Weed control and peanut (Arachis hypogaea L.) response to formulations of imazapic

Field studies were conducted from 2006 to 2008 in the peanut (Arachis hypogaea) growing regions of Georgia, North Carolina, and Texas to ascertain two formulations of imazapic marketed as formulation-1 (Cadre®) and formulation-2 (Impose®). Both formulations controlled Acanthospermum hispidum, Eclipta prostrate, Richardia scabra, Verbesina encelioides, Amaranthus palmeri, Ipomoea lacunosa, Sida spinosa, Cucumis melo, Urochloa texana, Cyperus rotundus, and Cyperus esculentus at least 70% in most instances. Ambrosia artemisiifolia and Trianthema portulacastrum control was poor (>70%). Neither formulation of imazapic alone injured peanut in south Texas; however, in Georgia peanut injury ranged from 3 to 8% and in North Carolina injury was 8–20% when rated up to 27 d after herbicide application. Imazapic, regardless of formulation, applied with bentazon injured peanut 5–20% in Georgia and North Carolina but not in Texas. Either formulation of imazapic plus paraquat injured peanut 15–30% in Georgia, 8–17% in Texas, and 28–48% in North Carolina. Imazapic, regardless of formulation, in combination with paraquat reduced yield compared with imazapic alone at one of four locations.

► Both formulations of imazapic resulted in early-season stunting of peanut. ► This early-season stunting was evident across all peanut cultivars. ► By mid-season this stunting was no longer evident. ► Peanut yields were not affected by the stunting. ► Both formulations of imazapic provided excellent weed control.