How to Manage Pests

Shield bearers—Coptodisca spp.

Shield bearer larvae feed entirely within the leaves of plants, including apple, cottonwood, crape myrtle, oak, madrone, manzanita, poplar, and strawberry tree. Before pupation, each shield bearer larva cuts a round or oval area of mined foliage from the leaf approximately 0.25-inch long. This portion of the leaf drops to the ground or is carried by the larva and fastened to the bark. High shield bearer populations cause leaves to develop numerous holes, like those made with a paper punch.

The madrone shield bearer, Coptodisca arbutiella, attacks foliage of madrone, manzanita, and strawberry tree in Pacific Coast states. Adults are tiny silvery moths; they emerge in the early spring and lay eggs in leaves. Eggs remain inactive until the fall, when they hatch and the larvae begin mining. In the late winter, the mature black larva cuts an elliptical disk of foliage from the leaf, inside which the larva pupates. The madrone shield bearer has one generation a year. Other species, such as the resplendent shield bearer, C. splendoriferella, on apple, have two generations a year.