Quantitative Estimation of Alfalfa Insect Populations by Removal Sweeping 1

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Abstract
Insect populations were estimated from the reduction in catches in successive sweep samples taken from the same area. A model is provided which assumes that the probability of collecting an insect may change with successive samples. This model seems superior to previous models which assume a constant probability for capture. Population estimates are compared with results of D-Vac samples. Removal sweeping provided good estimates of Lygus lineolaris (Palisot de Beauvois), Adelphocoris lineolatus (Goeze), Empoasca fabae (Harris), Macrosteles fascifrons (Stal), Nabis sp., grasshoppers, and Hippodamia convergens Guerin-Meneville larvae. H. convergens adults were reasonably estimated in one experiment but overestimated in another case due to immigration during sampling. Estimates for Orius insidiosus (Say), Hypera postica (Gyllenhal) larvae, and Aphidius sp. were unsatisfactory. General considerations involved in obtaining optimum estimates are discussed.

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