Diseases:

Disease control is essential in the production of high quality pumpkin. A preventive program that combines the use of cultural practices, genetic resistance, and chemical control as needed, usually provides the best results.

Cultural practices are useful for limiting the establishment, spread, and survival of pathogen that cause pumpkin diseases. Many of the fungal, bacterial, and nematode pathogens survive in old crop debris and in soil; therefore it is recommended that fields should be rotated with non-cucurbit crops for at least three years to reduce pathogen levels.

Avoid acid soils or fields with a history of Phytophthora rot or root rots/ vine declines. The selection of well drained soils is essential for minimizing fruit rots.

Avoid the movement of contaminated soil or plant debris into clean fields on workers or farm equipment. Seeds can carry diseases such as angular leaf spot. This can lead to the introduction of disease into fields. Purchase seed from reputable sources as far as possible and apply a fungicide seed treatment prior to planting. Most foliar diseases are spread by water-splash or favored by long periods of leaf dampness.

Utilize drip irrigation or avoid frequent sprinkler irrigation with small amounts of water. Finally, use tillage practices that promote the rapid decomposition of old vines and fruit soon after harvest.

Management of foliar diseases such as powdery mildew may require fungicide sprays. Fields should be monitored at least weekly for early disease detection. Spray programs should be initiated shortly after the first appearance of disease, or beginning at flowering to prevent disease. A 14-day schedule has been effective in most instances, although a 7-day schedule may be required where powdery mildew is severe. Management of bacterial wilt may require the use of insecticide to control cucumber beetles, which spread the disease.

Some of the more common diseases affecting pumpkin production include:
Anthracnose, Gummy stem blight, Powdery Mildew, Bacterial wilt, Phytophthora root rot and Downy mildew.

• • Anthracnose-Colletotrichum lagenarium:

    Symptoms

    As the pathogen invades the foliage, small, yellow, water-soaked spots develop. These affected areas enlarge, turn brown and shatter, or occasionally the entire leaf dies.

    Rounded sunken spots appear on the fruit with a pinkish brown centre that later darkens.  Usually these sunken spots do not penetrate deep into the fruit, but damaged areas provide an entrance for soft rot organisms. Other symptoms include elongated tan spots in the stem.
     

    Disease Cycle

    The pathogen can survive in infected plant debris and in and on the seed. As spores are produced on infected foliage and fruit, they are easily disseminated to other plants by rain splash and by various pieces of equipment used in production. The disease is favored by warm, moist environmental conditions.

    Control

    It is important to plant disease-free seed, practice crop rotation with unrelated crops, and plant on well-drained soils. Fungicides should be applied regularly as plants begin to vine. Several applications may be necessary to control the disease.

   

   

  • Gummy stem blight (Mycosphaerella melonis):

  This disease can cause serious problems on stems, leaves, and fruit of pumpkins. This fungal disease is often first noted as a developing rot in the lower vine stem area but also may affect foliage.  The infection can cause the  fruit  to  soften or discolor or the stems of the fruit may shrivel, reducing the value of the fruit. Fruit may appear normal at harvest but may collapse in the stem scar area after shipment or sale.

  
  

  Control
  Apply Bravo®(chlorothalonil) 2 to 3 pts(1 litre-1.4 litre) per acre(0.4 ha) for flowables or 1.5lbs to 2.5lbs (0.7kg -1.1kg) per acre (0.4 ha) for dry formulations (WP, DF, DG). Begin applications when plants are in first true leaf stage or when conditions are favorable for disease development. Repeat at 7-day intervals or sooner under severe disease conditions.
  Apply Maneb® (maneb) 80 WP at 2lbs to 3 lbs(0.9kg-1.4kg) per acre(0.4 ha) for dry formulations (WP, DF, DG) or at 2 to 3 pts (1 litre-1.4 litre) per acre (0.4 ha)  for flowables. Addition of Benlate® to the spray schedule for powdery mildew control should increase the control of black rot.

   

  • Powdery Mildew:

  • Powdery mildew (Erysiphe cichoracearum) is common in pumpkin fields throughout the cropping cycle and more severe in the dry season.

    It is easily recognizable as a white powdery growth on upper and lower leaf surfaces. If not controlled, the disease completely destroys the foliage, and any fruit that survives will be sunburned and discolored. The loss of productive vines also severely restricts fruit yield and size. Fields should be frequently and carefully scouted and fungicides applied at the first sign of the disease.

  • Bacterial wilt (Erwinia tracheiphila):

  • Cucumber beetles infected by the bacteria, feed on the leaves of the pumpkin plant and acts as vectors of the disease.
    Wilt is caused as a result of slimy ooze, which plugs the entire water-conducting tissue of the plant. The wilted plant will not recover, even if water is adequate in the soil.

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  • The leaves of infected plant often appear chlorotic. This chlorosis, followed by death of the leaf tissue, usually starts at the margins of the leaves and progresses inward. Plants can be killed by bacterial wilt if infected when young or if large numbers of infective beetles are present.

    Symptoms

    Cutting a severely wilted stem at the base of a lateral branch or just above ground level and squeezing the cut end may distinguish bacterial wilt. Ooze will exude from the water-conducting tissue. By touching the ooze with your finger then slowly drawing your finger away, the milky, sticky ooze will string out into fine strands up to one-fourth inch long. A positive test is a strong diagnostic character, but a negative test does not mean that the plants do not have the disease. Another test is to place a freshly cut stem from a wilted part of the plant in a glass of water. If bacterial wilt is present, a milky exudate will appear at the cut ends. Both of these tests require patience, as the bacteria are in a sticky material and may not readily ooze from the cut stem.

    Control

    The most effective disease control is prompt elimination of cucumber beetles. The beetles can transmit squash mosaic virus as well as bacterial wilt and can cause severe damage by feeding on the leaves. Control should begin either when the first beetle is sighted or when the first cucurbit seedlings emerge. Remove or destroy any infected vines. Wilted plants cannot be saved.

     

    Phytophthora root rot:

    Phytophthora root rot (Phytophthora capsici ) is a serious fungal disease of pumpkins  where the soil remains  wet for extended periods. Phytophthora may cause root rot, stem lesions, or foliar blight. Fruit may also be severely infested and rot. Warm temperatures and poor drainage favour development of this disease. Phytophthora can move rapidly, and disease incidence may be higher in fields planted after tomatoes or peppers.