
                         THE VIRGINIAN-PILOT
                 Copyright (c) 1994, Landmark Communications, Inc.

DATE: SUNDAY, June 26, 1994                    TAG: 9406240113 
SECTION: HOME                     PAGE: G5    EDITION: FINAL  
SOURCE: BY ROBERT STIFFLER, GARDENING COLUMNIST 
DATELINE: 940626                                 LENGTH: Medium

PLANTS ARE OFTEN INFLICTED WITH MILDEW

{LEAD} IN TODAY'S Gardening Reminders, Virginia Beach extension agent Randy Jackson cautions local gardeners about the confusion between anthracnose and powdery mildew on dogwoods.

Indoors or out, a variety of plants are candidates for powdery mildew, especially if they grow where sunlight and air movement are restricted.

{REST} Mary Hausbeck, a plant pathologist at Michigan State University, says powdery mildew can be caused by several fungi. Most are host-specific, meaning if powdery mildew occurs on one plant, such as a lilac, it won't affect a pumpkin vine. But it will affect related plants, such as pumpkin and muskmelon.

The most obvious sign of the disease is a white to gray powder or webby coating on the surfaces of leaves, stems or buds. Infected plants become stunted with distorted leaves, buds and growing tips.

As the disease progresses, infected tissue may die, leaves may yellow and fall and the plant declines in vigor.

Wind carries the spores from plant to plant, where the spores germinate and produce threads that penetrate leaf tissues. Soon, chains of summer spores form on the plant, giving the fungus its powdery look.

Powdery mildew is most likely to occur when days are warm and humid and nights are cool. As the air cools after sunset, moisture condenses on plant foliage, raising humidity to levels that favor germination.

Among vegetables, melons, squashes and cucumbers are most often afflicted. In the flower garden, chrysanthemums, zinnias, roses, phlox, monarda (bee balm) and verbena are popular victims.

Lilacs, crape myrtle, azaleas, viburnums, English oaks and dogwoods are infected often. Even houseplants - such as the jade, African violet, begonia and grape ivy - can be affected.

Best control, Hausbeck says, is to plant resistant varieties. That doesn't help when you see the disease on your plants. Spray plants with fungicides such as Daconil 2787, Funginex, Phaltan or Flotox, a sulfur spray. Always clean up infected leaves that fall off the plant. That helps prevent powdery mildew from carrying over from one year to the next.

Place susceptible plants in areas with plenty of sunlight, well-drained soil and good air circulation.

Prune trees and shrubs to improve air circulation and sunlight. Avoid overhead irrigation because it helps spread the disease. by CNB