If the disease is severe enough to warrant the use of fungicides, several are available for home garden use (Table 2). Purchase seeds from a reputable source since the disease can be seed-borne. Rotation of crops in the garden for three years is also important to minimize disease. Prevention & Treatment: Remove and destroy old cucurbit vines and residues since this is where the fungus survives the winter. Infected fruits have black, circular, sunken cankers of different sizes. The diseased tissue dries, and the center of the spots fall out, giving a “shot-hole” appearance. The first symptoms of anthracnose are spots on the leaves that begin as yellowish or water-soaked areas. Zachary Boon Snipes, ©2015 Clemson ExtensionĪnthracnose is caused by the fungus Colletotrichum obiculare, and requires rainy, cool weather for several days for the disease to develop. If the disease is severe enough to warrant chemical control, preventative fungicides are available (Table 2). Rotate crops with nonhost plants, such as corn, for two or more years as an effective way of reducing the incidence of this disease. Remove and destroy all plant debris in the garden since the disease can survive on plant debris from year to year. This disease may be seed-borne, so purchase seed from a reputable source. Prevention & Treatment: There are no varieties that are resistant to this disease. Gummy stem blight also can be found on the petioles (leaf stems) and the midvein of leaves as a water-soaked or reddish-brown wet spot. Some leaf spots of gummy stem blight have a ringed or target look. Leaf spots of gummy stem blight are larger than individual spots of downy mildew. To distinguish gummy stem blight on watermelon from downy mildew, look at the size, shape, and position of leaf spots. Affected fruits have irregular circular spots, and a wet rot occurs where the fungus penetrates the rind. Infected stems die one after another, and seedlings and entire individual vines may be killed. Infected vines usually wilt after the middle of the season. A brown, gummy substance may be evident on the surface of these open wounds. The stems may split to form open wounds called cankers. Symptoms include leaves with brown or tan spots of various sizes that may eventually cover the entire leaf. This fungus also causes a fruit rot called black rot. Gummy stem blight is a stem and leaf disease of cucumber, cantaloupe, pumpkin, and watermelon caused by the fungus Didymella bryoniae. Leaf spots caused by gummy stem blight on watermelon leaf.Ĭlemson University – USDA Cooperative Extension Slide Series, Remove all infected plants to reduce the spread of bacterium by beetles. Apply all chemicals according to directions on the label. Bees pollinate many of these vegetables, so spray all insecticides in the late afternoon. Insecticides that control striped and spotted cucumber beetles in the home vegetable garden include bifenthrin, cyhalothrin, or cypermethrin (see HGIC 2207, Cucumber, Squash, Melon & Other Cucurbit Insects). The beetles spread the wilt bacterium by feeding on infected vines and then feeding on healthy plants.īacterial wilt can be reduced in your garden if the beetles are kept under control at the first sign of activity. The bacteria are carried from plant to plant by striped or spotted cucumber beetles. Prevention & Treatment: There is no chemical control for bacterial wilt once plants become infected. Bacterial wilt is most severe on cucumber and cantaloupe and less severe on squash, pumpkin, and watermelon. However, as the disease progresses, more leaves wilt, and eventually, the entire vine is affected. The disease is caused by the bacterium Erwinia tracheiphila, and at first may only affect a few vines on a plant. The main symptom of this disease is severe wilting of the vines, followed by rapid death of the plant. See also Fact Sheet CE-6 Cucurbit Diseases, an Aid to Identification. More information about growing cucurbit plants is available in the fact sheets: HGIC 1304, Cantaloupe & Honeydew Melon HGIC 1309, Cucumber HGIC 1321, Summer Squash and HGIC 1325, Watermelon.
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