MSU Extension Integrated Pest Management

Mining pests

Many leafminer types, such as wasps, caterpillars and flies, may attack herbaceous perennials. Adult leafminer flies are 2 to 3 mm long and black to yellow, with yellow bands or markings on the abdomen. They resemble houseflies. Larvae are approximately 3 mm long, shiny and yellow to white. Leafminers usually pupate in growing medium or soil. Leafminers that attack herbaceous perennials include columbine, verbena and larkspur leafminers.

Leafminer larvae feed between the leaf tissues, creating winding or serpentine tunnels or, in some instances, blotches.

Management

Remove and dispose of infested plant parts such as leaves and stems. Remove weeds from adjacent areas – many weeds serve as a reservoir for leafminers. Avoid overfertilizing plants with nitrogen-based fertilizers – this may enhance the attractiveness of herbaceous perennials to adult females and increase the number of eggs laid per plant. Insecticides with systemic or translaminar properties may be used to control leafminers.

Although leafminers don’t usually kill plants, the damage may reduce the aesthetic appearance of infected plants.

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