Hi there, my boxwoods are covered in what I have identified positively as the Boxwood MothCaterpillar.
I have searched endlessly for recommendations on how to get rid of them and what product to use and while there are lots of articles about the pest, I cannot find any information on your site on how to treat or get rid of them.
Thank you for your question.
Without a picture it is hard to determine for certain that it is the Box tree Moth but it certainly sounds like you have done a thorough investigation to confirm that it is.
The Box tree moth is native to eastern Asia. It was first discovered in Britain in 2008 and recently discovered in North America (in Etobicoke, Ontario) in the late summer of 2018.
According to Landscape Ontario, the larvae feed on Boxwood foliage from mid-May to early September. Signs include chewed leaves, larvae, webbing and fine powdery droppings (frass).
The Royal Horticultural Society advises that newly hatched caterpillars are greenish-yellow, with black heads. Caterpillars reach up to a length of 4 cm and have a greenish/yellow body with thick black and thin white stripes along the length of the body. Pupae are hidden in a cocoon of white webbing spun among leaves and twigs.
The webbing should not be confused as spider webbing.
If practical, remove the caterpillars by hand or prune out stems covered in the webbing and caterpillars and destroy.
Landscape Ontario provides a flyer which includes colour images of feeding damage and explains best practices for control and removal.
Royal Horticultural Society
Landscape Ontario is requesting that homeowners report any suspected findings of the box tree moth. You may wish to go to the Landscape Ontario website and report your findings.
Many thanks for choosing our website to inquire about this newly concerning invasive insect.