12/16/2023 0 Comments Bacterial blight of endive![]() ![]() Under warm, wet conditions, the fungus will continue to grow upward into the leaf blades, and destroy them as it grows from leaf to leaf. If conditions are unfavorable for the fungus, the rust colored spots on the petioles will dry and turn chocolate brown. While these spots are being formed, they may ooze a light brownish or amber colored liquid. These spots can be very small or can grow rapidly to cover the entire petiole/midrib area. Slightly sunken spots, rust-colored to chocolate brown, appear on the leaf petioles and midribs. Before this happens, the fungus enters the plant through lower leaves which are touching the soil. The first symptom seen from above is usually wilting of the outer leaves. Plants are usually affected when they are nearly mature. It is now a greenhouse and field disease and is favored by warm, wet conditions. This worldwide disease was first identified on lettuce in 1900 in Massachusetts greenhouses. It is important to time chemical applications carefully in order to combat this disease.īottom Rot is caused by the fungus Rhizoctonia solani, which affects lettuce, escarole, endive, potato, pepper, eggplant, radish, cucumber, and many other fleshy plants. See current recommendations for chemical control measures. Immediately plow debris under after harvest. Trim outer leaves after harvest, before packing, to avoid rot of the plants in storage. Removing infected plants from small plantings is effective in preventing spread of the disease to other plants. Flooding soil for 23 to 45 days destroys the resting structures of the fungus. Space plants widely and avoid overhead irrigation to keep the soil surface dry. Steam greenhouse soil for one hour at 131o F or for 36 hours at 113o F. Plant in well- drained soil and/or use raised beds. The small grains are non-hosts for this fungus and are often included in rotations. Use long rotations away from lettuce, beans, celery, or carrots. Snowy white web-like fungal growth is present. Black structures, as small as a mustard seed or as large as a bean, may be formed in this web of fungal growth, usually on the undersides of the leaves touching the soil. Under moist conditions, a snowy white mass of fungus, resembling spider webs, is produced over the entire head. The inner leaves usually remain moist enough for the fungus to completely invade them, and reduce them to a slimy mass. As the fungus grows up the plant, each leaf is affected in turn. This causes the leaves to droop and wither, and their tips to touch the soil or rest on the leaves below. As the fungus grows into each leaf, the base of the leaf rots. The fungus will grow from this point down into the roots, and up through the rest of the stem. Before the leaves wilt, however, a water soaked area caused by the fungus as it begins to grow, appears on the stem near the soil. Usually, the first symptom that is noticed is wilting of the outermost leaves. Under moist conditions, the entire plant may collapse in two days. Infection of the plants occurs mainly as they near maturity, but may occur at any time during the season. It is now believed to be found worldwide wherever there is cool, moist weather and lettuce is grown. Sclerotinia drop is a serious disease, and was first reported in the 1890’s in Massachusetts. These fungi can affect lettuce and many other plants, including almost all vegetables except corn. Sclerotinia Drop is caused by the fungi Sclerotinia sclerotium and S. Lettuce mosaic and aster yellows are discussed here. There are also yellows and viral diseases of lettuce. All produce fungal growth under wet conditions that allow the diseases to be distinguished. All are favored by moist conditions, although bottom rot is favored by warm and moist conditions and the others are favored by cool and moist conditions. There are three major fungal diseases of lettuce found in Connecticut: Sclerotinis drop, bottom rot, and gray mold. ![]()
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