Kimberly from Hickory Corners, Mi writes
Merit is not recommended for most bark beetles because the beetles are under the bark but above the level where the Merit would trans-locate through the tree. Infected trees should be cut down (before the newly hatched beetles fly out of the trees in the spring/summer) and the wood burned or chipped, while other still healthy trees should be sprayed annually to protect them. Because of the natural boring behavior of the beetle they are protected from topically applied insecticides and systemic insecticides (those injected into the tree or applied as a root drench such as Merit) have proven ineffective for pine bark beetle infestations. Healthy trees can be protected before the beetles attack by topically spraying them with a synthetic pyrethroid like Talstar or Permethrin SFR. The trees should be sprayed from the ground to 15 ft up the trunk to prevent future infestations. You should contact your local cooperative extension office to find out the best time to start spraying in your region.
Answer last updated on: 05/23/2012