No let-up in SWD battle


Challenging year as fruit fly pest shows up earlier and in greater numbers.


By Scott Trudeau R


eports of damage to soft fruits such as cherries can be attributed to another early appearance by the fruit fly known as Spotted Wing Drosophila, says agriculture ministry entomologist Susanna Acheampong.


Growers had a challenging year dealing with the SWD, she explained, because the pest was out in numbers that were the highest since trap monitoring began in 2010. More than 200 apple cider vinegar traps were set up and monitored throughout the Okanagan, Similkameen and Kootenay regions during the first week of May.


Acheampong said there were reports at packinghouses of SWD damage in some of the early and late cherry varieties, which led to some of the fruit being rejected. In previous years the SWD population built and damage was discovered in the later cherry varieties, but that changed because the pest was active earlier this year.


SWD is a vinegar fly native to Asia first detected in this region in 2009 and has since established itself and proven to be a pest of commercial berry crops and soft fruits grown in the Okanagan, Similkameen and Creston areas. Damaged apples can also become a host for SWD.


Each season’s population growth is dependent on temperatures, but the faster growth occurs during hot weather.


A similar pattern of increased SWD numbers has been detected in other regions as well, including Washington state and coastal B.C.


Acheampong said sanitation is important when it comes to reducing the number of SWD and emphasized the importance of making sure any


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remaining cherries are not left on the trees and picked off the ground. Erin Carlson, whose family owns a


Summerland orchard, harvests 26-acres of cherries, agreed growers need to clear away as many of the remaining fruits as possible, but she noted that for growers with larger- sized orchards it can require a significant


SCOTT TRUDEAU


Cherry grower Erin Carlson of Summerland examines one of the cherry trees which were affected by Spotted Wing Drosophila this year.


time investment, especially when that part of the crop isn’t going to yield a return.


Carlson didn’t recall seeing too many SWD back in 2010 or 2011, but the following year they continued to increase; by 2013 they seemed to be almost everywhere.


She said SWD’s earlier appearance than in previous years also meant she was finding more trees affected by the pest, although not all their cherry blocks were affected to the same degree. Similar to other growers, they recovered more of their crop by harvesting earlier than normal. The purchase of a new defect sorting machine on the Carlson property improved this year’s harvest because more of the cherries could be picked, especially in those blocks that were more heavily affected. “Last year, we would’ve just abandoned them,” said Carlson. Growers currently have five different types of approved emergency registration sprays to control the fly. In 2013 they were Delegate, Entrust, Malathion, Ripcord and Pyganic. The available pesticides can only be used on the adult population and must be applied before eggs are laid. The limited number of available products for controlling SWD presents a challenge, but Acheampong said the Pacific Agri-food Research Centre is exploring new products.


Research work is under way into the possibility of rearing parasitoids of


SWD to control populations, but as yet it is incomplete.


She said that at this time the flies will be overwintering, which means there is little growers can do during this time. Carlson is optimistic that with all the research scientists are conducting around SWD, they’ll eventually discover a way to manage the pest, but she admitted until that time arrives it’s going to make cherry harvests more difficult and unpredictable. “This really affects cherry growers and it’s affecting growers on the coast,” said Carlson, who also stressed that even those people who are not commercial growers and have only a few fruit trees in their yard should be clearing their properties of fruit and disposing of it at the landfill. Acheampong said even though SWD numbers have increased since it was first discovered, likely population levels for 2014 cannot be predicted. She emphasized the importance of harvesting fruit earlier in order to prevent the spread of SWD to later- maturing crops and to collect all fruit, including fallen fruit, to eliminate potential host material and prevent increased populations.


Disposal of infested fruit should include bagging it securely and leaving it in the sun for a week before getting rid of it, or burying it at least a foot deep.


For detailed information about SWD and registered control 0products for control, go to the ministry website at: www.agf.gov.bc.ca/cropprot/swd.pdf.


British Columbia FRUIT GROWER • Winter 2013-14


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