Wednesday, August 12, 2015

Summer 2015 Fruit Fly Bulletin

2015: We have had a very difficult time here so far this summer with fruit fly.  SWD (Spotted Wing Drosophila).  They bred up early.  Many people lost almost all their cherry crops.  Even the gardeners who knew the routine and tried to ‘pick early, pick often’, etc, had their cherries rotting on the tree almost before picking could begin.  Some braved it and still made juice or jelly.  A few people have said they got a percentage of good picking before the ‘worms’ and deterioration started.  Several, further out in the country mostly, seemed to have a bit longer time to pick before the damage.  And curiously, every now and again, I heard from people even in town who picked a really good cherry harvest with scarcely any larvae.

As you know, we have been trying to ascertain whether all the damage to our cherries was due to SWD, or whether we also have the CFF (Cherry Fruit Fly) here.  We had sticky traps baited for CFF set out on 18 properties.  These were collected in the past few weeks, but we don’t seem to have caught any flies with the distinctive striped wings.   So we don’t have any firm evidence of the presence of CFF here - although several growers feel sure that there were larger holes in the cherries, not just the ‘stings’.  And one gardener thought she saw a CFF but was unable to catch it.  (If we don’t have CFF here, and all the damage is being done by SWD, you can forget about the strategy of covering the ground under your tree with ground-cloth, etc. . . because SWD don’t drop down and pupate under the tree.  SWD can over-winter anywhere - wood-piles, house siding, under bark, etc.)

Interestingly, one trap set up near the Town Centre Mall did have a small fly with patterned wings but it did not look quite like the pictures I’ve studied of CFF.  I mailed it off to the entomologist, Tracy H, and she has replied that it was a Currant Fruit Fly - same rhagoletis family as the CFF, but it does not host on cherries - just specifically on currants and gooseberries. We knew they were here; they have been around for years.  (So if you grow currants or gooseberries it is helpful to cover the ground under the bush.)

A number of people are talking about just cutting down their cherry trees.  Others, reluctantly, are starting to wonder about spraying next year.  So I wrote to Tracy about that: "Question about sprays: A seller from the Okanagon brings lovely cherries into town every week,” I wrote. "They must be spraying regularly.  (There’s no way anyone here could have produced cherries like that here this summer.)  What do the Okanagon and Fraser Valley growers use ?  People here, who didn’t want to even consider sprays, are now starting to ask me.”  I have included her reply at the bottom of this email.  It has a lot of information about the range of sprays and the timing involved.  I will leave that to you to decide what you think. 

Re other fruit: I did quite well picking my raspberries daily for about three weeks, and it was just in the final week of the crop that I started to get some soft mushy ones with larvae in them.  Our blackberries ripened so I would suggest that anyone wanting blackberries should pick them soon before the berries get damaged by SWD.  And store them cool after picking.

Happy gardening, just the same!


July 13
Hello Margaret,  

Thank you for the update.   I am sorry to hear about the devastation you have experienced.  
Yes there are spray options, as well as bagging trees (with mesh to prevent flies). 
The commercial cherry and berry growers are spraying on a regular basis (weekly) from the time the fruit starts to colour through harvest.  If they don’t, the fruit gets loaded with SWD and is ruined.  Here are some of the web postings with the commercial information for your consideration.  Organic producers are also spraying regularly, but their insecticide choices are much more limited. 

These links are all on our main SWD page: 


Tree covers/netting:  if people have single large trees, or rows of small trees netting may be an option.  Here is the link to Kootenay Covers, a company that makes mesh bags to protect fruit trees from insects (cherry fruit fly, SWD, etc).  


Tracy Hueppelsheuser
Entomologist, Plant and Animal Health Branch
British Columbia Ministry of Agriculture

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