Development and implementation of a reduced-risk integraged pest management program for lepidopteran pests of fresh market sweet corn in Ontario and Quebec

Project Code PRR07-460

Project Lead

Bernt Solymár - EarthTramper Consulting Incorporated

Objective

Implement IPM (Integrated Pest Management) on farm through demonstrations. Test reduced risk alternative control products and cultural management practices. Conduct summer tours and distribute results to growers.

Summary of Results

Background

Fresh market sweet corn is a high-value crop produced in all provinces of Canada with the majority of production in Ontario (10,000 hectare (ha)) and Quebec (8,500 ha) with a Farm Gate value of ($72 million) (Statistics Canada 2012). The European corn borer (ECB) is considered the major economic pest of sweet corn in eastern Canada. This pest feeds directly on the ears rendering them unmarketable. The ECB is active from early June through late August and affects early season through late season corn.

A second pest of concern, the corn earworm (CEW), is a sporadic pest that can economically impact late-harvested sweet corn, particularly in Ontario. In both years of this study, the CEW was not an issue for sweet corn growers during the period of the field trial season and for this reason this project focused on ECB.

A number of broad-spectrum insecticides are registered for ECB control and up to 6 applications may be made to a planting, depending on the level of ECB pressure. With increasing concerns regarding the impact of these materials on the environment, non-target organisms and human health and the development of resistance in some pests to certain pesticides, there is interest in finding alternatives to the traditional broad-spectrum control products.

There are several alternatives to traditional pesticides available to sweet corn growers including: biological control agents, newer reduced risk pesticides and the use of Bacillus thuringiensis (Bt)-corn varieties. However, commercial adoption of these technologies has been slow for a variety of reasons that include: lack of confidence/experience with alternative strategies, zero tolerance for pest injury in sweet corn ears and concerns about increased pest damage when using alternatives, increased economic losses and in the case of Bt-corn, consumer concerns about genetically modified organisms. This project was established to increase grower confidence in these alternative methods of pest control.

Approach

Field trials were conducted in 2007 and 2008 on 12 farms, in 3 distinct regions in eastern Canada; Norfolk County in southern Ontario, the Ottawa Valley in eastern Ontario and the Monteregie region, south of Montreal. At each site, 0.75 – 2.5 acre plots were established to compare either a reduced risk or biological control program to the grower’s conventional insecticide program. Reduced risk and biological approaches included: reduced risk products such as Bacillus thuringiensis and spinosad; biological control agents Trichogramma brassicae and T. ostriniae and Bt corn. Where feasible, treatments were replicated 3 times.

Plots were monitored by consultants, who worked closely with the growers to time the applications of reduced risk products and inoculations of Trichogramma wasps. Corn borer presence and damage was assessed weekly. Prior to harvest, 200 ears per plot were assessed to rate the efficacy of treatments in preventing damage from the ECB.

Participating growers were surveyed to obtain background information on their use of IPM practices and their impressions of the trial.

The Cornell University Environmental Impact Quotient (EIQ) was used to assess the potential for pesticide risk reduction with the use of biological controls and reduced risk pesticides as compared with conventional insecticides.

The economics of using conventional pesticides, reduced risk products and biocontrol programs were compared using a retail pricing list provided by N. M. Bartlett Incorporated, a major horticultural crop protection material supplier in Canada.

Results

Although insufficient data were collected for statistical analysis, damage assessments suggested that registered “reduced risk” products, Dipel (Bacillus thuringiensis) and Success (spinosad), provided good control under low ECB pressure conditions, early in the season, but were less effective than conventional programs under high corn borer pressure. Trichogramma wasps provided comparable control to conventional insecticide programs in early- and mid-season harvested sweet corn. With late harvested corn, and when European corn borer populations were high, economic levels of damage were sustained in the plots inoculated with Trichogramma spp. Plots planted to Bt corn did not sustain any damage from ECB however low numbers of corn earworm were detected.

Calculations of the EIQ showed that the environmental impact of reduced risk products such as Dipel, Success and Entrust used in this study were much lower than broad-spectrum, conventional insecticides commonly used in sweet corn production. The pyrethroid insecticides, however, had EIQ field use ratings similar to the reduced risk products. Reduced risk programs tended to be more costly than conventional programs.

The trial provided an opportunity for the sweet corn growers and the private consultants that cooperated in the trial to gain experience and confidence in using alternatives thereby facilitating the wider adoption of biological control agents and reduced risk pesticides for the management of ECB in sweet corn.

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