Harvest time important for control of SWD
Cool, soggy spring was no reason to let up in fight against berry pest.
By Judie Steeves T
his year’s late spring gave growers a break from the early- season threat of Spotted Wing Drosophila, and numbers in monitoring traps stayed low until late July.
However, agriculture ministry entomologist Tracy Hueppelsheuser figures low counts through to mid- July were simply due to the cool, wet spring which continued into early summer.
She warned growers it’s important to protect fruit as it is colouring through until harvest is over. Last year, SWD counts in
monitoring traps exploded in August through the fall, as fruit ripened and provided host material in which adult flies could lay their eggs.
With up to 16 eggs laid a day, each female can lay more than 384 eggs in her lifetime and they hatch in 12 to 72 hours, depending on conditions. The larva matures in three to 13 days and the pupa resides in or outside fruit from four to 15 days before turning into an adult and flying to lay eggs on new fruit. Unless sprays are applied to protect your crop by destroying the adult flies, there’s little chance it will not become infested.
Wild blackberries are believed to provide food and breeding sites for SWD through winter. Control of such plants around the field perimeters so they don’t fruit is important. Early in the season, it’s believed Indian plum, salmonberry and seedling cherries serve as hosts for SWD.
It’s also important to remove or bury cull fruit to eliminate further sites for SWD to feed and breed. If
16 British Columbia Berry Grower • Fall 2011
culls and wastage is not carefully cleaned up during harvest, infested fruit from those early crops can infest later crops.
Because SWD does not respect field boundaries or property lines, do what you can to ensure SWD is under control on adjacent property as well.
During harvest, pick early, pick cleanly and pick frequently, to help prevent infestation or spread of SWD. As one grower commented, this is the only pest that is capable of wiping out an entire crop at harvest, so it’s vital growers are prepared to take all possible steps to prevent infestation.
Research on SWD biology and management continues by researchers and organizations throughout western North America, but there are still gaps in what is known about its behaviour.
Typical plastic trap for monitoring Spotted Wing Drosophila. Apple cider vinegar is easy to use and relatively inexpensive. However, the bait will catch other vinegar/fruit fly species as well. For more information on SWD monitoring, contact the Ministry of Agriculture at 604-556-3001. Guidelines for monitoring SWD can be found at
www.agf.gov.bc.ca/ cropprot/swd_monitoring.pdf. For berry management recommendations, go to
ww.agf.gov.bc.ca/cropprot/swd_ management.pdf
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