Insect Pests of Fruit, Plantation, Medicinal & Aromatic Crops (2+1)

5. Shot-hole borer

5. Shot-hole borer: Xylosandrus compactus (Coleoptera : Scolytidae)

• The short hole borer is a major pest of robusta coffee.
Life history

• The adult beetle is brown to black with a short, sub-cylindrical body.
• The pest usually infests the green succulent branches of old plants.
• In young plants, the main stem also may be attacked.
• After entering into the twig through the shot hole made on the underside, normally between the nodes, the female makes a longitudinal tunnel.
• The beetle then lines the wall of the gallery with an ‘ambrosia’ fungus.
• After growing the fungus, the female lays about 50 eggs in batches.
• The eggs hatch in 2 to 3 days, the milky white larvae feed on the ambrosia.
• The larval stage lasts for 13 to 21 days, and the pupal stage for about 11 days. Egg to adult emergence takes four to five weeks.
• Matting occurs inside the gallery.
• Unmated females give birth to male progeny. Males have no functional wings.
• The short life cycle enables the pest to complete several generations, in quick succession, under favourable conditions.
• The incidence is generally low before the onset of the southwest monsoon, reaches a peak from September to January, and gradually declines during the dry period.
Damage

• Withered or dried branches with shot holes indicate the presence of the pest.
• The attacked branches dry up fast. Leaves distal to the point of attack fall prematurely.
• The terminal leaves wilt, droop and dry up.
Control measures

• Prune the affected twigs 5 cm to 7.5 cm beyond the shot hole and burn.
• This operation should be commenced from September onwards and continued as a routine measure at regular intervals.
• Remove and destroy all the unwanted/infested suckers during summer.
• Maintain thin shade and good drainage.