What do I do about the powdery mildew on the leaves of my yellow squash plants? It is growing rapidly. I have heard about a milk solution and also a baking soda solution to spray on it. What is best to combat this problem?

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Powdery Mildew is a fungal disease common to many plants in Kentuckiana. The heat and humidity of Ohio Valley summers provides just the right environment for the fungus to proliferate. The tell tale symptom of powdery mildew disease is a white or gray powdery substance on the upper surface of leaves. That substance is actually fungal spores and strands that will spread in either wet or dry weather by rain or wind.
Cultural practices will go a long way in controlling this disease. Make sure that you clean up around the base of the plant VERY well during the growing season and in fall as leaves fall. The fungus will overwinter on fallen leaves and then re-infect the plants next year if plant debris is allowed to remain at the base of the plant.
Pruning the plants to “open them up” or thinning plants to avoid over crowding and encourage air circulation will also help. So will watching your watering practices. Water the soil, not the plants, and water in the morning to give the leaves time to dry off. If the plants are in sun more than shade, they will also be able to resist the fungal infections better.
There may be varieties of your plants on the market that are resistant to powdery mildew, choose these plants whenever possible.
Once your plants get powdery mildew, you can’t get rid of what you’ve got, but you can prevent the disease or prevent it from spreading by making regular application of a fungicide. If you had problems last year or are dealing with particularly susceptible plants, you can start in early spring as new growth with your spray program, follow label directions carefully of course.

Baking soda is a natural fungicide, you might try mixing 3 tablespoons in a gallon of water and using that as a spray.

Thanks Cindi! I tried the baking soda and it is working GREAT for the yellow squash and cucumber plants that only had small spots of powdery mildew on the leaves. On the other hand, the yellow squash plant that I had that was getting overtaken by it doesn't have powdery mildew anymore, but the majority of the leaves have turned brown and dried up since I sprayed and the plant is now in peril. Do you know why?

There are also wilt diseases that will affect squashes and cucumbers. Cucumber wilt is a bacterial disease that causes irreversible, incurable wilting and plant death.

The plant leaves wilt and dry and may be chewed up a little bit. Wilted leaves might recover at night, only to wilt again in the sun the next day, and will eventually die. Fruits will be shriveled.

To test for this bacterial wilt disease, cut a stem off at ground level, squeeze the stem and look for a white sap-like ooze. Touch a knife to the cut stem and if the white comes off in a string on the knife tip, chances are you have bacterial wilt.

The bacteria spend the winter months in cucumber beetles and then are spread to the plant when the beetles feed. Once infected, an entire plant can die in less than two weeks.

There are no chemical controls for bacterial wilt. Remove and discard all infected plant parts. To help control the disease, plant resistant varieties and use row covers to keep beetles away from the plants early in the growing season.