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

1. White stem borer

1. White stem borer - Xylotrechus quadripes (Coleoptera: Cerambycidae)

• White stem borer is a very serious pest of Arabica coffee in India.
Life history and damage

• Adult is a slender beetle, 1 to 2 cm long.
  
• The forewings are black with white bands.
  
• Adults are active in bright day light.
  
• Female beetles deposit eggs in the cracks and crevices and under the loose clay bark of the main stem and thick primaries preferring plants exposed to sun light.
  






• Young grubs feed in the corky portion just under the bark for about two months.
  
• Consequentially, the bark splits and appears as a ridge on the stem.
  
• Later the larvae enter the hardwood and make the tunnels in all directions.
  
• In some cases the tunnels may extend even into the roots.
  
• The tunnels are tightly packed with excreta of the grubs.
  
• The grub stage lasts for about 9 to 10 months.
  
• Larva pupates in a chamber close to the periphery of the stem.
  
• The pupal stage lasts for 3 to 4 weeks after which it transforms into an adult.
  
• The adult remains in the tunnel for 3 to 7 days and emerges out by cutting an exit hole in the bark.
  
• The borer completes its life cycle in about a year.
Symptoms of attacks

• Infested plants show external ridges around the stem.
  
• Such plants may also exhibit signs like yellowing and wilting of leaves which will be distinct after the onset of monsoon when the healthy plants starts putting new growth.
  
• The young plants (7 to 8 year old) attacked by the borer may die in a year white older plants withstand the attack for a few seasons, yielding more of floats.

Borer infested farm




Nature of damage

Flight periods

• There are two flight (emergence) periods from April to May and October to December.
Control measures

• Maintain optimum shade
• Trace the infested plants prior to flight periods (i.e.,in March and September) every year by looking for ridges on the main stem and thick primaries. Collar prune the infested plants, uproot if the borer has entered the root and burn the affected parts. Storing of infested stems on the estate will result in continuous infestation.
• Proper agronomic practices to retain plant vigour
• Remove loose scaly bark to discourage egg laying
• 10% lime application on main stem and thick primaries during flight periods
• Repeated application of neem oil on the stem
• Use of pheromone traps to monitor incidence
• Judicious and timely application of pesticides on the stem during flight period