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A large potted knockout r... #137212 - Ask Extension

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A large potted knockout r... #137212

Asked June 27, 2013, 12:44 PM EDT

A large potted knockout rose purchased from Meadow Farms tow months ago. Plant was very healthy when purchased but within the last month or so the leaves are being chewed and very lacy and skeleton looking-The plant is in part shade. No pesticide or fertilizer applied

Montgomery County Maryland

Expert Response

It would be helpful to submit a photo so we can see what you may be dealing with. Go to our Plant Diagnostic website and view photos of a possible insect that may be causing the damage called the rose slug.  http://plantdiagnostics.umd.edu/level3.cfm?causeID=60

It is neither a slug or caterpillar (even though it looks like one), but the larvae of a species of sawfly. Adults are very small flying insects related to wasps. The larva is small and “slug-like” in appearance. It feeds mostly from the underside of the leaf eating many holes and causing considerable damage. Severe rose slug feeding will stunt the rose’s growth and flowering. Apply insecticidal soap or horticultural oil, or a systemic insecticide labeled for rose slugs or sawfly larvae.
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