Assessment of baculovirus agents for cabbage looper control in greenhouses

Project code BPI06-180

Project lead

Martin Erlandson - Agriculture and Agri-Food Canada

Objective

To assess the comparative infectivity and virulence of three baculovirus isolates against cabbage looper in small scale greenhouse trials

Summary of Results

Background

Greenhouse vegetable production is a significant component of the agri-food industry in Canada, representing more than $1 billion in farm gate value and 10,000 employees in 2010. The cabbage looper (Trichoplusia ni) is a major insect pest in greenhouse vegetable production in Canada, which causes severe economic losses through defoliation and contamination of vegetables with excrement, a particular problem late in the production cycle. Moreover, this pest has recently developed a high level of resistance to the commonly used biocontrol product Bacillus thuringiensis (Bt). As the greenhouse industry relies extensively on biological control solutions to control insect and disease problems, there is an immediate need to provide an alternative to Bt products for cabbage looper control.

Previous investigations of pathogenic micro-organisms associated with cabbage looper larval populations in greenhouses indicated that several indigenous baculoviruses may have potential as biological control organisms for this pest species. Baculoviruses belong to a family of insect-specific virus pathogens that have been previously exploited as biopesticides for control of insect pests in forestry and agriculture. These viruses have good potential as host-specific microbial insecticides, particularly against lepidopteran insects. Efficacy data generated in this project is intended to support the registration of a baculovirus control product for cabbage loopers on greenhouse vegetable crops in Canada.

Approaches

Indigenous baculovirus strains from cabbage loopers were first identified and characterized. Laboratory and greenhouse spray trials were then undertaken to investigate the efficacy of these indigenous baculovirus isolates for control of cabbage looper in greenhouse vegetable production.

Greenhouse spray trials were conducted using individual caged plants and walk-in cages to determine virus deposition and uptake from sprayed cucumber plants. These experiments were used to determine the optimal virus dose to apply in the larger scale efficacy trial that was conducted in a split plot design. All greenhouse trials were conducted at the AAFC-PARC (Pacific Agri-Food Research Centre) greenhouse complex in Agassiz, BC.

Baculovirus dose response bioassays were conducted using standard laboratory approaches to determine the best candidate isolates for cabbage looper control. Standard molecular biology techniques and DNA sequencing approaches were used to characterize baculovirus isolates at the gene level in collaboration with the National Research Council's (NRC) Plant Biotechnology Institute (PBI) sequencing facility in Saskatoon, SK and AAFC-PARC Summerland.

Results

Indigenous baculovirus isolates with potential as biopesticides for control of cabbage looper larvae were characterized in depth at the genome sequence level providing ample agent characterization for biopesticide registration purposes. Several types of contained greenhouse spray trials demonstrated that the characterized baculoviruses can successfully control cabbage looper infestations and significantly decrease damage to vegetable crops. Adequate control potential was achieved for various insect developmental stages and even under high pest pressure.

Importantly, biopesticides based on indigenous baculovirus isolates have potential as an alternative to Bt for control of cabbage looper larvae and could eliminate the need for chemical insecticide treatments in greenhouse vegetable crops (particularly late in the crop cycle or summer seasons) to control this pest.

It is hoped that development and registration of one or more isolate(s) as a cabbage looper control product will be the outcome of further work, providing greenhouse vegetable producers with a reduced risk tool for cabbage looper management.

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