How to Manage Pests

Parasites of tentiform leafminer

Several parasitic wasps help control the leafminer. Parasite activity is usually highest and easiest to see following an outbreak of leafminers. The actual level of parasitization is highest, however, when leafminer populations are low.

Female parasites usually lay their eggs in the leaf mine formed at the beginning of the tissue-feeding stage. After hatching, parasitic larvae generally attach themselves to the outside of fourth- or fifth-instar leafminers. The parasite grows rapidly and consumes the leafminer by its fifth instar. It then pupates within the leaf mine, at about the same time as the leafminer would have. Although smaller than a leafminer pupa, the parasite pupa can be distinguished by its larger head and eyes and flattened body. Following pupation, the adult parasite cuts a hole in the leaf and emerges. Adult parasites are small but easy to spot when populations are abundant because they fly in groups that hover near infested trees. Adult parasites feed on the sap-feeding leafminers.

A leafminer parasite larva

Parasite pupa (bottom) and leafminer pupa