Two species of bark eating caterpillars — Indarbela tetraonis and Indarbela quadrinotata — are very destructive to a wide range of fruit trees.
The caterpillars bore into the bark, making tunnels into the main trunk and shelter under silken galleries. It predisposes the stem to bark decay. The caterpillars spin a silken web consisting of their excreta and chewed wood particles which are seen hanging loosely on the bark of the affected tree.
In other words, thick, ribbon like, silken webs are seen running on the bark of the main stem. Generally a single caterpillar is found inside a tunnel but heavily infested trees may contain 15-30 larvae.
Old trees are more susceptible to the attack than young ones. Particularly, neglected orchards are more prone to this infestation.
The pale brown moths lay eggs in cuts and crevices in the bark and after ten days of hatching the dirty brown caterpillars with reddish brown head remain hidden in the galleries and are nocturnal. They develop in up to 10 – 11 months and pupate for about 25 days within the tunnel. Moths emerge in summer and are short lived. There is only one generation in a year.
— Avoid growing susceptible varieties. Collect and burn, loose, damaged barks and affected branches.
— Kill the caterpillars mechanically by inserting an iron spike into the holes made by the caterpillars
— Clean the affected portion of the trunk and insert into the hole a swab of cotton wool soaked in petrol or kerosene.
— During September and October inject 5 ml dichlorvos in the bore hole with the help of a syringe or wash bottle and plug the hole with mud. Carbofuran 3G granules may be placed at 5 gm per bore hole and plugged with mud.
— Padding with monocrotophos at 10ml / tree could help. Swab the trunk with carbaryl 50WP at 20gm/lit. Use light trap at 1no/ ha to attract adult moths.
(Dr. J. Jayaraj is Professor and Dr. M. Kalyanasundaram is Professor & Head, Department of Entomology, Agricultural College and Research Institute, Madurai-625 104, Phone No. 0452-2422956 Extn.214, email: firstname.lastname@example.org)