Safe removal of boxwood affected by box tree moth

August 28, 2020

Safe disposal of boxwood plants and clippings will help to prevent the spread of the pest.

Box tree moth (Cydalima perspectalis) is an invasive pest found in urban landscapes within the Greater Toronto Area that selectively feeds on boxwood shrubs. High populations of box tree moth caterpillar may defoliate boxwood plants; in some severe cases this can result in plant dieback. It may be necessary to remove or trim the shrub.

Effective removal and disposal of infested plants is crucial to slowing the spread of box tree moth. Please follow the measures below to help prevent the spread of this pest to locations where it is not present:

Place the infested shrub or branch clippings in a black plastic garbage bag and secure the bag to ensure it is closed tightly.
Place the bag outside in direct sunlight for 48-hours.
After 48 hours, larvae should be dead and the plant materials can safely be added to yard waste bins.

Moving forward, it is recommended that boxwood plants receive continual management to ensure box tree moth is controlled and to prevent further plant damage. Plants should be inspected during the general predicted larval periods for each generation of box tree moth, during the following dates:

May 15 to June 15
July 15 to Aug. 15
Sept. 1 to 20

If caterpillars are found actively feeding on the plants, an application of BTK (Bacillus thuringiensis kurstaki) should be applied. Re-inspect the plants 5-7 days after application to ensure it was effective. If live, actively feeding caterpillars are still found, another application should be applied. Routinely monitor the condition of your boxwood plants and presence of caterpillar larvae and feeding damage. BTK application is most effective when used two or three times a year during the time frames listed above.