White stem borers are the most serious pest of coffee in Nepal. The adults are slender, elongate (2-2.5cm in length) black beetles with white bands on their forewings. Female beetles lay about 100 eggs in the cracks and crevices of the bark and prefer the plants exposed to sun light. Eggs hatch after 9-15 days. Hatched out grubs bore into the stem and feed for about 2 months. The tunnels are filled with grub excreta. The grub stage lasts about 10 months, after which the grub will pupate in a chamber close to the bark. The fully grown larva is about 2-3 cm long, pale yellow and broader at the head region. The pupal stage lasts for 3-4 weeks. The adult remains in the tunnel for 3-7 days, and emerges out by cutting an exit hole.
Affected plants show externally visible ridges around the stem. They may also exhibit signs like wilting and yellowing. Infested plants (up to 7-8 years old) die in a year, while older plants withstand the attack for a few seasons. However, such plants are less productive, yielding more floats.