Royan from Shadow Hills writes
Merit 75 WP would be applied at the rate of 1.4 level teaspoons per inch of trunk diameter (D.B.H.) or 2 oz per 30 cumulative inches of trunk diameter (D.B.H.) as a soil drench around the base of the tree as directed on the product label. Unfortunately there is no easy solution when it comes to pine beetles. 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) have proven ineffective for pine beetle infestations. Healthy trees can be protected before the beetles attack by topically spraying them with a product called Tengard. The tree should be sprayed from the ground to 15 ft up the trunk to prevent future infestations.
Answer last updated on: 10/06/2018
