BALSAM WOOLLY APHID, ADELGES PICEAE (HOMOPTERA: PHYLLOXERIDAE), SEASONAL AND SPATIAL DEVELOPMENT IN CROWNS OF BALSAM FIR, ABIES BALSAMEA

Abstract

The balsam woolly aphid, Adelges piceae (Ratz.), in Newfoundland is dimorphic and has three generations a year in the crowns of balsam fir trees. Two generations of the sistens, or diapausing form, predominate. Progredientes are more common than elsewhere in North America and occur on nearly all parts of a branch. They do not mature on current needles. The ratio of progredientes to sistentes is about 1:40 in balsam fir flowering years and 1:80 in non-flowering years. Aphid development in the spring is earliest at flowered internodes, 11 to 14 days later at 2-year-old nodes, a further 4 to 8 days later at older nodes, and latest at the shoot tips. Intra-crown and inter-tree differences in aphid development are small but measurable. Stratification of the tree crown is required for sampling during the first aphid generation.