Seasonal History and Control of the Alfalfa Weevil in North Carolina 1

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Abstract
The alfalfa weevil (Hypera postica (Gyllenhall)) is the most important pest of alfalfa in North Carolina where multiple treatments of malathion or methoxychlor are necessary for good protection in the spring. Granulated heptachlor when applied in mid-October or mid-November gave optimum weevil control in tests conducted in 1959 and 1960. Near perfect control was attributed to the destruction of adult weevils prior to oviposition which normally commences in mid-November. Insecticide residues, however, limit the 1 lb. per acre rate to a mid-October application of heptachlor. Experiments initiated in the fall, 1960, compared formulations, rates, and timing of heptachlor for weevil control. Excellent control of adults was obtained with rates as low as 0.5 lb. per acre in mid-October with indications that a mid-November treatment was at least as effective. Insecticides were less effective when they were applied after oviposition commenced or too far in advance of the time when the estivating adults return to alfalfa. Control obtained with one-half pound of granulated heptachlor applied in mid-October was equivalent to that obtained with 2 lb. per acre applied in mid-September. Thus, an intimate relationship exists between climate and weevil activity which in turn governs the optimum time for control of the overwintering weevil population.

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