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Insect and agronomic responses in canola and wheat intercrops Open Access


Other title
Aleochara bilineata
Type of item
Degree grantor
University of Alberta
Author or creator
Hummel, Jeremy
Supervisor and department
Dosdall, Lloyd (Agricultural, Food and Nutritional Science)
Examining committee member and department
Clayton, George (Agricultural, Food and Nutritional Science)
Boivin, Guy (Horticultural Research and Development Center, Agriculture and Agri-Food Canada, Saint-Jean-sur-Richelieu, Québec)
Leiffers, Vic (Renewable Resources)
Spaner, Dean (Agricultural, Food and Nutritional Science)
Keddie, Andrew (Biological Sciences)
Department of Agricultural, Food, and Nutritional Science

Date accepted
Graduation date
Doctor of Philosophy
Degree level
Intercropping systems offer potential benefits relative to monocultures of increased crop yields and improved pest control through physical, chemical, or behavioural interference and the enhancement of natural enemy populations, prompting increased predation and parasitism. Intercrops of canola (Brassica napus L.) and wheat (Triticum aestivum L.) in various proportions were investigated at three sites in Alberta, Canada, in 2005 and 2006, to determine effects on 1) agronomic parameters, including crop grain and biomass yields, crop quality (canola oil and canola and wheat protein), lodging, soil microbial communities, and wheat leaf diseases; 2) pest insects, including flea beetle (Phyllotreta spp.) (Coleoptera: Chrysomelidae) damage to seedling canola and root maggot (Delia spp.) (Diptera: Anthomyiidae) adult collection numbers, egg populations, and canola taproot damage; and 3) beneficial insects, including ground beetles (Coleoptera: Carabidae) and the predator-parasitoid Aleochara bilineata Gyllenhal (Coleoptera: Staphylinidae). Crop yields were similar in intercrops and monocultures, and benefits of intercropping were observed in enhanced crop quality characteristics in some site-years. Neither soil microorganisms nor wheat leaf diseases generally responded to intercropping regimes. Intercropping did not reduce flea beetle damage to canola seedlings. Flea beetle damage was greatest at the first true-leaf stage of canola development. Although a thiamethoxam seed treatment reduced flea beetle herbivory, untreated plots generally did not sustain greater than 20% damage, suggesting that seed treatments were usually unnecessary. Adult Delia did not respond to intercropping canola with wheat, but egg populations were lower in intercrops on a land area basis. Canola taproot damage was as much as 13% reduced in intercrops compared to monocultures. Carabid beetles appeared to respond to qualities of the intercrops and monocultures, such as ground cover, rather than to the level of vegetational diversity itself, but carabid diversity was enhanced in diverse intercrops compared to canola monocultures in one site-year. Aleochara bilineata adult populations and parasitism rates were favoured in canola monocultures, but a temporal shift in A. bilineata adult collection numbers suggests reduced preference for canola monocultures in early summer. Benefits of canola-wheat intercrops identified in this study do not appear sufficient to recommend these cropping systems for widespread adoption in western Canada.
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