Box Tree Moths – should I treat now?

(Question)

I missed the first two treatments, should I do a treatment mid-September or wait until May?

(Answer)

Thanks for reaching out to Toronto Master Gardeners. We have a Box Tree Moth Gardening Guide which you may be familiar with.

September is one of the times when vigilance and treatment for box tree moth may be required. Particularly if you experienced damage earlier in the year treating the plants now is advisable. As noted in the guide:

Use a pressurized sprayer to spray, and focus on the bottom of the leaves. You can keep spraying every 5 – 7 days, but only as long as you see any caterpillars or pupae on the plants.  Preventative spraying for long periods of time will affect other good moth caterpillars.  OMAFRA (Ontario Ministry of Agriculture, Food and Rural Affairs) recommends that the first time to treat your plants and spray the larvae  is between early May and mid-June. The second spraying is done in mid-July. The third spraying is done in mid September.

Note that observations this year suggest that larvae may be present and treatment may be necessary now.

For additional information on this pest:

Landscape Ontario box tree moth resource page: https://landscapeontario.com/tag/box%20tree%20moth

OMAFRA’s blog: Ontario nursery crops blog (also for landscape plants) by Jen Llewellyn; search box tree moth: https://onnurserycrops.wordpress.com/tag/box-tree-moth/

From OMAFRA: https://onnurserycrops.wordpress.com/2020/05/29/now-is-the-time-to-treat-for-box-tree-moth-larvae-in-toronto/

Good luck with you box trees.