Disease Table

Back

	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 74°F).	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 60°F 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.