EFFECT OF APHIS-SPIRAECOLA AND A-POMI (HOMOPTERA, APHIDIDAE) ON THE GROWTH OF YOUNG APPLE-TREES

One-year-old 'Redchief Delicious' apple trees grown in pots in an unheated greenhouse with screened ends were inoculated during the summer with either spirea aphid, Aphis spiraecola Patch or apple aphid, A. pomi DeGeer. Photosynthesis and greenness (the extent of chlorophyll colour) of apple leaves were reduced by increasing accumulated aphid-days for both species. Accumulation of fresh and dry weights in leaves, lateral shoots, rootstock and roots during the first growing season were affected by both species. Differences in dry weight were still present when trees were harvested at the ten-leaf stage the following spring. The percentages of non-structural carbohydrates (NSC) in shoots, roots and leaves were reduced by both aphids; amounts of NSC were reduced in all tree partitions. At the ten-leaf stage of the second season, the percentage and amount of NSC were reduced in all tree partitions. Tree response to the two aphid species was generally similar.