, bur Aspen, large-toothed Oak, pin Balm-of-Gilead Oak, post Birch, gray Oak, red Birch, paper Oak, scarlet Birch, red Oak, shingle Blueberry (Vaccinium angustifolium) Oak, swamp white Boxelder Oak, white Gum, red Poplar, Lombardy Hawthorn Rose, pasture Hazelnut Serviceberry Hazelnut, beaked Spruce, blue? Larch, American Sumac, mountain Larch, European Sumac, scarlet Linden, American Sumac, staghorn Linden, European Willow, glaucous Mountain-ash Willow, sandbar Oak, black Willow, white Oak, dwarf chestnut Witch-hazel Cuiass 2.—Species that are favored food for the gypsy moth after the earlier larval stages Beech, American (1)4 Pine, western white Cedar, red (4) Pine, white Chestnut Plum, beach Hemlock Spruce, black Pine, jack Spruce, Norway Pine, pitch Spruce, red Pine, red - Spruce, white Pine, Scotch Cuiass 3.—Species that are not favored but upon which a small proportion of the gypsy moth larvae may develop Barberry, European Elm, slippery Bayberry Gum, black Birch, black Hickory, bitternut Birch, yellow Hickory, mockernut Blueberry, low Hickory, pignut Blueberry, tall Hickory, shagbark Butternut (4) i hie Hophornbeam Cedar, southern white (4) Hornbeam, American Cherry, sweet Maple, Norway Cherry, wild black Maple, red Cherry, wild red - Maple, silver Chokeberry Maple, sugar Chokecherry Pear Cottonwood ; Poplar, silver. Cranberry, American Sassafras Elm, American Sweetfern Elm, European Sweetgale 4 Numbers in parentheses refer to the original classification of plants that have been reclassified. Blue (fea spruce has been subsequently added. bi GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL Cuass 4.—Species that are wnfavored food for gypsy moth larvae Arborvitae Arrowwood Arrowwood, maple-leaved Ash, black Ash, blue Ash, red Ash, white Azalea, white and flame Balsam, fir Blackberry, high Blueflag, larger Catalpa, hardy Cornus Cranberry tree Currant, red Cypress, bald Dangleberry Dock, narrow Dogwood, flowering Elder, American Eubotrys, swamp Feverbush F Grape Greenbrier Hackberry Hardhack, pink Hardhack, white Holly, American Honeylocust Honeysuckle, bush Huckleberry, highbush Inkberry Juniper, common Kentucky coffeetree Lambkill (sheep laurel) Locust, black Maple, mountain Maple, striped Mountain-laurel Mulberry, red Mulberry, white Osage-orange Osier, red Pepperbush Persimmon Poison-ivy Privet Raspberry Sarsaparilla Skunkeabbage Spicebush Sweetbrier Sweet pepperbush Sycamore Tea, Appalachian Tuliptree Viburnum, sweet Walnut, black Willow, bay-leaved Winterberry, smooth 13 MEANS OF SPREAD Egg clusters of the gypsy moth deposited on trees, lumber, stone, and other products that are likely to be shipped may be carried long distances and cause new colonies of the insect to be established. The only way to prevent spread of this kind is to inspect such products and treat any clusters found on them before they are shipped. Larvae of the gypsy moth may be carried on such moving objects as trains and automobiles. Horse-drawn vehicles and freshets may also transport them for limited distances, and egg clusters on debris may be carried by high water. The danger of such spread is depend- ent upon the extent of infestation along railroads, highways, and streams. | : It is probable that the principal agent in the spread of the gypsy moth is the wind. The chief trend of spread of the insect, since its introduction into New England, has been to the north and northeast, which is the general direction of prevailing surface winds after the hatching season. Since the newly hatched larvae are abundantly supplied with hairs, they are easily carried by the wind. Probably few larvae are ever blown loose from their supports by the wind. An enormous number, however, spin down from tree tops when disturbed and are intercepted by air currents; the strand of silk is broken and they are whirled away with this silk attached to their bodies. Spinning larvae normally sever the strand of silk by biting only when they come to rest upon some object; they seldom do this while hanging free. The distance that a larva may be carried aloft by currents of air depends to some 14 CIRCULAR 464, U. S. DEPARTMENT OF AGRICULTURE extent upon the length of silk attached to its body. Larvae have been captured onscreens more than 20 miles from the nearest known infestation, and one larva has been taken on a screen attached to an airplane at a height of about 1,800 or 1,900 feet above the ground (2,000 feet above sea level). The height to which they may be carried varies from day to day and may greatly exceed 2,000 feet. Once lar- vae have reached such heights, they may encounter cross currents of air and be blown in the direction opposite to which surface winds are blowing. Transportation of larvae by the wind is, however, less serious than it would appear. The farther the larvae are carried the more widely they are separated and the less chance they have of falling close enough together to establish infestations. ‘There must be a large number of such larvae present to offset natural mortality. Millions of larvae, however, may be blown out of an infestation, fall nearby, and succeed in spreading the infestation short distances. That undoubtedly is why the infestation in New England has progressed only a few miles per year. Were it not for the tremendous natural mortality of larvae, the insect would have become established in new localities far more rapidly than it has. For this reason special efforts are made to destroy egg clusters before hatching, particularly those that are in exposed or wind-swept locations. Wind spread takes place primarily on hot days when convection currents from the heated surface of the ground are prevalent. The appearance of cumulus clouds signifies the existence of convection currents and the days when danger of wind spread is greatest. EFFECT OF CLIMATE The effect of climate, in all its phases, upon the gypsy moth has never been fully investigated, and is therefore little understood. The effect of extremely low temperatures upon overwintering eggs has received more study than any other single factor. It has been deter- mined that all egg clusters are killed when exposed to a temperature of —25° F. and that some eggs are killed at —15°. In the field, however, temperatures fluctuate greatly within very short distances. For instance, a temperature of —25° F. at a weather station in a town or city does not necessarily mean that such a tem- perature is common to the entire town. For this reason it has been impossible to estimate accurately just what was happening to gypsy moth eggs in towns from which temperature records were available. Winter temperature is an important factor in gypsy moth abund- ance in most of New England. In some winters the temperature does not get low enough to be fatal, but in other years mortality from this cause is heavy. In northern Maine, northern New:iHamp- shire, and most of Vermont except the Champlain and Connecticut River Valleys, minimum winter temperatures are low enough to kill ege clusters that are not protected by snow, ice, or otherwise, and in most of these areas infestations have become established slowly and. the increase of the species has been retarded. Late frosts in the spring sometimes cause severe damage to foliage, and this usually results in heavy mortality of the small larvae. This is most likely to occur locally, but was noticeable in many sections of the infested areas during the spring of 1936. Frequently there is GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL 15 also a considerable mortality of newly hatched larvae during long periods of rainy weather accompanied by low temperatures. Evaporation is another climatic factor that is known to influence caterpillar activity. Feeding is noticeably greater when evaporation is high, the loss of water from the caterpillar’s body probably acting as the stimulus. This may account for the more rapid feeding in the upper part of the crown than in the lower part. Such feeding serves to open the crown canopy, admitting more light, raising the tempera- ture, permitting a freer circulation of air, and increasing the evapora- tion rate below. Thus the entire crown becomes more and more susceptible to rapid feeding. Young larvae seem to be attracted and older larvae repelled by strong light. NATIVE ENEMIES No insect enemies of the gypsy moth native to New England cause any noticeable reduction in its numbers. This is shown by the fact that from 1900 to 1905, when no systematic effort was made to sup- press the insect, alarming i injury resulted, and native insect enemies did not increase to any marked degree. ‘The same is true of native insect-eating birds. While they undoubtedly feed to seme extent on gypsy moth caterpillars, there is no record of their being able to control the insect. The “wilt,” a disease that attacks and kills the cater- pillars and pupae, has probably occurred in this country for many years. During some seasons it kills an enormous number of the caterpillars and is often an important factor in reducing the infesta- tion locally. As a rule this disease is more common in heavy infesta- tions, although many caterpillars have been killed by it when the infestation has been relatively light. INTRODUCED PARASITES AND OTHER ENEMIES In 1905 the State of Massachusetts, in cooperation with the Bureau of Entomology, began to introduce parasites and other natural enemies of the gypsy moth from its native home in Europe and Japan. Since that time a large quantity of parasitized material has been received, and as a result some important natural enemies have become estab- lished in this country and are assisting in the control of the pest. The enemies which have become established, and which destroy the largest number of gypsy moth caterpillars and pupae, are the beetle Calosoma sycophanta L.; two species of parasitic flies, Sturmia scutellata R. D. and Compsilura concinnata Meig., one of which attacks the caterpillars of the brown-tail moth as well as those of many native insects; and a small wasplike fly, Apanteles melanoscelus Ratz. Two tiny important parasites of gypsy moth eggs have also been estab- lished, one, Oencyrtus kuvanae How., having been introduced from Japan and the other, Anastatus disparis Ruschka, from Europe and Japan. Two other introduced parasites, Hyposoter disparis Vier. and Phorocera agilis R. D., are established in this country, but they have not increased sufficiently to be important factors in gypsy moth control. The work of the natural enemies of the gypsy moth has greatly reduced the numbers of the insect. In some sections the reduction has been greater than in others, and their effectiveness has also varied from year to year. 16 CIRCULAR 464, U. 8S. DEPARTMENT OF AGRICULTURE Since 1911 annual examinations have been made at observation points scattered over the infested area to determine the intensity of the infestation and the percentage of eggs, larvae, and pupae killed by introduced natural enemies. These points were located in York County in southwestern Maine; in Strafford, Merrimac, Hillsboro, and Rockingham Counties in southeastern New Hampshire; and in Essex, Middlesex, Worcester, Norfolk, and Plymouth Counties in eastern Massachusetts. The results indicated a rapid building up of the natural enemies, with an increasing percentage of the eggs, larvae, and pupae being destroyed, until 1923. In the meantime the intensity of the gypsy moth infestation, which had already reached a high level in 1912, remained high until 1921, when it declined rapidly until 1924. Since then there have been fluctuations in both the intensity of the infestation and the percentage of moths destroyed, but since the natural enemies have become thoroughly established the infestation has not reached the high level attained in the earlier years in some portions of the area. To evaluate correctly the benefit derived from parasites and natural enemies, other factors, including climatic conditions, must be taken into consideration. Without doubt, however, these beneficial insects have played a useful role with other control agencies in decreasing damage by this pest. CONTROL METHODS GENERAL METHODS A number of standard methods are in use for controlling the gypsy moth. They may be applied singly or in combination, depending on the tree growth, the density of infestation, and other local conditions. The essential information concerning each method is given in the following paragraphs, but each owner or operator should select the procedure that will give the best results when applied to his particular problem. USE OF GYPSY MOTH CREOSOTE The application of gypsy moth creosote with a brush will destroy ege clusters without removing them from the trees or objects on which they are deposited. This work can be done between the first of August and the time of hatching in the spring, which is about the first of May. ‘Treatment can be given most satisfactorily when there is no snow on the ground. Gypsy moth creosote is on sale in the infested area and is a low- grade coal-tar creosote which has been impregnated with sufficient coal-tar pitch to discolor the egg masses and thus indicate those that have been treated. A satisfactory grade can be bought in quantity under the following specifications: Specificporayity sea) - ee) ees ie 4. . ie ae Beets 0.990—-1.025 at 15.5° C. ParSaC Gs es Se ere ee 10 to 15 percent. Coaletar iby drocarponses 2 =. sang ee 80 to 85 percent. Water-anotrmoresuhan 2eee ie: 2h) - Se ee eee 2 percent. Flasht point = Preheat s genie iiiei tet |. 5 ee OR eee 70°—75° C. No separation of naphthalene at 0° C. - Initial boiling point, 170°—180° C.; 95 percent over at 285°—295° C. In addition, not less than 6.5 percent nor more than 8.5 percent by weight of coal-tar pitch shall be added to the creosote furnished under GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL 17 this specification, in order that the finished product shall bave a color suitable for the proper staining of gypsy moth egg masses. This material must remain fluid and workable at subzero temperatures. USE OF BURLAP BANDS Gypsy moth caterpillars usually seek shelter during hot, sunny days, and if a band of burlap is attached to a tree (fig. 7) large numbers FIGURE 7.—Burlap band on tree showing caterpillars beneath. of them will crawl beneath it, where they may be crushed each day. A strip of burlap about 8 inches wide is placed loosely around the tree trunk, and a piece of twine is passed around the center and_tied to hold it in place. The top part of the burlap is then folded down to make a double shelter beneath it. This method requires considerable hand labor, but is effective in many places. If brown-tail moth caterpillars are present on the 35349 °-—38——_3 18 CIRCULAR 464, U. S. DEPARTMENT OF AGRICULTURE trees, burlap should not be ap- plied until after June 15, when most of these caterpillars have pupated. Otherwise they may form their cocoons beneath it, and the workmen may be poi- soned by the poisonous hairs that accumulate there. USE OF STICKY BANDS Bands of sticky tree-banding material, which may be obtained on the market, may be used on tree trunks (fig. 8) after the bark has been scraped so that the material can be applied evenly in a thin layer with a paddle. These bands prevent caterpillars from ascending the trees, and if proper treatment of egg clusters has reduced the number of lar- vae sufficiently, this is a very effective measure. Further- more, as the caterpillars are usually massed in large numbers beneath the bands, conditions are favorable for wilt disease to develop, and the caterpillars often die in large numbers from this disease and from starva- tion. Every week or 10 days during the caterpillar season a comb or similar implement should be run over the band to keep the surface from harden- ing and to bring up fresh, sticky material from the part near the bark. This material is expen- sive, and considerable labor is required to prepare the trees and apply and tend the bands. In some locations, particularly where there has been a heavy deposit of egg clusters on debris on the ground or in stone walls, FIGURE Sea imunk below its use is advisable. USE OF GYPSY MOTH TREE-BANDING MATERIAL A black greasy substance called “gypsy moth tree-banding material” is sometimes used to prevent caterpillars from crawling up the trunks of trees. It is similar to the product known as ‘‘Raupenleim” that GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL 19 has been used in German forests for many years. It has to be applied with a special gun in a thick narrow band encircling the tree trunk. At the present time it is not manufactured in this country, but infor- mation concerning its preparation and use can be sopalicdl by the Greenfield, Mass., office of the Bureau of Entomology and Plant Quarantine. SPRAYING The most effective spray material is lead arsenate. To make it adhere firmly to the foliage 4 fluid ounces of fish oil or raw linseed oil should be placed in the spray tank for each pound of lead arsenate. The oil should be added after the poison is well mixed with water in the tank, and while the whole is being agitated. Agitation should be con- tinued while the spray is being applied. The best grade of fish oil, known as ‘light pressed,’’ should be used. Five pounds of lead arsenate to each 100 gallons of spray is required to kill larvae that are half grown. A slight reduction in dosage may be made for the smaller larvae. In areas where there is mixed growth it is impractical to begin the spraying until the trees that produce foliage the latest—and they are usually the oaks—are ready for treatment. Under such circumstances larvae are found in several stages of development, and use of the stronger dosage may obviate the necessity of respraying. Many investigations are being carried on to develop low-priced non- arsenical insecticides which will not be harmful to man or domestic animals. Improvements along this lme would be most useful for gypsy moth spraying operations. Warning.—Lead arsenate is a stomach poison and is toxic to animal life. Itis unsafe to allow animals to graze underneath trees that have been recently sprayed. When fish oil is used as an adhesive, the spray will disfigure paint on buildings or vehicles unless it is removed with clear water before it has an opportunity to dry. Water may be provided by a low-pressure pump or from a hydrant. Fruit trees should not be sprayed with lead arsenate after the fruit is half grown, as it is difficult to remove the residue. CLEAN-UP AND THINNING WORK In many areas satisfactory control work cannot be attempted with- out the removal, and usually the burning, of infested rubbish and worthless trees. This should be done in such a way as to improve the property. Woodland areas may be thinned to advantage by removing trees that are favored as food by the gypsy moth caterpillars and encouraging the growth of better species of the less favored classes. When it is necessary to remove dead or useless wood in trees, the best practice of pruning and tree care should be employed. EQUIPMENT In creosoting work a brush with a round handle, which can be fitted with a cork stopper into a can containing creosote, is useful for treating ege clusters within easy reach. Those higher up can be treated w ith brushes that are attached at an angle to the tip of bamboo poles ranging from 8 to 18 feet in length. Axes, saws, and bark knives for marking trees are also necessary. 20 CIRCULAR 464, U. S. DEPARTMENT OF AGRICULTURE For applying burlap ee ds knives should be supplied for cutting the burlap and the twine and destroying the caterpillars. For applying sticky bands, knives or steel brushes should be used to destroy the caterpillars, and tree scrapers will be required to smooth the rough bark before the bands are applied. The most expensive item in gypsy moth work is the spraying ma- chinery and the equipment necessary to operate it. If orchard trees or low growth is to be treated, an orchard sprayer equipped with one or more lines of hose and with nozzles of the vermorel or bordeaux type will be satisfactory. The object of treatment is, of course, to cover all the foliage evenly with a thin deposit of spray. The higher the trees the more difficult it is to apply the material without waste. When large shade, park, or woodland trees are to be treated, high-powered spraying apparatus and use of the solid-stream type of treatment will enable the work to be done rapidly. For best results the machine should be equipped with hose 1 inch in diameter, and a nozzle pressure of 300 pounds per square inch should be maintained. The speed of the pump must be regulated according to the aperture of the nozzle. Since the quantity of Jiquid passing through increases with the diame- ter of the tip, the pump pressure has to be stepped up to furnish the 300-pound nozzle pressure necessary to break up the spray. As hose lines are lengthened or the elevation of the nozzle above the spraying machine increases, there is a loss of pressure at the nozzle due to the friction in the hose and the additional height to which the spray material must be forced. The pump should be of the triplex type, capable of delivering at least 35 gallons of liquid per minute for a short spray line. A spray tank of 300 gallons’ capacity is commonly used, and the tank and suction line should be provided with strainers to keep out foreign matter, which will either injure the pump or clog the nozzle. One-inch hose capable of withstandmg a working pressure of 600 pounds is satisfactory for most park and shade-tree work, where ex- tremely long lines of hose are not required, or where isolated areas are to be treated and the equipment has to be moved frequently. On larger and more extensive areas, or where a water supply is some distance away, a higher-powered machine and hose that will withstand a working pressure of 1,000 pounds per square inch are necessary (fig. 9). To perform a maximum amount of work the sprayer should be set at the water supply. If the machine is equipped with an auxiliary pump for drafting water to supply the tank, and the tank is divided, one section can be filled while the other is being emptied as the spraying operation proceeds, and continuous spraying will result. With equipment of this type and on areas where there are slight elevations, 4,000 to 5,000 feet of hose can be laid to reach outlying areas. In the intensive work that is being carried on by the Bureau of Entomology and Plant Quarantine in some of the outlying areas longer hose lines are necessary, and on account of higher elevations the sprayer and the hose are required to pass a performance test of 1,500 pounds’ working pressure. “As much as 12,000 feet of hose has been used on work of this type. Sprayers are constructed either with a power take-off or as individual units, so that they can be transferred to a truck and moved to points where they are needed in the field. With this type of machinery and the proper diameter of tip on the a GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL 21 nozzle, it is possible to spray thoroughly trees from 60 to 100 feet high. By using the same type of machine under reduced pressure and attaching to the nozzle a device known as a spreader, low growth may be treated rapidly and satisfactorily. Tests have been made during several seasons with airships, both heavier-than-air and dirigible types, to determine whether infested woodland areas could be dusted satisfactorily and economically. This method has not proved entirely satisfactory up to the present time. _ During the past year spraying with an autogiro has been tried, and the results have been more promising. This method has not yet been perfected sufficiently, however, to warrant its general adoption for woodland spraying, although for applying dust insecticides on certain low-growing crops it has given excellent results in some sections of the country. METHODS TO BE APPLIED IN ORCHARDS Of the fruit trees, apple trees are the most likely to be infested with this insect, and some injury to peach trees has been noted. FIGURE 9.—High-power truck sprayer. Apple orchards that are sprayed with lead arsenate for the control of other insects are protected from the gypsy moth. If systematic care or spraying of the orchard is not the practice, a program consisting of the removal of deadwood and defective trees, treatment of egg clus- ters, and spraying with lead arsenate and fish oil shortly after the blossoms fall should be put into operation. Orchards that are in close proximity to infested woodlands are sometimes severely damaged as a result of dispersion of small caterpillars by the wind or migration of the larger ones. ‘This can be prevented for the most part by proper care of the surrounding woodland. PROTECTION OF SHADE, ORNAMENTAL, AND ROADSIDE TREES Protection of shade, ornamental, and roadside trees is vital to the communities and rural districts in which they grow, as they increase property values. In most thickly settled communities, when street planting has been done in recent years, maple, elm, and other varie- ties that are not favored by the gypsy "moth have been planted, but 22 CIRCULAR 464, U. S. DEPARTMENT OF AGRICULTURE in many areas poplar, linden, willow, and, to a less extent, some of the oaks have been used. In the rural sections there has been rela- tively little roadside planting, and most of the shade trees are seedlings or have developed from sprouts from trees that have previously been cut. On private grounds there is a wide range of species, both native and exotic, and on such properties there are frequently many trees that are suspectible to gypsy moth attack. To obtain information as to the species that are growing on trunk- line roads, in the summer of 1936 a hurried survey was made on one of the principal State roads from the New York State line through central Massachusetts, swinging southeast, and extending diagonally through Barnstable County to Orleans on Cape Cod. The route covered 260 miles of road, 48 miles of which was classified as city and 212 as rural. The tree growth for 50 feet on each side of the road was noted, because trees growing within these strips will even- tually furnish shade for the highway. As a result of this survey 38.5 percent of the trees were rated as favored species, 27 percent were conifers and beech, which are highly favored during certain stages of the insect’s development, 26.5 percent were far less favored but occa- sionally defoliated, and 8 percent were in the unfavored group. About 51 miles of this road was open country with no trees, and there were additional areas where trees had been cut and were being replaced by sprout growth. These sprout, or brush, areas were about 50 per- cent favored food. The species growing in the wooded areas adjoin- ing these strips along the highway, and in the forest areas that were more remote, varied greatly in different localities, but it is estimated that more than half the tree growth was of favored species. A survey of this type does not show what conditions exist in sec- tions north or south of the road that was selected or on rural or unim- proved roads. A larger percentage of favored food plants might be expected southward toward Long Island Sound, and of less favored ones in southern Vermont, New Hampshire, and Maine. ‘The information obtained, however, indicates the necessity of protecting roadside trees from the oypsy moth. Officials in charge of tree pro- tection could well afford to have maps indicating the growth along the streets under their control as a basis for planning for protection or replacement of the most desirable species. An endeavor should be made to remove as much of the favored growth as possible and to encourage the growth of nonfavored trees. When it is impractical to do this, treatment should be applied for the protection of the favored species. Where solid woodland adjoining the road is heavily infested with the gypsy moth, roadside trees will be denuded by migrating caterpillars. In such cases protective work should be done to prevent defoliation, and the methods that can be most economically employed should be put into practice in an area adjoining the trees along the roadway. The size of this area will depend upon the severity of the infestation. THE WOODLAND PROBLEM 7 In the barrier zone and the adjoining areas, as well as in isolated infestations beyond the zone, intensive methods must be applied to curtail the infestation, not only for the benefit of the locality where it exists, but to prevent the spread of the pest beyond the known infested area. This makes necessary the use of a combination of the methods that can be most cheaply applied. GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL 22 In the generally infested area it is impracticable to apply such intensive methods to large woodlands unless the property is of special esthetic value or to protect other areas that have been intensively treated. On account of the low value of most of the forest growth, some relief can be obtained by the adoption of a thinning program based on the removal of the most favored food trees in order that the food of the insect may be reduced. This work, together with the encouragement of the growth of nonfavored species, will assist in preventing damage by this insect. It can be done by the owner himself if he makes proper selection of the trees to be removed. Obviously the best silvicultural practice should be followed in such selective thinning (figs. 10 and 11). In pure or nearly pure stands of favored trees clean cutting and the planting of unfavored species is the best method of building up a resistant stand even though the cost is considerable, but there are many areas scattered through the infested territory where clean cutting is not necessary to improve the stand. The same principles of thinning, aimed at the creation of more resistant growth, can be applied by owners even if their property is not infested, as this will reduce the opportunity for establishment of this pest. In young plantations of white pine or other conifers favored species should be removed, and if there are adjoining areas of favored erowth as many of such species as possible should be removed to prevent the insect from migrating into the plantations. RECENT CONTROL WORK IN NEW ENGLAND AND NEW YORK WOODLANDS In both the barrier zone and the outlying infested areas intensive work is being done, most of it in woodland, to exterminate the insect and to prevent westward spread. In the zone itself such treatment has eliminated the insect in many localities in Vermont, Massachusetts, and New York. Isolated colonies are now (1937) being treated in southwestern Massachusetts and northwestern Connecticut, and in a few towns in the southern part of New York State. On Long Island and in the Borough of the Bronx in New York City the infestation has been greatly reduced. In 1936 a colony was found in Shawangunk, west of the Hudson River, and intensive treatment is being applied in this locality. Between the barrier zone and the Connecticut River isolated colonies have been found, especially in the territory nearest the river in Vermont and over a wider area in Massachusetts and Connecticut. Work similar to that in the barrier zone is being carried on here, the number of infestations is being reduced, and infestations have been exterminated. RECORD OF CLEAN-UP OF OUTLYING COLONIES A few colonies of the gypsy moth have been discovered at points quite distant from the generally infested New England region, notably at Geneva, N. Y., in 1912; at Cleveland, Ohio, in 1914; at North Castle, Westchester County, N. Y., in 1914; at Rutherford, N.J., in 1914: and at Greenport, near the eastern end of Long Island, in 1921. In practically all these cases the Federal Government was assisted by the States involved in ferreting out the limits of the AGRICULTURE DEPARTMENT OF = Ne) CIRCULAR 464, U. 24 FIGURE 10.—Mixed stand of hardwoods and conifers before thinning. Here white ed from danger. as been rele —Same woodland shown in peure 10 after favored food trees had been removed. pine as FIGURE 11 GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL 25 colonies and applying intensive clean-up measures, and in every case the colonies have been exterminated. Since 1921 several other small, scattered infestations have been found on Long Island (fig. 12), and clean-up work here was undertaken by the New York Department of Conservation. Owing to its geo- graphical location and the general trend of spread of the insect away from rather than to this island, sufficient field work should furnish ample protection from this pest. EXTERMINATION PROJECT IN NEW JERSEY In July 1920 a State inspector found the gypsy moth on a large estate near Somerville, N. J. When discovered, the infestation centered in a large plantation of blue spruce trees, several acres of which were defoliated. There were dead trees in the worst-infested portion of the plantation, with indications that they had been killed by complete defoliation (fig. 13). The trees in this plantation had been imported from the Nether- lands about 10 years before, and the infestation came with the shipment. FIGURE 12.—Locations, outside of the large New Jersey and Pennsylvania infestations and the barrier zone, where the gypsy moth has been exterminated: 1, Cleveland (Bratenahl), Ohio; 2, Loretto, Pa.; 3, Geneva, N. Y.; 4, Schenec- tady, N. Y.; 5, North Castle and Garrison, N. Y.; 6, Brooklyn, Roslyn, Kew Gardens, Patchogue, Shelter Island, and Greenport on Long Island, N. Y.; 7, Deal Beach, Wyckoff, South Orange, Scotch Plains, Paterson, Madi- son, Glen Rock, Elizabeth, and Rutherford, N.J.; 8, Henrysburg, Quebec. This was prior to the en. actment of the Plant Quarantine Act, and emphasizes the pressing need for precautionary measures to keep out dangerous pests. FIGURE 13.—Blue spruce defoliated and killed by the gypsy moth. 26 CIRCULAR 464, U. S. DEPARTMENT OF AGRICULTURE Scouting during the fall of 1920 and the spring of 1921, financed by the State of New Jersey and the Federal Government, revealed infestations of this insect in scattered localities over an area of more than 400 square miles surrounding Somerville (fig. 14). FIGURE 14.—Area in New Jersey infested by the gypsy moth in 1921. Dots indicate location of colonies within the infested area, and dots enclosed in circles indicate isolated colonies. Previous successes in cleaning up local infestations led to the adoption of a cooperative plan to clean up this large, newly discovered infestation. State and Federal funds were appropriated, and the work was organized under the direction of the field office for gypsy moth control of the Bureau of Entomology. When the limits of infestation had been determined, the area was placed under State quarantine, which required as a condition of movement the certifica- tion of freedom from infestation of all products likely to carry any stage of the gypsy moth. Thorough inspection, which permitted certification, was made in cooperation with the Federal Government and by Federal inspectors. The area under regulation has been gradually reduced as a result of the clean-up work, and in 1932 Federal opera- tions were stopped and all inspection requirements were withdrawn. As soon as active work was under way in New Jersey, it was learned that trees had been shipped from the estate on which the insect was first discovered, and that the danger of its establishment in many Q) GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL D7 localities was very great. Fortunately, a record of all these ship- ments was available. It was found that 261 shipments had been sent to the District of Columbia and the following States: Connecticut, Delaware, Florida, Illinois, Indiana, Kentucky, Maryland, Minnesota, Missouri, New York, North Carolina, Ohio, Pennsylvania, Virginia, and Wisconsin. ‘These shipments were traced and the planted stock was inspected by State or Federal officials. In addition, 318 ship- ments that had been distributed in New Jersey were followed up the same way. As a result of this work small infestations were found at Loretto, Pa.; Garrison, Roslyn, and Kew Gardens, N. Y.; and Deal Beach, Wyckoff, South Orange, Scotch Plains, Paterson, Madison, Glen Rock, and Elizabeth, N. J. These small infestations were cleaned up the following year, and repeated scouting has failed to indicate the presence of the pest. In the meantime the center of the infested area was receiving in- tensive treatment, including spraying, and an enormous number of ego clusters were destroyed. It is significant that no trees in New Jersey have suffered from gypsy moth feeding since that time. During the next 4 years scouting and clean-up operations were continued throughout the known infested area, particular attention being paid to extensive woodlands north of Somerville, known as the Watchung Ridge. These areas were heavily wooded and were difficult and expensive to work. Since 1925 the gypsy moth has been steadily reduced in numbers. The scouting and clean-up work covered over 2,369 square miles, although the towns in which colonies were found were in an area of 924 square miles. Federal operations were discontinued in 1932, as no infestations had been discovered since 1929. Since 1932 the State force has been making inspections in many localities and has uncovered a few small infestations along the northern border of the old infested area. ‘These have been treated by the Federal Govern- ment in cooperation with the State. Although a large amount of intensive work has been done, no infestation has been found during the past 2 years. Table 1 shows the number of townships in the barrier zone, New York, and New Jersey where the gypsy moth has been eradicated and the number of infestations that have been cleaned up. It indicates the protection that has been afforded to other sections of the United States. TaBLE 1.—Townships in the barrier zone, New York, and New Jersey, where gypsy moth infestations have been eradicated, with the number of infestations cleaned up, fiscal years 1920-19385 Infestations Infestations Infested Infested = State A extermi- State extermi- townships ata d townships mated In barrier zone: Number Number South and west of barrier Connecticut_________- 20 92 zone: Number Number Massachusetts_______- 27 362 New Jersey__.___-___- 38 878 ING Wa VOnKe ee 24 75 ING winViOE kee 17 567 WeLmMonte eee ese 18 78 a Mo tales. Sates re 55 1, 445 MRotaltaee Boe = 89 607 ——_ | ———— Grand total_______- 144 2, 052 28 CIRCULAR 464, U. S. DEPARTMENT OF AGRICULTURE EXTERMINATION PROJECT IN PENNSYLVANIA Late in July 1932 a serious infestation was discovered near Pitts- ton, Luzerne County, Pa., through the location of male moths by a biology student. A survey was made and scattered infestations were found over a wide area. An eradication program was adopted under the supervision of the officials of the Federal Bureau of Ento- NEW YORK ™ wa ci ; eo FISCAL YEAR i935 GYPSY MOTH PROJECT NORTHEASTERN PENNSYLVANIA ———=_ DELIMITS KNOWN AREA OF GYPSY MOTH INFESTATION= APPROXIMATELY 410 SQUARE MILES J => 1} WiLKES}BaRRE® ono ' NEW JERSEY e INFESTATION HARRISBURG © ISOLATED INFESTATION ez, MARYLAND Mmm PENNSYLVANIA QUARANTINE — SEPTEMBER I, 1934 APPROXIMATELY 880 SQUARE MILES FIGURE 15.—Gypsy moth infestation in northeastern Pennsylvania in 1935. mology in cooperation with the Pennsylvania Department of Agricul- ture and Department of Forests and Waters, and an office was estab- lished in Wilkes-Barre. From the fall of 1932 to the spring of 1933 over 1,200 acres of tree growth were thinned and cleared of brush and worthless and dead trees in the worst infested portion of the area. During the same period about 2 million egg clusters were destroyed by creosoting. In the summer of 1933, 3,200 acres of woodland and thousands of trees in residential sections and open country were GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL 29 sprayed. A larger area was thinned and cleaned during the fall and winter. The work has been intensified and expanded since that time, and there has been a marked decrease in the number of egg clusters treated each year. Some new infested points have been found, and they have been promptly treated. No defoliation has been noted since the first summer. The infested areas and some of the surrounding town- ships have been placed under a State quarantine, and movement of materials likely to carry the insect is not permitted until they have been inspected and certified by officials from the Wilkes-Barre office. The area infested in 1935 is shown in figure 15. The present infested area aggregates 680 square miles, and additional areas sur- rounding it totaling 320 square miles are covered by the quarantine and inspection regulations. This includes Coolbaugh and Foster, which were added in 1936. Substantial progress has been made on this project in Pennsylvania, and excellent cooperation has been received from the State. The territory is located in the heart of the anthracite district, and much of the country is wooded and mountainous, and therefore difficult to work. Part of this area is in the valley of the Susquehanna and Lackawanna Rivers, and some infestations have been found in the Pocono Mountain range. This infestation is located the farthest west of any in the United States, and the importance of reducing the abundance of the insect and bringing about its final extermination can- not be overestimated. If the work is not continued aggressively, the insect might spread rapidly to surrounding territory and to other States where it is not now known to exist. THE BROWN-TAIL MOTH HISTORY OF THE PEST IN THE UNITED STATES The brown-tail moth (Nygmia phaeorrhoea Don.) was first found in the United States in Somerville, Mass., in the summer of 1897, and was undoubtedly introduced several seasons previous to that time on imported nursery stock. The insect increased enormously, and as the caterpillars were fond of the foliage of fruit and ornamental trees and shrubs, they became an unbearable nuisance, particularly in residential sections. Not only was complete defoliation common early in the summer, but as the hairs from the caterpillars caused serious poisoning to human beings the presence of this pest became a veritable scourge in densely populated areas. The insect extended its range very rapidly, because the moths of both sexes fly freely. This species occurs in many parts of Europe and is frequently very injurious. The State of Massachusetts applied suppressive measures from the winter of 1897 until February 1900, when it discontinued the work along with that of the gypsy moth. By 1905 the brown-tail moth was extremely abundant in eastern Massachusetts. It was also present in enormous numbers in Rhode Island, southern New Hampshire, and southwestern Maine. Not only did fruit and shade trees suffer defoliation, but large areas of oak woodland, particularly sprout erowth, were completely defoliated. 30 CIRCULAR 464, U. S. DEPARTMENT OF AGRICULTURE The insect continued to spread until 1915, when most of the area east of the Connecticut River, with the exception of a portion of northern New Hampshire and Maine, was heavily infested. Some infestation also existed in Vermont and west of the Connecticut River TJodener. pipe: : FIGURE 16.—Life stages of the brown-tail moth: A, Winter nest; B, male pupa; C, female pupa; D, cocoon in leaves; H, young caterpillars on leaf; F, full-grown caterpillar; G, female depositing eggs on a leaf, and egg mass also on leaf; H, egg mass removed from leaf and with some of the eggs exposed; J, male moth; J, female moth. All about three-fourths natural size. in Massachusetts and Connecticut. Suppressive work carried on by the States and the Federal Government kept the residential sections fairly free from this pest. The area now infested by the brown-tail moth is shown in figure 1, and is much less extensive than formerly. Low winter temperatures, Oi GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL 31 particularly in the northern part of the territory, coupled with the work of natural enemies and disease and the continuous repressive measures used in the residential sections, have caused a remarkable decrease in the abundance of this pest. The insect has been found in Nova Scotia and New Brunswick, but has not been reported from there in excessive numbers for several years. This pest can easily be shipped on woody plants, but general spread in this manner has been prevented by the strict enforcement of inspection and quarantine regulations. LIFE HISTORY The different stages in the development of the brown-tail moth are shown in figure 16. THE EGGS The female moth deposits a small cluster of from 200 to 400 eggs on the underside of a leaf. They are usually laid in July, and are covered with brown hairs from the body of the female. Hatching begins about August 15. THE LARVAE The newly hatched larvae, or caterpillars, feed on the epidermis of the leaf. After molting once or twice they construct a winter web. This is made by drawing together several terminal leaves and fasten- ing them with silk which they secrete. The larvae from one or more ege clusters live and feed in common, and as cold weather approaches they retire to the web, in which they remain during the winter. In the spring, as soon as the buds begin to develop, the larvae leave the web and feed upon the bud scales and small leaflets. As they increase in size they consume most of the foliage. They become full grown late in June. The full-grown larva, which is hairy, is about 14 inches long. The head is light brown. The body is dark brown to almost black, with a broken white line on each side and two conspicuous reddish spots on the dorsum near the posterior end. THE PUPAE After the caterpillars have finished feeding, they spin loose silken cocoons in which to pupate. These cocoons may be constructed sep- arately, or large numbers may be spun in a single mass. Sometimes leaves are drawn together as shelters; in other cases the cocoons are attached to trees or other objects. About 2 weeks is spent in the pupal stage. THE ADULTS Emergence of the moths usually begins the first week in July. The adult is pure white, except for the tip of the abdomen, which is covered with brown hairs. The body of the female is much larger than that of the male. These moths are attracted to strong light, and as they fly at night they are often seen around electric lights in cities and towns during the first half of July. FOOD PLANTS The caterpillars of the brown-tail moth feed on the leaves of apple, pear, cherry, oak, and willow, and they are sometimes found in con- siderable numbers on other common deciduous trees and shrubs. 32 CIRCULAR 464, U. S. DEPARTMENT OF AGRICULTURE They never attack conifers and are seldom found on hickory, ash, or other trees. Oak foliage is one of the favored foods of the brown-tail moth cat- erpillars in Europe and was severely injured in New England for a number of years after this insect became established there. It has not suffered in this way in recent years except in Maine and New Hamp- shire in 1933, when the insect was unusually abundant, and then some webs were found on oak trees and the caterpillars caused considerable defoliation locally. INJURY CAUSED BY THE BROWN-TAIL MOTH The principal injury caused by the brown-tail moth is due to the feeding of the larvae in the spring. ‘The caterpillars are often numer- FIGURE 17.—Apple trees defoliated by the brown-tail motn. Note the hibernating webs on the twigs. ous enough to devour the leaves as fast as the trees are able to develop them. As the webs are made on the terminals, the growth of the trees is often severely checked. In severe infestations trees may be completely stripped (fig. 17), but as the larvae grow rapidly during the first part of June there is usually an opportunity for the trees to produce new leaves before midsummer. The larvae hatch in August and frequently skeletonize the leaves, but this does not damage the trees seriously, as the growing period for the season is nearly over. The bodies of the caterpillars are provided with poisonous hairs. A microscopic examination of these hairs shows that the edges are barbed in such a way as to cause intense irritation when they come in contact with the human skin. They are also hollow and contain a substance which acts on the blood corpuscles. Poisoning and irrita- tion caused by this insect are accompanied by external swelling, and is known as the brown-tail rash. Persons differ in their susceptibility to this poison, but many cases are reported each year in the infested area. Many camps and summer cottages cannot be occupied with GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL 30 any comfort during the early summer if the caterpillars are abundant. If clothing is hung on the line near badly infested trees, the hairs frequently find lodgment and are brought into the houses, with consequent poisoning of the inhabitants. NATIVE ENEMIES One of the important native enemies of the brown-tail moth is a fungus disease (Hntomophthora aulicae Reich.) which attacks the caterpillars. It was first reported in this country by Roland Thaxter in 1888. Like all diseases of this nature, the benefit derived from it is regulated largely by weather conditions. This fungus sometimes works to a slight degree on the small caterpillars in the fall, and is found occasionally in the winter webs. As a rule, however, the greatest mortality of caterpillars takes place in the spring, when they are nearly full grown, and the pupae may, under the most favorable conditions, be almost completely exterminated. Native parasites and predacious insects have done little to check the increase of the brown-tail moth. INTRODUCED PARASITES AND OTHER ENEMIES Compsilura concinnata Meig., one of the species introduced as an enemy of the gypsy moth, attacks the caterpillars of the brown-tail moth freely, while two others, Apanteles lacteicolor Vier. and Sturmia midicola Towns., that were introduced from Europe at about the same time are also important enemies of the insect. Other imported enemies, Carcelia laxifrons Vill., Meteorus versicolor Wesm., and Eupteromalus nidulans Foerst., that have become established help to reduce the numbers of the moth but are not usually of great importance. EFFECT OF LOW TEMPERATURES Extremely low temperatures in the winter often prove fatal to a large proportion of the small caterpillars in the webs. When unpro- tected by snow or other covering, they are usually killed by tempera- tures below —25° F. METHODS OF CONTROL The brown-tail moth can be controlled by cutting off the winter webs and burning them before the caterpillars begin to emerge in April. These webs should be destroyed by fire, for if they are simply cut from the trees and left on the ground, the caterpillars will emerge and no benefit will result from the work that has been done. In orchards it is sometimes inadvisable to cut the winter webs, for where an infestation is heavy the cutting is likely to leave poorly shaped trees. Spraying in the spring is not a satisfactory remedy unless the infestation is very light, because large numbers of cater- pillars do not allow the tree to put out sufficient foliage to hold the spray material. An effective method in orchards is to spray the trees before the middle of August, using 3 pounds of powdered lead arsenate to 100 gallons of water. Before doing so the orchardist should determine to what extent the trees are infested with egg masses of the brown- tail moth. In spraying fruit trees, particularly early fall varieties, 34 CIRCULAR 464, U. S. DEPARTMENT OF AGRICULTURE caution should be used to avoid excessive spray residues. The foliage should be treated, particularly the terminal shoots, and care should be taken not to cover the fruit. Late fall or winter varieties of fruit may be sprayed with lead arsenate in August, and although an occasional spot may be found on the fruit at the time of picking, no injury will result from it. Where only a few choice fruit trees are sprayed, it is practicable to wipe the fruit before packing it for sale. The damage caused by the brown-tail moth is ordinarily not so severe as that due to the gypsy moth, because the brown-tail moth does not have so wide a range of food plants and, since most of the feeding is done early in the season, the trees have an opportunity to recover before midsummer. In the territory where both insects exist the caterpillars of the gypsy moth supplement the feeding done by those of the brown-tail moth, and the injury is therefore greatly increased. Thorough destruction of the webs in residential sections and in orchards has materially reduced the infestation in such places. Elim- ination of worthless apple and wild cherry trees would help greatly in reducing the pest. RECENT CONTROL EFFORTS In the winter of 1933-34 an extensive Civil Works Administration brown-tail-moth project was carried on, under the direction of the Bureau of Entomology in cooperation with the New England States, in which almost 24 million webs were cut and burned. Although the insect was much less abundant the following summer, during the winter of 1934-35 almost 2 million webs were cut and destroyed by State officials using local or State funds. The following winter a Works Progress Administration project was conducted by the Bureau in cooperation with the States, and more than 4% million webs were destroyed. The work was continued during the winter of 1936-37, and up to the end of March more than 2% million webs had been cut and destroyed. The destruction of such large numbers of winter webs has resulted in a decided decrease in infestation over much of the infested area. Prior to the C. W. A. work heavy defoliation was common in many parts of this area. During the past summer little defoliation was found. ‘Towns have been found in all the infested States where no infestation could be located, and it should be possible to reduce the affected territory materially if the work is continued. ORGANIZATION AND STATUS OF WORK AGAINST THE GYPSY MOTH AND THE BROWN-TAIL MOTH Each State infested with the gypsy moth and the brown-tail moth is carrying on control work, and many of the towns and cities are similarly engaged. The Dominion of Canada and several of the Provinces have also taken up control and eradication work. MAINE In Maine the work is in charge of the commissioner of agriculture, who has authority to appoint assistants to supervise the operations. In the southwestern part of the State the gypsy moth infestation is >| = GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL 35 general and, in places, severe; the northern part of the insect’s range is only lightly infested. The severity of infestation increased in 1932 and 1933, and many heavily infested sections have been found since that time. Several small infestations were found in the eastern part of Washington County in 1936. The brown-tail moth was very abundant in the southwestern part of Maine from 1931 to 1933, but the wholesale cutting of the webs has greatly reduced the in- festation. Over 12,000 square miles in the State are infested with the gypsy moth, and about 7,000 with the brown-tail moth. The latter has been spreading to new territory since 1931. NEW HAMPSHIRE The moth work in New Hampshire is in charge of the State ento- mologist. Over 8,000 square miles are infested with the gypsy moth and about 5,000 square miles with the brown-tail moth. Most of the territory from Lake Winnipesaukee south to the Massachusetts line has suffered severe and repeated defoliation from the gypsy moth. The territory directly north and northeast of the lake has also had considerable defoliation. The same areas were heavily infested with the brown-tail moth from 1931 to 1933. Since that time the infestation has been greatly reduced by control work, and also, in some sections, by winter mortality of the larvae. VERMONT In Vermont the moth work is in charge of the commissioner of agriculture, who appoints an entomologist to carry on the field work. After intensive scouting for the gypsy moth in the winter of 1933-34, the area under quarantine was reduced from about 6,000 to 4,500 square miles. The heaviest infestations are located along the Con- necticut River. Only a few brown-tail moth infestations have been found in Vermont in recent years. A survey along the eastern border of the State in 1933 and 1934 indicated a number of scattered in- festations, and this area was placed under quarantine. As a result of work done since that time no infestation by this insect has been found during the last 2 years. MASSACHUSETTS The commissioner of conservation has charge of the moth work in Massachusetts. Each infested town is required by law to select a local superintendent, whose appointment must be approved by the commissioner. Owners are required by law to keep their property free from these pests, but cannot be compelled to expend for this puruose more than $5 per year on each $1,000 assessed valuation. owns and cities must provide for proper treatment of the street trees and those in parks and on public grounds. After the amounts fixed by law are expended, financial aid may be supplied by the State. The gypsy moth at present (1937) occurs in every town in the State east of Berkshire County. It has increased in abundance over much of the infested area during the last 3 years, especially in the towns directly east of the Connecticut River. The area infested by the brown-tail moth is a little over 4,500 square miles. 36 CIRCULAR 464, U. S. DEPARTMENT OF AGRICULTURE RHODE ISLAND In Rhode Island the commissioner of agriculture has charge of the moth work, which is done under the supervision of the State ento- mologist. The gypsy moth occurs in all towns in the State. Since 1931 the infestation has increased rapidly, and in 1934 much defolia- tion was noted. The conditions approximate those which the State of Massachusetts has encountered for many years. No brown-tail moth infestation had been found for a number of years prior to 1936, when a few webs were found in two towns in the eastern part of the State. CONNECTICUT In Connecticut the work is in charge of the State entomologist. The brown-tail moth has not been found in this State for several years. The area infested by the gypsy moth is now about 3,000 square miles. During the past 3 years the infestation has increased noticeably in some localities in the eastern part of the State. NEW YORK In New York State the work is supervised by the Department of Conservation, which is cooperating with the Federal Bureau of Ento- mology and Plant Quarantine in the New York section of the barrier zone.