How to stop sawfly larvae from hitting on hibiscus

GARDEN Q&A

August 18, 2007|By Ellen Nibali and David Clement | Ellen Nibali and David Clement,Special to the Sun

My outdoor Hibiscus moscheutos is being eaten up. I love the plant and hate to see it this way. Is there is something I can do?

Larvae of the hibiscus sawfly are difficult to detect, because they are the same color as leaves and feed underneath. They may have finished feeding by now, but if you still find them in numbers, you can spray with insecticidal soap, horticultural oil or Spinosad. Be sure to spray when it's below 85 degrees and use a summer dilution rate for soap or oil. Or knock the larvae off into a bucket of soapy water.

Am I the first person in history to kill English ivy? I usually have to keep it from taking over the yard, but now its stems are dying from the ground up. What gives?

English ivy gets several fungal and bacterial diseases. Bacterial leaf spot and stem canker are fairly common. Remove infected plant material. Thin remaining ivy (mowing works) and rake out accumulated debris to improve air circulation. Avoid overhead or evening watering. Send us a plant sample for a definitive diagnosis.

Checklist

Don't bother spraying fungicides on powdery mildew at this time. However, next spring you can spray horticultural oil at the summer rate on plants that had powdery mildew this year.

Keep mulch pulled a few inches away from plant stems or trunks.

Ellen Nibali, horticulture consultant, works at Maryland Cooperative Extension's Home and Garden Information Center, and David Clement is the regional specialist. The center offers free gardening information to Maryland residents. Call the center's hot line at 800-342-2507 (8 a.m.-1 p.m. Monday-Friday) or e-mail plant and pest questions through the Send a Question feature at hgic.umd.edu.

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