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Fungal diseases can take an entire crop if not quickly identified and treated.

The damage can include wilting, scabs, moldy coatings, rusts, blotches and rotted tissue, among other symptoms.

Learning to identify what is attacking your plants can help you stay ahead of the damage and prevent it from spreading, as well as find ways to avoid it in the future.

Crop Disease Symptoms
Alliums (Garlic, Leek, Onion)
Downy Mildew Early symptoms are sunken spots on leaves; later, a purplish mold develops over spots
Pink Rot Roots turn pinkish or red, eventually rot; plant is stunted with wilted tops
Smut Black spots on leaves and between the sections of the bulbs; young plants may have twisted leaves; common in northern regions
Asparagus Rust Reddish-yellow spots on stems, branches; gradually entire plant yellows, weakens, and eventually dies
Fusarium Wilt Wilted, stunted spears with brownish surface color
Bean, Lima
Bacterial Spot Reddish-brown lesions on stem leaves, and pods; young diseased pods may fall from plant
Downy Mildew Plants are mottled with white, fuzzy fungus strands on them.
Bean, Snap
Anthracnose Dark red, sunken spots on leaves and stems; pinkish-red spots on pods; seeds are often black
Bacterial Blight Large brown blotches on leaves, possibly bordered with yellow or red; water-soaked spots on pods; seed may be discolored
Mosaic Leaves crinkled with mottled areas; pods may be rough misshapen
Rust Many small reddish-orange to brown spore masses on leaves and possibly stem; leaves rapidly yellow dry up, and drop
Beet Leaf Spot Small, round, tan to brown spots on leaves and stems; later leaves turn yellow and drop
Brassicas (Broccoli, Brussels Sprouts, Cabbage, Cauliflower, Turnip) Black Rot Leaves yellow, veins become black; plant becomes stunted and heads of cabbage, cauliflower, or Brussels sprouts are one-sided or nonexistent; stem cross section shows a brown, woody ring
Leaf Blight Yellow to whitish spots on leaves; girdling of roots; water-soaked spots or lesions on roots
Root-Knot Nematode Small galls on lateral rootlets; pimple-sized swellings on main root; plants may be yellow and stunted
Blights (Early and Late) Greenish or water-soaked spots on leaves; sunken lesions possible on stalks; growth may be visible in wet weather
Fusarium Wilt (Celery Yellows) Reddish tissue on stalks and leaves; yellowing of foliage
Pink Rot Water-soaked spots on stalks; bitter-tasting, rotted stems; damping-off may occur in an infected seedbed
Bacterial Wilt Pale, streaked leaves; yellow, sticky substance exudes from a cut stem
Corn Smut Large galls develop on stalk, ears, and roots; later, grayish galls blacken and release spores; ripened spores appear oily or powdery
Cucurbits (Cucumber, Pumpkin, Squash)
Anthracnose Small, dark spots on leaves; eventually spots grow together and entire leaf is destroyed; frutis may blacken and drop; problem develops in warm, moist conditions
Bacterial Wilt Leaves wilt quickly, possibly while still green; white, sticky material might be seen when a stem is cut
Downy Mildew Yellow to purplish spots start on leaves, gradually cover entire plant
Mosaic Leaves of cucumber and squash develop rough, mottled surface; cucumber fruit may be entirely white; plant may be stunted and yellow in several places
Powdery Mildew Round, white spots on undersides of leaves; eventually entire leaf is covered with powder; fruits ripen prematurely and have poor flavor and texture
Scab Dark spots on fruit of cucumber and pumpkin; leaves may have water spots and stems may have shallow lesions; sap oozes from fruits, then greenish mold develops
Fruit Rot Brownish spots on leaves; damage is particularly bad during wet weather when fruit may develop small, tannish cankers which later rot
Verticillium Wilt Yellowing of foliage and gradual defoliation; plants may become stunted
Ascochyta Blight Leaves shrivel and die; roots and lower stems may blacken and rot; disease overwinters on plant debris
Bacterial Blight Brownish or yellow blotches form on leaves and pods; stems may turn purplish; leaves eventually yellow
Powdery Mildew Stems, leaves, and pods dusted with white powdery mold; black specks appear later in the season; plants are stunted and vines shriveled
Root Rot Yellowed, gangly plants with rotting roots and lower stems; plant may die before pods form
Anthracnose Dark, round spots on fruit; entire pepper may rot or dry up; serious problem particularly in southern or central regions
Bacterial Spot In dry areas, leaves develop yellowish spots with darker margins; older leaves eventually drop
Blackleg In warm, moist climates, plants become stunted and leaves yellow and roll; stem base develops brown, rotted areas on the inside; inside of tubers shows darkened blotches and a soft rot that worsens during storage
Early Blight Spots develop in rings on leaves; eventually leaves may die; tubers develop puckered skin and shallow rough lesions; mold may result
Mosaic Mottled, crinkled foliage; brown specks appear on tubers, and plants may droop and die prematurely
Rhizoctonia Dark brown cankers appear on young sprouts; mature stalks may become brown; tubers are covered with hard, black “scurfs”; tubers may also be roughened in a cross-patched pattern
Verticillium Wilt Late in season, older leaves yellow; affected vines die prematurely; stem tissue discolors from base; tubers may be pinkish
Spinach (also Swiss Chard)
Blight Yellowish, curled leaves; stunted leaves and plants
Downy Mildew In moist areas, leaves develop yellow spots with fuzzy, purplish growth beneath
Sweet Potato
Black Rot Small, round, brown spots on potato tubers; stem may also show decay
Soft Rot Soft, watery rot on stored tubers
Stem Rot Young infected plants may die after trans-planting; survivors develop bright yellow leaves, and later stems rot; harvest is of poor quality
Anthracnose Fruits develop small, round, water-soaked spots; later, fruits darken and rot
Blights (Early and Late) Irregular, water-soaked spots may develop on leaves; plant becomes partly defoliated; seedlings may girdle; stem end of fruit becomes grayish-green; blossoms or young fruits may drop
Fusarium Wilt Leaves yellow and droop; cross section of stem shows brownish liquid within; fruit usually decays and drops
Mosaic Mottled leaves; young leaves are bunched or puckered; plants are stunted; yield is reduced; in some types of mosaic, fruit is also mottled