The red turnip beetle, Entomoscelis americana Brown, is native to North America and can occasionally become pests of canola and mustard across western Canada.
It overwinters in the soil as reddish-brown oval eggs. The eggs hatch in early May and the larvae (grubs) feed only on the foliage of cruciferous plants, such as canola (including volunteer canola), flixweed, shepherd’s purse. Mature larvae are black, about one centimetre (0.4 of an inch) long, with a rough-skinned, segmented body. After feeding, they enter the soil to form bright orange pupae in which they will transform into adult beetles 1.
The adult beetles appear from early June until early July and are seven millimetres (0.3 of an inch) long with bright red and black patches on their heads and three distinct black stripes running down their backs. After feeding into mid July, the adults burrow into the soil, rest for the summer and then leave the soil in late July or early August to mate and lay eggs. The beetles are often found in groups scattered throughout canola fields, mating near the tops of maturing plants. After mating, the adults do not migrate to the fringes of the field, but lay eggs randomly throughout the field. There is only one generation per year.
The larvae and adult beetles both feed on canola, but the newly-emerged adults are most damaging to the establishing crop in early June. The beetles do not fly in spring. Damage occurs when beetles move into a canola field from a neighbouring field sown to canola the previous year. Unless canola is planted on canola, the beetles remaining in the previous year’s canola field will feed on volunteer canola and cruciferous weeds until the food supply is exhausted or the field is cultivated, forcing migration in search of food.