Different types of insects cause different types of damage, like :

Defoliaters :

These are those insects which destroy the foliage of trees by

• direct eating up of the leaf or its parts
• rolling the leaf or its part so that it withers away
• boring in the leaf tissues
• cutting the leaf or its part e.g. Sagwan, Shisham

Skeletonizers :

Those which eat up all the leaf leaving the nidrib and veins intact.

Leaf eators :

Those which eat all the leaf tissues.

Shoot borer :

The insect attacks the shoots of the trees, with the result that the growth gets checked and the young plants assume a bushy appearance. e.g. semal.

Bark borer :

The attack is confined to green trees including newly-felled or wind blown trees. It is also a serious pest of seedling and saplings in regeneration areas where the young plants get killed.

Cambium and wood borer :

The insect causes two kinds of damage to sal trees:

1. The larva during the course of its feeding period eats up the cambium layer and thus kills the tree.

2. It bores long galleries in sap and heartwood and thus greatly reduces the commercial value of the timber.