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How to Manage Boxwood Pests: Leafminers and Box Tree Moths

This past weekend, my parents and I spent hours picking off box tree moths off our boxwoods. Every time I thought that we might have been close to the end, more and more kept showing up. At the end of the weekend, we must have picked off hundreds of tree moths! If you’ve ever dealt with them you know what a pest they can be.

In the past years we have also had leafminers, and unlike box tree moths, these pests can’t just be picked off. They invade the leaves of the boxwoods and are a nuisance.

box tree moth on plant

What are leafminers?

Leafminers are commonly found on boxwood plants and like their name these pests mine their way into the leaves of the boxwoods. Adult boxwood leafminers only live for a few weeks and they look like little mosquitos, however they lay eggs inside the leaves of the boxwoods, and the eggs hatch into a bunch of larvae. They hatch around spring/early summer and they live and grow inside of the boxwoods leaves for months before they become an adult and start the cycle over again.

What are box tree moths?

Recently, within the past few years, box tree moths have been found all over residential areas in Toronto. Before they hatch you will see white cocoons and webbing on your boxwoods, and if you see white or green larvae with a dark colored head, that is a box tree moth.

Boxwood leafminers

How do I get rid of leafminers?

There are a few different approaches to getting rid of leafminers, and it has to do with what stage of the lifecycle they are at and how infested your boxwoods are.

  • If you are thinking of planting boxwoods, it is good to plant one that has a stronger resistance to leafminers, like ‘Suffrutoicosa’ or ‘Vardar Valley’.
  • If it is only lightly infested, you can prune the affected areas in the early stages before they turn into adults
  • There are also insecticides which are very effective at killing the leafminer larvae, however, they contain harsh chemicals and will also kill surrounding pollinators.

How do I get rid of box tree moths?

  • The method that I have been using is picking them off the boxwoods, and while it takes longer it has not caused any damage to my boxwoods or garden.
  • There are also insecticides that can treat them during the larval stage and it is the same as the gypsy moth insecticide.
box tree mothes in tub

Leafminers and box tree moths are some of the biggest threats to boxwoods. They invade the plant, which is why it is important to stop this problem early on. They are able to cause the leaves to turn yellow or brown, and in more severe cases, can kill boxwoods.

If you’re struggling with other common garden pests, check out our guide to dealing with garden pests.

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