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Management of western bean cutworm Striacosta albicosta (Lepidoptera: Noctuidae) and mycotoxins in Ontario maize

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Title: Management of western bean cutworm Striacosta albicosta (Lepidoptera: Noctuidae) and mycotoxins in Ontario maize
Author: Smith, Jocelyn Leigh
Department: Department of Plant Agriculture
Program: Plant Agriculture
Advisor: Schaafsma, ArtHallett, Rebecca
Abstract: Western bean cutworm, Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), is a pest of maize, Zea mays (L.), that has recently established in Ontario, Canada following a range expansion from the western United States. In addition to yield loss, ear feeding by S. albicosta was expected to exacerbate infection of mycotoxigenic fungi in maize grain, especially in southern Ontario where environmental conditions frequently favour infection of maize by Fusarium spp. The objective of this research was to determine effective management strategies for S. albicosta in Ontario. Specifically, the efficacy of Cry1F Bacillus thuringiensis (Bt) transgenic maize was evaluated for control of S. albicosta injury in field experiments from 2011-2015, and the susceptibility of Ontario field-collected S. albicosta to Cry1F was investigated using laboratory concentration-response bioassays. Non-Bt and Bt (Cry1F and Vip3A × Cry1Ab) maize hybrids in combination with insecticides and fungicides were evaluated for control of S. albicosta injury and accumulation of mycotoxins, particularly, deoxynivalenol (DON), under natural field infestation conditions from 2011-2014. The most effective application timing of pesticides was also investigated. Lastly, the relationship between S. albicosta injury and DON accumulation in maize was investigated based on field experiments in 2012-2014. A simple calculation for estimating the risk of F. graminearum infection during the silking and insect feeding periods was used to develop parameters to describe the relationship between S. albicosta injury and DON accumulation using multiple regression analysis. The results of this research provide evidence for field-evolved resistance to Cry1F within Ontario populations of S. albicosta and confirm the lack of efficacy of Cry1F-expressing hybrids for control of S. albicosta. Excellent control of S. albicosta injury was achieved with the Vip3A event and control of non-Bt and Cry1F maize was improved with insecticide application; however, low levels of DON were observed regardless of Bt event. A combined application of insecticide and fungicide at the full silking stage is recommended for maize hybrids lacking tolerance to F. graminearum infection. Lastly, these results confirm that injury by S. albicosta can increase the risk of DON accumulation in maize grain in Ontario; however, hybrid tolerance to F. graminearum and environmental conditions are predominant factors in DON accumulation.
URI: http://hdl.handle.net/10214/11500
Date: 2017-08


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