Powdery Mildew

• Numerous species of fungi can lead to powdery mildew on pumpkin plants and other closely related crops like cucumber, squash, zucchini and melons. A translucent to opaque white, patchy film begins to cover infested leaves. Powdery mildew may occur on both the top or bottom of leaves, and may be small spots or spread across the indented veins on the pumpkin leaf. Often powdery mildew isn't fatal to pumpkin plants, but it will make them look a bit ugly, especially in the latter weeks of summer when the pumpkins being to mature before picking.
  
  

Favorable Conditions

• Powdery mildew tends to appear when the garden basks in warm temperatures. Fungal spores carried by the wind may land all over the garden, but germinate when there's high humidity. Still air, wet foliage and cloudy days contribute to mildew start and spread. Once in a pumpkin patch, splattering rain drops can project the mildew onto nearby leaves. Foliage with the white bloom may continue to become further covered even if humidity or soil moisture is low. Warm temperatures alone promote powdery mildew proliferation once it exists in the garden. Even drought conditions lead to severe infestations, according to Purdue University plant pathologists.
  
  

Control

• If powdery mildew tends to recur year after year in your garden, a few cultural modifications may diminish the problem. Do not overwater and make sure plants receive ample sunshine. Spacing plants farther apart may increase air flow among crops and slow the mildew's start and inevitable spread. Horticultural oil, low-toxicity sulfur-based fungicides and 10 percent solution of skim milk work against powdery mildew. Preventative spraying of foliage can prevent bloom from developing on pumpkin leaves. Alternatively, once the white bloom appears, spraying horticultural oil or milk solution best contains the spread to other leaves, stems or nearby plants.
  
  

Tips

• Always read pesticide labels directions and note any cautions about the use of the product on edible crops. There may be a need to wait before harvesting crops after treatment. Some fungicides are better suited to edible crop gardens than others, so look for label commentary that mentions appropriateness for edible crops and specifically pumpkins or squashes. Avoid spraying the pumpkin foliage with treatments on cloudy days. A sunny morning is always better, since temperatures are cool and the sunlight ensures the pumpkin leaves dry well before sundown.