Insects

a) White stem borer

• White stem borers are the most serious pest of coffee in Nepal.
• adults are slender, elongate (2-2.5cm in length) black beetles with white bands on their back.
• Female lay around 100 eggs in the cracks and crevices of the bark and prefer the plants exposed to sun light.
• 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.
• 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.

Control

• Spray the main stem and thick primaries with neem kernel extract •
• Spray 10% lime (i.e. spray lime at 10kg in 100 litres of water along with 100ml of a binder e.g. Fevicol DDL) on the main stem and thick primaries before the flight periods
• Use a coffee white stem borer pheromone trap.

b) Coffee green scale

• Coccus viridis is a soft scale insect in the family Coccidae with a wide host range.
• The adult scale insect is a glossy pale green colour with black internal markings that are visible through the chitinous body wall.
• The scale insects excrete honeydew on which bees, wasps, ants and other insects feed.
• Sooty mould fungus often grows on the honeydew and this decreases the area of leaf available for photosynthesis, spoils the appearance of the plant and reduces the marketability of fruit.

c) Mealy bug

• Mealybug females feed on plant sap, normally in roots or other crevices, and in a few cases the bottoms of stored fruit.
• They attach themselves to the plant and secrete a powdery wax layer (hence the name mealybug) used for protection while they suck the plant juices.
• If the infested plant can tolerate the cold, place the plant on a windowsill during cold weather. This will attract the mealybugs to the leaf furthest from the window, where they can be wiped off with a cloth.
• Ladybird larvae and adults feed on mealybugs, and can be used to control an infestation.
• Mealybugs can be controlled using the fungus Lecanicillium lecanii.

d) Coffee berry borer

• The coffee berry borer female (1.4-1.78 mm) attacks immature and mature coffee berries from about eight weeks after flowering up to harvest season (>32 weeks).
• Females bore a hole into the coffee berry and then construct galleries in the seeds (beans) where the eggs are deposited, followed by larval feeding on the coffee seed