Management program for clearwing borers on pome fruits

Project Code SCR08-010

Project Lead

Karen Bedford - Agriculture and Agri-Food Canada

Objective

The objective of this project was to assess a number of reduced risk approaches for the management of the apple clearwing moth and the dogwood borer in apple orchards. A number of reduced risk products were tested for efficacy when used as preventative and curative sprays. The efficacy of a pheromone used for mating disruption of the apple clearwing moth was also tested in organic orchards.

Summary of Results

Background

Clearwing borers (Lepidoptera: Sesiidae) can be serious pests of pome fruits. In eastern orchards the native species, Dogwood Borer (DWB), Synanthedon scitula (Harris), has become an increasing problem in high-density apple orchards. DWB does not occur in western Canada, but in 2005 an infestation of Apple Clearwing Moth (ACM), Synanthedon myopaeformis (Borkhausen), was discovered in an apple orchard in Cawston, British Columbia (BC). In North America and Europe conventional control of apple clearwing borers and related species like Peach Tree Borer (PTB), S. exitiosa (Say), has depended on the use of organophosphate insecticides. These chemicals currently have limited permitted uses in most jurisdictions and are targeted for re-evaluation or removal in the near future. Conventional control of DWB in Ontario involves the use of a synthetic pyrethroid mixed with mineral oil.

This project evaluated the potential and efficacy of a number of reduced risk products including biopesticides for the control of ACM and DWB in conventional orchards. The project also assessed the efficacy of Isomate-P for control of ACM by mating disruption in apple orchards.

Approaches

A series of screening trials were conducted in 2008 and 2009 in Ontario and B.C. testing potential insecticides for the control of Synanthedon myopaeformis Borkhausen, ACM, and Synanthedon scitula Harris, Dogwood Borer (DWB). In each of the trials conducted in Ontario or BC insecticide treatments were applied using a hand gun sprayer and application was made to the tree trunks. Included in the trials were products of potential use in conventional and organic apple production. The results of the trials on ACM and DWB have potential application for the control of other Sessiidae pests of ornamental and fruit hosts.

In Ontario, a total of three screening trials were conducted, two for DWB (2008, 2009) and one for ACM (2009). The DWB trials were conducted in a commercial orchard in Ilderton, Ontario on five year old Honeycrisp trees (2008) or three year old Northern Spy trees (2009). The ACM trial was conducted in Fingal, on ten year old Empire trees. Each trial included five insecticide treatments applied to four replicates of 9-10 trees. Certain materials were only tested in one year. In each trial a single summer application was applied as a preventive treatment during adult emergence as determined by catches in pheromone baited traps. Data assessments were made of larval infection of the experimental trees in the season of the application. Trunks were examined for DWB or ACM damage in the form of insect tunnels. The number of tunnels and the number of live larvae present in tunnels were recorded.

In B.C., three screening trials in 2008 and two trials in 2009 targeted for different developmental stages of ACM were established with insecticides for conventional and organic apple production in a high-density mixed-variety apple planting in Cawston, B.C. In 2008, single pre-season trunk sprays were applied in May as curative treatments targeting two-year-old apple clearwing larvae. Efficacy of treatments was assessed by counting pupal exuviae (moulted matter) protruding from tree trunks. Exuviae counts were equated to adult emergence. Assessments were made on the same trees in August 2008 and 2009.

From 2006 to 2008, the efficacy of Isomate-P, a pheromone-based, mating-disruption control product for ACM was also assessed in commercial organic apple orchards in B.C. and in Ontario.

Results

In the Ontario trials, no significant differences in the number of tunnels present was found in any of the trials, but differences in the number of live larvae present in the tunnels were evident. The number of live larvae of DWB was reduced by RIMON, DELEGATE, and ALTACOR in 2008 and 2009. In 2009 BELT was included as a treatment and also significantly reduced the number of live DWB larvae present in the trees in addition to the previously tested effective treatments. In the 2009 ACM trial the number of live larvae were reduced by the RIMON and BELT treatments.

For trials conducted in B.C., only RIMON provided a significant reduction in adult emergence when used as a curative treatment. By contrast, RIMON, BELT, DELEGATE, ALTACOR and ENTRUT 80W, when used in summer 2008 as preventive sprays caused significant declines in adult emergence in 2009, with RIMON being the most effective, providing a 96% population decline year-over-year.

The results from this study indicate that RIMON could be recommended for minor use label expansion for control of clearwing borers on apples under conventional production. In addition, label expansions for BELT and DELEGATE would offer effective rotational products to be applied during the adult flight period for control of clearwing borer larvae.

More trials are required to determine the efficacy of various products for organic production, including Isomate-P for control of clearwing borers on pome fruits.

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