Effect ofBradyrhizobiaInoculant Formulation with Phorate in New Peanut Fields

Abstract

Peanut (Arachis hypogaea L.) is a legume and requires nodulation by Bradyrhizobia to convert atmospheric N into a plant usable form. Peanut inoculants place large volumes of viable Bradyrhizobia near the emerging root of the plant to infect it ensuring N-fixation. Peanut seedlings are susceptible to feeding by thrips (Thysanoptera: Thripidae), which transmit Tospovirus leading to tomato spotted wilt (TSW) and can result in yield decline. Phorate is a common in-furrow insecticide used to reduce thrips feeding on the plants, and hence reduce the risk of TSW infection. However, placing phorate in the same furrow with living Bradyrhizobia has raised concerns about phorate potentially reducing efficacy of inoculants. Experiments were designed to test liquid and sterile peat formulations of Bradyrhizobia inoculant with two peanut cultivars in-furrow at planting, both with and without phorate insecticide to determine yield, grade, and growth parameters on peanut. Research was conducted on a non-irrigated loamy sand with no prior history of growing peanut in Tifton, GA in 2013 and 2014. There were no negative effects on peanut yield or grade, or other measured parameters when phorate was included in-furrow with inoculants. Yields with inoculants were equal or greater (up to 32% more) than noninoculated peanut, and grade was improved (+1.2 to 1.4%) when using the liquid formulation instead of the sterile peat formulation or noninoculated peanut. Other indicators of improved plant performance using inoculants over noninoculated plants included the abundance and activity of nodules on the roots and time to row closure (vegetation overlap of bare soil). These data indicate there are no detrimental effects to peanut inoculant when also including phorate insecticide in-furrow.

Influence of Inoculation with Bradyrhizobia and Nitrogen Rate on Yield and Estimated Economic Return of Virginia Market‐Type Peanut

“…Certain pesticides and fertilizers applied with commercial inoculants can impact BNF (Jordan et al, 2010). For example, the fungicide pyraclostrobin adversely affected BNF while prothioconazole and the insecticides acephate, imidacloprid, and phorate did not affect BNF (Jordan et al, 2010(Jordan et al, , 2017Tubbs et al, 2015). Co-applying fungicide with crop protection and enhancement products could explain inadequate inoculant performance that requires correction with applied N.…”

Peanut Yield and Injury from Thrips with Combinations of Acephate, Bradyrhizobium Inoculant, and Prothioconazole Applied in the Seed Furrow at Planting

“…In contrast to tebuconazole, pyroclostrobin applied in the seed furrow reduced the efficacy of the inoculant and, subsequently, yield (Jordan et al, 2010). Tubbs et al (2015) reported that phorate applied in the seed furrow did not adversely affect nodulation or peanut response to Bradyrhizobium inoculant. In addition to concerns over inoculant performance, seed is the single most expensive input in peanut crops (Bullen and Jordan, 2015), and determining if agrochemicals adversely affect peanut stand establishment is important.…”