- Author: Ben Faber
Ambrosia beetles, which are a large group of several thousand species worldwide, belong to the bark beetles. All species are characterized by the ability to cultivate fungi. Invasive Shot Hole Borers that attack avocado and a range of native and landscape trees in California and the Laurel Wilt Disease that hammers avocado in Florida are ambrosia beetles. These beetles cultivate fungi in living trees and over time, the fungus is what kills the tree.
Beetles share the work of cultivating their fungal gardens: some clean the tunnel systems that are being eaten into the wood; others clear the dirt from the nest and clean their fellow workers -- always with the aim of optimizing the symbiosis of beetle and fungus.
It's been long known that alcohol is produced by weakened trees and that these trees are recognized and colonized by the beetles. Traps baited with alcohol are used to catch the insects when they fly. Alcohol is very attractive to the beetles in large part because the fungi they feed on performs best in an alcohol-rich environment. Alcohol is normally used as a preservative to impede other fungi, such as molds from growing, and this is the case for the fungi associated with these beetles. They prefer to grow in an environment where other fungi don't grow.
Here's an interesting article showing how this preference by disease-causing fungi allows them to thrive in a normally harsh environment. Maybe it can be exploited.
Christopher M. Ranger el al., "Symbiont selection via alcohol benefits fungus farming by ambrosia beetles," PNAS (2018). www.pnas.org/cgi/doi/10.1073/pnas.1716852115
Photo: Party Beetles
Credit: Gernot Kunz