Powdery mildew season is upon us

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I looked at my pumpkin leaves and they have some kind of dusty white stuff on the leaves. Then a couple of days later, I looked at the leaves and they were yellow, brown and then they collapsed. Is this another horrible, strange disease killing leaves?

There’s nothing too strange about it, because the fungus that is affecting the leaves is a native son, powdery mildew. This fungus is found on the top or bottom of leaves. Soon after the white mildewy stuff happens, leaves develop yellow-green spots and shut down. Powdery mildew is around each summer when conditions are warm and there is air humidity.

For many kinds of powdery mildew, dry leaves are also part of the invasion deal. Many plants get one kind of powdery mildew or another. On the common garden variety list are lilacs, phlox, monarda and perennial asters. In Veggie Land, tomatoes, potatoes, peppers and eggplant may have some powdery mildew but rarely does it ever need to be treated.

On the kick-em-and-give-em-a-wedgie list are cucumbers, pumpkins, melons, summer and winter squash. Plants can get powdery mildew and go down fast. As they say, the best defense is a strong offense, so before powdery mildew slips in on little cat feet, put on a preventative fungicide. The usual fungicide is chlorothalonil, a commonly used fungicide. If you have plants outside the vegetable garden with powdery mildew, check to make sure that chlorothalonil will work. If you are organic, products that offer prevention are horticultural oils, neem oil, sulfur and baking soda. There are dozens of websites that will give information and instructions.

A biological fungicide called Serenade is a new, excellent option. Regardless of the product, the key to prevention is to regularly repeat applications before powdery mildew appears. Be sure to repeat after a rain or overhead watering because all your protection just dripped off. Trying to stop it after it is found becomes very difficult. Keep in mind, our native son comes home every July or August, so be prepared.

I had several chunks of lawn next to my driveway just die this year. It turned brown in July. One neighbor says it is grubs and the other neighbor tells me to nuke it with some lawn disease stuff. What do I do?

First, buy some ear plugs. Neither guess is leading you anywhere. Sometimes, dead grass is just dead grass. July is too early for grub damage and fungicide can’t help the deceased. Death does not allow any miraculous resurrection. So start over.

Aug. 15 to Sept. 15 is considered the best seeding opportunity of the fall. Notice that is “best” and not “only.” Usually, the weather is a bit cooler and nights cool off nicely. Often moisture appears from the sky and we have to water less. There is enough time for grass to germinate and grow to be able to stand Michigan in the winter.

First job is to get rid of dead grass and work up the soil lightly to loosen it. Sprinkle on the seed and either lightly roll the soil or water gently to settle the seeds into place. Do not bury them. Lightly distribute straw over the seeds so it looks like a lattice. You need to be able to see soil between the pieces of straw. Sprinkle again.

Now, for the bad part. Keep the soil evenly damp for as many weeks as it takes. Rye grasses will be up in about a week; fescues in about two weeks. But those pokey ol’ bluegrass seeds take three to four weeks.

If the grass seed and soil dry out any time within those four weeks, some grass seeds will never be hatched. As seeds become green blades, pick off some straw and keep picking as it germinates and grows. By the time you mow three times, your baby grass is all grown up.

You can contact Gretchen Voyle, MSU Extension-Livingston County Horticulture Educator , at (517) 546-3950.

About Gretchen Voyle 51 Articles
Gretchen Voyle is the MSU Extension-Livingston County Horticulture Educator. She can be reached at (517) 546-3950.