Digging into the Coffee Borer Beetle
Coffee was originally discovered in Ethiopia, so it should come as no surprise that one of coffee’s biggest foes, the coffee borer beetle, is also endemic to central Africa. Commonly referred to as “la broca” in Spanish, it has spread to most coffee producing areas through accidental introduction of contaminated seeds. As of 2017, only Nepal was free from it.
Although caffeine often serves as a natural insecticide by inhibiting the nervous system and ultimately leading to paralysis and death in many susceptible bugs, the broca is the only known pest to both live in and feed exclusively on the coffee cherry. The beetles have 14 types of bacteria in their digestive tract that break down the caffeine.
Females attack the cherry beginning about 8 weeks after flowering and continue throughout the harvest. They make a small (1mm) puncture in the fruit and proceed to lay 35-50 eggs. After they hatch, the new insects then mate inside the seed and the cycle continues. Since the females can travel from one plant to the next, it is easy to imagine how devastating this pest can be. Severe crop loss is common and salvageable coffee may be of lessor or poor quality.
Preventing attacks is critical and begins with careful inspection of beans and border controls to prevent contaminated seeds from entering agricultural areas. Once at the farm, various methods can be combined including chemical control, biological control, and rigorous maintenance practices. Pesticides are only effective before the female perforates the fruit. After that, natural predators including birds, ants, and nematodes that attack the larvae or adult beetles can be effective, although the fruit will already be ruined. Fungal entomopathogens are also used by covering the infected plant with a mildew that is toxic to the beetle. Organic farmers have experimented with wasps native to Africa, but have found low effectiveness.
Since the broca continues breeding in out of season berries, it is critical to remove all fallen cherries and any remaining on the plant. In addition to correct harvesting, prevention practices continue throughout the farm, including mill sanitation, proper storage, and disposal of any unused cherries. Poor handling after a harvest can result in many beetles returning to the fields.
While there is hope that science and technology will one day develop an effective method to control these pests, meticulous farming practices currently prove critical to protecting crops. Mismanagement can cost not only the current harvest, but the following year’s as well.
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