About Invasive Shot Hole Borers (ISHB)
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| I am securing the binder clips on a trap near the San Diego River, close to a parking lot. |
The
polyphagous (paw-li-fa-gus) shot hole borer
(try saying that five times fast! If you don't say "short hole borer"
at least once, I'll be very surprised.) is an invasive species of beetle
less than a couple of millimeters long, that bores holes into trees to
lay their eggs. A species of genetic difference but identical appearance
is the Kuroshio Shot Hole Borer. Along with ISHBs came a fungus shot
hole borers carried, known as Fusarium euwallaceae. This fungus blocks water transport in trees, causing
fusarium dieback,
a condition where the shoots or branches of plants or trees die from
the tip inward. Shot hole borers, however, need this fungus as food
after their eggs hatch. This is used as a food source, similar to leaf
cutter ants. The tunneling itself also weakens a tree, and as this goes
on, invasive shot hole borers can lead to tree death. Some especially
affected host trees are the box elder, avocado, even sycamore trees.
Experts suggest that shot hole borers arrived through wood shipments
from overseas. Using this information, we can prevent further outbreaks.
Some things within our control are: buying firewood in the location we
will burn it, to prevent transport, and disposing of wood waste
properly. SHBs can survive for weeks in cut wood. Therefore, infested
wood should be chipped and solarized, kiln dried, or composted. If none
of these are done, chips can only be used as mulch.
Symptoms of Shot Hole Borer Activity
Naturally, the first thing to look for is the entry holes, almost perfectly round, and less than a millimeter in diameter. If this is seen, dark staining or gumming may be seen. A white powdery substance could also be exuded from the tree. Frass could also be seen (looking like sawdust).
Citizen Science
My mom had heard about this opportunity for citizen science through the San Diego Audubon, a group I have been volunteering with for many years to help the California Least Tern. To read more about my experience, please see my Ornithology Files blog, as well as another Slogs post about this. This event is organized by the US Forest Service in partnership with the SD Natural History Museum. The training took place in Tecolote Canyon and we were supposed to perform the activity in many locations, each one mile apart from the next. We were to set up traps. There are three main types, the Lindgren/Funnel trap (a large black trap appearing to be made of many funnels stacked on each other, seen in the Guy Fleming trail in Torrey pines), the panel trap (a sticky piece of cardboard type paper that the beetles will fly into (only females fly as the males are tending the nest), and the bottle trap (two bottles stuck together by their caps). The traps we were setting up were the panel traps. Normally, for small areas and precise counts, it is recommended to count visually, but for large areas, traps are more efficient for management. My mom and I learned most of the information above from the training, as well as how to set up the panels. This is the materials list and the procedure.
Materials:
- Rebar
- Conduit pole
- Metal mallet
- Sticky panel
- Lure and ties
- Gloves
- Large binder clips
Procedure:
- Using the metal mallet, hammer the rebar into the ground until stable
- Fit the conduit pole over the rebar firmly.
- Open the trap and fold the other way so the sticky substance is on the outside. Gloves are recommended.
- Using the ties, attach the lure to the outside (sticky side) of the trap.
- Fasten the trap around the conduit pole using the binder clips.
Each pair (I was with my mom) of volunteers had two locations along the river. We were setting up a trap near Fashion Valley mall and another near the San Diego River. Once we reached our locations, the hardest part was finding a location close enough to a host tree but not too close (or the lure will bring them to the tree not the trap) and in soft ground but not too soft. We soon finished setting up the traps and returned the equipment. My mom was mostly doing the malleting and I secured the trap around. We had to improvise in Fashion Valley when we had lost a tie. Luckily, I found one of my hair ties in my backpack and my mom snapped it and used that to tie the lure (my idea)! Sometime in September, we will be checking on our traps and seeing if any vandalism occurred, or if the trap can be fixed. Until then, we are just hoping the rubber band holds!
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The above picture was just near Fashion Valley mall. Though we were given a GPS, we didn't use it as there was a map given to us. As we had left the ties in the car, we used the hair tie to secure the bait onto the trap. In the picture above, my mother has already hammered the rebar and I fixed the conduit pole. I am getting ready to open the trap and handle the sticky side as I am wearing gloves.
Stay tuned for more citizen science posts!
