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Surveillance turns up strawberry, raspberry pest

Low levels of spotted wing drosophila (SWD) females and males (one to two per trap) have been found in traps in southern Manitoba, the provincial government reported Tuesday.

As raspberries start to change colour and ripen in mid-July, an insecticide could be applied to protect that harvest, which is expected to start in one to two weeks’ time, then repeat with an alternate insecticide seven to 10 days later, the province said in a release.

At risk now would be the later picking of late season June-bearing strawberries, so may not be worth spraying unless significant harvest remaining.

As more wild hosts and other commercial berry crops begin to ripen, expect SWD numbers to start building up significantly by late July, the province said.

Berries are susceptible to SWD infestation from the start colour starts to appear on the berry all the way through harvest. Producers have many chemical control options to control SWD.

It is important to constantly rotate every application through different insecticide chemical groups to avoid potential insecticide resistance issues with SWD.

Making its first appearance in Manitoba in 2013, SWD is a vinegar fly of east Asian origin that can cause damage to many soft-skinned fruit crops. SWD pierces seemingly healthy fruit, and lays its eggs. The eggs hatch in about three days; the larvae feed on the fruit and emerge as adults after six to 28 days.

Early detection is critical because symptoms often do not appear until after the fruit is harvested. Commonly confused with the common fruit fly, Drosophila melanogaster, SWD differs as it attacks unripe to ripe fruit, whereas the common fruit fly feeds on overripe and rotting fruit.

SWD most commonly affects raspberries, strawberries, blueberries, cherries and plums. For more information visit Manitoba Agriculture’s SWD web page.

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