Coffee Borer Beetle Thrives on Caffeine

A constant threat to coffee production is an infestation by the coffee borer beetle. This insect burrows into the coffee bean and lays its eggs. The larva thrives by eating the bean after it hatches. The coffee borer beetle is not bothered by the caffeine in the coffee bean although caffeine is essentially poisonous to other beetles. Why is it that the coffee borer beetle thrives on caffeine? A recent article in National Geographic tells how with the help of bacteria the coffee borer beetle thrives on caffeine.

The beetle is the only animal that can feed solely on coffee beans. Others might occasionally nibble the seeds or other parts of the coffee plant, but they don’t dedicate themselves to the task. There’s a reason for that: caffeine. This stimulant draws many of us to coffee, but it effectively deters plant-eating animals. Not only does it taste bitter, but at the doses found in coffee seeds, it can poison and paralyze any wayward insect. Any insect, that is, except for the coffee berry borer. As a larva, it’s practically bathed in caffeine, and yet it survives. Even the most caffeine-rich beans fail to deter it.

Javier Ceja-Navarro from the Lawrence Berkeley National Laboratory has discovered its secret: it has bacteria in its guts that can detoxify caffeine.

Bacteria in its gut are the reason the coffee borer beetle thrives on caffeine. Dr. Ceja-Navarro treated the beetles with antibiotics and their protection against caffeine went away. The question is if organic coffee growers would want to treat their field with massive doses of antibiotics in order to combat the coffee borer beetle.

Dealing with the Coffee Borer Beetle

Because no one wants to go out and give a penicillin injection to every coffee borer beetle larva there must be other approaches to controlling infestations of the coffee borer beetle. Options for coffee borer beetle infestations include spraying with a fungus that is toxic to the beetle. Bassiana fungus is mixed with water, soap, oil and even fertilizers and sprayed on the soil as well as on the coffee beans. It tends to reduce infestations to the 2% range.

According to Kona coffee farmers integrated pest management includes field sanitation.

Simple sanitation is vital, and can be cost-effective with a few preventative measures.  Many CBB experts consider it the most effective form of control. The beetle can live in the infected bean for up to 5 months without feeding.

  • Do a “final round” gleaning of the field to break the life cycle. In a well-picked field, it should take approximately 16-24 man-hours to glean old crop from 5 acres of trees.
  • Remove all infected beans before pruning each tree.  One beetle can multiply into 200 if left behind.
  • All CBB-infested beans or floaters should be placed in black garbage bags and left in the sun for several days.  The heat will kill the beetle. Freezing will also work.
  • Train your harvesters not to discard green beans out of the picking bucket.  Also train them to spot La Broca  (Spanish for CBB) damage so that they may report trouble areas.

Sanitation is consistent with organic coffee management and so are traps. Traps do not significantly reduce the coffee borer beetle population but are a good way to spot area of higher infestation. And last of all dry all beans to lower than 12% moisture as this hardens the bean and the beetle cannot enter.

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