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S1-53 Digitized by the Internet Archive in 2010 with funding from University of Illinois Urbana-Champaign http://www.archive.org/details/dutchelmdiseasei53cart — my =. *} ge . ei 7 ce ? ast ag — - ~ — aah ai * ¥ \ ‘3 Dutch Elm Disease in Illinois J. Cedric Carter Circular 53 ‘ Now 29” psy THe OOO 5 tus NOVZD UNIVERSITY OF ILL Mat . vi ILLINOIS NATURAL HISTORY SURVEY ES AT a WD Nee Be og ee RA ee a Gh STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION BOARD OF NATURAL RESOURCES AND CONSERVATION JoHN C. Watson, Chairman; THOMAS PARK, Ph.D., Biology; L. L. Stoss, Ph.D., Geology; RoGER ADAms, Ph.D., D.Se., Chemisiry; RoBERT H. ANDERSON, B.S.C.E., Engineering; CHARLES E. OLMSTED, Ph.D., Forestry; W. L. Everitt, E.E., Ph.D., Representing the President of the University of Illinois; ROGER E. BEYLER, Ph.D., Representing the President of Southern Illinois University. NATURAL HISTORY SURVEY DIVISION, Urbana, Illinois SCIENTIFIC AND TECHNICAL STAFF GEORGE SPRUGEL, JR., Ph.D., Chief HERBERT H. Ross, Ph.D., Assistant Chief ROBERT O. WATSON, B.S., Assistant to the Chief ALICE P. CAMPBELL, B.A., Secretary to the Chief Section of Economic Entomology WILLIAM H. LUCKMANN, Ph.D., Entomologist and Head Wiis N. Bruce, Ph.D., Entomologist WAYNE L. Howek, Ph.D., Entomologist RONALD H. MBYER, Ph.D., Associate Entomologist JAMES E. APPLEBY, Ph.D., Associate Entomologist Rospert D. PAuscu, Ph.D., Assistant Entomologist RALPH E. SECHRIEST, Ph.D., Assistant Entomologist DELMAR B. BROERSMA, Ph.D., Assistant Entomologist JosepH V. MaAppox, Ph.D., Assistant Entomologist EDWARD J. ARMBRUST, Ph.D., Assistant Entomologist CLARENCE E. WHITE, B.S., Research Assistant RANU BANERJEE, B.A., Technical Assistant DouG.as K. SELL, B.S., Technical Assistant SuB E. WATKINS, Junior Scientific Assistant Howakp B. Petty, Ph.D., Entomologist, Extension STEVENSON Moors, III, Ph.D., Entomologist, Extension RoscoE RANDELL, M.S., Technical Assistant, Extension STANLEY RACHESKY, M.S., Technical Assistant, Extension DoNALD E. KUHLMAN, M.S., Technical Assistant, Exten- sion AMAL C. BANERJEE, Ph.D., Research Associate JEAN G. WILSON, B.A., Research Associate MARGARET J. JENSEN, M.S., Research Assistant KEUN S. PARK, M.S., Research Assistant KETURAH REINBOLD, M.S., Research Assistant Section of Faunistic Surveys and Insect Identification HERBERT H. Ross, Ph.D., Assistant Chief and Head MILTON W. SANDERSON, Ph.D., Taxonomist LEwis J. STANNARD, JR., Ph.D., Taxonomist Puitip W. SMITH, Ph.D., Taxonomist WALLACE E. LABERGE, Ph.D., Associate Taxonomist DONALD W. WEBB, M.S., Assistant Taxonomist JOHN D. UNzICKER, Ph.D., Assistant Taxonomist BERNICE P. SWEENEY, Technical Assistant BEss C. WHITE, A.B., Technical Assistant Section of Aquatic Biology GEORGE W. BENNETT, Ph.D., Aquatic Biologist and Head WILLIAM C. STARRETT, Ph.D., Aquatic Biologist R. WELDON LARIMORE, Ph.D., Aquatic Biologist D. HoMER Buck, Ph.D., Associate Aquatic Biologist ROBERT C. HILTIBRAN, Ph.D., Associate Biochemist DONALD F. HANSEN, Ph.D., Associate Aquatic Biologist WILLIAM F. CHILDERS, Ph.D., Associate Aquatic Biologist DENNIS L. DooOLEy, Technical Assistant MARY FRANCES MARTIN, Technical Assistant C. RUSSELL ROsE; Field Assistant CHARLES F. Tuoits, III, B.A., Research Associate STEVEN O. LOUNSBERRY, Project Assistant JON STELTER, Project Assistant CONSULTANTS: HERPETOLOGY, HoBartT M. SMITH, Ph.D., Professor of Zoology, University of Illinois; PARASITOLOGY, NORMAN D. LEVINE, Ph.D., Professor of Veterinary Parasitology and Veterinary Research, University of Illinois; W1LD- LIFE RESEARCH, WILLARD D. KuimstRA, Ph.D., Professor of Zoology and Director of Cooperative Wildlife Research; Southern Illinois University; STATISTICS, HORACE W. NORTON, Ph.D., Professor of Statistical Design and Analysis University of Illinois. Section of Applied Botany and Plant Pathology J. CEDRIC CARTER, Ph.D., Plant Pathologist and Head ROBERT A. EVERS, Ph.D., Botanist JUNIUS L. FORSBERG, Ph.D., Plant Pathologist EUGENE B. HIMELICK, Ph.D., Plant Pathologist R. DAN NEELY, Ph.D., Plant Pathologist D. F. SCHOENEWEISS, Ph.D., Associate Plant Pathologist J. LELAND CRANE, Ph.D., Assistant Mycologist WALTER HARTSTIRN, Ph.D., Assistant Plant Pathologist GENE E. REID, Technical Assistant BeETTy S. NELSON, Technical Assistant Section of Wildlife Research GLEN C. SANDERSON, Ph.D., Wildlife Specialist and Heaa FRANK C. BELLROSE, B.S., Wildlife Specialist HAROLD C. HANSON, Ph.D., Wildlife Specialist RICHARD R. GRABER, Ph.D., Wildlife Specialist RONALD F. LaAsBisky, M.S., Associate Wildlife Specialist WILLIAM R. EDWARDs, M.S., Associate Wildlife Specialisi W. W. CocHRAN, JR., B.S., Assistant Wildlife Specialist | ROBERT E. GREENBERG, M.S., Research Associate | HELEN C. ScuuLtz, M.A., Technical Assistant , CAROLYN S. Evers, B.A., Technical Assistant | ROBERT D. CROMPTON, Field Assistant | Mary ANN JOHNSON, Technical Assistant | RONALD E. DUZAN, Technical Assistant WILLIAM L. ANDERSON, M.A., Research Associate JAMES A. BAILEY, Ph.D., Research Associate JACK A. Euuis, M.S., Research Associate STANLEY L. ETTER, M.S., Research Associate WILLIAM J. FRANCIS, Ph.D., Research Associate G. BLAIR JOSELYN, M.S., Research Associate RONALD L. WESTEMEIER, B.S., Research Associate JEFFREY C. HANSON, M.S., Research Assistant KEITH P. THOMAS, M.S., Research Assistant ELEANORE WILSON, Project Assistant Section of Publications and Public Relations OWEN F. GLISSENDORF, M.S., Technical Editor and Heaa ROBERT M. ZEWADSKI, M.S., Associate Technical Editor PHYLLIS K. BONFIELD, B.J., Assistant Technical Editor WILMER D. ZEuR, Technical Photographer RICHARD M. SHEETS, Technical Illustrator Technical Library Doris F. Dopps, B.A., M.S.L.S., Technical Librarian Administration and Service ROBERT O. WATSON, B.S., Assistant to the Chief GRACE C. FINGER, B.S., Financial Records MELVIN E. SCHWARTZ, Property Control, Trust Accounts J. WILLIAM Lusk, Mailing and Distribution Services JAMES B. CurTIS, Greenhouse Superintendent RoBERT O. ELuis, Garage Superintendent CONTENTS SrtiDs Tal (CHG Le Se See ee eee ee ee re 5 FROMEENCBPNSEASCESPREACS Be o1r see Fo id oe sera as see Sk rants Sg dae 9 UTEECE (CETTHTEGSS peau lense iene 9 Hee AG at Trarsiniasion. 2 ee ee ne Paneer eee ae eee eens (7 Susceptibility of Different Species. BP eye Aa Atay Soon ae oe ea aN ae RN WIseASeROOniLOWEEACHCeSs. 6.4... 5 hc sc nok oe ane usk Sec been phan cams won 13 SHDMES ATOM. 5 oft chee OSI RE ee ee eee ee pte Oe (3 Spraying. . A oh GRRE, 3 ANRC An RO Eee Meee grt tr Re. > em 15 Kelis Grafted Roots. ERAS een BES ee ro ers eel ee rte oni) Treatments. .<.--- ces. Ee, 17 The Dutch Elm Disease Lesson.......... Se at Seer ee oly AM Aad. 1 ¢ SOME This circular, printed by authority of the State of Illinois (Ch. 727 IRS, Par. 58.21), is a contribution from the Section of Applied Botany and Plant Pathology of the Illinois Natural History Survey. URBANA 44697—6 M— 514 OCTOBER, 1967 1 over the Uni- yana (above) are gone. The area has been re- planted (below) with other species of deciduous trees. 1 { -like are al d a cathedr at forme s th ‘an elm Americ ately The st versity of Illinois broadwalk in Urt Dutch Elm Disease in Illinois J. Cedric Carter UTCH ELM DISEASE has killed millions of elm trees since its introduction into the United States. It was discovered at Cleveland and Cincinnati, Ohio in 1930, and in Connecticut, Mary- land, New Jersey, and New York in 1933. Although the disease ap- peared at Indianapolis, Indiana in 1934, it was not found in Illinois and Michigan until 1950. Since 1950 the disease has spread rapidly throughout the midwestern states and by 1966 was present in 30 states, the District of Columbia, and three provinces of Canada. It occurs from the Atlantic Coast west to Nebraska and Colorado and from Georgia, Arkansas, and Oklahoma north to the Canadian prov- inces of Ontario, Quebec, and New Brunswick. By 1959 the disease was found in every county in Illinois. Some Illinois cities lost nearly all of their elms to Dutch elm disease in a period of 10-12 years. After a rapid buildup of the disease during an initial period of 5-7 years, losses have ranged from 15 to 20 percent of the existing elm population each year. These losses have continued until about 95 percent of the elms once present have been killed. This rate of dying means that, in a city that once had an elm population of 20,000 trees, 19,000 have been killed. The cost of removing 19,000 elms at $75 per tree is $1,425,000, and removal cost of $75 per tree is less than the average paid by many cities. A control program that holds the annual loss of elms to 2 percent or less of the current elm population is desirable because it avoids exorbitant tree removal costs, prevents devaluation of real estate, and ensures the continued enjoyment of elms as shade trees. SYMPTOMS AND CAUSE The first noticeable symptoms of Dutch elm disease are wilting, curling, and yellowing of leaves on one or more branches, a condi- tion often called “‘flagging.’’ These symptoms are followed by dying and browning or premature falling of leaves, and death of affected branches. Some affected trees first show wilting of leaves on one or a few branches (Fig. 1), followed by wilting of leaves on additional branches and finally death of the affected trees. Elms affected in this manner in early summer may die during the same growing sea- son. Those affected in late summer may die during the winter, soon after leaves appear in the spring, or slowly over a period of a year or more. Other elms may show foliage wilt on most or all of their branches at one time and die within a few weeks (Fig. 2). Trees that 5 6 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 53 Fig. 1.—The earliest visible symptoms of Dutch elm disease are the wilting, curling, and yel- lowing of leaves on one or a few branches. On this tree the wilted and curled leaves are evident on the branch at the left. wilt and die rapidly probably became infected during the previous erowing season, at which time they would have shown no wilt symp- toms or only limited and relatively inconspicuous symptoms. Brown streaking develops in the sapwood of diseased branches. It appears mostly in the springwood of the current-season growth. In a cross-section of a branch, browning may appear as a series of dots in a single wood ring (Fig. 3) or the dots may be so abundant that the entire wood ring appears brown. In branches on which leaves wilt before summerwood is produced, the discoloration is usually conspicuous as fine streaks on the surface of the wood when the bark is carefully peeled from the diseased branch (Fig. 4). The outer sur- face of sapwood on trunks may also be brown (Fig. 5). The presence of brown discoloration in young sapwood is used in the field as a diagnostic symptom of Dutch elm disease. Although several wilt diseases of elm cause similar browning of young sap- wood, trees showing this discoloration in areas where Dutch elm disease occurs are most likely affected with Dutch elm disease. How- ever, if the presence of the fungus in the tree must be determined, it is necessary to make laboratory tests of specimens from the diseased tree. With these tests the organism involved is isolated and the spe- cific disease present is determined. However, in some instances the DUTCH ELM DISEASE IN ILLINOIS 7 fungus is not obtained by a culture test even though the tree is af- fected by the disease. Dutch elm disease is caused by the fungus Ceratocystis ulmi (Buisman) C. Moreau. In living trees this fungus grows in the sap- wood, most frequently that of the current season, and causes the Fig. 2.—Some affected elms, such as this one, show foliage wilt on most or all of their branches at one time and die rapidly. Fig. 3.—In cross-section, the brown streaking caused by Dutch elm disease may appear as a series of dots, as shown here, or as a solid brown band in a single wood ring. 8 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 53 brown discoloration (Fig. 3, 4, and 5) described above. In dying and dead trees invaded by bark beetles, the fungus grows in the galleries made by the larvae or grubs of the beetles (Fig. 6). These galleries are in the inner layers of bark with groovings on the outer surface of the sapwood. Fig. 4.—The removal of bark from branches that wilt in early summer usually reveals long, broken, brown streaks on the surface of the sap- wood. Fig. 5.—Brown discoloration of the outer surface of sapwood on the trunks of wilting elms is a common symptom of Dutch elm disease. DUTCH ELM DISEASE IN ILLINOIS 9 Fig. 6.—Galleries in which the smaller European elm bark beetles lay eggs are parallel to the grain of the bark and wood; they are few and relatively large. Galleries made by the larvae or grubs of this bark beetle are perpendicular to the grain of bark and wood; they are numerous and relatively small. When the bark is removed, the white larvae are conspicuous at the tips of many of these galleries. HOW THE DISEASE SPREADS The Dutch elm disease fungus is transmitted to healthy elms in two ways: (1) by insects, (2) through roots that become grafted to- gether between diseased and healthy trees. Insect Carriers The insects that transmit the Dutch elm disease fungus in the United States are the smaller European elm bark beetle, Scolytus multistriatus (Marsham), and the native elm bark beetle, Hylurgopi- nus rufipes (EKichhoff). The smaller European elm bark beetle (Fig. 7), principal car- 10 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 53 rier of the fungus, feeds mainly in crotches of 1- and 2-year-old twigs (Fig. 8). The fungus spores (Fig. 9), deposited in the feeding wounds (Fig. 10), grow and spread in the vessels of the young sapwood. In- fection occurs mainly in May and early June, when the springwood vessels are adjacent to or near the inner surface of the bark. In time the leaves on branches invaded by the fungus wilt and the branches die. In Illinois there are two broods of the smaller European elm bark beetle each year. The first brood of adult beetles (which have overwintered as larvae in elm bark) starts emerging in May and con- tinues to emerge until mid-July. Emerging beetles make small holes in the bark (Fig. 11). Peak emergence of this brood occurs in mid- June. The second brood, which develops in 5-7 weeks from eggs laid Fig. 7. Adult of the smaller Eu- ropean elm bark beetle. It is shiny, dark reddish brown, and about one- eighth inch long. Fig. 8.—Close-up of a bark beetle feeding in the crotch of a young shoot. Spores of the Dutch elm disease fungus adhere to the body of this beetle. DUTCH ELM DISEASE IN ILLINOIS 11 Fig. 9.— Magnified view of fungus that oe Dutch elm disease. : | hese colorless, oval Se Ron LINN SS" ~ spores, produced on short Tr =) \ / fungus strands, are not . "e f Seuers ne p/ x visible to the naked eye. ~\ f )} Os wets * | } ‘ io 4 tas ar “ft % Of ae FT EN * f “ halal Rien