The following information was provided by Tracey Baute, field crop entomologist, OMAFRA.
Cereal leaf beetles feed on wheat, oat, corn, forages and grassy weeds. Spring plantings are most attractive, particularly late plantings, though some winter wheat can be infested in the spring. Both adults and larvae cause damage by chewing long strips of tissue between the leaf veins, leaving the top layer of the leaf intact (see image below). This creates a window-pane or “skeletonizing” effect. Most of the injury is caused by the larvae in June. Heavily damaged fields appear silver.
The cereal leaf beetle adult is a metallic, blue-green beetle, approximately five mm in length, with a reddish-orange head and legs (see image at top).
The larvae are six mm in length when mature and yellowish in colour, but this colour is obscured by a black deposit of fecal material making it slug-like in appearance (see image below).
Control is warranted if an average of three larvae per tiller are found before the boot stage. One cereal leaf beetle adult or larva per stem warrants control after boot but prior to heading. If significant feeding is taking place on the flag leaf in the early heading stages, control may also be warranted. Malathion 500 EC is the only insecticide registered for the control of cereal leaf beetle in wheat, barley and oats.