Effect of balsam woolly aphid, Adelges piceae, infestation on the food reserves of grand fir, Abies grandis

Abstract

Effects of balsam woolly aphid infestation on the concentration of ethanol-soluble and -insoluble carbohydrates were investigated in four age classes of needles and six age classes of twigs of grand fir, before and after bud break.In March, before bud break, sugars made up about two-thirds of the total carbohydrate content of the foliage. Aphid infestation did not affect the concentration of sugars in needles but reduced starch by 28%. In twigs, sugar concentrations were less in infested trees while starch concentrations were unaffected. Both older needles and twigs contained higher concentrations of starch than younger needles and twigs.After bud break in June, starch constituted the major form of carbohydrate, accounting for 65% of the total carbohydrate in non-infested foliage and 53% in infested foliage. Total carbohydrate content increased over that in March, in both infested and non-infested foliage, but the non-infested tissue showed the greatest increase. Starch content of infested foliage was reduced by 36%, while starch concentration of infested twigs was reduced by 18%.