Early Season Insect Control in Alfalfa, 1996

Eight chemical insecticide treatments were evaluated for efficacy in controlling AW larvae and aphids infesting the first crop of a fourth year stand of TCI 630’ alfalfa at the Southcentral Research Station, Chickasha, OK. Pretreatment samples indicated a population of 30 larvae/25 stems and 68.7 aphids/stem. Insecticides were applied on 8 Apr using spraying system TK SS-5 flooding nozzles calibrated to deliver 20 gpa at 24 psi when traveling at 3 mph. Treatments were arranged in a RCB design on plots 5 X 10 m in size, replicated 4 times. Sampling was conducted 3, 8, and 13 DAT by pulling samples of 25 stems per plot and placing them in standard Berlese funnels to extract insects for counting. Subsamples of aphids were identified on each date to determine the proportions of species present. Dry matter yields were estimated for 1 st harvest on 16 May by removing forage from 1 X 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.