Melanie Bondera- November 2010
Beauvaria bassiana fungus and Coffee Borer Beetle
I went to the CBB Farmer meeting at Yano Hall on Tuesday, 11/8/10. I was not satisfied with the material being presented, but was very curious about a comment by another coffee farmer. He suggested that we’ve actually had Coffee Borer Beetle for a number of years and the Beauvaria bassiana fungus. The fungus has kept the beetle in check, much like the white halo fungus keeps our green scale in check. When we had the worst drought in recorded history this year, the fungus died back and the CBB exploded. The worst hit farms are in the driest areas of South Kona. This theory was the only one that made any biological or ecological sense to me.
So, I went home to find the fungus. I researched online about it. I was annoyed to find that due to its basic biology, it should not be banned for us to use. Beauvaria bassiana is naturally occurring in the soil, and we have it here already. There are many strains of it and they are very host specific, so I doubt a strain that kills CBB could kill the native spiders that Fish & Wildlife are worried about. My aha moment came when I started using google images and found pictures of the fungus on coffee cherry. I had seen it the day before while picking!
I went out to my worst CBB area and looked through about 100 infested beans before I started finding it. a bit of white crystalline stuff sticking out the beetle exit hole. When I cut these beans in half, I found dead beetles stuck in the exit with the fungus growing out of their bodies. So, I took the photos you see below. Then I contacted Bob Smith, our representative to the CBB task force.
We are sure this is the B. bassiana fungus, but think we should test it to make sure. We’re going to collect it, grow it out and spray it back on the coffee trees. The coolest thing about this fungus is that its endophytic, which means it gets into the tissue of the coffee trees and lives there year after year, infecting and killing CBB. If we do nothing, probably the CBB will go down over several years as the moisture regrows the population of the fungus, but we can hasten this by spraying an inoculation of it on our trees (and save more crop, more income!). If we grow out the Kona typica CBB B. bassiana, it will be more effective as its locally adapted, than any commercial sprays we could buy from off island (if released). We’ll probably need to practice some of the sanitation practices as well to keep the population of CBB down as the beetle and fungus come back into balance. B. bassiana is not a silver bullet, but it will sure keep our threshold down in the manageable range. And it looks like it has been doing that for years!
Check back here for protocol on how to grow it out. Go out in your orchard now and see if you can find the B. bassiana fungus. Collect those beans.
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