WSU Extension

Hortsense

Boxwood
 
Disease
Box blight 
Canker 
Leaf spot 
Phytophthora root rot 
Insect
Boxwood leafminer 
Boxwood mite 
Boxwood psyllid 



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Caption: Boxwood leafminer
Photo by: A.L. Antonelli
  
Boxwood : Boxwood leafminer
(revision date: 3/10/2017)


Biology
Leafminers feed by removing green tissue from between the upper and lower leaf surfaces. Feeding by leafminers can be detected by the presence of yellow to brownish blotch-like mines or by a blistered, thickened appearance of the leaves. The larval stage of the boxwood leafminer is a small yellow to green maggot found inside the mined leaves. The adult is a small (1/10") orange to yellow fly which emerges in early May. Damage is mainly aesthetic, but repeated severe infestations may damage shrubs.
Management Options


Non-Chemical Management
  • Plant varieties of English boxwood (Buxus sempervirens) such as 'Suffruticosa', 'Pendula', and 'Argenteo-varigata', which are reported to be seldom damaged.
  • Pinch to kill maggots in infested leaves when practical.
  • Pick and destroy infested leaves when practical.
  • Provide proper culture to maintain plant health. Healthy plants are more tolerant of insect damage.
  • Natural predators may help control populations. Encourage predators such as green lacewings and spiders.
Select non-chemical management options as your first choice!

Chemical Management

If you choose to use a pesticide, apply when leaves are fully formed (around May 1st). Make a second application between mid-June and mid-July.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bonide Systemic Insect Control
    Active ingredient: acephate  |  EPA reg no: 239-2461-4
  • Safer Brand BioNEEM Multi-Purpose Insecticide & Repellent Conc [Organic]
    Active ingredient: azadirachtin  |  EPA reg no: 70051-6-42697
  • This list may not include all products registered for this use.
Images

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Caption: Boxwood leafminer
Photo by: A.L. Antonelli