Boxwood leafminer treatment

Asked April 13, 2020, 10:12 PM EDT

Hi, I have 3 big boxwoods in my front yard with a terrible leafminer infestation. A few days ago I heard loud crackling sounds near them, did a google search and learned about the leafminer. I checked the leaves and there were lots of larvae inside! What can I do? Can I treat with systemic insecticide? There is extensive leaf damage already. Thanks, Alessandra

Delaware County Pennsylvania

1 Response

The boxwood leafminer is a serious pest of Pennsylvania plantings of boxwood. The adults are orange-yellow mosquito like flies about 1/8" long, they will swarm around boxwood in late April and early May. Chemical to control adults include abamectin, acetamiprid, azadirachtin, bifenthrin, carbaryl, imidacloprid, malathion, permethrin, spinosad, and trichlorfon. Applications to control adults should be made from mid-May to early June-repeat applications may be needed. Applications to control larvae should be made early to mid-summer. Systemic products such as imidacloprid and acetamiprid or those with translaminar activity such as azadirachtin or spinosad will provide better control of larvae in the leaves. Be aware that all of the products labeled to control boxwood leafminer are toxic to bees. There is only one generation per year. Be sure to follow pesticide labels exactly. More information can be found here: https://extension.psu.edu/its-spring-and-soon-the-boxwoods-will-sing