The coffee berry borer, Hypothenemus hampei, is a beetle about the size of a pinhead, with females reaching only 1.8 millimeters, yet it is the most destructive coffee pest on Earth and threatens the income of more than 20 million families. It skips the leaves and roots and goes straight for the seed. Between 8 and 32 weeks after flowering, a female drills into a developing coffee cherry, carves galleries through the endosperm, and lays 35 to 50 eggs. Her brood is skewed 13 females to every male, and the flightless males never leave the bean: they mate with their sisters inside and die there. Females wait for the humidity of rain before flying out, and with a cycle of 24 to 45 days, one cherry can host up to 100 beetles.

Caffeine should kill it. Genome work, with a draft in 2015 and a full assembly in 2021, showed the immunity comes from gut bacteria, prominently Pseudomonas, that break caffeine down with the enzyme caffeine demethylase, and mothers pass those microbes to their eggs. Native to Central Africa, the beetle hitchhiked in seeds to Brazil by 1926, Guatemala and Mexico in the 1970s, Colombia in the late 1980s, Puerto Rico in 2007, Hawaii’s Big Island by 2010, and now Taiwan. Sprays rarely reach it inside the fruit, and in New Caledonia it resisted endosulfan, which pushed growers toward birds, wasps, and fungi.

• Inbreeding helps resistance spread fast, since one resistant mother passes the trait to 13 daughters who mate with a brother.
• In Costa Rica, yellow warblers and rufous-capped warblers cut beetle numbers in half in some areas by catching females in flight.
• The African wasp Phymastichus coffea, found in Togo in 1987, is mass reared and released in Colombia, protecting organic certification.
• An aggressive imported wasp backfired by stinging farm workers and leaving them with severe dermatitis.
• Hawaiian growers used Beauveria bassiana fungus products such as BotaniGard and Mycotrol, which kill beetles inside their own galleries.