Gardening: Be sure to protect oak trees quickly

Nancy Szerlag
Special to The Detroit News

Last week, I received an important oak wilt prevention update from David Roberts, a plant pathologist from Michigan State University. He asked me to clarify and stress the importance of quick action when dealing with oak tree damage.

If storm damage occurs on your oak tree, corrective pruning should be done within 12-24 hours for best results. However, when any pruning is done, whether maintenance or corrective, any exposed injuries should be painted with tree paint or latex paint ASAP – as soon as the last cut is made. Unfortunately sap beetles that spread the deadly oak wilt begin feeding within minutes after a fresh wound occurs.

In the case of a jagged branch end from storm damage, an arborist would make a corrective pruning cut at least a couple of feet back from the injury within (12-24) hours; this would eliminate any infection that might have taken place on that branch within hours of the storm. That fresh wound created by the arborist needs to be painted immediately after the cut is made to avoid further re-infection. For more information on oak wilt, other tree diseases and tree care, visit Dr. David Roberts’ website at

Home brew for prevention of powdery mildew on cucumbers, squash and other cucurbits: If, like me, you’re an organic gardener and hate using chemicals in the vegetable garden, there’s an interesting blog to check out about using milk to fight off dreaded powdery mildew. Stephen Scott from Underwood Gardens, (home of Terrior Seeds, purveyor of organic heirloom seeds) writes at under garden advice.

Scott suggests home gardeners use about 20 percent milk to 80 percent water; so for a small batch he would mix up 1 cup of milk to 4 cups of water. Scott says you can use whole, low fat or skim milk. However, milk spray users in Australia protecting grapevines for wine making say whole milk is more effective.

Applications should be made once or twice a week or after a rain. Be sure to spray both sides of leaves. Make your applications in the early morning or evening after the bees have left the garden.

If you’re growing old-fashioned zinnias that often suffer from powdery mildew, spray them also. Milk spray is best used before the disease strikes so don’t wait until the leaves of your plants look like they have been dusted with powder to begin the program.

Nancy Szerlag is a master gardener and Metro Detroit freelance writer. Her column appears Fridays in Homestyle. To ask her a question go to and click on Ask Nancy. You can also read her previous columns at