BLIGHTS OF LILIES AND 6ll transmit them, their host range, and varietal reactions. Until more detailed knowledge is available there is little basis for suggesting a sound program of control. Dr. Magie, in the North American Blights of Gladiolus Council Bulletin No. 20, December 1949, suggested the value of certifying planting stock of gladiolus, Lilies and comparable to the program of certify- ing white potatoes. The stocks, he wrote, might be "produced in parts Tulips of the country where disease spread is naturally light or absent." He was concerned mainly with fusarium rot C. J. Gould control, but he also mentioned virus control. Such a program would be Whether one grows tulips or lilies good if it could be put into practice. for fun or for profit—in Brooklyn, But no one knows now which areas are Keokuk, or Seattle; in the garden, favored by light spread of gladiolus field, or —he probably has viruses; more research is necessary more grief from botrytis blights than before the gladiolus industry can fol- from any other cause. low the path of the potato industry; The blights, or "fire" as they are and the number of gladiolus varieties sometimes called, are world-wide in in the trade, already enormous, is con- distribution and most prevalent in tinually augmented by the new pro- cool, moist areas. They are caused by ductions of hundreds of amateur similar, but distinct, fungi. Most com- breeders. Therefore we find less inter- mon on tulips is Botrytis tulipae. Most est in protecting the present commer- common on lilies is Botrytis el lip tica. cial varieties than in developing new blight begins with a diseased sorts. Of course the situation would or with contaminated soil in improve if breeders of gladiolus w^ould which the fungus is living on old re- take all possible care to avoid exposing mains of the tulip . As the young their seedlings to sources of infection tulip shoot pushes through the ground, so that only disease-free new varieties it becomes infected if it comes in con- might enter the trade. tact with the fungus and may be changed into a distorted, grayish- PHILIP BRIERLEY, a senior pathologist brown body covered with powdery in the Bureau of Plant Industry^ Soils, and masses of spores. Sometimes only part Agricultural Engineering, has been em- of a is diseased. Often the entire ployed by the Department of Agriculture shoot is affected. Soon the of the since ig22. nearby tulip become spotted FLOYD F. SMITH is a senior entomolo- with small, circular, yellow or brown gist in the Bureau of Entomology and dots. Many of the spots remain small Plant Quarantine. For many years he has and dry up, but others, (especially if done research on insects that affect green- the weather is cool and moist) enlarge house and ornamental plaîiis. He holds rapidly. Their color becomes a gray- degrees from Ohio State University, ish brown or brown, with a dark water- FRANK P. MGWHORTER in igjo en- soaked margin. Powdery masses of tered cooperative employment by the Oregon spores often form in the center. Agricultural Experiment Station and the These, when blown to other plants, Department of Agriculture. initiate more spots, which may become Since then he has specialised in virus dis- visible within 24 hours. eases of bulb and legume crops. Large spots near the leaf base often 6l2 YEARBOOK OF AGRICULTURE 1953 cause the leaf to break. Several spots under certain conditions according to may fuse and decay a leaf completely» tests by Neil A. MacLean at Washing- Spots on stems are similar and may ton State College. Other of also cause the stems to break. Botrytis, including B. cinérea^ can some- are very susceptible and often are times attack tulips. made unsalable by white or brown Although B. tulipae can attack spots covered with spores. Not even healthy leaves, its entrance is facili- the bulb escapes. On its outer fleshy tated by injuries from frost, hail, and scale the fungus may produce sunken, equipment. The Dutch have tried to yellow or brown craters. In them, on reduce frost injury by treating the the outer bulb husk, and on spots on to delay growth in the the upper plant parts, small, hard, until the danger is partly over. This black circular masses of the fungus artificial retarding is accomplished by may develop. Such black bodies, the storing the bulbs at approximately 70^ sclerotia, have a function somewhat F. and delaying planting until October similar to in that they enable the or November. fungus to live over winter, either on Much can be done to control the the bulb or on dead tulip parts. Then, disease in commercial fields and home when infection from the sclerotia occurs gardens by proper cultural practices: in the spring, the cycle is continued by Digging every year; not replanting the spores. tulips in the same location for at least The disease probably occurs wher- 3 years; planting so as to provide good ever tulips are grown, but it is most air circulation and low humidity by serious when conditions are cool and proper selection of site, proper spacing, moist. Consequently it is prevalent and thorough weeding; removing in the , southwestern promptly and destroying diseased , and the Pacific Northwest. shoots, old and infected flowers, and Local conditions, however, arc im- dead plant remains; and planting only portant: In western , for healthy bulbs. example, the disease is more serious in Since the original infections arise the valleys near Puyallup than it is from diseased bulbs that escape de- go miles to the north near Mount tection, it would seem logical to treat Vernon, where the plants are exposed them with a fungicide in order to to a more or less constant wind from destroy the fungus. Many treatments Puget Sound. have been tested and a few have been The method of planting tulips com- recommended, such as Uspulun and mercially in beds about 3 feet wide, as Aretan, in Europe. Such treatments practiced in Holland and some parts have not met with general success, of the United States, is more conducive however. Either they injured the bulbs to botrytis blight than is the row system or failed to control the disease ade- used in the Pacific Northwest. Not only quately. is the relative humidity higher in the Early attempts to prevent plants beds, but there is also a greater oppor- from becoming diseased by using tunity for infection. Likewise the dis- fungicidal sprays were likewise not ease is often found in gardens in massed very successful. Although copper- plantings or on plants in shaded places. containing compounds such as bor- Most, if not all, tulip varieties are deaux mixture were found capable of susceptible, but there is some variation. controlling the fungus, they often Among varieties that are very suscept- caused considerable injury to the ible are the popular William Copland, leaves and flowers. However, in New William Pitt, and Bartigon. Baronne York in 1940 L. W. Nielson and C. E. de la Tonnaye is supposed to be resis- Williamson found that silver nitrate tant. This species of Botrytis can also sprays compared favorably with the attack bulbous plants other than tulips 1.5-4.5-50 bordeaux mixture in fun- BLIGHTS OF LILIES AND TULIPS 613 gicidal action. One spray, contain- the soil level and so injure them that iag silver nitrate, manganese sulfate, the foliage above turns yellow. and hydrated lime was adopted by Spots on the flowers usually are bulb growers on Long Island. brown and in cool, moist weather Meanwhile tests in 1938 in the Neth- rapidly convert the flowers into wet, erlands had shown promising results slimy masses covered with powdery with thiram, one of the new organic- layers of spores. In warm, dry weather sulfur compounds. I tested it and the spots on leaves and flowers stop related sulfur com^pounds in compar- enlarging and dry up. With ample ison with silver and copper fungicides moisture and an optimum tempera- at the Western Washington Agricul- ture near 60^ F., however, a new spot tural Experiment Station beginning may develop within 24 hours and new in 1942. Then and later the best re- spores within a few days thereafter. sults were had with ferbam, another Given suitable moisture and temper- organic sulfur compound. Large-scale ature conditions, the cycle may repeat tests by growers in 1943 corroborated itself every few days throughout the the experimental trials. Afterwards it growing season. Meanwhile, hardened came into general use in the Pacific masses of the fungus are forming in Northwest and the Netherlands. the diseased portions. These masses, Four applications of ferbam are usu- the sclerotia, are first white and later ally enough in the Northwest, begin- black. They may be rounded, elliptical ning when the shoots are 2 to 4 inches or irregular, and one-thirty-second to tall and continuing at 7- to lo-day one-quarter inch in size. Under favor- intervals. The spraying must be ac- able conditions the sclerotia germinate companied by the prompt removal of the following spring to produce spores. infected plants as soon as detected. The fungus overwinters in at least By combining the proper cultural three ways: It can survive in the form practices and a spraying program, the of sclerotia. It can live saprophytically disease can now be conquered. in lily debris. It can survive in the basal rosettes of leaves of such lilies BOTRYTIS BLIGHT OF LILIES, like tulip as the Madonna lily. It may also blight, is an old enemy. Apparently possibly survive in nonlily hosts, since distributed all over the world, it is Neil A. MacLean of the State College infectious to all species and varieties of Washington discovered that some of lilies. Some species, such as other plants are susceptible to the candidum, the Madonna lily, may be fungus. Fie demonstrated also that the killed to the ground if conditions fungus sometimes could rot lily bulbs. favor development of the blight. The That implies another method of over- fungus most often responsible is Botrytis wintering of the fungus, although it elliptica, but a few other species of apparently seldom happens in nature. Botrytis, including the common B, Moisture is necessary for the ger- cinérea, can parasitize lilies under mination of spores of the fungus and certain conditions. also for their formation. A saturated Although B. elliptica may occasion- atmosphere is required for formation ally rot the growing point of small at 80° F., although at lower tempera- plants, the usual visible symptom is a tures a slightly lower humidity per- leaf spotting. The spots at first are mits development. Under favorable small, circular or elongated, and conditions spores may form on infected brown or reddish-brown, with a yel- spots and become mature within 9 lowish or water-soaked margin. Under hours. Germination can only occur in cool, moist conditions they may en- a film of water. Under favorable con- large, becoming paler in color, and ditions the fungus can produce visible sometimes completely rotting the leaf. water-soaked areas within 10 hours The fungus may attack stems near after lodging on a leaf. Although the 614 YEARBOOK OF AGRICULTURE 1953 optimum temperature for infection is practice, especially in commercial near Go'^. once the fungus has entered plantings and in home gardens on the plant it then grows best at 70^. such very susceptible types as the Since a high relative humidity is Madonna lily. Bordeaux mixture, necessary for both spore formation and with a wetting and sticking agent, germination, it is evident that areas of gives good results if it is applied before high rainfall or heavy dews should be the disease has become extremely favorable for the fungus, provided the serious. A weekly application is neces- temperature is cool enough. Thus the sary in wet weather, but otherwise a heavy rainfall of the west coast and spray every other week is usually Gulf States accounts for the severity sufficient. in those places; according to C. E. F. Many other types of copper sprays Guterman, the heavy dews explain and dusts would likely serve as well the prevalence of the disease in Long as bordeaux mixture if proper coverage Island and Bermuda. The disease is is obtained. Fer bam has given good also common in , espe- control of the botrytis blight of tulips, cially during periods of cloudy, wet but it failed to give more than fair weather in the fall before heat is control of the lily blight in tests I have turned on. conducted in Washington. Although all lilies are apparently Also necessary is sanitation—the susceptible to botrytis blight to a cer- elimination of the sources of spores. tain extent, they vary in susceptibility. The diseased leaves and old flowers The very susceptible species include should be removed in home gardens. L. candidum, L. chalcedonicum^ L. hum- Many growers also have found it de- boldtii, and L. testaceum. L. speciosum sirable to remove the flowers from is somewhat less susceptible. Among commercial plantings. If all debris is the resistant types are L. giganteum and destroyed at the end of the growing L, willmottiae. The Easter lily, Lilium season, a major source of infection is longiflorum^ is classed as susceptible, eliminated. It has also been suggested but F. P. McWhorter has pointed out that the basal rosette leaves of L. that the variety Ace is more resistant candidum be cut off just below the than the more commonly grown ground line in midwinter. This variety Croft. should be separated from less suscep- tible ones and all types should be re- CONTROL MEASURES are largely a planted in a different location when- matter of changing the factors that ever dug. favor the survival of the fungus. Al- Control measures therefore for lily though not much can be done about blight are nothing more than the rain and dew, it is possible to lower application of general good growing the humidity by planting lilies in procedures, supplemented with fungi- locations with good air circulation, cidal sprays when necessary. avoiding low or shaded spots, avoiding massed plantings, and preventing weed ONE OF THE MOST POPULAR lilies is growth. Lilium longiñorum, the Easter lily. Of One should also avoid cultivating or the several varieties, the one usually otherwise disturbing the plants when seen in florists' shops at Easter is the they are wet with dew or rain. In Croft, which was developed in the greenhouses the judicious use of heat West Coast States, where the center and ventilation together with proper of production still exists. At the time watering should help keep the humid- of its introduction and for many years ity down to a point unfavorable for thereafter Crofts were grown in green- the fungus. houses without much trouble from Protection with fungicides is usually diseases. Then a puzzling leaf spotting a necessary addition to good cultural or scorching began to be reported BLIGHTS OF LILIES AND TULIPS 615 occasionally in different parts of the periments in the greenhouse, using country. Finally, in the 1947-1948 various types of fertilizers. He found forcing season it became prevalent on that under his conditions nitrogen Croft lilies in many greenhouses in fertilizer alone reduced the leaf burn- tlie Eastj and since has become in- ing, but the inclusion of phosphorus creasingly serious in many sections. and potash in the mixture counteracted The condition has been called leaf the beneficial effect of the nitrogen. spot, leaf burn, tip burn, and leaf He reported the experiments in 1949 scorch. The last is the generally ac- with the statement that "more than cepted term. The symptom usually one factor is concerned in the leaf- seen begins near the end of the leaf as spotting problem." a semicircular spot, which may en- The soundness of the statement has large until the entire tip is afíected. been emphasized by later work. The Such spots develop most often on the beneficial cITect of nitrogen has l)een upper part of the plant and after the substantiated generally by experiments buds appear. Usually only a by John G. Seeley at Pennsylvania few leaves are affected, but in severe State College and A. N. Roberts and cases nearly all may be spotted. The his associates at Oregon State College. condition is usually most severe on Many treatments have responded quite plants with light-colored leaves or on differently in various parts of the coun- those forced rapidly. It appears more try, however. Deficiencies of boron frequently following bright sunny days and magnesium, for instance, appeared than cloudy ones. Such spots so dis- to increase scorch in one sand-culture figure the plants that the leaves may test and and not in another. Results have to be trimmed with scissors be- with nitrogen have not always been fore they can be marketed. consistent. Although fumigation with nicotine Some of these variable results can for insect control had produced some- perhaps be explained now as a result what similar injury, leaf scorch some- of cooperative tests made by Stuart times appeared where nicotine had at Beltsville and William Skou and never been used. The disorder also D. C. Kiplinger at Ohio State Univer- resembled botrytis--blight in many sity. One of their treatments gave respects, but the usual blight control particularly interesting results. Am- measures were ineffective. It differed monium sulfate at a rate of i ounce from the blight in that the spots regu- in 2 gallons of water was applied ev^ery larly occurred on the margins of the 2 weeks to lilies in the greenhouse. leaves, usually an inch or two from, At Columbus the treatment produced the tip, and never on the flowers; the the least scorch. The total numbers of botrytis spots were scattered on the scorched leaves were much below those leaves and numerous on the blossoms. occurring on unfertilized plants. The, The possibility that it was caused by treatment produced the most scorch at a fungus was discarded when research Beltsville, however, and nearly three workers demonstrated that the fungus times as much as occurred on the un- could not be detected in typical fertilized plants. scorched spots. So it appeared to. be a The average number of scorched physiological problem, and investiga- leaves per treatment was 32 at Ohio and tions since have proceeded on that 188 at Beltsville. What factors could basis. be responsible for such different re- Neil W. Stuart at the Plant Indus- sults? The investigators suggest that try Station at Bcltsville, Md., noticed perhaps they were due to the differ- in 1945 that lilies fertilized with nitro- ences in soil acidity and water. At gen during forcing showed fewer Columbus the unfertilized soil had a scorched leaves than unfertilized plants. pH value of 7.3; the water had a pH He followed the observation with ex- of 10.5; the soil after treatment with 6i6 YEARBOOK OF AGRICULTURE 1953 ammonium sulfate had a pH of 6,7. pH of 5.0. They raise the question At Beltsville the original soil had a whether the value of the lime is in its pH of 5.8; the water had an average neutralizing effect or in its ability to pH of 7.3; and the soil after treatment supply calcium to the plant. with ammonium sulfate had a pH of In those studies and others it was 3.9. Thus, the soil acidity was markedly- noticed that plants grown from bulbs different at the two locations. They produced on different farms varied in also reported that in another experi- the amount of scorch. In the 1950-1951 ment at Beltsville the least scorch was season, F. P. McWhorter assembled present on plants grown in quartz bulbs from 21 growers in , sand with a complete nutrient solu- Oregon, and Washington. The bulbs tion plus 25 grams of calcium carbon- were forced at Beltsville, Ohio State ate per pot. A similar benefit was University, and Oregon State College. obtained by adding dolomitic lime- Not only was there a different response stone to infertile acid soil. by different stocks—the relative per- The effectiveness of lime in prevent- formance often was different at the ing scorch of Croft lilies during forcing three locations. It was evident that the was investigated by A. N. Roberts, field "history" of the bulbs had a R. E. Stephenson, and S. E. Wads- marked effect on the amount of scorch worth at Oregon State College in 1950 that developed when no fertilizer was and 1951. Although an application of used during forcing. nitrogen alone completely prevented Mr. Roberts and others at Oregon scorch, the plants were yjoor and were State College in 1948 began studying apparently severely affected with a the possible carry-over effect of fertili- deficiency of phosphorus or potassium zer treatments in the field on forcinc: or both. Plants that received a com- performance and scorch development plete fertilizer (nitrogen, phosphorus, in the greenhouse. Their experiments potash, and sulfur) and lime at a rate demonstrated also that the field "his- of 8 tons an acre grew very well with tory" of the bulbs had a definite bear- only a small amount of scorch. The ing on the amount of scorch that complete fertilizer without lime re- developed but that none of the field sulted in a high rate of scorch, espe- treatments tested prevented subse- cially in the presence of high amounts quent scorching in the greenhouse. of manganese and aluminum. Lime at One field treatment containing nitro- a rate of 5 tons an acre was less effec- gen, phosphorus, potassium, sulfur, tive than at the 8-ton rate. Also, a and manganese actually increased the high rate of lime overcame the scorch- number of scorched leaves in the ing tendency of an unbalance of nitro- greenhouse. A field treatment with gen and sulfur in one combination and nitrogen, potash, potassium, sulfur, phosphorus plus potassium in another and lime was ineffective in reducing combination. The lime naturally scorch, but in that test the lime was changed the pH of the soil somewhat; used at a rate of 3,480 pounds an acre, generally the scorch was more severe which may have been too low. In in the most acid soils. V. A. Clarkson general, they found that the more at Oregon State College showed that complete the nutrition was in the field typical scorch could be induced within and the better the growth, the greater about 10 days by the addition of dilute was the likelihood that scorch would sulfuric acid to the soil. appear in the greenhouse. Such data indicate that the pH In addition it may be more of a might be the determining factor, but field problem than has been realized some of the additional data from Ore- heretofore, since F. P. McW^horter and gon show that there was no significant C. J. Anderson in Oregon pointed out difference in scorch on two soils, one in 1951 that "it is probable that a with a pH of 6.2 and the other with a considerable portion of the injury BASAL ROT 617 formerly attributed to Botrytis blight may have been due to the physiological disease, scorch." Our knowledge of the cause and control of scorch is far from complete, although the studies I have reviewed have helped gready. Apparently scorch follows unbalanced nutrition. The dis- order is generally most severe in very Narcissus acid soils and can be prevented to a great extent in them by heavy appli- cations of calcium and nitrogen. In Basal Rot moderately acid soils it can appar- ently be alleviated by the use of nitro- gen fertilizers alone. But the exact role W, D. McClellan of nitrogen and calcium, and the possible influence of aluminum, man- Considerable concern was felt in ganese, and magnesium are not en- England in 1890 about a troublesome tirely clear. rot of narcissus bulbs. The affected Finally, in developing a suitah)le plants were stunted, the tips of the treatment, commercial factors other leaves tui'ned brown, the flowers de- than leaf scorch must also be consid- veloped imperfectly, and the base of ered—height of the plant, color of the bulb was soft and rotten. leaves, number of flowers. The control The cause of the rot was not deter- program ultimately based on the cause mined. Some invesdgators blamed un- must be one that not only prevents favorable conditions of soil or climate. the development of scorch but also One person thought it was due to a one that promotes a good culture. fungus. But little effort was made to investigate the trouble until the hot C. J. GOULD is a plant pathologist at summer of 1911, w^hen large numbers ¿he Western Washington Experiment Station of bulbs rotted during storage in Eng- {State College of Washington), He has land and the Netherlands. been investigating diseases of ornameiital J. Jacob, in an article in The Gar- bulbs since ig^r. Dr. Gould has degrees den in 1911, stated that the rot was from Marshall College and State due to the combined action of heat and College. He has studied bulb diseases in Fusarium bulbigenum. That fungus, de- Holland under a Fulbright grant and has scribed in 1887, ^^^ been found on received with Dr. Neil Stuart the Society narcissus bulbs l3ut had not been recog- of American Florists^ Award for outstand- nized as the pathogen. Later studies ing research in ig§o. indicated that the fungus w^as nearly always present with , which also can cause a rot of dafl'odils. Jo- hanna Westerdijk in the Netherlands in 1917 distinguished between the disease and the bulb rot due to Fusarium. Before 1924 about 77 million nar- cissus bulbs were imported annually into the United States, primarily for greenhouse forcing. The Secretary of Agriculture promulgated a quarantine against narcissus because of nematodes and bulb flies, to become efl'ective July a, Fusarium spores; b, ascî. 15, 1926. Increasing nuinbers of bulbs