Stop the Powdery Mildew Cycle this Fall

Gardening Tips

by Sandy Swegel

Powdery mildew had a grand time in my garden this year. I often have a nonchalant attitude to it growing on a few leaves and don’t mind a little bit. But it started early this year on roses, then showed up on the bee balms and finished out the season inundating the sweet peas and squashes. By the time I paid attention, it was out of control.

But now it’s Fall and my inner lazy gardener says…ah well this season is over. Next year it will be different. But if we want to make progress against disease in our gardens, now is the time to act.

Do you Want Less Disease in your garden next year? Then take these steps now:

In the Vegetable Garden
As your squash and cucumbers and pea plants are dying back, remove those leaves and put them in the trash. Not in the compost pile. Don’t let them overwinter and deal with it in the Spring. Fungus and disease spores are sitting passively on the backs of those leaves, just waiting for rebirth next Spring. They do not reliably die in home compost piles. Powdery mildew will survive the winter by forming minute fruiting bodies called cleistothecia And tomatoes? I put the whole plants in the trash after frost. There are just too many diseases on them to risk.

In the perennial beds, leaves infected with powdery mildew like rose or phlox or bee balm often drop before Fall. Before the big tree leaf fall, I use the blower to blow the diseased leaves out of the bed and PUT THEM IN THE TRASH.

This vigorous sanitation is a good idea for all pests too. If you had bean beetles…get rid of those leaves that might have next year’s eggs.

But don’t be too clean.
That’s the important lesson here. In the non-diseased parts of the garden, ladybugs and lacewings and lots of beneficial insects are going to lay eggs and overwinter. We want them. I learned last year especially to let willow leaves be…there were dozens of beneficial babies at the base of willow plants last spring.

And next year…be attentive to the powdery mildew. I now promise to treat early and often with something gentle but effective such as horticultural oil or a baking soda. I lost a lot of production in my vegetables this year because I let the powdery mildew have its way. And the roses and phlox really took a hit. I’ll do better next year. I promise.

Photos:
ipm.ucanr.edu/PMG/PESTNOTES/pn7406.html
startorganic.org/tips-for-treating-powdery-mildew/