Effect of Bradyrhizobia Inoculant Formulation and Phorate Insecticide on Peanut Cultivars When Applied in-Furrow during Planting.

Peanut is a legume and requires nodulation by Bradyrhizobia to fix ample N to maximize yield and grade.  Peanut inoculants place Bradyrhizobia near the emerging root of the plant to infect the root for maximized N-fixation.  Although, young peanut plants are also susceptible to feeding by thrips, which transmit Tomato spotted wilt virus (Tospovirus) that can result in yield decline.  Phorate is a common in-furrow insecticide used to reduce thrips feeding on the plants, and hence reduce the chances of TSWV infection.  However, since phorate is toxic to many biological organisms, and Bradyrhizobia are placed in the same furrow, it has raised questions of whether phorate might reduce the efficacy of the inoculant.  This experiment was designed to test liquid and sterile peat formulations of peanut inoculant, both with and without phorate insecticide to determine yield, grade, and TSWV incidence on peanut.  The experiments took place in Tifton, GA in 2013 and 2014 on a non-irrigated loamy sand location with no prior history to growing peanut.   There was also an irrigated sandy loam site following a normal peanut rotation with five peanut cultivars at Plains, GA in 2013.  No negative effects on yield or grade of peanut were observed when phorate was included in-furrow with the peanut inoculant.  Peanut yield was improved when using either formulation (liquid = +693 kg ha^-1; peat = +591 kg ha^-1) over no inoculant in Tifton, 2013, and with the liquid inoculant paired with phorate (+569 kg ha^-1) than with phorate alone in Plains, 2013.  There were no differences in 2014.  These data show there are no detrimental effects to peanut inoculant when also including phorate insecticide in-furrow.