Boxwood plants are common across North America. They are very commonly used in landscaping as hedges, shrubs, or backdrops for flowers. Boxwoods are a type of evergreen, which means they have foliage year round, are extremely adaptable to various locations, and they can be pruned into a variety of shapes. All of these reasons make boxwoods very popular plants across the country. And where there are boxwood plants, there is often the boxwood leafminer. Keep reading to learn more about this damaging insect and how you can recognize its signs.
What do boxwood leafminers look like?
Many people might think that boxwood leafminers are worms, because the pest does its most damage in the larval stage—and at that stage they do appear distinctly worm-like. However, the worm-like creatures we see are actually the larvae of a yellow-orange midge. Boxwood leafminers aren’t worms at all—they are midges (small flies) whose larvae feed on boxwood leaves. An adult boxwood leafminer is also an orange color and resembles a mosquito, usually no larger than ⅛ of an inch. Sometimes when adult leafminers are swarming to lay eggs, people do mistake them for a swarm of mosquitoes.
When are boxwood leafminer larvae active?
In the spring, adult boxwood leafminers lay eggs directly underneath the leaves’ surface. Adult female boxwood leafminers have ovipositors, tubes that they will use to lay their eggs by inserting them into a leaves. One female leafminer can insert up to about 30 eggs into a single, new boxwood leaf. The female adult will die shortly afterwards. Within a few weeks, these eggs hatch, and leafminer larvae begin feeding between the lower and upper leaf surface. Boxwood leafminers complete their destructive behavior in the larval stage, growing and continuing to eat more as they grow. Sometimes damage is not noticed a few months or until later in the summer, when larvae are larger. The distinct feeding habits of these insects create trails in the leaves that are called mines. Leaves can blister where multiple mines come together. Boxwood leafminer larvae will overwinter within the leaf, before pupating and emerging as adults the next spring. Adults will then lay eggs in new boxwood plants and the cycle begins again.
What are the signs of boxwood leafminers?
Like with other common garden pests, the boxwood leafminer causes dam age with distinctive signs. While the most obvious and distinctive sign of boxwoods leafminer activity is the tunnels they make, other signs of boxwood leafminers include:
- ● Mine tunnels in leaves
- ● Blistered leaves, or leaves with obvious blisters or punctures
- ● Yellow spots on leaves
- ● Dead twigs (worst case)
While damage from boxwood leafminers rarely causes plant death, it can cause significant aesthetic damage. And, since boxwoods are often used for landscaping and aesthetic purposes, this is often a nuisance and disappointment for the homeowner. Damage from boxwood leafminers should not be confused with boxwood blight, which is a fungal infection that causes distinctive brown spots. Unlike boxwood leafminers (for the most part), boxwood blight can cause plant death.
How can you get rid of boxwood leafminers?
Maintaining healthy plants free of stress with adequate water and proper pruning will help plants withstand low to moderate levels of infestation. Scouting is also important – watch your plants early and often to catch pest problems before they get bigger. Boxwoods leafminers are most easily controlled as larvae. Early to mid-spring is the best time for control applications. The best way to manage them is to call a landscape professional.