![]() But when adult beetles are numerous, they invade the crop, gradually moving inward from the margins, destroying the crop as they go. When red turnip beetle populations are low, only plants at the edges of the fields are at risk. Small seedlings are more susceptible to damage than larger seedlings. Depending on the size of the seedlings and on beetle abundance, damage will vary from the loss of small portions of the cotyledons and true leaves to complete defoliation and death of plants. The larvae and adults feed on the cotyledons, true leaves, petioles, and stems of seedlings. Occasionally, crop damage may occur in patches throughout the crop when volunteer canola, rapeseed, mustard or weeds belonging to the mustard family were abundant the previous year and the canola, rapeseed or mustard is direct seeded with conservation tillage equipment. Invading beetles are usually concentrated in a moving front only a few yards wide. Adult beetles normally walk to the new food source. DamageĬrop injury in canola, rapeseed, or mustard fields usually occurs along field margins when beetles move in after cruciferous plants in adjacent fields are either consumed or controlled. ![]() The use of direct seed, "zero till" and "chemical summerfallow" practices may contribute to this insect becoming an important crop pest. ![]() Although present in Washington, Idaho, Montana, Wyoming, Colorado, North Dakota, Minnesota, and Wisconsin, it rarely damages cruciferous crops. It is native to North America and relatively abundant throughout the Aspen Parkland Region of the Canadian Prairies and the Peace River District of Alberta and British Columbia. Red turnip beetles are an occasional pest of canola, rapeseed and mustard in the northern Great Plains of North America. In May and June, infestations of both larvae and adults originate in stubble fields of canola, rapeseed, and mustard or in other fields containing heavy stands of weeds of the mustard family ( Cruciferae), which have not been controlled by cultivation or treated with herbicides during the fall or early spring.
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