University of Illinois Extension

University of Illinois Extension

Hort Answers

Fungal Disease

Yarrow problems
Achillea sp.

5 (1 = rare 5 = annual)
2 (1 = very little damage 5 = plants killed)

Plants Affected

Gray mold (botrytis) appears as brown dead areas and under proper moisture may have a gray fuzzy appearance.

Powdery mildew is described as a white powder on the leaves. Powdery mildew tends to be worse on plants growing in shade.

Spittlebug produces a protective foam that looks like "spit." The foam helps protect the insect from ultra violet light and predators and insecticides.

Life Cycle

See Gray mold (annual & perennial for more information on gray mold.

See Powdery Mildew for more information on powdery mildew.

See Spittlebug for more information on spittlebugs.


Fungicides and sanitation are helpful for gray mold.

Fungicides and sanitation are helpful for powdery mildew as well as increasing sunlight and air circulation when possible.

Use a strong spray of water to wash the foam the insect. The resulting exposure to UV light will kill the insect and expose it to predators. A stronger spray of water may also remove the insect from the plant in addition to the "spit."

Related Resources
Home, Yard & Garden Pest Guide
Illinois Commercial Landscape and Turfgrass Pest Management Handbook
U of IL - Distance Diagnosis through Digital Imaging
U of IL - Plant Clinic