Question
July 2008.  I have young trees planted this past December.  Height approx 15 feet.  Just noticed several half inch branches severed and found larvae borer in branches.  Does it make sense to apply any kind of insecticide at this point. I've read several articles on the internet and this point is not clear.  Thanks.

Answer
It sounds like if the branches were cut off that you have an insect called a twig girdler or pruner. The beetles lay their eggs in the branch and then cut the branch letting the branch hot the ground. The egg hatches and the larvae goes into the ground and completes the life cycle. These type "borer" can be controlled by picking up the fallen branches and destroying the branch either by burning of removing the branch with the eggs in them from the area. This reduce the population next year. Insecticides that are applied to the soil may control the boring by the roots transporting the insecticide to the branches and when the beetle lays its eggs the beetle will be killed. Bayer Advanced for trees is one of these systemic insecticides. Check with your local nursery for this insecticide.