Water-soaked areas on roots, hypocotyls and stems. Advanced infections show shrunken brown stem tissue, wilting and plant death.
-----Pythium damping off
Linear or circular reddish-brown shrunken lesions or cankers. Advanced
infections show a brick-red discoloration in the central part of the lower
stem. Seedlings and young plants may die or break off at infected part of stem.
Often occurs in circular patterns in the field.
-----Rhizoctonia root rot
Stunted, yellowed plants scattered through field. Reddish brown streaks on
roots and hypocotyl up to soil surface.
-----Fusarium root rot
Stunted, yellowed plants with tan to brown leaf margins. Infected plants
also exhibit reddish-brown vascular discoloration.
-----Fusarium wilt or yellows
Young plants chewed through at the base. Dull colored worms or caterpillars can be found under debris and in the soil around plants.
-----Cutworms (several species)
Seeds or young seedlings tunneled by small, legless, white worms. May be
associated with reduced stands and wilted or dead seedlings. Damage to growing
point may cause typical "snakehead" damage symptom. Mechanical damage
may cause similar problems.
-----Seedcorn maggot
Seeds tunneled and roots damaged by yellowish, thin, hardbodied larvae up to
0.75" in length. May be associated with reduced stands and wilted or dead
seedlings. More common in drier parts of irrigated fields.
-----Wireworms
Roots damaged by large white larvae with a typically "C"-shaped
body. May be associated with reduced stands, wilted plants.
-----White grubs
Seedlings with cupped and distorted leaves. Undersides of leaves with tiny, yellowish, cigarette-shaped insects. Problem most common in furrow irrigated fields and near maturing winter wheat.
-----Onion thrips
Small (1/16 inch in diameter), greasy, water-soaked spots on leaflets later become larger water-soaked spots surrounded by a 1/16-1/ 2 inch greenish-yellow halo. Severe infections can lead to yellowing and death of new foliage.
-----Halo blight
Similar to halo blight, except mature lesions turn brown. Lesion center may
fall out, causing a shothole appearance.
-----Bacterial brown spot
Small, irregularly shaped lesions which later enlarge to large dark brown
lesions along the edge of the leaflet. Lesions often surrounded by a narrow,
lemon-yellow margin.
-----Common bacterial blight
Wet, soft lesions on leaves, branches, stems and pods. These later become
watery, rotten masses of tissue covered with white (not blue or grey) moldy growth.
Infected parts wilt and die, and then take on a characteristic bleached
appearance.
-----White mold
Small yellow or white spots on leaves which later enlarge to reddish-brown
or rust-covered pustules, often bordered in yellow, about 1/ 8
inch in diameter. Spores released from pustules give the leaf a rusty
appearance. Severely infested leaves may curl upwards, turn brown, and drop
prematurely.
-----Rust
Upper leaf surfaces show a reddish-brown flecking. Affected leaves can
eventually turn yellow and drop. Similar in appearance to rust, but
discoloration cannot be rubbed off and occurs only on upper leaf surfaces.
-----Ozone bronzing
Similar to above, except leaves are thickened and bronzing not limited to
upper surfaces. Areas between leaf veins can turn brown and fall out. Plants
can also be stunted and exhibit delayed maturity. Severely affected plants can
have white leaves and eventually die. Symptoms may occur in spots or throughout
field.
-----Zinc deficiency
Leaves have a silvery or bronzed appearance. Microscopic animals found on
the undersides of leaves. Often associated with drought stress.
-----Spider mites
Plants with curled or cupped leaves. Leaves show a green to bluish green
mottling or mosaic pattern. Leaf veins can be slightly darker than areas
between veins.
-----Bean common mosaic virus
Similar to above, but no leaf cupping and mottling also involves yellow and
white leaf tissue. Occurs in a very low percentage of plants in commercial
varieties.
-----Leaf variegation (genetic)
Similar to above, with younger leaves showing green veins and yellow tissue
between veins. Leaf may eventually become white. More common in older plants
and after irrigation.
-----Iron deficiency
Young leaves on plants brittle, glossy and curled downward. Early symptoms
are small yellow spots often surrounded by a yellow halo. Shortened internodes,
excess branching, stunting and delayed maturity can also be observed.
-----Bean Yellow Mosaic Virus
Plants with downward curled or cupped leaves which are often greatly
distorted or puckered. Leaves often become yellow and plants become stunted. In
contrast to Bean Yellow Mosaic Virus, older leaves rather than younger are most
likely to be curled and cupped.
-----Curly top virus
Plants with cupped and distorted leaves. Undersides of leaves with tiny,
yellowish, cigarette-shaped insects. Problem most common in furrow irrigated
fields and near maturing winter wheat.
-----Onion thrips
Yellow grublike insects with branched spines which skeletonize leaves. Common on young plants and again during pod fill. May be associated with yellowish eggs and spineless immobile pupae.
-----Mexican bean beetle larvae
Bronze beetles with black spots on wings, similar in appearance to lady
beetles, found skeletonizing bean leaves. May be associated with groups of
yellowish eggs found on undersides of leaves.
-----Mexican bean beetle
Leaves with large, ragged feeding damage. Damage more common in edges of
field. May be associated with large, active, jumping insects.
-----Grasshoppers
Nodes between leaf petioles and stems with reddish discoloration, often with
reddish streaking of leaf veins and veinlets. Plants can be stunted or killed.
-----Tobacco streak virus
Groups of round or pear-shaped insects feeding on the undersides of leaves
or on tenderstems. Variable in color. Often associated with virus diseases.
Heavy infestations may give plants a wilted appearance.
-----Aphids (several species)
Wet, soft lesions on leaves, branches, stems and pods. These later become
watery, rotten masses of tissue covered with white (not blue or grey) moldy
growth. Infected parts wilt and die, and then take on a characteristic bleached
appearance.
-----White mold
Small (1/16 inch in diameter), greasy, water-soaked
spots on leaflets later become larger water-soaked spots surrounded by a 1/16-1/
2 inch greenish-yellow halo. Severe infections can lead to yellowing and
death of new foliage. Pod lesions are small water soaked spots or streaks
commonly associated with a light cream or silver-colored ooze.
-----Halo blight
Similar to halo blight, except mature lesions turn brown. Lesion center may
fall out, causing a shothole appearance. Infected pods may be twisted and
kinked with circular brownish water-soaked spots.
-----Bacterial brown spot
Small, irregularly shaped lesions which later enlarge to large dark brown
lesions along the edge of the leaflet. Lesions often surrounded by a narrow,
lemon-yellow margin. Infected pods have circular water-soaked areas often
associated with yellow masses of ooze.
-----Common bacterial blight
Pods with reddish-brown concentric rings. Infected pods can be shriveled and
puffy and not produce seeds. Nodes between leaf petioles and stems with reddish
discoloration, often with reddish streaking of leaf veins and veinlets. Plants
can be stunted or killed.
-----Tobacco streak virus
Blossoms contain tiny, brown, cigarette-shaped, rapid moving insects. Large
numbers of insects may be associated with flower and pod abortion.
-----Flower thrips
Holes chewed in pods and developing seeds. Brown caterpillars with a
distinct brown band across the body just behind the head may be found hiding in
soil and under debris around the plant on sunny days. At night and on cloudy days
caterpillars may be found feeding on plan.
-----Western bean cutworm
Categories: Bean field key, Bean Diseases, Bean Pests, Pythium Damping Off, Rhizoctonia Root Rot, Fusarium Root Rot, Fusarium Wilt, Fusarium Yellows, Cutworms, Seedcorn Maggot, Wireworms, White Grubs, Onion Thrips, White Mold, Rust, Halo Blight, Bacterial Brown Spot, Common Bacterial Blight, Ozone Bronzing, Zinc Defliciency, Spider Mites, Mosaic Virus, Onion Thrips, Grasshoppers, Mexican Bean Beetle, Tobacco Streak, Aphids, Cutworm
Date: 06/13/2002