Spotted Wing Drosophila (SWD) Update – July 9, 2016

SWD numbers are starting to increase now. This past week we have seen an increase in the number of sites where SWD has been captured, and an increase in the number of SWD in the traps. Also, more SWD are being trapped in crops, not just the wild hosts around the farm.

So far our trap captures have been mostly in southern Ontario. We have trapped SWD in the following counties and regions: Essex, Kent, Middlesex, Oxford, Norfolk, Waterloo, Brant, Elgin and Niagara.

Fruit which is ripening in these areas, and anywhere else in southern Ontario, is at risk for SWD damage. SWD should be managed by picking fruit early, thoroughly and often. Sweet cherries, sour cherries and raspberries will be attractive to SWD at this time, as well as strawberries. A list of registered insecticides for SWD can be found here: Ontario.ca\spottedwing – products registered for SWD . Weekly sprays will help keep SWD under control, and will be required in blueberries, blackberries, fall-bearing raspberries and day neutral strawberries later in the season.

During this early stage, as SWD populations begin to ramp up, there are still many questions about when to start spraying. Salt water assessments of harvested fruit should be done routinely as an early warning of SWD problems.

In summer fruiting raspberries, growers have typically managed SWD with few problems by harvesting thoroughly every day or two. However, a pre-pick spray in late varieties, or an in-season spray may be required. A postharvest spray on raspberries is a good idea if fruit is left behind as you move from one variety (ie Prelude) to the next.

Strawberries should be mowed and renovated as soon as possible after harvest. Mowing strawberries will help fruit to dry up and make it less attractive to SWD. Growers who are renovating strawberries do not need to spray for SWD unless they have raspberries or blueberries or other susceptible fruit close by. Cygon or Lagon, when sprayed to control aphids in strawberries, is also toxic to SWD flies, and would be a good choice at renovation.