Pumpkin diseases: learn more about pumpkin diseases and their treatments

Whether you’re planting pumpkins to eventually carve them with the kids or one of the delicious varieties to use in baking or canning, you’re bound to have problems with growing pumpkins. It could be an insect infestation or some other insect that chews pumpkins, or one of the many pumpkin diseases that threaten your crop. Identification of pumpkin disease is of paramount importance in the treatment of pumpkin diseases. The following article contains information on pumpkin diseases and their treatment.

Identification of pumpkin disease

It is important to identify diseases that affect pumpkin cultivation as early as possible. Early detection will allow you to treat symptoms in time and hopefully save the crop. It is useful not only to recognize the symptoms of infectious diseases, but also to know how they spread and survive. Diseases affecting pumpkins can be foliar or fruit borne. Leaf diseases often open the plant to other infectious diseases and sunburn.

Diseases and treatments of pumpkin

Pumpkin leaf diseases often affect pumpkin crops. Powdery mildew, mildew, white spot (Plectosporium), gummy stem blight and anthracnose are the main causes of leaf diseases.

Powdery mildew

The mold dust is exactly what it looks like. First observed on the underside of the leaf, powdery mildew is a white “dusty” layer of spores that move from the underside of the leaf to the top, eventually defoliating pumpkin plants. The spores survive in the soil and in crop residues, and are dispersed by the wind.

It is one of the easiest diseases to identify and, unlike other leaf diseases, it tends to get worse during periods of drought. To control powdery mildew, rotate with non-mucilage crops and treat with a fungicide at the first sign.


Late blight appears as lesions on the upper surface of the foliage. Initially, the lesions are yellow spots or angular areas soaked with water. Lesions become necrotic as the disease progresses. Cool, moist conditions are conducive to this disease. Again, spores are dispersed by wind.

Broad-spectrum fungicides are somewhat effective against late blight. Planting varieties early in the season can also reduce the risk of late blight infiltration into the crop, as the disease is generally more common late in the growing season when conditions are cool and rainfall is more likely.

Anthracnose, White spot, Gummy stem burn

Anthracnose begins as small light brown spots with a darker margin that widens as it progresses. Eventually, the leaves develop small holes and the fruit may also show lesions.

White spots, or Plectosporium, also appear as spindle-shaped lesions on the leaf surface. The fruit may be affected, showing small white spots which are more circular than the diamond-shaped lesions on the leaves.

Rubber stem blight affects most cucurbits and is caused by both Didymella bryoniae and Phoma cucurbitacearum . This disease is more common in the southern United States.

Applying fungicides at the first sign of any of these diseases will reduce and control them.

Additional disease problems related to pumpkin cultivation

Black Rot

Black rot caused by Didymella bryoniae , the same fungus that causes rubbery stem blight, resulting in large grey spots on the fruit which become black rot areas. Hot, humid summer nights favour black rot. Spores are dispersed by water and wind.

There are no disease-resistant varieties. Treatment of this pumpkin disease by crop control alone is insufficient. Combine crop rotation, planting of non-susceptible crops, fall tillage and summerfallow areas with a history of chemically controlled diseases. Fungicides should be applied at intervals of 10 to 14 days, beginning when vines have dense foliage.

Fusarium crown rot

Although the names are similar, fusarium crown rot is not related to fusarium wilt. Wilt is a sign of crown rot and yellowing of the entire plant. Over a period of 2 to 4 weeks, the plant eventually decomposes. Leaves will be marked with water-soaked or necrotic areas, while fruit symptoms vary depending on the Fusarium pathogen.

Again, the spores survive in the soil for long periods of time and are spread by the use of agricultural equipment. There are no disease-resistant varieties. Crop rotation will reduce the population of pathogenic fusarium. There is no chemical control for this disease.

Sclerotic Rot

Sclerotinia rot is a cold season disease that affects many types of vegetables. The pathogen produces sclerotia that can survive indefinitely in the soil. Cold temperatures and high relative humidity favour the development of a white, fluffy mould around water-infected areas. Black sclerotia grows between the moulds and is the size of watermelon seeds.

The whole plant, including the fruit, rots. The spores are spread by the wind. There are no disease-resistant varieties of squash. Fungicides can be effective if applied to young plants.

Phytophthora Blight

Phytophthora blight is a serious disease caused by a pathogenic fungus that can reside indefinitely in the soil and spread rapidly. Primary symptoms can be observed on the fruit and spread to the vines. Slight rot combined with an extensive area of white cottony mould is observed. It also affects many other crops.

Phytophthora blight is most severe in late summer when it is cool and humid. Spores are dispersed by water splashes, wind and the use of equipment. There are no disease-resistant varieties of squash available. Crop rotation can reduce disease severity for future crops, as well as avoid planting in poorly draining soils or soils that tend to have stagnant water. Fungicide applications can reduce losses.

Bacterial spot on fruits

Bacterial spots on fruit are common on pumpkins and other fall squashes. They appear as small lesions on the fruit. The foliage has small, dark, angular lesions, but they are difficult to detect. Lesions on the fruit occur in clusters and are similar to scab. They enlarge into blisters which eventually become flattened.

Bacteria spread through infested crop residues, contaminated seeds and water splashes. Rotate crops with seedless crops. Apply copper spray at the onset of fruit formation to reduce the incidence of bacterial spotting on fruit.


There are also a number of viral diseases such as Cucumber Mosaic Virus, Papaya Ringspot Virus, Zucchini Mosaic Virus and Yellow Zucchini Mosaic Virus that can affect pumpkins.

The foliage of virus-infected plants tends to be mottled and distorted. Plants that are infected early in their development or near or before the flowering season are most affected and produce fewer fruits. The fruits that do develop are often deformed. If the plant is infected after the pumpkins have reached their maximum size, fruit quality is rarely affected.

Viruses survive in host weeds or are spread by insect vectors, usually aphids. Late maturing pumpkins are more susceptible to virus infection, so early maturing varieties should be planted. Keep the area free of weeds to reduce the risk of infection.

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