Boxwoods are an elegant shrub that can keep your landscape looking sharp. It is a slow growing shrub making maintenance a much less daunting task than other hedge options. Boxwoods, like all plants, are subject to pest infestation so routine plant health care should be performed to keep them in top shape.
There are a few significant pests which feed on Boxwood but the most destructive is the Boxwood Leaf Miner. This pest feeds on the interior of the leaf, “mining” out the tissue between the two outer layers of the leaf. This mining causes blistering and eventual death of the leaf. In heavy infestations the plant can be severely damaged, stressed, and in the most extreme cases, the plant can die.
What is the Boxwood Leaf Miner?
The Boxwood Leaf Miner is a small orange fly (Diptera family) and infest and feeds on the leaf in the larval stage (maggot). The larvae pupate in May when the adult emerges from the bottom side of the leaf. This leaves the shed skin of the larvae hanging out of the leaf. Once the adult emerges it mates and the female will lay eggs by inserting them into the bottom side of the leaf. The adult is about the size of a mosquito and they die shortly after mating and laying eggs.
The eggs then hatch and the maggot then burrows into the leaf and begins feeding and growing. The larvae feed from early summer into the winter where they become dormant due to the the cold. They feed, again, as the temperatures warm and then pupate to start the cycle over again. There is just one generation per year.
The best treatment is using a systemic insecticide in late June and throughout the summer to control the new larval stage. The adult can be controlled using insecticidal soap, though this treatment requires accurate timing and repeated applications. Because the adults pupate over several weeks in late April to mid May, it is imperative that you routinely inspect your Boxwoods to stay ahead of these pests.