Boxwood bushes often are used as hedges in many yards and gardens. While boxwoods are generally healthy, they are susceptible to insect infestations that can affect their health and appearance. The boxwood leafminer is the most common pest of all boxwoods, but slow growing cultivars are generally less susceptible to this pest.
The boxwood leafminer was introduced into the United States from Europe and commonly infests American boxwood, English boxwood and Japanese boxwood. Boxwood leafminers emerge in the early spring and are tiny, orange flies. These flies swarm around boxwoods and lay eggs in the boxwood leaves. Tiny maggots hatch inside the boxwood leaves. These maggots are typically 1/8 inch long and are yellow in color. Boxwood leafminer maggots feed on the inside of leaves until they turn into pupae. Once mature, the pupae emerges as an adult fly.
Boxwood bushes infested with boxwood leafminers have water-soaked blisters on the lower portion of the leaves. These leaves are typically smaller, off-color and drop prematurely. Although boxwood bushes are not usually killed by infestations of the boxwood leafminer, heavy infestations can cause poor color and thin foliage development. Boxwood bushes infested with this pest generally have reduced vigor as well.
Planting boxwood bushes that are less susceptible to the boxwood leafminer is one way to prevent infestations. Slower growing boxwoods such as the English boxwood, Pendula and Suffruticosa are somewhat resistant to this pest. There are natural predatory insects such as green lacewigs and parasitic waps that feed on boxwood leafminer keeping them under control.
Chemical control methods are often effective in controlling heavy infestations of boxwood leafminer. Pesticide sprays and soil drenches are available at your local garden center for leafminer control. These products are most effective if applied during the spring just as the boxwood leafminer begins to fly.
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