Control of Green Peach Aphid on Green Cabbage, 2014 *

The objective of this study was to evaluate the residual efficacy of three industry standard insecticides at low label rates against green peach aphid in cabbage tested under desert growing conditions. Cabbage “Gazzelle” was direct seeded into double row beds on 42-inch centers on 24 January 2014. Plots were two beds in width by 45 ft in length and bordered by two untreated beds. Stand establishment was achieved using overhead sprinkler irrigation and irrigated via furrow thereafter. Four replications of each treatment were arranged in an RCB design. Formulations and rates for each compound are provided in Table 1 . Two foliar sprays were applied on 25 February and 19 March as a broadcast application delivered through two TXVS-18 ConeJet nozzles per bed at 20 gpa and 40 psi. Evaluations of GPA populations were assessed by estimating the number of apterous aphids per plant in whole plant, destructive samples. On each sample date, five plants were randomly selected from each plot and placed individually into large 5-gal tubs. Each plant was sampled by visually examining all plant foliage and counting the number of live aphids present. Because of heterogeneity of mean variances, data were transformed using a log ₁₀ ( x  + 1) function before analysis and subjected to analysis of variance; means were compared using Turkey’s HSD test ( P  ≤ 0.05). Means from nontransformed data are presented in the Table 1 .

GPA population pressure was heavy during the trial. Pre-spray aphid counts were an average of 86.5 GPA per plant. All three spray treatments significantly reduced GPA numbers at each sample interval relative to the untreated check following both applications ( Table 1 ). In terms of knockdown efficacy, Sequoia provided the most significant reduction in GPA numbers at 3 d following each application. By 7 d, differences among the three treatments were not observed. In terms of residual efficacy, Movento had lower numbers of GPA than Assail at 21 DAT for both applications. Overall, GPA control was most consistent in the Sequoia and Movento treatments. This study suggests that use of these products at low rates can provide significant GPA control. However, given the low tolerance for aphid contamination on cabbage by local grower and shippers, higher rates or tighter spray intervals may be required to achieve commercially acceptable control.

Author notes