Shield bearers—Coptodisca spp.
Larvae of more than one dozen species of shield bearers feed entirely within the leaves of plants, including apple, cottonwood, crape myrtle, oak, madrone, manzanita, poplar, and strawberry tree. The madrone shield bearer, Coptodisca arbutiella, attacks foliage of madrone, manzanita, and strawberry tree in Pacific Coast states. Adults are tiny silvery moths; mature larvae are black. 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.
In the fall, larvae hatch and begin mining leaves. In the late winter, mature larvae cut round or oval areas of mined foliage from the leaves, 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. Infested leaves may become partially necrotic and drop prematurely.
No effective controls have been documented for most shield bearers in landscapes. Pick and dispose of infested leaves on small plants if damage cannot be tolerated. Spraying for shield bugs is not recommended. Much of their life cycle is spent within plant tissue protected from insecticides. Spraying disrupts the parasites that may help to limit shield bearer outbreaks to a short duration.
Poplar shield bearer larvae
Madrone shield bearer damage to manzanita