First it attacked the lily of the valley, then the caryopteris, now the...

Asked June 24, 2013, 8:38 PM EDT

First it attacked the lily of the valley, then the caryopteris, now the spinach and the rose. What is it? How to combat it?

Carroll County Maryland horticulture

1 Response

My suspicion is that the "it" is probably not one thing, but several different offenders. It would be very unusual to have one particular type of pest damaging the wide variety of plants you listed.
Your first step to managing these pests is to ID them. Sometimes we can get a pretty good idea of who these critters are by the type of plants damaged, when they are attacked (time of day & year), the damage inflicted (foliage, stems, roots or entire plant) and nature of the damage (small holes, ripped stems, brown patches …). In many cases the pest is not a pest at all but a non - biological factor such as storm damage, herbicides, fertilizers ….
I know this will require a bit more work but, if possible, please send pictures of the damage on the various plants you have listed with a short synopsis that answers the various diagnostic components I have outlined above. It would probably be best to send these to me directly via email. My email address is hortman@umd.edu.
As for the rose, the damage, at least from the picture provided, looks like rose slug is the culprit. This is from our home Garden Information Center:
Rose Slug: The rose slug is a very common pest of landscape roses. It is neither a slug or snail but the larvae of a species of sawfly. 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 another insecticide labeled for rose slugs.
Please see the following links to better help you with this potential problem: http://plantdiagnostics.umd.edu/level3.cfm?causeID=202 http://www.clemson.edu/extension/hgic/pests/plant_pests/flowers/hgic2107.html General roses pest from Clemson.
You may also want to look at this general fact sheet on about Integrated Pest Management in the home garden: IPM Series: A Common Sense Approach to Managing Landscape Problems http://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/HG62%20IPM%20A%20Common%20Sense%20Approach%20to%20Managing%20Problems%20in%20Your%20Landscape.pdf