If you noticed the tip of your spruce tree wilt last year, and then turn brown and die, you were likely the victim of White Pine Weevil. This insect mainly attacks young spruce trees under 10 feet tall, but occasionally will attack larger trees. Here’s what Utah State Universtiy Extension had to say about it in their Weekly Pest Update for Woody Ornamentals dated today, April 9, 2014.
White pine weevil adults start becoming active at forsythia full bloom. During that time, and within two weeks afterward, is the time to treat, targeting the adults.
This pest attacks the terminal leader of blue spruce in many parts of Utah. It rarely attacks pines in the West, but is a common pest of pines in the East.
Adult weevils spent the winter in leaf litter. In spring, females emerge from the ground and either crawl up the bark to the top of a nearby tree or will fly a great distance to the top of another host.
They feed on tissue just below the terminal bud, and soon after, they lay their eggs within the feeding sites. A single female can lay about 100 eggs on various host trees. The eggs hatch into grub-like larvae that bore into the terminals, resulting in wilting and tip dieback, which is evident by mid summer.
- Thoroughly spray the upper portion of the tree (bark and needles) with a pyrethroid insecticide such as one containing the ingredient bifenthrin or permethrin. On larger trees, homeowners should get a professional to apply the insecticide. Depending on the product used, a second application may be required 2-3 weeks later.
- At the first sign of wilting (in summer), prune out the shoot and destroy (the larvae will be inside).
I recommend spraying Fertilome Bug Blaster containing bifenthrin now and again in two weeks.