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large rose sawfly and dormant oil??

Posted by clareqc quebec..chelsea (My Page) on
Tue, Apr 25, 06 at 7:53

I have some rose bushes that have been hounded by large rose sawflys the past few summers and I am wondering if dormant oil spray would help to lessen their numbers.
I understand they overwinter as pupae in the soil?? and hatch into adults in the spring. There again to begin their cycle?
So if these are the facts can I use dormant oil spray to stop their growth and can I spray around the plant, say the base and the soil?
Not sure what else to do as I am loathe to use other chemicals...

Follow-Up Postings:

RE: large rose sawfly and dormant oil??

I don't know if or where the adults overwinter, but I believe the eggs are laid in the shoots, and the larvae emerge in the spring. If they were in the soil then dormant oil would be of no use. If your rose is beginning to leaf out, as the ones around me are, then an application of dormant oil right now will harm the leaves. It is supposed to be of some use in controling sawflies though, when used at the right time (before budbreak). So it might be something to consider for next year (unless you're a lot further north than I am).

For now, handpicking of the larvae is quite effective if you are religious about it. Keep a tin of soapy water handy, and do a quick check as often as you are able, tin in hand. Pick the larvae off and drop them into the tin. Check the underside of the leaves.

The larvae usually show up in mid to late May around me, but they might be a bit early this year because we've been so warm.


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