Cashew stem and root borer is a serious pest both in East and West coasts of India capable of destroying an entire cashew tree. Adults are medium in size, dark brown in colour and measure 30-40 mm long.
During the grub stages, the pest feeds inside the tree trunks or branches, boring tunnels causing the tree to wilt. Leaves turn yellow in colour, twigs dry up and the tree dies in 1-3 years depending on the extent of pest infestation.
Infestation extent
Plantations over 15 years old are often infested with this pest. Infestation ranges from 4-10 per cent in affected crops. Adult beetles lay dull white single eggs under loose bark of the stem and roots. Eggs hatch in 4-6 days.
Grubs riddle holes into the stem and bore down into the root. Openings of tunnel are plugged with reddish mass of chewed fibre and excreta with exuding sap at the base of the stem. Larval stage lasts for 6-7 months. Full grown larva measures 7.5 cm long and is creamy white in colour with a brown coloured head. It pupates inside the bore hole in a thick calcareous cocoon. Pupal period lasts for two months. The pest completes one generation in one year.
Control measures
— Survey the plantations during fruiting season and eradicate severely infested trees.
— Adopt phyto-sanitation methods by completely removing the dead trees in advanced stages of infection
— Cut and destroy damaged branches along with eggs and grubs
— Locate loose bark and boreholes and spike out eggs and grubs and kill them periodically.
— Train the newly planted grafts to bear branches at a height of 1metre above ground level. Use light trap at the rate of one per hectare to attract the pest.
— Swab the trunk with a mixture of coal tar and kerosene at the ratio of 1:2 or chloropyrifos 0.02 per cent twice a year once during March-April and again during November-December. Root feeding with monocrotophos at 20 ml/tree is also promising.
(R.K. Murali Baskaran & J. Jayaraj, Department of Agricultural Entomology, Agriculture College and Research Institute, TNAU, Madurai, email: muralibaskaran2007@rediffmail.com, mobile: 9655677669)
