White powder could be mildew


XENIA — If you are noticing that some of your plants look like white baby powder has been sprinkled on them or that they are covered with what looks like cobwebs, it could be powdery mildew.

There are several different fungi that cause powdery mildew. Some of the fungi only affect one or two different plants, some powdery mildews attack a wide range of plants.


— Infected plants may appear to be sprinkled with baby powder or covered in cobwebs.

— White to gray, powdery spots, blotches or felt-like mats on leaves, stems and buds.

— In some plants, leaves turn purple to red around the infection.

— If young leaves are infected, they may become distorted or twisted as they grow.

— Severely infected leaves may turn yellow and fall off.

— Tiny, round, orange to black balls may form within white fungal mats often at the end of the growing season.

— This disease is most severe on plants or plant parts in shaded areas with poor air movement.


— Replace severely infected plants with a resistant variety or with a plant from a different family.

— Powdery mildew resistant varieties are available for some flowers. Look for powdery mildew resistant varieties in seed catalogs, on seed packages and on plant labels.

— When planting, space the plants to allow adequate air circulation through them.

— Prune to thin the foliage. This increases airflow and light throughout the plant.

— Fungicides should only be used to protect high-value plants that cannot be replaced and have a history of severe infection.

— Fungicides must be applied to healthy green tissue early in the growing season before infection begins.

— Fungicides must be applied to healthy green tissue early in the growing season before infection begins.

For more information, visit https://extension.umn.edu/plant-diseases/powdery-mildew-flower-garden.

According to Norma Landis, OSU Extension Greene County master gardener volunteer fall webworms (Hyphantria curra) may be seen in local trees through October.

These caterpillars produce a fine silk web over terminal branches, skeletonizing the leaves within the web as they turn into mature larvae.

Management may include the use of Bt (Bacilius thuringiensis), horticulture soaps or insecticidal soaps … these products protect our beneficial insects.

Another option may be pruning out the webbed terminal branches and destroy them. Fall webworms do little damage to well-established trees, although they are unsightly.

Find more information at https://extension.psu.edu/fall-webworm.

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