Effect of swathing and clear-cutting alfalfa on insect populations in southern Alberta
1990
Harper, A.M. | Schaber, B.D. | Story, T.P. | Entz, T.
Swathing alfalfa (Medicago sativa L.) for hay greatlyreduced the populations of several pest insects and their insect predators for 2 and oftenfor 4 wk after swathing in southern Alberta. Clear-cutting alfalfa reduced pest and predatorinsects usually for 3-4 wk, but the predator populations recovered rapidly in some fields. Thepest insects were Hypera postica (Gyllenhal), Acyrthosiphon pisum (Harris), Lygus spp., Adelphocoris lineolatus (Goeze), and Sitona scissifrons Say. Predators were Aeolothripsfasciatus (L.), Nabis alternatus Parshley, Orius tristicolor White, and Coccinellidae. There was a difference in insect populations among fields because of management of the alfalfaduring the growing season. These results have led to the recommendation for southern Albertathat, if pea aphid populations are high and the alfalfa is near the 10% bloom stage, the cropshould be cut rather than treated with an insecticide.
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