Insecticide Evaluations in Soybean for Control of Twospotted Spider Mite, 2015

The objective of this test was to compare efficacy of two rates of Zeal miticide applied at two volumes of carrier (5 and 15 gpa) against three standard insecticide/acaricides applied at 15 gpa for the control of twospotted spider mite (TSM). The test was conducted in a soybean field at Hinton, OK at the Roger Musick farm. Soybean variety ‘HBK RY 4620’ was planted on 22 Jun into a sandy loam soil with 30-inch centers and planting rate of 125,000 seeds/acre. Plots measuring three rows by 25 ft with 5-ft alleys were arranged in a RCB design with four replications and six treatments. In each plot, only the center row was treated and the outer two rows served as a buffer. Plots were sprayed with a hand held CO₂-charged sprayer with two nozzles spaced 12 inches apart. Flat fan nozzles XR Tee Jet 8004VS were used for the 15-gpa sprays and flat fan nozzles Tee Jet 8001VS were used for the 5-gpa sprays. The plots received 6.55 inches of irrigation water in addition to 4.6 inches rainfall from planting to termination of the test. Pre-treatment counts were taken on 22 Aug and treatments were applied on 24 Aug. Samples were collected at 7, 14, 21, and 28 days after treatment (DAT) by collecting one trifoliate from the middle portion of the canopy from ten randomly selected plants per plot. Data were analyzed using a 2-way ANOVA and means separated by protected LSD (P ≤ 0.05).

Pre-treatment densities of TSM were determined by counting all mites on 15 randomly selected trifoliates from the trial. Spider mite populations were significantly lower in all insecticide-treated plots compared to that in the untreated check at 7 and 14 DAT. At 21 DAT, all treatments, with the exception of the Lorsban treatment, resulted in significantly lower numbers of TSM than the untreated check. Twenty eight DAT, the untreated plots, due to poor plant quality, had equal of lower TSM numbers than the Lorsban, Brigade or Oberon treated plots. Twospotted mite numbers in the Zeal plots were significantly lower than the untreated check at 28 DAT. However, there were no significant differences in TSM numbers between the 5- and 15-gpa volumes of carrier with Zeal at any rate. This research was supported in part by industry gifts of pesticides and/or research funding.

Author notes