Dosdall: Identifying Agronomic Practices that Conserve and Enhance Natural Enemies of Insect Pests of Canola
Date: May 2010
Term: 3 years
Status: Completed
Researcher(s): Dr. Lloyed Dosdall, Deparment of Agricultural, Food and Nutritional Science, University of Alberta, AB
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: ACPC
Project Summary
Yield losses from infestations of root maggots (Delia spp.) can be severe in canola crops in central Alberta. Researchers at the University of Alberta conducted a three- year study to determine the effects of tillage regime, seeding rate and row spacing on canola yield and quality, as well as the effects on root maggots and its principal natural enemy, the staphylinid beetle Aleochara bilineata. Results of this study showed lower root maggot infestations and higher parasitism in zero-till plots relative to plots tilled conventionally. Therefore, canola producers in areas infested annually with high population densities of root maggots are encouraged to adopt, or continue to utilize zero or reduced tillage systems in conjunction with 5.0 kg per ha to 9.0 kg per ha seeding rate and approximately 30 cm row spacings.
Yield losses from infestations of Zero root maggots (Delia spp.) can be severe in canola crops in central Alberta. Researchers at the University of Alberta conducted a three-year study from 2007 to 2009 to compare agronomic practices that have potential to affect crop yield, root maggot infestations and the survival and abundance of the rove beetle or the staphylinid beetle Aleochara bilineata, which is an important natural enemy of root maggots.
The objective of part one of the study was to investigate the impact of conventional versus zero tillage systems, used in conjunction with four seeding rates and three different row spacings on seedling emergence, seed yield, seed weight, and percent seed protein and oil contents of the herbicide-tolerant hybrid canola variety InVigor 5020. For part two of the study, the objective was to investigate the effects of tillage regime, seeding rate, and row spacing on infestations of Delia spp. and population density and parasitism of the predator-parasitoid A. bilineata.
The study was conducted at two sites in central Alberta, Lacombe and Vegreville. Plots were seeded to barley in the years preceding the study. The zero-tillage plots were seeded directly into the cereal stubble with minimal disturbanceofia the surface crop residue. The conventional tillage plots were worked with at least two cultivations to a depth of approximately 8 cm prior to seeding. Plots at Lacombe were seeded with a Conserva Pak® no-till drill whereas plots at Vegreville were seeded with a double-disc no-till drill.
Row spacings used in the study were 22, 30, and 45 cm, and seeding rates were 2.5, 5.0, 7.5, and 10.0 kg per ha. Seed number was adjusted for each seeding rate and row spacing to achieve target canola densities of 60, 120, 180, and 240 plants per square meter. For each plot, plant emergence counts, canola seed yield, 1,000 kernel weight, and canola seed oil and seed protein contents were collected. In addition, assessments of root maggot oviposition, root maggot damage ratings, rove beetle activity density and parasitism levels on root maggot puparia were also conducted.
The study results showed that the predator-parasitoid A. bilineata is important for reducing populations of root maggots in canola in central Alberta. Parasitism rates of 38 to 74% were found for Delia spp. puparia and in some site-years large numbers of adults indicated vast numbers of root maggot eggs were removed by these insects. In general, there was a higher percentage of parasitism of Delia spp. by A. bilineata observed in zero than in conventional tillage. There were no consistent effects observed on A. bilineata activity in relation to seeding rate and row spacing.
The study also found canola yields in relation to seeding rate and row spacing to be variable. The research found no evidence to conclude that tillage regime had a significant effect on canola seed yield. However, the research showed that adopting zero or reduced tillage in conjunction with a recommended seeding rate of at least 5.6 kg to 9.0 kg per ha and row spacing of 30 cm will bring advantages in terms of improved management of root maggots and other important canola pests like flea beetles and weeds, while helping maintain reasonably good seed yields. Canola producers in areas infested annually with high population densities of root maggots are encouraged to adopt, or continue to utilize zero or reduced tillage systems because results of this study showed lower root maggot infestations and higher parasitism in zero-till plots relative to plots tilled conventionally.