I noticed leaves with yellowy blotches and opened a few up to find tiny yellowish-orange larvae inside. I think I have boxwood leafminers. As it is only mid-May, is it too early to shear the boxwoods? What time is best to spray with an insecticidal soap?
Thank you for contacting the Toronto Master Gardeners
Your description confirms that your boxwoods are attacked by Boxwood Leafminer (Monarthropalpus flavus). The leafminer is the larva (immature form) of a small, orangish mosquito-like fly. Here is a link to a previous Toronto Master Gardener post on ‘time to deal with boxwood leaf miners’, which you may find informative: Boxwood leaf miner?