One of the problems is that the BTM can be feeding on your plant for a while before you see significant damage. One of my entomology colleagues, Joe Boggs, Extension Educator in Hamilton County, noted that research has indicated that boxwoods can go from green to completely brown in 14 days.
Horticulturists always joke about the fact that “plants don’t die overnight!” It appears that the BTM is close to taking down boxwoods almost overnight.
BTM starts feeding in the internal portion of the plant and can feed there for a while. You won’t notice it unless you are actively looking. Open the plant down into the center and innermost foliage and look for symptoms (dead foliage) and the caterpillars.
BTM is a caterpillar that feeds exclusively on boxwoods, killing the plant if it is completely defoliated. The first instars feed on the leaves and aren’t easily noticed. As they continue their growth, they can defoliate an entire plant, leaving the outer edge of a leaf at times.
Keep in mind we also had other boxwood issues last year, including winter damage, Volutella blight and some suspected boxwood blight. You may see dead foliage due to winter damage and Volutella blight. I have not seen any boxwood blight in our area and symptoms are quite different for this disease.
The good news is that BTM can be controlled but must be sprayed with a pesticide. There are biocontrols as well as synthetic insecticides that work. The challenge is that you must absolutely get all the caterpillars, especially those hiding inside of the plant.
If you don’t get all of them, they will continue to develop, pupate, become an adult, and lay eggs again for the next generation. BTM can have up to five generations per year, but currently we have only seen three generations.
The link below has more information as well as a list of control options. If you want to keep your boxwoods, you need to act and inspect and determine if you have this pest, treat if the caterpillars are present.
If you suspect that you have it, currently, report it on the GLEDN app. This can be found in your app store. It’s the Great Lakes Early Detection Network (www.gledn.org for more information) and is available for people to upload photos of a suspected invasive species. You can also email photos to me.
For information on pesticides and other details go to http://go.osu.edu/byglbtm and for information on BTM specifically, go to https://bygl.osu.edu/node/2262.
Pamela Corle-Bennett is the state master gardener volunteer coordinator and horticulture educator for Ohio State University Extension. Contact her by email at bennett.27@osu.edu.
Credit: Contributed
Credit: Contributed
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