Effectiveness of Miticides Against Spider Mites in Peanut, 2019 Open Access

The objective of this study was to evaluate the effectiveness of miticides to control two-spotted spider mite, the dominant mite species on peanuts in Alabama. This study was completed at the Chilton Regional Research and Extension Center, Clanton, AL. Peanut, GA O6-G, was planted on 22 May under a high tunnel to exclude rainfall. Spider mite infestations were induced by applying bifenthrin (Tundra, Winfield Solutions, St. Paul, MN) on 14 Aug and zeta-cypermethrin (Mustang Maxx, FMC Corporation, Philadelphia, PA) on 28 Aug. Six treatments were arranged in an RCB design with four replications. Peanut plots were 25 ft long with one treated row separated by 5 ft alleys. Insecticide treatments were applied using a CO₂ backpack sprayer with three TX-VS12 hollow cone nozzles mounted on a boom operated at 30 psi and 32 gpa. Miticide treatment were applied on 17, 24, and 30 Sep, and 4 and 10 Oct. Spider mite densities were determined by sampling 10 terminal leaves per plot on Oct 14. Samples were processed by washing in alcohol and counting the number of spider mites per sample. Data are reported as an average number of mites per leaf. Peanut plots were inverted manually on 14 Oct and pods were harvested using a small plot combine. Spider mite counts and yield data were analyzed using ANOVA and means were separated using Fisher’s protected least significant difference (LSD, P < 0.05).

The year 2019 was marked by a flash drought (rapid extreme heat and dry period) in September that increased spider mite activity resulting in high pest pressure. There were statistically significant differences between treatments for the number of spider mites (Table 1). The untreated plots had the highest spider mite numbers with nearly 50% plant burn and extensive webbing of peanut terminals. All the miticides reduced spider mite densities compared to the untreated check. Also, plots treated with Comite had fewer mites than plots treated with Portal. However, there were no differences among treatments for yield. No phytotoxicity was observed from any of the miticide treatments.¹

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