Tender Fruit and Grape Report - September 14, 2011What do Spotted Wing Drosophila finds mean to Ontario stone fruit and grape growers?OMAFRA specialists are monitoring the development of the new pest, spotted wing drosophila (SWD) in Ontario. With the help of consultants and agribusiness scouts and funding by Ontario Highbush Blueberry Growers Association and the Niagara Peninsula Fruit and Vegetable Growers' Association, a network of 50 sites in 16 counties across Ontario has been established. To date, SWD has been identified in traps in orchards in Essex and Niagara and in traps in berry plantings in Essex, Kent, Norfolk and Oxford. The first positive was identified in a Niagara orchard the week of August 8 and the number of positive sites has increased every week since then. There are no reports of infested tender fruit or grapes. SWD is not like the vinegar flies to which we're accustomed, the ones that show up in the presence of over-ripe or injured fruit. SWD lay eggs inside sound fruit before harvest. The eggs hatch and the larvae develop inside the fruit, causing extensive damage. Once the eggs have been laid, they are no longer susceptible to insecticides. The wounds are entry points for brown rot in stone fruit and botrytis in grapes. In addition, like other vinegar flies, SWD can carry yeasts and bacteria that cause sour rot in grapes and spread this sort of infection. The population of SWD increases as the season progresses, so late harvested crops are at a higher risk for damage.
Peach fruit injured by SWD egg-laying and larval activity (Photo credit BC Ministry of Agriculture)
SWD egg-laying wound and larva The host range of SWD includes all stone fruit and berries. Reports from Washington and Oregon indicate that table grape varieties are susceptible as well. Research in Oregon suggests that SWD are more likely to lay eggs on injured grape berries than intact ones. Although the pest is established in BC, growers there were very proactive this summer and chose insecticides that controlled SWD as well as other common pests for their pre-harvest sprays. We do not know the impact of SWD on stone fruit and grapes in Ontario. The best strategy is to use a product that is effective against SWD when applying pre-pick sprays for Oriental Fruit Moth and Grape Berry Moth or Multi-coloured Asian Lady Beetle. Many of the reduced risk insecticides (eg. Altacor and Assail) used to manage other pests are not effective against SWD. SWD are killed by direct spray contact and/or when they are exposed to residues of insecticide on the treated fruit and leaves. Several insecticides have received Emergency Use registrations effective until November 30, 2011. The following tables summarize the products registered for control of SWD.
If you see symptoms that you suspect are SWD injury in tender fruit or grape, please contact Wendy McFadden-Smith at wendy.mcfadden-smith@ontario.ca.
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