Coffee is equipped with an excellent defense against herbivory: caffeine. Caffeine is one of many alkaloids that evolved in various plants to prevent them from being eaten by insects. Evolution doesn’t stand still, however, and some insects have fought back. Coffee is attacked by several pests and diseases. Here are the most important, the ones that are most frequently combated with pesticides.
Coffee cherry/berry borer or “Broca” (Hypothenemus hampei). Native to Central Africa, but now found in many coffee-producing nations. The female of this tiny beetle (shown here on a green coffee bean) bores into the coffee cherry and lays about 15 eggs; the larvae feed on the developing bean. Usually, the cherry drops from the tree. The best defense is making sure there are no unpicked beans left on the trees or laying on the ground. Because they spend much of their life inside the cherry, controlling borers with insecticides can be difficult or downright ineffective. (Update: both Back to the Grinder and jimseven have nice photos of green beans with broca damage.)
Coffee leaf miner or “bicho mineiro” (Leucoptera coffeella). The leaf damage from the larvae of this small moth means less leaf surface is available for photosynthesis, resulting in stunted plants and reduction in yield. Native to Africa, but now found in many coffee-producing nations. This insect has developed resistance to insecticides in some areas.
Other insect pests include root nematodes (Meloidogyne spp.), green scale (Coccus viridis), and twig borers (Xylosandrus compactus).
Although not an insect, the next pathogen also prompts chemical onslaughts:
Coffee rust (Hemileia vastarix). A fungus that causes yellow spots on leaves, reduced photosynthetic ability, and eventually leaf drop. This causes a lack of nutrients going to growing shoots, and so can impact future growth of the plant. Spores require rain to germinate (high humidity is not adequate). Disease spreads more quickly in dense plantings and is less severe in shaded plantings, as the spores require a certain light intensity to germinate. Temperatures at farms at higher elevations are often too cool for the fungus. Native to Africa, but now found in many coffee-producing nations. Some coffee cultivars have resistance, notably the catimor variety, and also catuai and mundo novo.
Next in this series: Common pesticides used on coffee farms.
Coffee berry borer on bean photo by P. Greb.