Maryland Grows

Q: I found a group of caterpillars on my blueberry plants. Some branches were completely stripped of leaves. I have several plants around my yard such as milkweed so hope to ID these before taking action to eradicate.

A: These are Yellownecked caterpillars, a native species that can feed on azalea and various other host plants. They won’t cause severe damage to the plant, even if it’s defoliated, by chewing leaves this late into the growing season. However, if you want to remove them, just pluck them off by hand or knock them into a container of soapy water to kill them. (Or, just knock them off into a dry container and toss them elsewhere for birds and other animals to eat. Yellownecked caterpillars are preyed upon by various insects and other animals, so some will be eaten before they mature.

No pesticide is needed in this case, but if they cause problems in a future year, young, smaller caterpillars can be treated with Btk (Bacillus thuringiensis variety kurstaki), a derivative of naturally- occurring soil bacteria that kills caterpillars without harming other insects. Older caterpillars are not as vulnerable to Btk, so if you miss that life stage and only find them when they’re larger (as pictured here), they can be managed with a spinosad application instead. Spinosad is a relatively low-risk insecticide derived from a soil microorganism and approved for use in organic farming. Follow all product label directions for use, and ensure the chosen product can be used on edible plants.

By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun and Washington Gardener Magazine. Read more by Miri.

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