4. Mango nut weevil: Sternochaetus mangiferae (Curculionidae: Coleoptera)

Distribution and Status : India, Pakistan, Bangladesh, Srilanka, Burma, Malaysia, South Vietnam, Philippines, East Australia, Africa and Hawaii.

Host range: Mango

Damage symptoms

The grub tunnels in a zig-zag manner through the pulp endocarp, seed coat and finally reaches the cotyledons and destroys them. As the fruit develops the tunnel get closed.  The adults that emerge from the pupae also feed on the developing seed and hasten the maturity of infested fruit.

Bionomics : Adult lay eggs singly on the marble sized fruits by scooping out the surface tissue and covering over with transparent secretion. Egg period - 7 days, grub period - 20-30 days yellow creamy grub apodous with five larval instars. Pupation occurs inside the nut along the concave side; pupal period 7 days. Adults stout, 6 mm long, dark brown in colour.  Life cycle completed in 40-50 days.        

IPM

• Under-sized fruits left on the tree should be picked and destroyed.
• Undertake general cleanliness and destruction of the weevils on the bark during August If the trees are few, bag the fruits with cloth or try paper bags for protection.
• Collect and destroy the fallen fruits and stones
• Spray application of malathion 50 EC 1ml/L; Carbaryl 3-4 kg (4 g/L of water) or Quinalphos 3- 4 L (2 ml/L of water) in 1500-2000 L water per ha in Sept-Oct on the tree first at marble stage of the fruit second at 15 days interval.
•  During non flowering season direct spray towards the base of the trunk.
• The infested bark should be washed with kerosene emulsion.
• Spray deltamethrin spray 1.5 - 2.0 L (1 ml/L of water) in 1500-2000 L water per ha after six weeks of fruit set.