DiseaseTable

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Several fungi and their related environmental conditions that cause common crop diseases.
Causal Organism Diseases Air Soil Host range Comments Examples
Oomycetes Pythium Damping off, seed rot, root rot   Wet Wide Mostly a seed and seedling disease controlled by seed treatment. Damping off of most crops
Phytophthora Root rots, damping off, lower stem rots Cool (59 to74 F) Wet Narrow Cause disease on a range of hosts from seedlings to fully developed trees. Soybean root rot, late blight of potatoes
Peronosporaceae Downy mildew - Foliage blights Downy mildew infection is favored by high humidity, long durations of leaf wetness and cool weather (daytime temperatures ranging from 60 to 74F). N/A Specific Disease development requires film of water on above ground plant tissues and warm but not excessively hot temperatures. Downy mildew of grapes, lettuce, cucurbits; crazy top in corn
Zygomycetes Rhizopus Soft rots of fruits and vegetables Control by storing in cold temperatures (<50-54 F) N/A Wide Terrestrial - Saprophyte (can live without host plant) Soft rot of sweet potatoes, strawberries, cucurbits, stone fruits.
Ascomycetes Erysiphales Powdery mildew of small plants or on leaves of other parts of more mature plants. Warm to cool temperatures (60 to 85 F) in moderate humidity (40 to 79%) during the day and temperatures of 60F and relative humidity of 90% or higher at night. Infection is practically ceases above 85 F and is severely reduced by rain which washes off spores. N/A Specific Obligate parasites (Lives on host only). Commonly on upper side of leaves. Powdery mildew on many crops including cereals, cucurbits, ornamentals, soybean, and trees.
Alternaria Leaf spots, leaf blight, and damping off Range of temperatures; High humidity N/A Wide Often saprophytic, growing on weak or old plant tissues. Early blight of potato and tomato, blight of carrot and crucifers, fruit spot on apple, and rots on lemon and oranges.
Heliminthosporium Group Cochliobolus / Bipolaris and Pyrenophora / Drechslera Leaf blight, leaf spot, and root rots of grasses. Warm to hot temperatures (66-90 F). Humid conditions; often retarded by dry conditions. N/A Wide Weak saprophytes. Imperfect stages: Bipolaris and Drechslera. Includes organisms formally known as Helminthosporium Southern corn leaf blight, northern corn leaf blight, spots and blotches of small grains.
Cephalosporium/ Hymenula cereals Cephalosporium stripe (fungus leaf stripe) of winter cereals Common in cool conditions. Wet soils and low pH soil.   Infection related to root injury during freezing and thawing. Cephalosporium stripe of barley and wheat.
Claviceps Ergot. Disease of grain. Rain and high humidity during flowering. Moist Specific Hardened, misshapen grains are toxic to mammals. Ergot of rye, wheat, and millet.
Monilinia Brown rot of stone fruits High humidity during fruit flowering. Moist Specific Infected fruit dries into 'mummy'. Brown rot of peaches, cherries, plums, apricots and almonds.
Ascomycetes Sclerotonia White mold, cottony mold, stem rot, crown rot, and blossom blight. (S. sclerotiorum) High humidity. Moist Very wide Survival structures (sclerotia) darken and harden over time. Saprophytic. White mold of sunflower, peanuts, canola and other legumes, cottony rot of carrot, watery soft rot.
  Storage organ rot. Cool. Wet Wide Often infects fruits laying on the cool, wet ground. Black scurf of potatoes, rots of cucumber, tomatoes, eggplants, peanuts, sunflower, and beans.
Ceratocyctis/ Ophiostoma Dutch elm disease.     Narrow Fungus spread by elm bark beetle. Dutch elm disease.
Dueteromycetes Fusarium / Gibberella Head blight or scab, stalk rot and vascular wilts. Warm soil.   Wide Wide host range. Infectected grain may produce poisonous mycotoxins. Scab of small grains, corn stalkrot, wilt of tomato, take-all of wheat.
Verticillium Wilts Warm temperatures (68 to 82 F).Tends to induce wilt in most hosts at cooler tempeperatures than Fusarium. Inoculum tends to increase over years. Wide Wide host range. Symptoms are similar to Fusarium. Although it can effect young plants it typically appears on the lower or outer branches of older plants Verticillium wilt of alfalfa, potato early dying disease.
Cercospora / Mycosphaerella Leaf spots Favored by wet and warm temperatures and is most destructive in summer. Conidia require water to germinate which can be supplied by heavy dews. Moist Specific Cercospora produces a toxin that kills cells in light. Gray leaf spot of corn and Cercospora leaf spot of soybean.
Macrophomina Charcoal rot. Warm to hot. Moderately dry. Disease associated with drought. Very wide Soil borne saprophyte that spreads when plant experiences drought. Microsclerotia, small dark structures. Charcoal rot of 284 hosts.
Colletotrichum / Glomerella Anthracnose. Disease of foliage, stems or fruits associated with dark spots of sunken lesions. Warm temperatures. High humidity. Moist Wide Survival stuctures known as acervuli. Anthracnose of grasses, cucurbits, tomato and onion smudge.
Cryphonectria/ Endothia Chestnut blight N/A Moist Narrow Can attack oaks and other trees but not as severly as American chestnut. Chestnut blight
Basidiomycetes Uredinales Rust of leaves and stems High humidity. N/A Specific Heteroecious types complete life cycle on two hosts. Stem rust of wheat, cedar apple rust, coffee rust, corn and sobean rusts.
Ustilaginales Smuts and bunts of grains and grasses. N/A Warm, moderately dry. Specific Galls form on fruit (grain) and some vegetative tissues. Corn smut, loose smut of cereals.
Basidiomycetes Rhizoctonia / Thanatephorus Damping off, stem rot, stem rot, stem canker. Also storage organ rots. For most races, cool to warm temperatures. Optimum temperature for infection 59 to 80 F. Infecton greatest in wet conditions but symptoms more pronounced in hot, dry environment. Wide Most likely to be a problem when host, especially seedling, growth is slow. Reddish brown lesions are common. Brown patch on turf grass, seedling canker. Soreshin (stem canker) of cotton.

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