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Ag Chat from 2/25/26: Gummy Stem Blight is a fungus
From our Small Farms Agent, Anass Banna
Gummy stem blight is a stem and leaf disease of cucumber, cantaloupe, pumpkin, and watermelon caused by the fungus Didymella bryoniae. This fungus also causes a fruit rot called black rot.
Symptoms include leaves with brown or tan spots of various sizes that may eventually cover the entire leaf. The stems may split to form open wounds called cankers. A brown, gummy substance may be evident on the surface of these open wounds.
Infected vines usually wilt after the middle of the season. Infected stems die one after another, and seedlings and entire individual vines may be killed. Affected fruits have irregular circular spots, and a wet rot occurs where the fungus penetrates the rind.
To distinguish gummy stem blight on watermelon from downy mildew, look at the size, shape, and position of leaf spots. Leaf spots of gummy stem blight are larger than individual spots of downy mildew. Some leaf spots of gummy stem blight have a ringed or target look. 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.
Prevention & Treatment: There are no varieties that are resistant to this disease. This disease may be seed-borne, so purchase seed from a reputable source. Remove and destroy all plant debris in the garden since the disease can survive on plant debris from year to year. Rotate crops with nonhost plants, such as corn, for two or more years as an effective way of reducing the incidence of this disease. Avoid wetting the leaves when watering. If the disease is severe enough to warrant chemical control,
preventative fungicides are available.
Call The Caswell County Extension for more information.
