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

2. Red palm weevil - Rhynchophorus ferrugineus Oliver. (Curculionidae: Coleoptera )

Damage

• The grub enters in to the stem and feeds on the internal tissue of the trunk causing a small hole on the stem with protruding chewed fibrous materials and oozing out of a brown liquid from such holes and eventually resulting in the toppling of the crown portion. In the advanced stage of attack, the central shoot shows sign of wilting and large mass of grubs, pupae and adults in fibrous cocoon could be seen inside the trunk at the damaged portion. In the grown up trees, the beetle causes damage by laying the eggs on the crown region. In such cases the grub easily enter into the growing point or cabbage of crown and causing yellowing of inner leaves and gradual drying of central shoot in the crown.





Bionomics

• The weevil is reddish brown with 6 dark spots on the thorax a conspicuous snout with tuft of hairs. The female weevil lays eggs in small holes scooped out by her on the soft regions of young palms up to 7 years of age. In the grown up trees the eggs are laid in the cuts or wounds present on the trunk or leaf stalk. The plant sap oozing out of wounds and cut attract the weevil for ovipositon. The eggs are creamy white in colour. The eggs hatch out in 2-3 days time into soft white grub. The grub is apodous which tunnel into the trunk and feeds on the internal succulent tissues. The larval period ranges between 45 and 75 days. The full-grown grub is stout, fleshy, and apodous with a conical body bulged in middle and tapering towards the ends. It pupates in a fibrous cocoon made out of fibrous strands.
• The pupal period last for 2-3 weeks. The total life cycle is completed in about 4 months. The adult weevils are reddish brown with long curved, pointed snout. The male weevil can be distinguished from the female by the presence of tuft of hairs along the dorsal aspect of snout.


Management

• Remove and burn all wilting or damaged palms in the garden.
• Avoid injuries or wound on stems as they serve as oviposition site for weevil.
• Fill all the holes with cement on the stem or trunk of coconut.
• Avoid the cutting of green leaves. If needed they should be cut about 120 cm away from the stem.
• Set up attractant traps (mud pots) containing sugarcane molasses 2.5 kg + toddy 2.5 litres + acetic acid 5 ml + yeast 5 g + longitudinally split tender coconut stem/logs of green petioles of leaves of 30 numbers in one acre to trap weevil.
• Set up male aggregation pheromone, ferruginol (4 methyl 5 nonanol) trap -ferrolure to attract the weevil.
• Follow the root feeding of monocrotophos 36 WSC 10 ml + 10 ml of water per tree.
• Insert one or two tablets of aluminum phosphide inside the tunneled trunk and plug all the holes with clay and cement mixed with copper oxy chloride to kill the insect by the fumigant action.