Chemical Control of the Eastern Spruce Gall Aphid with Observations on Host Preference and Population Increase1

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Abstract
Field insecticide studies demonstrated that lindane (1 lb. actual toxicant per 100 gallons of water) gave good control of eastern spruce gall aphid (Chermes abietis L.) when applied between the time of last freeze and start of terminal shoot elongation. Sevin® (1-naphthyl methylcarbamate) (2 lbs.) was less effective, while dimethoate (2 lbs.), malathion (1 lbs.), and Phosdrin® (1-methoxyearbonyl-1-propen-2-yl dimethyl phosphate) (1 lb.) gave little or no control Statistical analyses of infestations over a 2-year period show (1) a 15% greater incidence of attack on white as compared with Norway spruce; (2) a 6% increase in over-all infestation from 1958 to 1959; (3) a strong tendency for infestations to recur on previously infested trees. This suggests that by harvesting infested trees, a grower could reduce the infestation in a given planting, if such a program were initiated before the percentage of attacked trees was too high. Finally, the view that certain trees are resistant to aphid attack is questioned, using as a basis the tendency of this insect to reinfect previously infested trees. It is reasoned that, even though new and previously uninfected trees appear to be randomly attacked each year, the rate of spread is so slow that one-fifth of the trees in the study area are expected to remain uninfected for 5 consecutive years, owing to insect behavior alone.

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