Carpenterworm (Prionoxystus robiniae) killing fig tree?

East Sahuarita, AZ

I think my green fig tree has been attacked by carpenterworms. I read an article in "SF Gate Home Guide" titled, "Bug Spray for Fig Trees," and the author suggests pruning wood judiciously to slow down the infestation. The article also suggests using entomophagous nematodes (Steinernema feltiae) Neoaplectana carpocapsae such as Scanmask to control the carpenterworm larvae.

Several of the limbs have suffered significant boring, and large segments of the limb bark have become dry and are loose from the limbs. With my hand or with a small putty knife I have pryed off the dry bark. The wood underneath is dry, with many boring holes and with sawdust evident.

In an effort to stop the infestation, I have purchased the Spectracide Pruning Seal, and have sprayed the open wounds or dry wood profusely with the black pruning seal.

What can I now do to stop or curtail the larvae before they destroy the tree?

Thanks for taking the time to reply.

Thumbnail by Thomboy70 Thumbnail by Thomboy70
Contra Costa County, CA(Zone 9b)

All you want to know about the pests, and were not afraid to ask...

Note: Spraying black anything on the bark or any part of the tree can make it too hot to heal, and can seal in fungus spores that may then attack the tree. Much better is to simply clean up the wounds back to healthy wood. Leave them open to the air to dry and heal.

East Sahuarita, AZ

Thanks for the link to the site describing the growth, and one of the few ways to slow the progression of the carpenterworms using Steinernema feltiae. This solution, however, of Injecting the tunnels seems like a very tedious process, but if the nematodes are unable to live outside the larvae tunnel, then there is no real cure except removal, or injection.
Two of the dominant limbs show severe damage, and may only be helped by removing them, i.e. "heavily infested branches should be removed back to the point of attachment." Unfortunately, one of the two bad limbs with large areas of no bark was sprayed with pruning seal, which is impossible to remove, so this one will probably have to be cut off.
I have seen what look like small gray hummingbirds (similar to the pictures of female carpenterworms in the article) flying around blooms on vines attached to my block wall close to the infected Fig Tree, which now seems like the actual source of the problem.
The information contained in the article paints a dire picture of the future for this fig tree, given the extent of damage, which will probably require complete removal to solve the problem.
Thanks again for your reply.

East Sahuarita, AZ

I have one remaining question regarding the carpenterworm pupals. The holes or tunnels in my fig tree are in no way large enough to allow a pupal of the size shown in the article referred to in Figure 7 to be inside the limb. Could this be another boring insect rather than a carpenterworm? Maybe I have not identified the corrrect culprit of the damage??

Contra Costa County, CA(Zone 9b)

Well, that is possible, there are quite a few beetles, caterpillars and other groups of insects that can infest the tree.
I think local help is best in a situation like this. Is the a department of agriculture office anywhere near you? They will know which pests are most numerous, and which are most likely to be the problem.

I would remove the worst affected branch, then cut into it carefully, photographing it as you go, hoping to find the critter. Get good photos of the shape of the tunnels. Each insect makes a different shape, bending and branching in different ways. Many times an expert can ID the pest just by looking at the tunnels.

Many of the insects that cause this type of damage do enough damage that the tree cannot heal. No matter what species is doing the tunneling, when it reaches the point that the tree is losing its bark, it is time to remove the tree. It is a hazard. Standing dead wood, ready to fall over onto you or anyone else, or damage buildings, cars or whatever else is nearby.

Definitely get an accurate ID, so you can do whatever prevention is possible on other trees and any new ones you may plant.

Prairieville, LA(Zone 9a)

A bit of info on Ficus borers

I agree that the best course of action is to know what you are dealing with. Here is the link for Pima county for University of Arizona Ag center. They should be able to identify what is killing your fig tree.

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