Detecting the Polyphagous Shothole Borer (PSHB)

PSHB is an invasive beetle that kills host trees by boring into them and depositing a fungus. It is very hard to detect until it is too late

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The polyphagous shothole borer is an ambrosia beetle about a mm across. It bores into trees and deposits a fungus in its galleries. A lot of detail can be found on the UC Riverside site, The photo above is of an infested tree. Many tree diseases look just like this, making it hard to diagnose. On a tree with rough bark, it can be nearly impossible to tell a tree is infested until tree branch tips start to die back, and again, many things cause that, too. Several people, including us, have been volunteer helpers at the Huntington Botanical Gardens assisting Nursery Manager Dan Berry. We have been brainstorming possible technologies to detect the beetle so that its spread can be characterized and so that individual trees can be assessed cost-effectively. The ideal solution would be easy to deploy on many trees, able to be distributed open source, cheap, accurate, and already in existence for some other application.

Extensive information about the beetle can be found at What makes it particularly bad is that it will infest many different types of tree. In Latin, "poly" means "many" and "phagous" means "eat-" so this is a bug that will eat many things. A complete list of known host trees is available at the link.

We have looked into citizen science projects to have people go out and look at trees. The iNaturalist project for this is in our list of links. However it is difficult to send non-experts out to look, since many tree diseases cause similar symptoms.

So - how can you tell, preferably without drilling into the tree, that it might be riddled with galleries a little over a mm across?

How can you stand in the middle of a grouping of dozens of trees, and tell where the bug might be just getting started?

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  • Update, 38% of trees in LA area later

    Joan Horvath04/20/2017 at 15:02 0 comments

    The LA Times is reporting today that 38% trees in the Los Angeles basin are dead or dying, mostly from a combination of PSHB and drought. I haven't updated this project in a while because we had failed to find a solution and run out of ideas. But maybe it is time to think harder...

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Javier Villalva wrote 01/22/2019 at 20:33 point

Some termites produce noise when chewing. The noise becomes detected by dogs, which can be trained to listen to them and report insect attacks. Possibly they could also be trained to smell them!
With modern speech recognition systems I can imagine that they could be detected and the typical noise of those insects when eating could be recognized (by its frequency, its modulation ...)

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unlisted wrote 05/03/2016 at 14:04 point

seems an ultra sound would detect the voids created.. albeit maybe to late.. 

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Joan Horvath wrote 05/03/2016 at 16:41 point

There are some patents in that sphere, but even they require scraping off a huge chunk of bark for the coupling to work. Ideally we would like to have something that does not expose the tree to infection when we are screening. (Also, as you say, probably hard to detect until it is too late.) One of the things that is challenging is that unless you have a baseline for each tree it is hard to detect small changes...

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unlisted wrote 05/03/2016 at 18:16 point

this Berkeley study used hot glue to detect termites , Performance in Acoustically Detecting Drywood Termites.pdf

and yes, to late tree in trouble

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Jarrett wrote 05/02/2016 at 18:35 point

Have you tried looking at it with a thermal camera? Or a UV camera, too. It's possible the signs might be a little more obvious when viewed in different spectra.

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Joan Horvath wrote 05/03/2016 at 05:51 point

 Joan Horvath

wrote a few seconds ago
Hi-  We tried one of the PublicLabs IR webcams,  and the bottom line is that IR doesn't seem to help particularly, at least at the level you can achieve with a low-cost IR  webcam. Our collaborator also borrowed a UV flashlight and is in the process of 
trying out various things with that. Because the holes are so tiny (a little over 1 mm) and the bugs burrow so deep so fast, anything that is  just surface observation, we think, is not likely to detect them directly. It would however be awesome to be proven wrong on that one.

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