Evaluation of Naturalis L for the management of thrips in greenhouse

Project Code BPR11-050

Project Lead

Les Shipp  Agriculture and Agri-Food Canada

Objective

To develop efficacy and crop tolerance data in support of a regulatory submission for Naturalis L (Beauveria bassiana strain ATCC 74040) for the management of thrips in greenhouse peppers

Summary of Results

Background

During the 2010 Biopesticides Priority Setting workshop Naturalis-L was selected as the priority biopesticide solution for the management of thrips in greenhouse peppers.

In Canada approximately 51,300 metric tonnes of greenhouse peppers are produced annually with a farm gate value of $166 million. Thrips are a major threat to the greenhouse pepper crop in Canada, feeding on the leaves, flowers, buds and fruit of peppers. This feeding behaviour results in silvery white streaks and spots on the fruit surface, fruit discoloration and deformation, which can make the crop unmarketable.

Thrips are difficult to control for a number of reasons including a broad range of hosts, high reproduction capacity, and a rapid life cycle. Resistance in thrips populations to insecticides is common and there is an urgent need for alternative control solutions that are compatible with biological control programs.

A potential solution to this issue is Naturalis-L, an entomopathogenic biopesticide that has been developed by Troy Corporation. This product works through a pathogenic mode of action, where the germinating conidia of B. bassiana infect and kill the targeted insect.

Approaches

Three greenhouse trials were conducted in Harrow, Ontario to generate value data to support the use against thrips in pepper production on the Naturalis-L label. The product is being advanced for first time registration in Canada, with regulatory support provided by the Pesticide Risk Reduction Program.

Each trial included 20 test plots in a randomized block design. Plots consisted of cages with 4 pepper plants inoculated with a small population of Western flower thrips (WFT), Frankliniella occidentalis, at the beginning of the trial. Treatments began one week after inoculation, and included applications of Naturalis-L at 3-4 day and 7 day intervals, an untreated control, a conventional commercial standard, and a mycoinsecticide commercial standard. Pest populations were evaluated weekly and data was subjected to statistical analysis.

Results

In the 2 weeks following the first spray application there was no significant difference found among treatments. By week 4, the twice weekly application of Naturalis-L resulted in a significant difference from the control, with an approximately 30% reduction in thrips population averaged over three trials. The weekly treatment with the Naturalis-L and with the mycoinsecticide standard also reduced the thrips population compared to the untreated control. No significant reduction in thrips was observed in the conventional standard treatment. Numerically, the largest thrips reduction was observed when Naturalis L was applied twice per week at the maximum rate shown on the US label.

Discussion and conclusions

The results from this trial demonstrate that B. bassiana ATCC 74040 has value as a reduced risk biological control option to assist with the integrated management of thrips in greenhouse-grown peppers. Existing data from prior research with this product further underline the value of Naturalis-L in an integrated system for thrips management. The Pesticide Risk Reduction Program has prepared a comprehensive value package for this use pattern and will submit this to the Pest Management Regulatory Agency as part of the Category A.1 submission (first time registration submission) for Naturalis-L, which is currently being prepared by the Pest Management Centre and the registrant.

Registration of this new use pattern will help growers reduce pesticide risk and will increase control options for this economically very significant pest.

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