Abstract
Fenitrothion accumulates in foliage tissue of balsam fir, Abies balsamea (L.) Mill., in the forest, but only until about 1.5 μg/g is reached. The balsam fir sawfly, Neodiprion abietis (Harris), which belongs to the family of forest insects known to be most sensitive to fenitrothion, has become rare but persists in New Brunswick in spite of the use of fenitrothion for control of spruce bud worm, Choristoneura fumerifana (Clemens).