Question
Jim:  I have a lake home in Northeast Oklahoma and we have had alot of rain this year, my two large pine trees are covered with little white worms ( about one inch long) and i have tiny bits of eaten pine needles falling on my deck which i believe is being done by these worms.the worms disappear at night and come out during the day. Question, what is this worm? How do I get rid of them? Will they kill my pine trees?

Answer
There are only a few insects that eat the foliage from pine trees. One is a caterpillar looking insect called pine sawfly. There are several different sawflies on pine. If I were to guess which pine sawfly I would think European pine sawfly.
The European pine sawfly, Neodiprion sertifer (Geoffroy), is the most common sawfly found infesting pines in landscapes, ornamental nurseries and Christmas tree plantations. Sawfly larvae look like caterpillars but they are the larvae of primitive wasp-like insects. They are common from southwestern Ontario through New England and west to Iowa. This pest was accidentally introduced from Europe.

In the landscape, this pest prefers mugho and table top pines. However it readily attacks Scotch, red, Jack, and Japanese pines. It will rarely feed on white, Austrian, Ponderosa, shortleaf and pitch pines, especially if these are intermixed with the preferred hosts.

The caterpillar-like larvae are grayish-green and have a light stripe down the back, a light stripe along each side followed by a dark green stripe. Full grown larvae are about one inch long. The larvae feed in groups or colonies, often with three or four feeding together on a single needle. Distributed larvae raise their heads and tails in a threatening manner.

Pines have two sets of needles and the sawfly will eat the older set. EPS larvae begin and complete their feeding activities before current-year needles are produced. Therefore, even if every single "old needle" were consumed, the plants would not be killed. Rather, the current year抯 growth (initiated after sawfly larvae have, for the most part, progressed into their pupal stages) would progress in a normal manner, providing photosynthates to support plant growth. If, however, EPS infestations occur over several successive seasons, it is possible for plant vigor to decline. Weakened plants would be more susceptible to other stresses (for instance excessive temperatures accompanied by drought conditions) which could result in eventual plant death.

They generally will not kill the tree but will reduce the growth.

They can be controlled with insecticides. Insecticides with the active ingredients acephate, malathion, carbaryl, esfenvalerate, rotenone and pyrethrin have longer residual properties, providing some extended control against European pine sawfly larvae