If you have confirmed Volutella blight (either by the clinic or someone who knows what they are talking about), prune out the damaged areas, beyond the stem cankers.
If you have winter damage only, remove the dead branches, stems down to the green branches. However, when we see winter damage, we also see that Volutella blight has moved in.
Volutella blight affects stressed boxwoods and has affected a lot of boxwoods in the Miami Valley due to the winter cold that put them under stress.
If you discover that you have box tree moth caterpillars or adults, alert the Ohio Department of Agriculture or your county Extension office immediately.
There are at least three major outbreaks in this area, the first one being discovered near Lebanon along the Hamilton/Clermont County line. The second and third outbreaks are in Montgomery County and one of these is in Kettering.
Boxwood psyllids and boxwood leafminers are two other problems that can go without treatment, or you can use a systemic insecticide to kill them when they are feeding next spring. You must follow label instructions and have the insecticide on the plant early enough so that it’s in the leaves when the feeding starts.
To get a confirmation on the problem, send a sample of the damage to the Ohio State University C. Wayne Ellett Plant and Pest Diagnostic Clinic (http://ppdc.osu.edu). When you go to the site it will give you the fee information along with what to send and how to submit the sample.
I recently gave a program on the Boxwood Dilemma, sharing all the different problems we are seeing with boxwoods. After seeing the program and the symptoms of each of these problems, participants had a better understanding of what they were seeing in their landscape.
Within this audience, the majority of the attended suspected that they had Volutella blight. This problem is quite prevalent in the Miami Valley, and not just in landscapes but in our nurseries as well.
I also have had people tell me that their landscaper told them to take out all the boxwoods, even before identifying the problem. Some have suggested that the soil can be treated.
Please please please – identify the actual problem before acting, especially if you have a lot of boxwoods. This is a major landscape plant and can still be used in the landscape if proper care is given, along with an understanding of the common pests.
Who knows where the boxwoods will end up in the future? Will we be using other plants to replace boxwoods, or will we figure out strategies to manage these pests?
Just don’t make rash decisions on removing all your boxwoods until you know what’s going on and have a strategy.
Pamela Corle-Bennett is the state master gardener volunteer coordinator and horticulture educator for Ohio State University Extension. Contact her by email at firstname.lastname@example.org.