Box tree moth (Cydalima perspectalis) is a newly detected invasive insect in our area that can devastate boxwood plants. A pest in Europe for more than a decade and identified in Ontario, Canada in 2018, the moth appeared in our area in 2021, traveling on an infested shipment of plants. A heavy infestation of box tree moths on your boxwood plants can result in plant death as the insects devour the leaves and then move on to consume the bark.

Box tree moths can cause dramatic defoliation and desiccated areas of leaves with a few telltale identifiers:

• the entire leaf except for the tough midrib may be chewed through leaving a branch of curly leaf ribs;
• the lower portion of the boxwood plant is apt to be most affected;
• the insects leave behind black-green droppings and easily detectable webbing on the interior of the plant while feeding.

The yellow green caterpillars hatch in cycles, May through September, and the adult moths emerge beginning in June in our area. Photos of the moths, their eggs and the caterpillars can be found in this fact sheet from the USDA.  

The insects are expected to expand their range and have been identified in several Midwestern states. If you detect box tree moths on your plants, you should:

• Report any occurrences to your state’s Department of Agriculture. Some links for reporting can be found here. The New York State Box Tree Moth Reporting Portal is here.
• Treat if possible. Control approaches are in the development stage and being assessed for effectiveness. Techniques include knocking caterpillars off into soapy water, pheromone traps and horticultural oils but you should contact your county’s cooperative extension office for the most up to date information on the management tools that are effective in your location. If you are in New York State, you can find The Cornell University College of Agriculture pest control information on their pest management webpage. (The webpage has excellent photos of the damage experienced from a box tree moth infestation.)
• Take precautions to prevent spread. In New York State, Cornell recommends that you securely bag any plant material that you remove, including entire plants, keep it on site and contact New York State Department of Agriculture through their box tree moth reporting portal for additional advice

You can learn more about boxwood pests and diseases from our Guide to Boxwood.

Courtesy of NYBG Plant Information office