The pine tip weevil takes the tops off of spruce trees

Our area continues to have problems with weevils in spruce trees.  First some background.  Weevils live in ground over winter.  In spring they climb to the top of spruces and mate then bore small holes in the bark and lay eggs.  This is in may – june.  The larvae from the eggs eat just under the bark and destroy the fluid carrying layer thus cutting off water & nutrients above them.  They work their way down and extent the amount of damage.  By mid to late August the larvae mature and leave the tree.  Damage is typically 1 to 3 feet off the top of the tree.  For a small tree this can be a serious setback to the growth of the tree.  For a large tree the damage is mostly cosmetic. 

Here are the larvae in mid summer

Too late for systemic?  Next best is to spray the tree to kill the adults.  Timing is critical.  The adults need to be in the trees while the insecticide is active.  Rain and wind can be a problem.

You missed all  the above and now the tops are dying.  Prune out the deat top as soon as the problem is noticed.  After each cut look at the color just below the bark – if it is green all the way around then you have cut enough; if brown then there are still live larvae in the tree.  Once cut out the larvae have lost their food source and will die. The tree will suffer no more damage this year.  It is now time to make a plan for next year.

The TreeHealers preferred treament is to get a systemic insecticide into the tree in the fall of very early spring this includes our BioMax fertilizer which will help the replacement of the top.  It has the added advantage of not duplicating the cost of labor that would occur if insecticide and fertilizing were separate operations.

If we are called to treat a tree in late spring we will resort to injecting the insecticide directly under the tree bark.  This speeds circulation through the tree and insome cases reduces the damage but may not eliminate  it.