Abstract
Abstract Nine chemical insecticide treatments were evaluated for efficacy in controlling AW larvae and aphids infesting the first crop of a third yr stand of ‘Cimarron’ alfalfa located at the Agronomy Research Station, Stillwater, OK. Pretreatment samples indicated a population of 0.8 AW larvae and 27.5 aphids/stem. Insecticides were applied on 1 Apr using a tractor-mounted boom sprayer equipped with flooding nozzles (Spraying Systems Co., TK SS-5) calibrated to deliver 20 gpa at 24 psi when traveling at 3 mph. Treatments were arranged in a RCB design on plots 5 × 10 m in size, replicated 4 times. Efficacy of treatments was determined for both AW and aphids at 3, 7, 13, and 20 DAT by pulling samples of 25 stems from each plot and placing them in standard Berlese funnels to extract insects for counting. At 18 DAT, an additional sample was collected by clipping 10 stems/plot and rinsing aphids into alcohol for counting. Subsamples of aphids were identified on each date to determine proportions of species present. Dry matter yields were estimated by removing forage from a 1 × 5 m area in each plot using a flail-type harvester. Subsamples were dried for determination of moisture content and yields were calculated on a dry weight/acre basis.
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