Effectiveness of Miticides Against Spider Mites in Peanut, 2017

The objective of this study was to evaluate the effectiveness of miticides to control twospotted spider mite (TSM), the dominant mite species on peanuts in Alabama. This study was completed at the Chilton Regional Research and Extension Center, Clanton, AL. ‘Virginia’ peanut was planted on 31 May under a high tunnel to exclude rainfall. Spider mites were induced by four applications of synthetic pyrethroids zeta-cypermethrin (Mustang Maxx, FMC Corporation, Philadelphia, PA) on 8 Aug and 22 Aug followed by bifenthrin (Tundra, Winfield Solutions, St. Paul, MN) on 5 Sep and 12 Sep. Five treatments (including untreated check) were replicated six times in an RCB design. 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 dates were 26 Sep and 4 Oct. Spider mite densities were determined by sampling 10 terminal leaves from 10 plants per plot and washing them in alcohol. Spider mites were counted in the laboratory and converted to average mites per leaf. Data were analyzed using ANOVA and means were separated using Fisher’s Protected LSD (P < 0.05).

Year 2017 was a very wet year that resulted in the need for four pyrethroid applications for inducing spider mites for this study. This is different from drought year when only one or two applications of synthetic pyrethroids result in spider mite induction in research plots. Untreated check had the highest spider mite density (Table 1) that resulted in extensive webbing of peanut terminals. TSM counts from plots treated with Comite (registered on peanuts), Portal, and Agrimek were significantly lower compared to the untreated check. Alternative miticide Aramite + Bemix mixture did not provide significant control of spider mites compared to the untreated check. No phytotoxicity was observed from any of the miticide treatments.¹

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