Preventative fungicide applications, as recommended for downy mildew control, should be made if weather conditions are favorable for disease development. Seed treatment, crop rotation and destruction of crop residues are important practices for the control of this disease. All above ground portions may be infected. Disease appearance in the field depends mainly on rainy, cool weather for a period of several days. Plants may be infected at any stage of growth. The fungus overwinters on old cucurbit vines and residues. When abundant moisture is present, the center of the spot is surrounded by a gelatinous pink mass. Symptoms on fruits consist of circular, black, sunken, cankers varying in size depending on the host plant. Diseased tissue dries and the center of the spots fall out, giving the leaf a “shot-hole” appearance. Spots enlarge and turn brown to black in color. See fungicide Īnthracnose – (fungus – Colletotrichum obiculare): First symptoms are spots on the foliage that begin as yellowish or watersoaked areas. Cucurbits, however, are sensitive to copper when young, and repeated applications of copper may cause yellowing of foliage around the edges of the leaves. Application of copper fungicide will assist in control. Crop rotation with non-cucurbit crops is helpful for control of angular leaf spot. The disease may reach epidemic proportions during periods of heavy rains, particularly if temperatures remain high. Hard rains splash the bacteria to stems and leaves. Bacteria overwinter in crop residue and on seed. Spots on fruit are usually smaller and circular in shape. Leaf spots often dry and fall out giving the leaf a “shot-hole” appearance, similar to those caused by anthracnose. Spots are small, angular, straw-colored and watersoaked. lacrymans): This disease appears on leaves, stems and fruit. (See Photo of Alternaria Leaf Spot)Īngular Leaf Spot – (bacterium – Pseudomonas syringae pv. A preventative fungicide program should be followed when the disease occurs consistently. Numerous air-borne spores are produced on diseased spots. The fungus overwinters in crop residue and on other cucurbit plants. Definite concentric rings and margins appear giving the diseased area a “bull’s eye” appearance. Alternaria Leaf Spot – (fungus – Alternaria cucumerina): Small, circular watersoaked spots first appear on the leaves, later enlarging to one and one-half inch or more in diameter.
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