Monday, September 22, 2014

Summary Of Summer FF Activity

In this bulletin I am trying to pull together a summary
 of how things have gone for us this summer in Powell River
with regards to all the various fruit flies -
 including a new one we have just discovered!

My observations are only based on the feedback that I have received, but here is what it is
looking like. . .

1. We did quite well with berries

This year, we do not seem to have been hit as hard by the Spotted Wing Drosophila (SWD)
during early and mid-summer as we were in 2013. Early (summer) berry crops that were
harvested regularly were usually in good condition. Occasional grubs began to be reported
towards middle and end of July. A grower in Paradise Valley who had a lot of trouble with his
blueberries last year says he only found a few blueberries damaged this season.

Tracy, my adviser from the Ministry of Agriculture, says that the infestation was also lower in
early and mid-summer in the Fraser valley. She says, based on winter and early spring trapping
data from the Fraser valley, there were fewer flies to start with, so that could also partially
explain the cleaner fruit earlier in the season.

That has got me asking, “Why the lighter infestation?” This is all speculation but. . .

  •  Did the freeze we had in February kill a good number of the over-wintering adult SWD?
  • Or, with the warmer and earlier summer that we had this year, and the berries ripening a couple weeks sooner, did we therefore manage to get the fruit picked earlier before the SWD had bred up too badly? The earlier the fruit can come off, the better.

2. However, by August SWD bred up.

One gardener told me that she did well with the summer raspberries but was shocked to find how
many grubs showed up in her ever-bearing raspberries during August. That, of course, is about
what we expected as the summer wore on. Ministry of Agriculture’s experience is that they have
built up by mid-late August every year so far.

The wild blackberries, also, behind my property were excellent until early August, but got
increasingly infested with SWD after that. By the end of August they were just no good at all.

  • I did not catch many SWD in my vinegar traps, but I will set them out again next year.Some of you did see ‘spotted wings’ in your vinegar traps, and Mark got that classic picture of a male SWD with its spotted wings.

3. Cherries are the big unanswered puzzle to me.
Cherries were one of the first crops to ripen. Yet we saw bad damage in some cherry crops in Westview. This surprises me because this was in early July, before many SWD had bred up.
  • SWD were definitely present in those cherries, but it makes me wonder if the initial and major damage was caused by the Cherry Fruit Fly (CFF) – a rhagoletis. Unfortunately we didn't succeed in trapping any flies for ID. But we had exit holes being reported and we think we may have found one CFF larva.

Please, if you had grubs in your cherry crop AND you saw exit holes, let me know so
I can get the traps out even earlier next year and try again.

4. Ground cover seemed to help against the Currant Fruit Fly (another rhagoletis)

One gardener told me that she'd had Currant Fruit Fly larvae in her currants last year so she took
the advice to cover the ground under the bush with mill-felt, and this year had an almost clean
crop. So she thinks that the ground cover helped. This is encouraging to hear. All rhagoletis
family have similar life cycle, so ground cover should help against the CFF too.

5. September now . . .

In mid-September we are harvesting apples and pears. SWD cannot penetrate the harder skins to
lay their eggs so they will not attack these fruits. But SWD – along with all their other
drosophila relatives who are swarming around at present – will feed on and infest any fruit that is
damaged or cracked. Tomatoes, plums and grapes too. So it is important to continue to practise
good garden hygiene, cleaning up fallen fruit, not throwing it in the compost, etc.

6. However we have new bad news: Apple Maggot Fly has been found in Powell River.

  • Early September we discovered grubs in Gravenstein apples from Invermere Court.
  • We recognized right away that these were not codling moth caterpillars, with which most of us are quite familiar. The damage looked quite different. There were little ‘sting’marks on the skin and the larvae had tunneled all through the flesh of the apples and quite ruined them.
  • Specimens sent to the Ministry of Agriculture lab at Abbotsford confirmed our suspicions: the apples contained larvae and pupae of the Apple Maggot Fly (AMF) –another rhagoletis.
  • This fruit fly has been on Vancouver Island for several years now and it was probably just a matter of time before it showed up in Powell River.
  • I will send a separate email immediately concerning the Apple Maggot Fly.
7. Some things we have learned
  • Gardeners are seeing the value of getting their trees back to a size they can manage, and their berry rows back to a width and length they can pick properly.
  • The Skookum Gleaners have provided an invaluable service this harvest season. It has worked well for them and for gardeners. A win-win all round. If you are still interested in having the Gleaners come in to pick a crop, the contact is David Parkinson or 604-485-7940

I must say that we have become much more aware of insects! As we have learned more
about the different species and their life cycles it has brought us some logic about how to
deal with them.

  • I continue to urge everyone to keep their later crops (apples, pears, plums, grapes) well picked, and to continue to practise good garden hygiene as we go into fall. You might like to re-read the first bulletins sent out in fall 2013. #1 is about Fall Cleanup. If you have not saved the bulletins, you can find them under the Fruit Fly tab at the top of the page.
  • Don’t let down your guard. The fruit fly can be managed, and we did quite well this year.

I hope all this is of interest. Other than for the bulletin about Apple Maggot, this will probably
be my last Fruit Fly Bulletin.
All the best,

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