How to Manage Pests

Pests in Gardens and Landscapes

Leafminers—Liriomyza spp.

Adult Liriomyza are small, active, black and yellow flies. The most important species are the serpentine leafminer (Liriomyza trifolii) and the pea leafminer (L. huidobrensisa). Larvae are yellow cylindrical maggots that feed beneath the leaf surface.

Identification of species | Life cycle

Damage

Leafminers attack many different vegetable and flower hosts, including cole crops, cucurbits, tomatoes, peas, beans, aster, begonia, dahlia, impatiens, lily, marigold, petunia, and verbena. Adult female leafminers puncture leaves and sometimes petals to feed on exuding sap. These punctures eventually turn white, giving foliage a stippled or speckled appearance. The most obvious evidence of leafminers is the twisting trails (or mines) the larvae leave as they feed beneath the leaf surface. The mine becomes longer and wider as the larva grows. Mining usually has little impact on plant growth and rarely kills plants. Unusually heavy damage can slow plant growth and may cause infested leaves to drop. Damage will not be serious on most plants older than seedlings, although it may make spinach or chard unsightly.

Solutions

Leafminers rarely require treatment in gardens. Provide proper care, especially irrigation to keep plants vigorous. Clip off and remove older infested leaves. Plant resistant species or varieties. Small seedlings can be protected by protective cloth. On plants such as cole crops, lettuce, and spinach, clip off and remove older infested leaves. Leafminers are often kept under good control by natural parasites. Insecticides are not very effective for leafminer control.

Leafminer adult
Leafminer adult

Leafminer mines and feeding punctures
Leafminer mines and feeding punctures

Adult serpentine leafminer
Adult serpentine leafminer


Statewide IPM Program, Agriculture and Natural Resources, University of California
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