Powdery Mildew - Knowledgebase Question

Racine, Wi
Avatar for ajrichey
Question by ajrichey
September 23, 2009
How do you get rid of Powdery Mildew on squash plant leaves?

Answer from NGA
September 23, 2009
Powdery mildew is unique among plant diseases in that it doesn't require a wet leaf surface to spread. It can thus thrive during hot, dry weather, as well as in high humidity. The first line of defense is to grow resistant varieties, and secondly, keep a close eye out for early infection, and use preventive measures to keep it from spreading. The general advise to inhibit the spread of fungal diseases is to avoid wetting leaf surfaces. In the case of powdery mildew, you can actually inhibit infection with periodic strong sprays of water to dislodge mildew spores (not so strong as to damage the plant.) Some people have had good luck with pesticides containing neem, a plant extract. You can also try using a homemade baking soda spray--mix 1 teaspoon baking soda per quart of water; add 1/4 tsp mild soap to help it stick to the leaves. Apply this once a week, and hose down plants between sprayings. Be sure than any fungicide you use is labeled for powdery mildew, since some are ineffective against this disease. If you believe the plants are beyond hope, remove all of the diseased plants and, bury or throw everything in the garbage. Unless your compost heap really heats up (at least 160F), the fungal spores can overwinter there and reinfect your garden. Plan to grow varieties resistant to the disease next year. Following the ideas above, your mildew problem should be better under control. Best of luck!

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