Leafminers and Needleminers

Pest Description

• adult leafmining insects include small beetles, flies, sawfly wasps or moths
• larvae are tiny grubs/caterpillars that fit between the upper and lower leaf tissues
• feeding causes telltale patterns in leaf tissue

Host Plants, Diet & Damage

• leafminers: many deciduous tree species
• needleminers: many coniferous tree species
• larvae feed on mesophyll cells on the interior of the leaf
• larval feeding creates silvery white blotches or tunneling in the leaf
• mining may turn leaves brown and translucent
• larval frass is typically present in the galleries
• damage is an aesthetic issue and rarely harms trees

Biology, Life Cycle & Damaging Life Stage

• life cycles are highly variable
• larvae may pupate in the leaf or in the soil below plants
• eggs laid in small groups or singly on or in plant tissue
• one or more generations occur every year, depending on the species

IPM Recommendations

• Manage trees to improve or maintain overall health.
• Pesticide applications are not typically needed for leafminers and needleminers.
• Predators and parasitoids typically manage larvae.
• Apply an insecticide (azadirachtin; neonicitinoid; pyrethroid; spinosyn) to foliage just prior to egg laying.
• Apply a systemic neonicitinoid as a soil drench after leaf expansion in spring.