Project Code: PRR10-050
Julia Reekie - Agriculture and Agri-Food Canada
- Develop and demonstrate to growers, sustainable IPM approaches to the management of apple maggot, incorporating the use of GF-120, under varying pest pressures, sources of pest populations and orchard characteristics
- To refine and demonstrate various application methods using common/ standard farm equipment in the application of this material
- Investigate the late season egg laying activities of apple maggot and establish the factors affecting the late season fecundity of females
- Demonstrate the economics of the use of GF-120 as opposed to conventional approaches to apple maggot management
Summary of Results
The apple maggot, Rhagoletis pomonella is a serious pest of apple in eastern Canada. Larvae feeding in the flesh of the fruit render the fruit unmarketable. Apple maggot is a quarantine pest for which there is zero tolerance in most export markets.
The apple maggot poses a threat from July until the end of the growing season and throughout this period, developing apple fruit must be protected from attack. In 2009, GF-120 Naturalyte Fruit Fly Bait (spinosad) received a Minor Use label expansion for the suppression of apple maggot on apple. In light of the impending phase-out of the registration of a number of organophosphate insecticides, this natural pesticide is a promising alternative for both organic and conventional orchards.
GF-120 is a bait formulation of spinosad and is applied as a coarse droplet spray in apple orchards. For efficacy, it must be applied every 7-10 days when the apple maggot is present and with droplets distributed to the interior and underside of the canopy to maximize its longevity.
In studies previously conducted by Agriculture and AgriFood Canada (AAFC) (BPI07-100: Evaluation of the efficacy of GF-120 to potentially replace organophosphate insecticides for control of apple maggots in organic and conventional orchards), GF-120 reduced apple maggot injury from 69% to 3% when used in successive years. Factors such as pest pressure, whether the pest is a resident or migrant pest and tree characteristics affected the efficacy of GF-120. The need to refine approaches for the use of GF-120 and to demonstrate the use of this material to growers was identified through stakeholder consultations under the AAFC Pesticide Risk Reduction Strategy for Organophosphate Replacement in Pome Fruit.
In 2010-2011, a total of six trials were conducted in commercial orchards in Nova Scotia (NS) and Ontario (ON). The orchards varied in size and varieties of apples grown. Apple maggot populations were non-resident in most test orchards and pest pressure varied from light to very high.
A number of different sprayer types and vehicles for mounting sprayers were used to demonstrate the ease of incorporation of this material into orchard pest management. While typically an all terrain vehicle is used to carry small sprayers, both tractors and golf carts were used in these trials. Where necessary, modifications were made to commercial sprayers to enable the application of GF-120 according to label instructions. Modifications included: the selection of appropriate nozzles, changes to the actual spray tank and changes to pressure regulators to ensure delivery at the correct rate, taking into account the travel speed of the vehicle. In small commercial orchard blocks, back-pack and hand-pump sprayers were used to apply GF-120. Bait and kill stations made of plastic cups containing GF-120 placed in plastic food containers (boxes) were tested at two locations. Apple maggot injury in all trials was assessed by incubation of harvested fruit for two weeks followed by examination for surface stings and maggot trails in the fruit.
To investigate the late season egg laying activity, apple maggots were trapped with yellow sticky traps in a certified organic research orchard. The traps were checked every 1-3 days from July to October. The apple maggot flies trapped, were counted, sexed and female flies dissected to assess the presence/absence of eggs.
Throughout 2010-2012 approaches to the use of GF-120 were presented to growers at a number of public events. Cost analyses of GF120 vs. conventional approaches were assessed.
Alternate row spraying of GF-120 with a tractor mounted sprayer in a NS orchard with moderately high apple maggot pest pressure (non-resident) proved to be highly effective. Trace apple maggot injury was detected in only one apple (<1%) in the treated trees, as compared with 23.5% in apples from the untreated controls. The use of GF-120 as bait in feeding stations reduced the levels of apple maggot in a test block. However the approach was unsuccessful due to extremely high pest pressure in the test area. Combined treatments employing both feeding stations as well as GF-120 applications with a backpack sprayer were also found to provide insufficient control. In other trials with back-pack sprayers, results were variable. In one case, lower apple maggot damage was exhibited than in a nearby Imidan treated conventional control block (1.9% damage vs. 5.7% damage). An ON study comparing GF-120 application (8 sprays) with border and cover sprays with Imidan, in different blocks of an orchard with low pest pressure, demonstrated GF-120 to be as efficacious as organophosphate insecticides in controlling apple maggot.
Studies on the late season egg laying activities of apple maggot showed that female apple maggots remained active and their egg-laying potential continued into September.
This work was presented at 6 public events including orchard tours, grower conventions, apple meetings and an agricultural college, reaching many growers in NS and ON.
For season long control, GF-120 was found to cost up to double conventional sprays and 9 X the older organophosphate sprays. While this will make the use of GF-120 less attractive to growers, GF-120 has no re-entry or pre-harvest restrictions and is very suitable for use when orchard activities cannot be interrupted.
A factsheet covering the reduced risk management of orchard insect pests will be developed based on the results of this and related projects.
For more information about this study, please contact Dr. Julia Reekie.