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Flowers, Fruits, and Frass

Powdery Mildew on Pumpkins and other issues

Mohammed Babadoost, University of Illinois go to plant pathologist, says, "This year's processing pumpkin crop is the best it has been in the last two decades. " Babadoost attributes the success of the pumpkin crop to new varieties, more successful management of diseases like downy mildew and phytophtera by the growers and drought during the summer that does not favor some of these disease pressures. Babadoost has spent years in his career being a resource to pumpkin growers across the state.

Some readers may not know that Illinois is the top producing pumpkin state in the United States, whether it is jack-o-lanterns or pumpkin for processing.

More than 90% of the pumpkin pie filling sold in the United States comes from two processing plants located near Peoria, Illinois. Babadoost also states, "This year the pumpkins feeding into those plants are yielding a record breaking 27 tons per acre. The average is about 23. This is pretty amazing given that a plant disease nearly wiped out the whole industry in the state a couple of decades ago." These processing pumpkins are not the jack-o-lantern or pie pumpkin type that reminds you of fall but are a different species that produces fine textured and dark orange flesh but look more like buff colored watermelons on the outside.

For those of us at home, who tried are thumb at growing pumpkins, may not have had the same success story. If the gardener did not have a preventative practice to controlling powdery mildew, they may have lost all their leaf covering causing their pumpkins to sunburn in the warm sunny weather of our late summer. Babadoost said, "Most growers use a preventative program for powdery mildew starting in the last week of July before they see the telltale white fungal spores on the leaves." He said that treatments like potassium of fatty acids and sulfur can be very effective on powdery mildew.

Powdery mildew also becomes prolific if the weather is hot and dry. It can affect other vine crops like cucumber, melons, squash, and ornamental gourds. It is spread by wind. The disease attacks the lower surface of the leaves first, meaning scouting for the disease during the appropriate environmental conditions is crucial. The white mycelium eventually covers the entire leaf. The following cultural tips can help you grow a better crop of pumpkins

  1. Do not overcrowd these plants as air circulation is crucial in preventing disease
  2. Rotate, do not plant your squash or pumpkins in the same place in the garden year after year
  3. Scout early and control early
  4. Harvest pumpkins if leaves have fallen off from disease and leaves three to four inches of stem so the pumpkins will keep well.

Other issues on pumpkins this year were lesions from sitting on moist soils, bacterial leaf spot, squash bug feeding damage and phytophtera.