Things You'll Need
Spray the pesticide in summer. Adult borers begin to emerge in late June and remain on the trees through August. Adult females begin to lay eggs almost immediately, so you want to spray the tree as soon as you spot the borers.
Always use pesticides in accordance with the manufacturer's directions, and wear protective eye, nose and mouth coverings.
Borers are destructive insects that burrow into the bark of a tree, leaving behind small, round holes. Many species of boring beetles attack aspen trees, often leaving them with "bleeding" wounds. Aspen borers emerge from beneath the bark in June, and the insects can spread rapidly from tree to tree. Killing aspen borers requires a systematic spraying of specially formulated pesticides.
Examine the trunk of the aspen trees for signs of holes, which indicate the presence of borers.
Fill a garden sprayer with an insecticide approved for use on aspens that is formulated for boring insects. These pesticides typically contain the ingredient permethrin or Sevin (carbaryl).
Put on gloves, a dust mask and safety glasses. Place a ladder next to the affected aspen tree trunk, and climb it with the garden sprayer.
Spray the entire trunk with a light layer of the pesticide, as well as the leaves and branches.
Move the ladder to any nearby aspen trees, and spray them with the pesticide as well. Spray the closest trees, even if no evidence of holes is seen, to prevent the borers from moving to those trees.
Wait one to two weeks, or the time specified on the pesticide label, and repeat the treatment of spraying the aspen trees.
Kimberly Johnson is a freelance writer whose articles have appeared in various online publications including eHow, Suite101 and Examiner. She has a degree in journalism from the University of Georgia and began writing professionally in 2001.