Derris alternative for plum sawfly?

Has anyone managed to use a successful alternative to Derris for Plum Sawfly? I bought a house and garden with 5 plum trees last year only to be disappointed at the diseased plums. I have just dug around the base of the trees to expose the larvae....and there were lots of the little blighters for the robin to eat, for sure,.....but the trees are scattered up the lawn and I don't want to dig up half my lawn, so I suspect there are more of them lurking ready to pupate in spring and continue their life-cycle in the 2010 plums. I can't seem to find any alternative to Derris which is now banned in UK. I would prefer organic if possible. Anyone got any ideas?

 

Hi wiseone and welcome to GC!
The only alternative to Derris that I'm aware of is 'Calypso' manufactured by Bayer and I think it's only available on the commercial market.
I spent a while 'Googling' for natural predators, but apart from ones with beaks and two legs, there don't appear to be any significant ones. Errecting a few bird boxes, if you haven't already got them, would help increase avian predation.
From what I've gleaned, disturbing the soil around the base of the trees to let the birds at the larvae seems to be quite effective in reducing the severity of attack.
One other thing I found was that there have been some trials using sticky white traps to catch the flies when they emerge in spring - these trials seem to have been at least partially successful.
Another strategy that came to mind is to dig up the turf for at least 1 metre around each tree, disturb the soil in winter and early spring to let the birds feed and then just before the adult flies emerge cover the soil with membrane to block the exit. I don't know how well this would work and if I was doing it I'd also sink some plastic edging strip down several inches around the boundary of the holes in the turf.
Best of luck!

 

I looked this up in my encyclopedia but I don't know if its answer is any use (or even up to date)? Here it is, just in case:

"Where possible remove by hand. Spray serious infestations with pyrethrum, permethrin, fenitrothion, pirimiphos-methyl, or malathion."

 

Thanks Dave. I have just bought some citronella cat repellent sticks because although the bird life is very active in my garden, so is the cat population k-l(none of them mine, of course!). I will have a go at increasing the radius of turf dug up around the tree. The robins and blackbirds certainly enjoyed their meals today. I wish I had spent a bit more time picking up and discarding the diseased fruit last year as it may have cut down my work a bit this winter! I did look at a nematode solution for caterpillars and gooseberry sawfly but not sure how effective that will be on these things. In all I want to avoid chemicals so it looks like i have a bit more manual labour to do this winter/spring!

 

Thanks Hartley, I know that malathion has also been on the banned list for some time, but haven't looked into the others yet.

 

The RSPB estimate that 55 MILLION birds are killed in the UK by cats each year and this is just based on reported and recovered prey so the total is probably greater.

Don't get me started on domestic cats, some of their owners, horticulture and garden birds:(

 

Not a problem, hope it's of some use.

I should probably look into getting a newer book...! :o