Acaricidal Control of Twospotted Spider Mites in Peanut, 2016

The twospotted spider mite (TSSM) is an important peanut pest due to feeding damage that can result in plant stress and reduced yield especially in hot, dry conditions. A trial was conducted to evaluate efficacy of miticides on TSSM eggs and crawlers in peanut. This trial was conducted from 17 to 31 Aug in Wilcox County, GA, in a nonirrigated, commercial peanut field that experienced moderate to severe drought stress from Jun until harvest. An RCB split plot design was used to evaluate the main plot factor of miticide and the subplot factor of surfactant. Main plots were 8-row wide and 25-ft long and were replicated four times on single row peanuts seeded at a rate of approximately 7 seed per ft with 36 inch between row spacing. Treatments were applied on 18 Aug using a CO₂ pressurized backpack sprayer with a 6-ft spray width operating at 4.2 mph and 35 psi with four nozzles (Conejet TXVS 26) delivering 20 gpa. TSSM populations were sampled by collecting 10 quadrifoliate leaves at random from each plot on each sample date. A single leaflet from the same position on each leaf was removed, and eggs and crawlers on 50% of the lower surface of each leaflet were counted using a dissecting microscope. Mites were sampled 1 day before application and 1, 4, 7, and 13 days after application. All data were collected from the two middle rows of each plot. All data were subjected to ANOVA for treatment effects. Means were separated using Fisher’s LSD (P ≤ 0.05) and are presented in Table 1.

Use of nonionic surfactant with Agri Mek resulted in significantly fewer TSSM crawlers 7 and 13 DAT, and fewer TSSM eggs 13 DAT compared to Agri Mek alone. The addition of a nonionic surfactant to all other treatments did not affect populations of TSSM eggs and crawlers when compared to the miticide treatments alone. Portal + NIS significantly reduced TSSM crawlers 4 DAT compared to all other treatments except Portal alone, and Comite II +Bifenture. Comite II + NIS, Comite II + Bifenture, Comite II + Bifenture + NIS, Portal, Portal +NIS, and Agri Mek + NIS significantly reduced TSSM eggs and crawlers at 13 DAT compared to the check, Bifenture, and Bifenture + NIS. Bifenture did not cause a significant reduction of TSSM eggs or crawlers compared to the check. Comite II + Bifenture did not reduce TSSM populations when compared to the use of Comite II alone.

Author notes