SWD threat growing


‘Stop-pick’ orders underscore need for more orchardists to get serious about helping to curb spread of drosophila fruit fly.


By Judie Steeves I


t’s been the year of the bug. The packinghouse co-operative issued ‘stop pick’ orders with discovery of Spotted Wing Drosophila larva from a number of orchards, and growers resorted again to sprays that are more toxic to try and manage the threat. Partway through the season, when it became apparent the recently-reported Asian pest of tender-skinned fruit was widespread throughout the Okanagan Valley, cherry growers such as Greg Norton of Oliver traded in their GF-120 for chemicals that might help to control SWD in their orchards as well as cherry fruit fly.


“It was heart-breaking. I was proud to be part of the process to get GF-120 approved.”


Norton noted that it’s pretty frightening to be told to stop sending fruit to be packed (the packinghouse co- operative has a zero tolerance for worms policy), after spending all your savings growing a crop, just because a couple of larvae are detected. Growers become pretty desperate when told to walk away from acres of fruit and their entire investment, he commented. Since there are no sprays available for the larva stage, adults must be detected as early as possible, and before fruit is ripe, since they lay eggs in fruit that’s ready to harvest—often too late for the application of sprays.


Norton is chair of the Okanagan Kootenay Cherry Growers’ Association and said he did avoid infestation of his cherries this summer, but admitted he is terrified about the implications of this new pest. “It’s a very aggressive beast.” SWD could doom the soft fruit industry if grape growers don’t pay more attention, he believes.


And, the federal government has a lot British Columbia FRUIT GROWER • Fall 2010 17


to answer for, since the pest has come into Canada on foreign fruit, despite the efforts of the Canadian Food Inspection Agency.


“I met federal Agriculture Minister Gerry Ritz in late March and gave him documented statements from entomologists that stated if this pest entered the country it would forever change the industry. However the CFIA continued doing nothing or only occasional testing.”


As well, in late August there were still only a couple of dozen SWD traps being used to monitor 900 acres of grapes in the Okanagan, while Norton said he has six on 10 acres of soft fruits. It’s frustrating to find many growers not embracing the education materials available on combating this pest, Norton said. He had to bury his neighbour’s cull pile because it was next to his peach block, and he was concerned they could become infested. Everyone has to work together to try and control the new pest. “We’re in a lot of trouble in this valley right now,” he


added. “Every grower of tender-skinned fruit has to become educated about SWD,” he said.


Of Norton’s 27 acres of tree fruits, only 130 trees are apples, and the rest are at risk of infestation by SWD. “It threatens my very existence,” he said. Sanitation is vital to control it. That’s echoed by Charlotte Leaming, from the Okanagan Tree Fruit Co- operative field services, who says sanitation and post-harvest cleanup are critical or it will explode in numbers in remaining fruit left on the trees or on the ground and it will then infest remaining crops.


She admitted they don’t have all the answers about how best to manage it, but there is a lot of research money being spent in Washington and Oregon to learn more about the pest. One thing they do know is that once SWD is in the fruit it’s home-free, so any cull fruit must be buried a foot deep, securely tied in heavy, black plastic bags or frozen, before disposing of it.


For current details, go to the OKCGA website at: bccherry.com


Leaming reported that of 345 traps in the valley, there were positive captures of SWD Aug. 11 in 170 of those sites, including orchards, grocery stores, fruit stands and backyards.


She also noted that one tree not sprayed late in the season, after harvest, was 80 per cent infested with SWD, yet a trap nearby did not indicate that. She said this suggests the bugs prefer ripe fruit to the traps—so don’t wait for large numbers in traps before applying a spray.


Delegate, Entrust, Malathion and


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