Diseases of Tulips

Contents Fungus Diseases __ ·------ ___ ____ ___ ________________ _______ _ 3 Blackleg ______________ ·--------------. ----------------- _ . __ __ 19 Virus Diseases _--------------------------------- ____ _______ __ 3 Botrytis Measles ___ _______ _ -- -------------------·--------- 19 Nematode Diseases ________________________ ----··-··-- __ 3 Fluorine _____ ---------·---------- ________ ----------- ------ __ ___ _ 19 Bacterial Diseases ---------------------------------------- 4 Fusarium Leaf Blight -------------- --------------·--- __ _ 19 Physiological Diseases __________________________________ _ 4 Miscellaneous N em a toes ------------------------ ---- - ___ 19 Rhizoctonia Blight ____ ______ --------------------··--------- 19 MAJOR D ISEASES Basal Rot ________________ ___________________________________ _ 4 Rust and Smuts _______ _--------------- ------------------- _ 20 Black Slime (Black Rot) __________________________ _ 6 Sclerotinia Sativa --------------------- ------- ______ _____ ___ 2 0 Skin Disease (La Reine) _______________ _____ ____ ______ 20 Blue Mold ----------------------------------------- ______ . ____ 7 Smoulder ___ _____ __ ______ __ __________________________ ----· __ ____ 2 0 Botrytis Blight (Fire) --··----------------------------- 7 Bulb and Stem Nematode (Eelworm) _______ _ 10 Sooty Bulbs ------------·----------------------·----------- ___ _ 20 Crown Rot (Southern Wilt) ____ _______ ___________ 11 PHYSIOLOGICAL PROBLEMS Foot Rot (Root Rot, Shoo trot, Shanking) _ __ 12 Blind, Blasted, or Deformed Flowers ______ __ ____ _ 20 Gray Bulb· Rot (Bad Soil) __________________________ 12 Blueing of Bulbs ( Blawgroeien) ___________ _________ 20 Pythium Root Rot and Soft Rot ____ ___ ____________ 13 Bud Necrosis (Core Rot or Kernrot) ____ __ __ ___ _ 20 Topple (Sugarstem or Wet Stem) _______________ 14 Ethylene Damage ____________ ________ ____ -··- ------ -- ______ 21 Frost Injury ___ ___________ _______ ________ ---------------·----. 21 V IRUS DISEASES Heat Damage ___ __ ______ _________ ____ ______ __ ____ ________ ____ 21 Major Virus Diseases of Tulips- Table __ ______ 16 Tulip Breaking (Mosaic) ________________ ____________ 16 Gun1mosis --------------------------------- --------- __ __ ___ __ 21 Nutrient Deficiencies _ ---------------------------------- 21 Yellow Pox _______ --------------------- ------------- ___ __ ______ 18 Mechanical Damage --------------------------------__ __ 22 MISCELLANEOUS DISEASES Hard Base ------------------------------------------------ __ __ 2 2 Anthracnose _______ __________ _____________________ __________ 19 KEY to Major Tulip Diseases _______________________ 23 Many of the recommendations in this bulletin are based upon cooperative research with other colleagues, particularly Mr. Vern Miller and Dr. Neil Stuart. We express our gratitude to them and to Mr. Worth Vassey and Mrs. Evelyn Morris for their research assistance; to Drs. Tom Allen, Alan Brunt, Gary Chas tagner, William Haglund, ]. ]. Hesling, David Price, Alen Rees, and Willis Wheeler for reviewing the manuscript; and to the Washington State Bulb Commission and the Northwest Bulb Growers Associa tion for their support in the research and publication of this bulletin. Issued by W ashington State University Cooperative Extension, ]. 0 . Young, Director, and the U.S. Department of Agriculture in furtherance of the Acts of May 8 and June 20, 1914. Extension programs are available to all persons without discrimination. Issued August 1979. 2 DISEASES OF TULIPS CHARLES J. GouLD, Plant Pathologist, Emeritus, and RALPH S. B);'THER, Extension Plant Pathologist, Western Washington Research and Extension Center, Puyallup In general, botrytis blight (fire) is the one able from Xerox University Microfilms, 300 N. serious disease of tulips that consistently occurs Zeeb Road, Ann Arbor, Michigan 48106) . in the Pacific Northwest. It is also the most ser ious in other growing areas of the world. Our climate is extremely favorable for the develop Fungus Diseases ment of this fungus disease. Other diseases that may cause trouble at times include crown rot, Many important diseases of tulips are caused basal rot, blue mold, and tulip break. by fungi. Fungi are small and rather simple plants The most threatening disease to the tulip in unable to produce their own food because they dustry is the bulb or stem nematode. It is not do not have the green coloring matter ( chloro known to be present here, but we urge growers phyll). Rather than manufacture their own food, to keep a sharp lookout. It is more destructive they feed on living or dead plants and animals than the race attacking daffodils, and it spreads resulting in disease or decay of the tissues they -easily. It is almost impossible to eradicate since attack. tulip bulbs cannot tolerate the full hot water Fungi produce very small seed-like bodies treatment. called spores. These microscopic spores can be spread by splashing rain or wind or carried along A key to the rna jor diseases is provided. In with the movement of soil or infected plant addition, there are many diseases listed as minor debris. Fungi survive from one season to the next, that are occasionally serious, so do not overlook either as dormant spores in the soil or as thread- . them when diagnosing a problem. If in doubt, like growths within a bulb or diseased plant take samples to a local expert who may be able tissue or as hardened lumps of tissue in the soil to help you. where the bulb grew. These masses of weather The controls listed are for commercial pro resisting fungus tissue are usually rounded, hard, duction. Disease Control Recommendations for and are called sclerotia. Tulips, EM 4315, is updated annually to identify currently registered pesticides for disease control. When chemical applications are recommended, Virus Diseases the hobbyist will probably find it necessary to spray as often as the commercial grower to obtain Virus particles are so small that they cannot adequate control. In general it is a good practice be seen with an ordinary light microscope but re to eliminate all abnormal plants or bulbs as soon quire the use of an electron microscope. When as noticed and change planting locations at least they gain access to a plant, they usually penetrate evety other year. into every part except the seed. Therefore, when ever a "daughter" bulb is taken from a virus-in The authors have drawn heavily upon the fected plant, it is usually also infected. Certain following publications and readers are referred insects, such as aphids, which feed on plant sap to them for additional information. can spread some virus diseases. MOORE, W. C. 1949. Diseases of bulbs. Min. Ag. and Fish. Bul. 117, London. (A re vision is in press.) Nematode Diseases REES, A. R. 1972. The growth of bulbs. Nematodes are very small thread-like worms. Academic Press. Many commonly live in the soil without doing General culture, forcing, etc. are covered in any harm, while others attack various plants. The more detail in the Handbook on Bulb Growing bulb nematode and root lesion nematodes, which and Forcing, edited by C. J. Gould, 1957 (avail- affect tulips, are too small to be seen without a 3 microscope. Nematodes survive from season to season as eggs. They also can survive for several years in bulbs or in infected plant tissue. Any movement of soil or infected plant parts can be responsible for the spread of nematodes. Farm equipment, irrigation, flooding, and planting in fected bulbs are common ways of spread. Bacterial Diseases Basal rot Bacteria are simple, microscopic, usually single the base. The roots are a dull gray. Small, gray, celled plants which depend upon other plant or slightly sunken spots with a dark edge appear animal sources for their food. Most are beneficial first on the bulbs. These may enlarge rapidly with and only occasionally do they cause trouble in a soft, dull white, gray to brown decay that has tulips. Spread and survival are dependent on the a sour odor. Later these tissues shrink, become presence of infected plants or plant tissues since firm, and often have felty masses of white or pink the bacteria are not able to survive for any period mold (mycelium) and powdery masses of spores of time in soil. in or under the husk. Often the infection is ring like with concentric rings of darker zones. The Physiological Diseases initial symptoms are often small and easily over looked. Symptoms increase during storage and All problems that are not caused by para usually the bulb continues to decay and is con sitic organisms are considered in this group. verted to a granular mass. Often this process is Tulips are quite susceptible to unfavorable weath aided by mites. Gum may be exuded during the er. Frost may injure their leaves, the sun may early stages. burn the bulbs, and undesirable temperatures may prevent flowers from forming, or ruin them after Factors Affecting they have formed. The fungus grows well at warm temperatures but is more capable of spreading through the relatively cool soils in the Pacific Northwest than either of the strains attacking iris or narcissus. Although infection can occur at temperatures as Basal Rot low as 7°C ( 46°F), it increases rapidly above l5°C (58°F). Particularly favorable infection Symptoms periods commonly occur during the last two to LEAVES. Plants in the field may fail to emerge three weeks before harvest. The fungus produces from diseased bulbs or emerge and later become abundant spores at 20-34 °C ( 68-93 oF) when stunted with leaves turning red,

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