The Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) has posted a notice reminding gardeners that those yellow / orange spots on boxwood leaves are the result of boxwood leaf miner pupating inside them. Since adult miners (midges) are emerging now, it’s time to get this pest under control.
Look closely to find empty pupal cases sticking out through tiny holes in the undersides of leaves. Adult midges lay their eggs on newly emerged leaves and those eggs will hatch into the next generation of leaf miners.
There are two actions gardeners should take:
- Use insecticidal soap sprays to suppress adults.
- Prune out new foliage in July/August. The clippings will dry out, making it impossible for the leafminer larvae to complete their lifecycle.