Cucumber & Green Bean Plant Diseases

Anthracnose

• Anthracnose appears on cucumber leaves as small, yellowish, watery spots that grow quickly into large, brownish lesions with central holes. Fruits are also infected by black, indented cankers often covered in pink spores. On bean plants, anthracnose appears on lower leaves as long, reddish or purplish lesions that turn brown or black. Infected upper leaves feature brownish or rust tinted lesions encircled by a black ring and rust colored border. In both beans and cucumbers, anthracnose thrives in moist environments at temperatures between 55 and 70 degrees Fahrenheit. For prevention, apply copper fungicides and rotate crops every three years. Choose anthracnose-resistant varieties such as "Cortez," "Dominator," and "Impact" cucumbers, and "Advantage," "Boone" and "Cadillac" beans.

Blight

• Leaf blight on cucumbers initially presents as small spots on the upper leaves, eventually growing up to 10 millimeters and presenting a target-shaped pattern of rings. Eventually, leaves fall off and fruit suffer from sunburn, which reduces their quality. Beans may suffer from common and halo blight. Common blight manifests as tiny, clear watery spots on leaves that grow into large, uneven brown lesions surrounded by a yellow band, killing stems and branches. On pods, lesions turn a rusty color. Halo blight appears similar, but with smaller, fluid-filled lesions encircled by a yellow, 1/2 inch halo. Pods are overtaken by red or brown watery spots. To prevent blight, try resistant bean varieties such as "Caprice," "Crockett" or "Dusky" and resistant cucumbers such as "Speedway." Rotate beans in the garden every three or four years and cucumbers every two years. Purchase certified bean seeds treated with streptomycin or use fungicide once beans begin to grow.

Angular Leaf Spot

• Angular leaf spot afflicts both beans and cucumbers, but is less common on cucumbers. It begins as brown, watery, oozing spots enclosed in a yellow halo. Spots eventually turn white and fall away, leaving holes in leaves. Infected fruit feature shallow indentations that grow deep if infested with bacteria. Leaf spot bacteria can live in the soil for up to two years. In beans, angular leaf spot has the same appearance but affects both leaves and pods. Resistant varieties of cucumber include "Fanfare" and "Indio," and resistant beans include "Espada." For both cucumbers and beans, prevent this disease by rotating crops every two years. Copper fungicide also controls the disease during wet periods.

Mosaic Virus

• The first symptoms of cucumber mosaic virus include wrinkled, curled leaves, inhibited growth and dying leaves. Fruit may appear pale or white, oddly shaped and have a bitter flavor. Beans suffer from bean common mosaic virus, which inhibits plant growth and causes irregularly shaped, yellowed leaves and dark lesions on roots, leaves and pods. Use insecticides on cucumber and bean plants to control infected insect populations such as aphids, or use resistant cucumber varieties such as "Monarch," "Superset" and "Calypso." Mosaic-resistant beans include "Ambra," "Benchmark" and "Derby."