How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

Leafminer adults are small flies with yellow and black markings. Females lay eggs on the surface of the leaves. When eggs hatch the larvae burrow into the leaves and feed on plant tissue. The larvae are small, legless maggots that are frequently found next to main veins.

DAMAGE

Both larvae and adults cause damage to plants. Larval feeding results in slender, winding trails on the leaves, which form large, white blotches when mining becomes severe. Adults damage plants by carving small pits on the leaf surface with their ovipositor and feed on plant exudates. There may be as many as 100 feeding punctures on a single leaf. Around 5% of these punctures may contain actively feeding larvae.

MANAGEMENT

The larvae and adults are most active in spring, with several generations that follow in quick succession. Natural enemies can provide good control of the pea leafminers and 50 to 90% parasitism of the larvae is not unusual. Several species of parasitic wasps from the genera Diglyphus, Opius, and Dacnusa attack leafminer larvae. Some of these species are commercially available.

No economic thresholds have been established, though plants appear to outgrow feeding damage by larvae and adults, and treatment is not usually required.

PUBLICATION

UC IPM Pest Management Guidelines: Sugarbeet
UC ANR Publication 3469
Insects and Mites
C. G. Summers, Entomology, Kearney Agricultural Center, Parlier
D. R. Haviland, UC IPM Program, Kern Co.
L. D. Godfrey, Entomology, UC Davis

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