donnan.com

  

Boxwood Leafminer

Boxwoods infested with leafminers look sparse

By: Sandy Feather ©2009
Penn State Extension


Q. My Boxwood’s leaves appear to have blisters on them. Is this anything to be concerned about with my Boxwood?

A. Blisters on boxwood leaves are characteristic of boxwood leafminer (Monarthropalpus flavus) damage. These insects overwinter as partially grown larvae in the leaves of susceptible boxwoods (Buxus spp.). It is common for more than one larva to occupy the same mine. Littleleaf boxwood (Buxus microphylla) and common boxwood (Buxus sempervirens) are both susceptible to boxwood leafminer, but individual cultivars of both species exhibit resistance to this pest.

As weather warms in spring, the pale yellow larvae feed and grow rapidly inside the leaves. They pupate in late April or early May, taking on a bright orange color. Adult leafminer flies emerge from infested leaves over a two week period as boxwoods begin to put on new growth, just about the time weigela begins to bloom. Females begin laying eggs in the upper leaf surface of the new growth soon after emergence, inserting them deep into the leaf tissue. She dies soon after laying the last of her eggs. The eggs hatch in about three weeks, and the larvae begin feeding inside the leaves. We have a single generation of boxwood leafminer in the Pittsburgh area annually.

Boxwood cupped leaf
Boxwood leaves are also affected by psyllids.


 


A heavily infested plant may appear sparse and unthrifty. While these insects are unlikely to kill your boxwood, they can reduce its ornamental appeal. Infested leaves generally are smaller, exhibit poor color, and drop faster than healthy ones.

Psyllids on Boxwood
Leafminer damage should not be confused with another Boxwood pest in the photo above: Psyllids

Control options include growing varieties of boxwood reported to be resistant to boxwood leafminer. You can also prune boxwoods prior to adult emergence or after egg laying to mechanically remove the larvae and eggs. Insecticide applications made in May while weigela is in bloom may reduce the population of boxwood leafminers for next year.


Insecticides

Insecticides labeled to control boxwood leafminer include Sevin (carbaryl), malathion, pyrethrins and piperonyl butoxide, and Montgomery Garden Insect Spray or Captain Jack’s Deadbug Brew (spinosad). Bayer Advanced Tree and Shrub Insect Control (imidacloprid) is a systemic product that will kill the small larvae while they are inside the leaves. It is best applied while the mines and larvae are very small, sometime in June.

MORE

Common stalk borer

Spraying pesticides

Pine Sawfly

 

    


home | terms of use | contact | search | site map
Copyright ©2017  DONNAN.COM  All rights reserved.