Influence of water and soil temperature on the concentration and efficacy of phenamiphos for control of root-knot nematodes.

Field plots of Tifton loamy sand were treated with phenamiphos for control of root-knot nematodes in a multiple-crop system of turnips, field corn, and southern peas. Preplant applications of phenamiphos protected roots of turnips and corn from damage by root-knot nematodes. Concentrations of phenamiphos at application in the 0-15-cm soil layer were near 6 mug/g on turnips and near 4 mug/g on corn and southern peas. After 30 d, concentrations were approximately 1 mug phenamiphos/g of soil for all crops. Concentrations of 2.0-3.8 mug phenamiphos/g of soil for 9-d duration appeared to be adequate for control of root-knot nematodes on field corn and southern peas in this multiple-crop system. Stepwise regression analyses indicated that 31%, 62%, and 22% of the variations in concentration of phenamiphos in the soil planted to turnips, corn, and southern peas, respectively, were attributable to the amount of water that the plots received. Soil temperature had no effect on concentrations of phenamiphos.