Diseases That Kill Pumpkin Plants

Rot

• Belly rot infects pumpkin vines during periods of warm, wet weather and causes watery, dark spots where the pumpkins touch the soil. The spots spread, rotting the pumpkins. Remove infected pumpkins and use stakes or old shingles to keep the pumpkins from touching the ground.

  Blossom-end rot spreads from the stem of the pumpkin into the fruit. Look for masses of white-stalked fungus with black heads on the pumpkins and you will find rotted fruit beneath. Remove infected pumpkins as soon as possible and apply a fungicide to prevent the fungus from spreading. Space the plants properly to promote air circulation and make sure the plants have well-drained soil.

Mildews

• Powdery mildew is one of the most common and deadliest diseases that attack pumpkins. Caused by a fungus, powdery mildew appears as a white, fuzzy coating on leaves. Unlike many other pumpkin diseases, powdery mildew grows best in hot, dry conditions, so the fungus is most active in late summer. It robs the plant of crucial nutrients, causing the stems to turn brown, leaves to fall off and fruit to fail.

  Downy mildew likes cool, wet weather and attacks the pumpkin foliage. This disease causes yellowing of the upper leaf surface, but the spores are on the underside, growing in what looks like white fuzz. It can defoliate the entire vine and kill it in a matter of days. Plant mildew-resistant varieties of pumpkins and provide the plants with good air circulation and weed control to prevent mildews.

Anthracnose

• Anthracnose infects pumpkin vines during cool, wet weather. The fungus hides in the soil and gains access to the vine through splashing rain or overhead irrigation. Pinkish-white spores mass on the leaves and stems. Small holes may appear in the leaves where the fungus has gouged lesions into the foliage. Young pumpkins may turn completely black and older pumpkins develop sunken, dark lesions with a pinkish discharge. Plant resistant varieties, dispose of all infected fruit and vines immediately after harvesting any healthy pumpkins on the vine, and do not replant the infected area with any cucurbit crops next season.

Blight

• Phytophthora blight is usually found where pumpkins grow in soil that is too wet. The disease can cause the entire plant to collapse suddenly. Look for blackish-brown patches that appear slimy and water-soaked. Greasy-looking masses of white spores may also appear, especially in warm, rainy weather. The disease causes the plant to stop taking water. If Phytophthora blight infects the plant after fruit set, you will find the slimy spore masses on the underside of the fruit. The pumpkins will turn soft and mushy. Remove infected fruit and dispose of it away from the garden immediately, before the spores can be spread to other plants and fruit.

  Gummy stem blight is also called black rot and is caused by fungus. This disease first affects the leaves and then the pumpkins, causing dark, watery blotches on the pumpkins that ruin the fruit. Remove all organic debris from the area and apply a preventative fungicide to prevent pumpkin vines from becoming infected. Purchase seeds produced in the arid regions of the U.S. to avoid planting infectious seeds.