Tillage regime, row spacing, and seeding rate influence infestations of root maggots (Delia spp.) (Diptera: Anthomyiidae) in canola

Infestations of root maggots (Delia spp.) (Diptera: Anthomyiidae) were assessed in Brassica rapa L. and Brassica napus L. grown under conventional and zero tillage regimes, at three row spacings (10, 20 and 30 cm) and three seeding rates (5.0, 7.5 and 10.0 kg ha−1 or 120, 180 and 240 plants m−2). The studies were conducted during two growing seasons (1995 and 1996) at each of two sites in central Alberta. Root maggot infestations were assessed by determining the numbers of eggs laid per plant during the growing season and by larval feeding damage to canola taproots assessed at the end of the season. Seed yields of the treatment plots also were determined. Plants of B. rapa were significantly more susceptible to root maggot infestations than were plants of B. napus. Root maggot egg populations and root damage were generally greater with zero tillage than with conventional tillage. Plants grown at higher seeding rates (7.5 and 10.0 kg ha−1) usually had less root damage than plants grown at the lowest (5.0 k...