White, woolly patches on the trunks, branches, and twigs of white pines are caused by pine bark aphids, which may also attack Scotch and Austrian pines and an occasional Balsam fir. The aphids are dark brown and covered with a woolly protective coat.
When severe infestations, a whole tree trunk may appear white, and white spots may also be found on the undersides of branches and at the bases of needles, especially those at the outer edges of the branches.
Controlling Pine Bark Aphids
Control: Ladybird beetles or ladybugs and various flies and their larvae feed on the pine bark aphid, but gardeners may have to resort to insecticides to bring an infestation under control.
The secret is to use a good wetting agent in the spray and to apply the spray under heavy pressure. To be effective, the spray must penetrate the woolly coat. The help of a professional arborist may be needed.
The best insecticide is malathion, four tablespoonfuls of a 25% wettable malathion powder to one gallon of water. Or use one tablespoonful of a 25% wettable lindane powder or a 12 percent benzene hexachloride (BHC) wettable powder to one gallon of water.
The BHC is the least expensive, but it has an objectionable odor. Whichever insecticide is used, add at least one teaspoonful of a liquid wetting agent, such as Triton X-100, or one level tablespoonful of a detergent, such as Dreft or Vel.
The usual recommendation is to spray two or three times a year. Dates in the latitude of New York are about May 25 and again about July 8 if the infestation is severe.
Home gardeners in this area who do not have the equipment to apply spray under heavy pressure might make a third application in early August. Repeat the sprayings each year to prevent re-infestation.
44659 by Robert H. Brewster