Insecticide Efficacy Against Spotted Alfalfa Aphid, 2014a *

The objective of the study was to evaluate the efficacy of the new and old insecticidal compounds used against SAA on alfalfa grown for hay production under desert growing conditions. A field study was conducted during the spring of 2014 at the UC Desert Research and Extension Center. A stand of alfalfa, ‘CUF 101’, was used for the experiment. The experimental design was an RCB using four replicates with 12 insecticidal treatments and an untreated check. Plots measured 13.33 ft by 50 ft and insecticide treatments were applied on 5 Feb 2014, using a ground broadcast application with a handheld CO ₂ backpack sprayer with a boom covering a 13.33 ft swath operated at 30 psi, delivering 20 gpa through 10 (TJ-80015) nozzles. The SAA population was measured in each plot with a standard 15-inch-diameter insect net consisting of ten 180 ^o sweeps; means reported in the tables are per sweep. Pretreatment samples were collected on 4 Feb, and indicated as 1 DPT in the table. Posttreatment samples were collected on 10 Feb or 5 days after treatment (DAT), 12 Feb (7 DAT), 19 Feb (14 DAT), and 26 Feb (21 DAT). Sweep samples were bagged, labeled, and frozen for later counting of SAA in the laboratory. Data sets were analyzed using a two-way ANOVA and means separated by Tukey’s honestly significant difference test ( P  ≤ 0.05).

The 2014 SAA levels were typical of what is found in Imperial Valley alfalfa during early-Feb to mid-Feb. There were no differences among the treatment means for SAA on 4 Feb, 1 DPT ( Table 1 ). All insecticide treatments resulted in SAA means that were significantly lower than the untreated check, the Cyclaniliprole 50SL treatments, and all Assail 30WG treatments at 5 DAT and 7 DAT ( Table 1 ). Only the insecticide treatments of Cyclaniliprole 50SL at 16.4 oz/acre and at 20 oz/acre did not reduce SAA compared to the untreated check at 14 DAT. Only the insecticide treatments of Lorsban Advanced, Transform WG at 1.5 oz/acre and Assail 30WG at 7 oz/acre significantly reduced SAA compared to the untreated check at 21 DAT. All insecticide treatments resulted in PTAs for SAA that were lower than the untreated check, except Cyclaniliprole 50SL at 16.4 oz/acre and at 20 oz/acre and Assail 30WG at 5 oz/acre. None of the insecticide treatments resulted in any injury to the alfalfa plants.

Author notes