SB434 Dutch Elm Disease and Its

AGRICULTURAL EXPERIMENT STATION KANSAS STATE UNIVERSITY OF AGRICULTURE AND APPLIED SCIENCE - MANHATTAN

GLENN H. BECK, Director Dutch Elm Disease and Its Control in Kansas 1 PADY 3 4 INTRODUCTION H. E. THOMPSON,2 S. M. and R. A. KEEN

Dutch elm disease was discovered in Kansas in October, 1957, in Kansas City, Kan., and has been spreading rapidly since then. This information was prepared because the disease attacks American elm, an important shade and ornamental tree. The disease is caused by a fungus that is carried from elm to elm by bark beetles. Control measures are aimed at destroying the bark beetle. Although the control procedures recommended will not completely prevent the spread of Dutch elm disease, a community program including all phases of control will reduce the annualNEMAHA loss BROWN of elms to a reasonable level.

JACKSON

1957

�RSON MARION 1958

HARVEY 1960

1959

Fig. 1. Map of known locations of Dutch elm disease in Kansas. 1. Contribution No. 783, Department of Entomology; No. 571, Department of Botany and Plant Pathology; and No. 310, Department of Horticulture, Kansas Agricultural Experiment Station, Manhattan. 2. Assistant professor, Department of Entomology. 3. Professor, bead, Department of Botany and Plant Pathology. 4. Associate professor, Department of Horticulture. (3) Dutch Elm Disease and Its Control in Kansas 1 PADY 3 4 INTRODUCTION H. E. THOMPSON,2 S. M. and R. A. KEEN

JACKSON

1957

�RSON MARION 1958

HARVEY 1960

1959

Fig. 1. Map of known locations of Dutch elm disease in Kansas. 1. Contribution No. 783, Department of Entomology; No. 571, Department of Botany and Plant Pathology; and No. 310, Department of Horticulture, Kansas Agricultural Experiment Station, Manhattan. 2. Assistant professor, Department of Entomology. 3. Professor, bead, Department of Botany and Plant Pathology. 4. Associate professor, Department of Horticulture. (3) I""I..V'L\.LVUL.LUL\.rt.L .a..:.,.Ar.C,,L\.l.1.V.l.C...L�.l lJJ..rt.J..lU.1.� .tlULLETIN 404: LJUTCH J:!.LM LJISEASE

---- :rc".��i:c ( Fig. 2). The fungus continues to History of the Disease WILTINI live in dead trees and bark beetles continue their tunneling. The fungus First described in Holland in 1921, grows and sporulates especially in its the disease marched across Europe in /,�, .., I :�:; ..,,...... ,... Graphium stage with its sticky masses 10 years. In 1930 it was found on SPRING SUMMER of spores ( Fig. 5). In May when four dead trees in Cleveland, Ohio, ,. .. rn•• the beetles emerge they carry the and by 1933, in New York, New Jer ADULTI U,\1�\S ____.,_ ___ _ spores to healthy trees and infect LARVAE sey, Connecticut, Pennsylvania, and IN DEAD JWOOi) them. Later beetle emergences are Maryland. By 1957 it was found in FALL Kansas City, Mo. Three positive col lections of the disease were made in Wyandotte and Johnson counties, Kansas, in October, 1957. In 1958 it ,uNeus OVERWINTERS IN was found in Leavenworth and Miami IROOO ULLERIU counties; during 1959, in Franklin, Douglas, Lyon, Cherokee, and Mont Fig. 3. Seasonal relationship between gomery counties; during 1960, in life history of the smaller European elm Atchison, Anderson, Allen, Bourbon, barkcause beetle Dutch and elmDutch disease elm disease. 6 but only Crawford, Linn, Neosho, Shawnee the first two are important in the U.S. counties ( Fig. 1). There is every Both grow, in dead elm wood, and indication that the disease is rapidly particularly in the tunnels made by increasing in the eastern third of Kan the beetles. Spores stick to beetles sas. It is present from the Atlantic and can live on them 3 months at 10- 0 coast west to Kansas, Nebraska and 20 C. and for 2 years in fresh frozen Oklahoma, and from eastern Quebec Fig. 2. Infected tree near Osawatomie beetles. Kansas, shows typical symptoms of Dutch Infection takes place only through and Ontario to the southeastern states. elm disease. The limb in the center already is dead; the left limb has wilted leaves and wounds made by bark beetles in May Symptoms of the Disease partial defoliation, while the right limb is ( Fig. 4a). Healthy bark does not wilting. The disease has since spread to Dutch elm disease is impossible to become infected. When beetles leave theproof elms of inthe the disease. background. Where the dis identify positively by sight, but its infected elm wood and fly to healthy ease is unknown, the fungus must be symptoms include: elms, they carry the spores with them. isolated to be sure the tree died from As they burrow into the bark and Dutch elm disease. wood, the spores are deposited in the a. Many dead branches on a tree or 5 a portion of a tree. Life Cycle of the Fungus tissues of the tree and immediately b. Leaves wilting, frequently turning start to grow. The fungus develops yellow or brown, and falling off early Dutch elm disease is the result of ( Fig. 2). . ( Note: Other diseases, an unusual partnership, a beetle rapidly and grows into the bark, the drouth, and bark beetles also may cambium, and the wood. When the cause this.) working with a fungus ( Fig. 3) that c. Weak growth of new branches. parasitizes elm trees but does not fungus is present in the large vessels d. Brownish coloring of outer rings of of spring wood, spores are produced the wood. ( Occasionally this symp harm the beetles. The beetles carry and carried rapidly up into the Piecestom doesof suspected not appear; elms also, otherare culdis fungus spores from infected wood to eases may cause browning.) branches where they infect new wood tured in a laboratory to determine if healthy trees. After the spores are in and cause it to turn a brownish color the Dutch elm disease fungus is pres troduced into the tissues by the Fig. 4a (left). Beetles feeding through ( Fig. 4b). A limb may wilt and die wounds such as this, introduce the Dutch ent. The fungus also may be isolated beetles, infection occurs. or the entire tree may die suddenly elm disease fungus into healthy tree. from beetles and tunnel debris. A Three kinds of infectious spores (Courtesy of Dept. of Entomology, Cornell University.) tree dying with beetles present is not Fig. 4b (right). Infected sapwood be 6. These are referred to as the Graphium, comes discolored around the infected sap 5. Ceratocystis ulmi (Buis.) Moreau. Cephalosporium, and Ceratocystis stages. conducting vessels. AGRICULTURAL .t;XPERIMENT STATION J:3ULLETIN 4:34: DUTCH ELM DISEASE 7 / tion emerges as adults early in July. ... "'l"UPA A third complete generation emerges I in mid-September. It is larvae pro ""'-' \AOut.T SPRING SUMMER duced by this generation that over ( \ winter under the bark. --- ... The life history of the native elm bark beetle is more complex but sim WINTER FALL I ilar to that of the smaller European elm bark beetle. Native elm bark beetles leave fungus-infected breed Fig. 5. Spore-bearing heads of the Fig. 6. This tiny one-eighth inch long ing wood in the fall and overwinter as Graphium stage of the Dutch elm disease beetle is the principal carrier of Dutch elm spore-bearing adults in the bark of fungus growing in an elm bark beetle tunnel. disease in Kansas. healthy trees. In late April, these adults tunnel to the sapwood where less likely to cause infection because fungus while feeding on small Fig. 7. Life history of the smaller European summer wood has covered theparasite, large branches and twigs of healthy trees. Hy elm bark beetle. the spores are deposited. vessels of the spring wood. Then they go, taking fungus spores Sanitation Besides being a vigorous with them, to weakened or dying ing and to dying or weakened elm the Dutch elm fungus can live sapro trees to breed. Trees weakened by wood in which they construct new Since beetles spread the fungus phytically on dead elm tissues (Fig. drouth and disease are especially at galleries and lay eggs. This genera- from infected to healthy wood by 3). This means that once it kills a tractive to bark beetles. They attack tree, it may survive from 6 to 12 such trees, tunnel through the bark months in dead wood and occasion to the surface of the sapwood, and allybeetles for may2 years. carry the spores to dead thus infect them with spores. Dutch elmIt logsis importantand trees to recognize that elm disease also spreads by root grafts. Roots from adjacent elm trees form and these may har natural unions through which the fun bor tremendous populations of both gus passes. beetles and spores. Dead elm wood Life Histories of Elm Bark Beetles is thus like an arsenal with ammuni tion (spores) and missiles (bark The smaller European elm bark beetles). beetle produces three generations each year (Fig. 7). In September, How the Disease Spreads adult females lay eggs in maternal Dutch elm disease in Kansas is galleries ( Fig. 8 ). During the fall,

spread by the smaller8 European elm after the eggs hatch, the larvae de bark beetle 7 ( Fig. 6) and the native velop in the tunnels they bore under elm bark beetle. The smaller Euro the bark. Late in the fall, as full pean elm bark beetle has almost elim grown larvae, they tunnel out into the inated the native elm bark beetle in outer bark, make a round cell, and Kansas during the last 10 years. spend the winter there. Early in April The habits of the two species of the larvae transform into pupae, and bark beetles differ, but the way they late in April the adults begin tunnel Hy Fig. 8. Elm bark beetle tunnels on inner surface of bark and outer surface of wood. infect healthy trees is the same. ing out. As soon as they emerge, they (a) (left) An adult female has tunneled through the bark and is constructing a maternal 7. Marsh. Spore-bearingScolyttU multistriatus beetles introduce the to nearby healthy elms and feed in gallery parallel with the grain of the wood; (b) one week later the gallery is extended over 8, HylurgopintU ,ufipea Eichh. an inch and eggs are laid in niches along each side of the maternal gallery; (c) even before twig crotches. the female completes ovipositing, eggs laid earlier hatch out young larvae that tunnel In a few days they finish their feed- away at right angles; (d) a nearly completed bark beetle gallery presents its typical pattern. 8 AGRICULTURAL �XPERIMENT :STATION .l:HJLLETIN 'iu':I:: .LIUTCH .l:'.-i:M .UISEASE carrying spores to healthy trees, the where they emerge to feedi�g places, smaller amount of a more concen first step in preventing Dutch elm dis they may Hy considerably farther in trated mixture. iost practical con Studies are being made to give trees ease from spreading is to kill bark search of breeding material. Healthy centrate is 12 per cent DDT. At this immunityPreventing from Dutch the Disease elm disease beetles. Overwintering larvae should trees should be protected annualiy concentration, one gallon of spray and to eradicate the disease after it be destroyed between October 1 and with a thorough dormant application mixture contains one pound of DDT. has appeared. More research is April 1 by burning or burying at least of DDT emulsion, covering the tree Two to 2½ gallons of 12 per cent DDT needed- as both are promising, but six inches deep all elm wood contain from twigs to trunk base. This spray emulsion satisfactorily covers a 50- not enough information is available ing them. must be applied during the dormant foot elm tree. Too much of this con at present to make recommendations. Destroying infested elm wood dur season to insure a heavy deposit of centrated spray mixture will kill ing the summer eliminates many adult DDT early in the spring when the buds and small twigs. bark beetles that would produce the bark beetles emerge. It may be ap Repeated dormant sprayings with Fertilizing, irrigation, and pruning General Tree Care overwintering brood. During drouth plied any time during the winter and DDT may allow injurious populations increase the health and vigor of elms. years weakened trees attacked by early spring when temperatures are of insects and mites to develop. Sum Elm roots are relatively shallow and ° many bark beetles for breeding would above 32 F. The heaviest and most mer sprays of DDT are not recom compete directly with a lawn for not survive. Where native elm bark effective deposit will be present when mended because bark beetle infec water and nutrients. Trees require beetles spread Dutch elm disease, the bark beetles attack if the spraying tion takes place primarily in the the same kinds of fertilizer as field larvae that would emerge as adults in is done in late winter or early spring spring; but sprays to control mites, crops. For most of Kansas, nitrogen October must be killed in August and just before leaves break out. Sprays aphids and fungus diseases may be and phosphorus are needed with September. applied as early as November, how applied as needed. Too often sanitation programs fail ever, have given good protection. DDT is poisonous to humans, warm potash added in southeastern Kansas. because they ignore elm wood that Early application also reduces dam blooded animals and birds. Precau County agents have information on has been cut and stacked or has died age to birds and other wildlife. tions on the label should be followed. fertilizer recommended in your lo from causes other than Dutch elm dis DDT may be applied with a high Aerial spraying will not deposit cality. The usual rate of fertilizing ease. Such wood holds and produces pressure, high-gallonage hydraulic enough to protect elms from elms is ½ pound of actual nitrogen per spores that are spread by the new sprayer ( Fig. 9a) or with a mist bark beetles. inch of trunk diameter. A tree 10 generation of beetles as they emerge. blower ( Fig. 9b). Either must have DDT It can not be stressed too strongly that capacity to reach tree tops. To reach any elm wood capable of breeding the top of a 50-foot elm tree with a bark beetles can serve as a reservoir high-pressure hydraulic sprayer it for Dutch elm disease infection. must deliver at least 20 gallons per Furthermore, destroying breeding minute with 600 pounds pressure. A material means eliminating any possi mist blower must move at least 10,000 bility of bark beetles emerging from cubic feet of air per minute to reach it. Storing elm for fire wood in a 50 feet high. cellar or a shed will not prevent bark DDT for bark beetle control is beetles from entering or emerging available commercially as 25 per cent from it. Stored elm wood should and 32 per cent. The 2 per cent emul have its bark stripped and burned. sion needed in a hydraulic sprayer is A less effective control is spraying the 8 gallons of 25 per cent concentrate bark with a 2 percent DDT solution added to 92 gallons of water or 7 in fuel oil. gallons of 32 per cent concentrate added to 93 gallons of water. Trees are sprayed until the material starts to run off. Spraying to Protect Valuable Although bark beetles usually do Mist blowers using air to carry the Shade Trees not Hy more than 1,000 feet from insecticide to trees apply a much Fig. 9. Spraying elm trees during the dormant season to protect them from bark beetle feeding in the spring; (a) (left) spraying with a high-pressure, high-gallonage hydraulic sprayer; (b) (right) spraying with a mist blower. 8 AGRICULTURAL �XPERIMENT :STATION .l:HJLLETIN 'iu':I:: .LIUTCH .l:'.-i:M .UISEASE carrying spores to healthy trees, the where they emerge to feedi�g places, smaller amount of a more concen first step in preventing Dutch elm dis they may Hy considerably farther in trated mixture. iost practical con Studies are being made to give trees ease from spreading is to kill bark search of breeding material. Healthy centrate is 12 per cent DDT. At this immunityPreventing from Dutch the Disease elm disease beetles. Overwintering larvae should trees should be protected annualiy concentration, one gallon of spray and to eradicate the disease after it be destroyed between October 1 and with a thorough dormant application mixture contains one pound of DDT. has appeared. More research is April 1 by burning or burying at least of DDT emulsion, covering the tree Two to 2½ gallons of 12 per cent DDT needed- as both are promising, but six inches deep all elm wood contain from twigs to trunk base. This spray emulsion satisfactorily covers a 50- not enough information is available ing them. must be applied during the dormant foot elm tree. Too much of this con at present to make recommendations. Destroying infested elm wood dur season to insure a heavy deposit of centrated spray mixture will kill ing the summer eliminates many adult DDT early in the spring when the buds and small twigs. bark beetles that would produce the bark beetles emerge. It may be ap Repeated dormant sprayings with Fertilizing, irrigation, and pruning General Tree Care overwintering brood. During drouth plied any time during the winter and DDT may allow injurious populations increase the health and vigor of elms. years weakened trees attacked by early spring when temperatures are of insects and mites to develop. Sum Elm roots are relatively shallow and ° many bark beetles for breeding would above 32 F. The heaviest and most mer sprays of DDT are not recom compete directly with a lawn for not survive. Where native elm bark effective deposit will be present when mended because bark beetle infec water and nutrients. Trees require beetles spread Dutch elm disease, the bark beetles attack if the spraying tion takes place primarily in the the same kinds of fertilizer as field larvae that would emerge as adults in is done in late winter or early spring spring; but sprays to control mites, crops. For most of Kansas, nitrogen October must be killed in August and just before leaves break out. Sprays aphids and fungus diseases may be and phosphorus are needed with September. applied as early as November, how applied as needed. Too often sanitation programs fail ever, have given good protection. DDT is poisonous to humans, warm potash added in southeastern Kansas. because they ignore elm wood that Early application also reduces dam blooded animals and birds. Precau County agents have information on has been cut and stacked or has died age to birds and other wildlife. tions on the label should be followed. fertilizer recommended in your lo from causes other than Dutch elm dis DDT may be applied with a high Aerial spraying will not deposit cality. The usual rate of fertilizing ease. Such wood holds and produces pressure, high-gallonage hydraulic enough to protect elms from elms is ½ pound of actual nitrogen per spores that are spread by the new sprayer ( Fig. 9a) or with a mist bark beetles. inch of trunk diameter. A tree 10 generation of beetles as they emerge. blower ( Fig. 9b). Either must have DDT It can not be stressed too strongly that capacity to reach tree tops. To reach any elm wood capable of breeding the top of a 50-foot elm tree with a bark beetles can serve as a reservoir high-pressure hydraulic sprayer it for Dutch elm disease infection. must deliver at least 20 gallons per Furthermore, destroying breeding minute with 600 pounds pressure. A material means eliminating any possi mist blower must move at least 10,000 bility of bark beetles emerging from cubic feet of air per minute to reach it. Storing elm for fire wood in a 50 feet high. cellar or a shed will not prevent bark DDT for bark beetle control is beetles from entering or emerging available commercially as 25 per cent from it. Stored elm wood should and 32 per cent. The 2 per cent emul have its bark stripped and burned. sion needed in a hydraulic sprayer is A less effective control is spraying the 8 gallons of 25 per cent concentrate bark with a 2 percent DDT solution added to 92 gallons of water or 7 in fuel oil. gallons of 32 per cent concentrate added to 93 gallons of water. Trees are sprayed until the material starts to run off. Spraying to Protect Valuable Although bark beetles usually do Mist blowers using air to carry the Shade Trees not Hy more than 1,000 feet from insecticide to trees apply a much Fig. 9. Spraying elm trees during the dormant season to protect them from bark beetle feeding in the spring; (a) (left) spraying with a high-pressure, high-gallonage hydraulic sprayer; (b) (right) spraying with a mist blower. AGRICULTURAL �XPERIMENT ;:,TATION lU .tlULLETIN 404: UUTCH 1!.LM UISEASE .l.L

10 11 12 13 inches in diameter five feet above the pery elm, rock elm, winged elm, danger that elms will disappear from and dying of trees from the tops ground requires 100 pounds of 5-10-5 September elm,15 cedar elm.14 Euro our landscapes is more from not being downward follows. or 50 pounds of 10-20-0 or 10-8-6. pean elms are16 susceptible, although17 planted than from all of them dying The only way the fungus is carried The amount of phosphorus and pot one species carries some resistance. from Dutch elm disease. from infected wood to healthy trees ash is not critical. The fertilizer Siberian elm18 and Chinese elm In Connecticut the Dutch elm dis is by elm bark beetles. Beetles breed ( the Asiatic species) are resistant. in infected dead wood and fly to should be applied in holes in the soil ease appeared in 1933, and spread Water elm and Zelkova are suscep slowly to every county in that state. healthy trees to feed, carrying spores punched with a crowbar or drilled tible. By 1940 it was thought that the elm of the fungus with them. with an auger on either side of the Hybrids of American and resistant was doomed; today, however, the pic Dutch elm disease is prevented drip line of the tree. The drip line is European and Asiatic elms are now ture has changed. Recent research from spreading by controlling elm the line where the outermost leaves being studied to develop resistant findings, including new chemicals for bark beetles. The principal step is to drip or the shadow line if the sun strains.15 At present some resistant control, and resistant varieties, have eliminate elm bark beetles by destroy were overhead. About one pint of selections from the European spe resulted in an optimistic outlook. ing dead and dying elm wood. fertilizer is placed in each hole. Sol cies are available. The commonest Healthy trees can be protected. Healthy elms may be further pro uble fertilizer may be dissolved in one is Christine Buisman which is now Summary tected by applying a heavy dormant water and forced into the soil with a being grown in this country. It also DDT spray. This spray gives maxi water lance on a power sprayer. resists phloem necrosis. Dutch elm disease, found for the mum protection when applied in the first time in Kansas in 1957, has spread Trees usually get enough water Shade trees to replace elms include spring just before the leaves burst through the eastern third of the state from a well watered lawn. In water these large trees for parks and large from their buds. However, when by 1960. Unless strenuous control ing it is best to soak 12 to 18 inches estates: pin oak, American planetree necessary, a spray applied during No programs are practiced, this rate of deep. Shallow watering wastes water (Sycamore), bur oak, cottonless cot vember may give adequate protection. spread can be expected to continue by increasing evaporation. The root tonwood, white oak, tuliptree, linden, The conscientious application of and to intensify. spread of an elm usually exceeds its Scotch pine, Austrian pine, baldcy these control measures will not eradi Dutch elm disease is caused by a branch spread. press, pecan, black oak, sugar maple, cate or eliminate the spread of Dutch fungus that prevents the flow of water First object in pruning elms is to green ash, and hackberry. Medium elm disease, but it will keep the loss remove all dead, dying, and broken trees include: red, chinkapin and from the roots to the leaves. Wilting of elms to a reasonable level. branches. Weak, shaded branches blackjack oaks, honeylocust, Norway should be removed. Tops of trees maple, sugar hack berry, Japanese pa should not be pruned severely because godatree, ginkgo, sweetgum, river that decreases tree growth and starves birch, horsechestnut, black sugar maple, and London planetree. roots and trunk as food is used to PRINTED IN THE STATE PRINTING PLANT make new top growth, which weakens Outlook for the Future TOPEKA, KANSAS trees and makes them very susceptible I 96 I Frequently, after Dutch elm disease � to bark beetle damage. Thin wood 28-7066 pruning may be practiced in the top invades an area, plans are made of the trees to permit light to reach to eliminate elms from future plant the inner branches and the lawn ings. It is recognized that plans should be made to balance plantings below. All pruned wood should be 10. U. fulva Micro:. burned immediately ( see page 8). with11. desirableU. thomasii species(racemosa) of Sarg. trees. The 12. U. alata Micro:. 13. U. serotina Sarg. Trees for Replacement 14. U. crassifolia Nutt. 15. U. carpinifolia Gleditsch. All American species of elms9 are 16. U. pumila L. susceptible to Dutch elm disease. 17. U. paroifolia Jacq. 9. Ulmus americana L. 18. Planera aquatica Gnel. This includes the American elm, slip- AGRICULTURAL �XPERIMENT ;:,TATION lU .tlULLETIN 404: UUTCH 1!.LM UISEASE .l.L

Entomology deals with the study of insects and their near relatives. In Kansas, as in most other state and countries, insects are the most important, destructive group of animals affecting man's health and welfare. There are more species on insects than all other species of animals combined. About 16,000 different species of insects occur in Kansas and 80,000 are known from the United States and Canada; and more than 700,000 are known in the world. This does not include the closely related spiders, mites, and ticks that also are included in entomological work. About 4,500 professional entomologists are employed in the United States. Approximately 25 per cent work for the U. S. Department of Agriculture pri marily doing research and animal and plant inspection; 10 per cent for other Federal agencies such as the U. S. Public Health Service, Army, Navy, and Forest Service; and about 15 per cent for State colleges, universities, and agri cultural experiment stations, doing primarily teaching, research and extension work. Other employers are insecticide manufacturers, commercial pest control firms, privately endowed colleges and universities, museums, and private re search foundations. Entomologists may specialize in (1) "applied" entomology, which stresses insects' relation to plants and animals, including man; and/or (2) "basic" ento mology, which involves fundamental studies of behavior, classification, physiology, toxicology, and various other studies in which insects are the animals under study. Four hundred million dollars are spent annually to combat insect pests. Over 3 billion dollars in insect damage is reported annually in the United States alone. Insects are known to transmit many virus, bacteria, and fungus diseases of plants and animals, including many diseases of man. There are also beneficial insects, such as honeybees, who pollinate plants as well as produce honey and beeswax. Other beneficial insects are those that kill harmful insects. Students with a Bachelor's degree generally go into commercial pest control, sales and development work with insecticides, high school teaching, give technical assistance in research work, or do inspection work. Students with M. S. and Ph. D. degrees become professional entomologists who supervise various entomological activities and teach or do research in colleges and universities. There are about 100 full-time entomologists in Kansas who are engaged exclusively in studying insects and/or in insect control work. Several hundred others are engaged in work which is partly concerned with insects and their control. Many youth who know that they cannot become farmers would like to hear of the many opportunities in entomology. You would do them, your profession, and your country a favor by making them aware of the opportunities-both in the United States and abroad.