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Dosdall, L. M., Florence, L. Z., Conway, P. M. and Cowle, N. T. 1998. Tillage regime, row spacing, and seeding rate influence infestations of root maggots (Delia spp.) (Diptera: Anthomyiidae) in canola. Can. J. Plant Sci. 78: 671-681. 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 kg ha -1 ) seeding rate, and canola grown at wider row spacings (20 and 30 cm) had less root damage and higher yields than canola grown at the narrowest spacing (10 cm). Response surface regression analyses determined that deposition of fewest root maggot eggs per plant, least root damage and maximum yields occurred at seeding rates ranging from 7 to 11 kg ha -1 and at row spacings ranging from 17 to 25 cm. Even though canola grown in zero tillage had greater root maggot infestations than canola grown in conventional tillage, higher yields still occurred with zero tillage. Zero tillage is therefore an appropriate agronomic practice in areas infested by high populations of root maggots. Sowing B. napus rather than B. rapa, increasing seeding rates and widening row spacings are also appropriate cultural control practices for reducing crop damage from these pests. Les analyses de régression de la surface de réponse ont servi à déter-miner que les pontes de la mouche les moins abondantes par plantes, les endommagements racinaires les plus bénins et les rendements maximums survenaient à une densité de semis allant de 7 à 11 kg ha -1 et à des largeurs de l'interligne se situant entre 17 et 25 cm. Même si le semis direct donnait lieu à des infestations plus graves que le travail classique, il gardait encore l'avantage sur ce dernier sur le plan du rendement. Il demeure donc une pratique agronomique convenable dans les zones de fortes infestations par la mouche des crucifères. L'utilisation de B. napus plutôt que de B. rapa, l'accroissement de la densité de semis et l'élargissement de l'interligne sont d'autres bonnes techniques culturales de prévention des dégâts causés par ce ravageur.

Dosdall, L. M., Yang, R.-C. and Conway, P. M. 2002. Do applications of sulfur or sulfate influence infestations of root maggots (Delia spp.) (Diptera: Anthomyiidae) in canola? Can. J. Plant Sci. 82: 599-610. While the importance of sulfur nutrition for the development of healthy stands of canola is well documented, the role of sulfur in the management of insect pest infestations has not previously been investigated in this crop. Field experiments were conducted at three sites in central Alberta in 1997 and 1998 to determine the influence of sulfur and sulfate applications on infestations of root maggots (Delia spp.) (Diptera: Anthomyiidae) in canola (Brassica rapa L.). Different formulations (granules, powder, prills, and sprays), application methods (either drilled in with the seed or top-dressed on the soil surface), and application rates were evaluated. To assess the degree of root maggot infestation, oviposition throughout the season and damage to taproots at the end of the season were monitored. Sulfur contents were analyzed from leaf samples collected mid-season and seed yields were measured from all treatment plots. Root maggot responses to the different sulfur treatments and application methods varied among years and sites, indicating that environmental factors have great importance in determining infestation levels by these pests, and the oxidation rate of elemental sulfur in soil. Sulfur formulation and application rate had significant effects on root maggot egg deposition and root damage for some sites and years, but even at high rates of application (112 kg ha -1 ) reductions in infestation levels were not substantial relative to the controls. While sulfur additions alone will not greatly reduce root maggot infestation levels in canola, growers should employ adequate sulfur nutrition for optimum crop health to enable plants to better compensate for damage by these pests. On a très bien étayé l'importance du soufre pour l'établissement de peuplements vigoureux de canola. Jusqu'à présent cependant, on ne s'était pas penché sur le rôle de cet élément dans la lutte contre les ravageurs de cette culture. Les auteurs ont effectué des essais sur le terrain à trois endroits, dans le centre de l'Alberta, en 1997 et 1998, en vue de déterminer les effets d'une application de soufre ou de sulfate sur la population de mouche des racines (Delia sp.) (Diptères : Anthomyidés) dans les champs de canola (Brassica rapa L.). Ils ont pour cela recouru à divers taux, préparations (granules, poudres, sphérules et pulvérisations) et méth-odes (application avec la semence ou à la surface du sol). Pour déterminer le degré d'infestation, les auteurs ont surveillé l'oviposition durant la saison de croissance et déterminé les dommages causés aux racines à la fin de cette dernière. Ils ont aussi déterminé la concentration de soufre dans les feuilles au milieu de la période végétative et établi le rendement grainier des parcelles traitées. La réaction du ravageur aux divers traitements et méthodes d'application varie avec l'année ...