EFFECT OF THE PEA APHID, ACYRTHOSIPHON PISUM (HOMOPTERA: APHIDIDAE), ON COLD-HARDINESS OF ALFALFA

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Abstract
The pea aphid, Acyrthosiphon pisum (Harris), infests alfalfa in southern Alberta and is known to reduce yield and quality of the crop (Harper 1972). From the literature on the pea aphid, recently reviewed by Harper et al. (1978), there do not appear to be any publications on the effect of the pea aphid on cold-hardiness of alfalfa or other host crops. Harper and Lilly (1966), however, found that some aphid-infested plants that were clipped in late fall did not survive the winter. We have observed that numbers of pea aphids often reach high levels on alfalfa in Alberta late in the growing season.