I have had borers in my sycamore for years. I used to try inserting a flexible wire into their tunnels, but the tunnels were too winding and long. I have tried digging them out with a knife, but they persist. Does anyone know of an organic way to rid the tree of these pests?

The only thing I can think of is to attract woodpeckers into your yard with special bars they have for them, or a bunch of peanuts. I get two different kinds of woodpeckers and they're always eating bugs off my apple tree!

mtullius,

Since you've already gone the "cut and insert wire" route, I won't suggest it. Basically, borers attack trees that are stressed, or not in the best of health.
(Like most pests and diseases do to other plants with compromised immune system).

But, there's promising news from several sources I checked that are advocating biological controls (beneficial nematodes) to combat borers. Just as they'd be used to rid your lawn of grubs, it's reported to have the same effect on tree borers:

"[u]Entomopathogenic nematodes, Steinernema spp.[/u],can be applied to the trunk from May to September to control borers already in a tree or shrub. These nematodes enter the tree through openings in the damaged bark. They move beneath the bark in tunnels made by the borers. Once a borer is encountered, they enter it through naturally occurring body openings. They multiply rapidly within the borer while also infecting it with toxic bacteria. The over-whelmed borer weakens and soon dies. The use of entomopathogenic nematodes will work best on trees that have not been sprayed with lindane or chlorphyrifos since insecticide residue on the bark could kill the nematodes.

The application of these living organisms requires some special care. It is best to use fresh nematodes. Order from a reputable distributor just before you plan to spray. Mix nematodes with warm water that is no higher than 90F. Shake the mixture for one minute or use a sprayer with an agitator that recirculates. Keep the mixture out of direct sunlight. Before spraying, check nematode viability in the mixture by examining them with a hand lens. They should be wiggling and have a slightly curved body, while dead ones will be straight. Always spray in the early morning or evening or during cooler, overcast weather. Wet the bark before application and concentrate the spray on wounded or cracked bark areas. Injecting the nematode spray solution directly into the borer holes with an eyedropper, baster or syringe should increase the level of control. Try to finish the application within three hours of mixing."

The source for this is from:
http://www.utextension.utk.edu/publications/spfiles/sp547.pdf

And recommended suppliers of guaranteed "live" nematodes can be found here:
http://www.oardc.ohio-state.edu/nematodes/nematode_suppliers.htm
(Make sure you get the nematodes specified in the above quote: Entomopathogenic nematodes Steinernema species.)
Boy, that's a mouthful!:O

Hope you can defeat the little buggers!

gardenz

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Thanks for the information. I'm going to try the nematodes.