Red Turnip Beetle

Table of contents

    Red Turnip Beetle (Entomoscelis Americana Brown)

    Red turnip beetles are native to North America and can occasionally become pests of canola and mustard across western Canada.

    Life Cycle and Appearance (Figure 37)

    Figure 37. Red Turnip Beetle Life Cycle

    The red turnip beetle overwinters in the soil as reddish brown oval eggs that hatch in early May. The grubs or larvae feed on the foliage of cruciferous plants such as flixweed, shepherd's purse and volunteer canola. Mature grubs are black, about 1 cm (0.4") long, with a roughskinned, segmented body. After feeding they enter the soil to form bright orange pupae, which transform into the adult beetles (Figure 38). The adult beetles appear from early June until early July and are 7 mm (0.3") 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.

    Damage

    Figure 38. Red Turnip Beetle

    Photo by Phil Thomas

    The larvae and adult beetles both feed on canola, but the adults are more damaging to the seedling crop. 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 sown 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. The beetles can move considerable distances to reach a canola or mustard crop. They feed only on plants of the mustard family. They may move through a cereal crop, feeding on the cruciferous weeds and volunteer canola as they go. The beetles move slowly, completely devouring canola plants as they move toward the centre from the field's edge, making the damage obvious from a distance. Damage from the red turnip beetle has been sporadic and usually local and minor in northern portions of the prairies.

    Monitoring

    Scout canola fields daily for the first 14 days after emergence.

    Economic Threshold

    No economic threshold has been developed for red turnip beetle.

    Management

    Cultural: Cultivate fields with red turnip beetles in late fall to early spring to bury eggs and reduce larval survival. The beetles have caused severe damage in canola fields situated next to fields where canola was under seeded the previous year to fescue and, therefore, not cultivated. Early spring cultivation removes cruciferous weeds and volunteer canola, destroying the food supply for the larvae.

    Insecticides: Check provincial crop protection guides for registered insecticides. Spraying with a recommended insecticide after the insects enter the canola crop can control the adult or larval stages. Since they move en masse, one or two passes with the sprayer along the field margin, over and in front of the invading insects, will provide total control.