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Weather, air circulation and plant susceptibility trigger powdery mildew disease

Fungus discoloration — Powdery mildew on honeysuckle turns green leaves white. © Jo Ellen Meyers Sharp

Fungus discoloration — Powdery mildew on honeysuckle turns green leaves white. © Jo Ellen Meyers Sharp

If I didn’t know better, I’d think my ‘Goldflame’ honeysuckle has white leaves instead of green.

That’s because my honeysuckle (Lonicera x heckrottii) is susceptible to powdery mildew, which shows up big time in late summer.

Honeysuckle isn’t the only plant that gets this disease. Hundreds of landscape plants may fall victim, including ninebark (Physocarpus), lilac (Syringa), Azalea, dogwood (Cornus), Zinnia, Phlox and roses (Rosa), to name just a few.

Powdery mildew is an apt description of this fungus disease because it looks like leaves, stems or flowers have a coating of white or grayish powder. Eventually, the leaves dry up and fall off.

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Rain may be cause of brown patches in lawn

Lawn disease - Dollar spot lesion. (Photo courtesy North Carolina State University)

Lawn disease - Dollar spot lesion. (Photo courtesy North Carolina State University)

Recently, there has been a spate of queries about lawn care and disease.

A woman wrote and sent photos to the Marion County Master Gardeners to ask about the brown areas on her lawn. The condition was diagnosed as the disease dollar spot. With dollar spot (Sclerotinia homoeocarpa), you usually see a tan band with a reddish border on a green blade of grass.

This is a common condition that may occur with heavy rains, such as we’ve had the last few weeks, explains Steve Mayer, a horticultural educator at Purdue University Extension in Indianapolis. Heavy rains wash the nitrogen through the soil faster than usual. Low nitrogen may allow this fungus disease to sprout. If there is low fertility or a lack of fertilizer, the disease may show up in the lawn.

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