Powdery mildew in the garden is tough to beat

Q. With powdery mildew running rampant this year, would it make sense to treat now to reduce the problem next season? I plan on doing a fall cleanup but am afraid I will not be able to get all the plant debris out of the garden.

A. I would skip the fungicides at this point of the season. Once the infection is severe, it is difficult to control. Keep in mind that powdery mildew is a common fungal disease with various strains that attack a variety of plants. A thorough fall cleanup will help reduce the source of infection next year but will not eliminate the problem.

Because powdery mildew fungi overwinter on leaf litter that may remain in surrounding properties, it can serve as a source of infection in your garden next year. You can reduce the risk of infection by growing plants in their preferred sunlight at the proper spacing. Thin, prune or divide overgrown and crowded plants to increase light penetration and airflow. Use powdery mildew-resistant varieties whenever possible.

Also avoid high-nitrogen fast-release fertilizers that encourage lush succulent growth that is more susceptible to this and many other diseases. Monitor the weather, and watch for early signs of the disease. Then decide if control is practical and necessary.

Q. We have a beautiful rose of Sharon bush that blooms like crazy. The branches droop under the weight and I want to trim it a bit. It is done flowering. Should I prune it now? I always hear you should wait

until after a shrub flowers to prune.

A. Prune summer-blooming shrubs like your rose of Sharon when the plants are dormant. These plants produce flowers each year on new growth.

Spring-flowering shrubs like lilac and forsythia should be pruned right after flowering if you want to control growth and still have flowers. These plants form their flower buds the previous summer. Pruning at other times will eliminate the bloom.

Q. I have a 20-yearold pine tree that I have fertilized with fertilizer spikes in the past. I have been watering and wonder when I should apply more fertilizer. The label says spring and fall. Is now a good time?

A. Proper watering and mulch are the best ways to keep trees and shrubs healthy. These plants have an extensive root system and need minimal fertilization. They get needed nutrients from fertilizer applied to the lawn, surrounding plantings, grass clippings left on the lawn and decomposing organic matter.

For best results, fertilize trees and shrubs in need of a nutrient boost in fall when they have gone dormant or in early spring before growth. Avoid late-summer fertilization that can encourage late-season growth subject to winter kill. Be sure plants need fertilizer before applying.