Field studies were conducted at three sites in Delaware from 1997 to 1999 to evaluate fall glyphosate applications followed by postemergence (POST) field corn herbicides on horsenettle control and shoot densities. The fall treatments were either no fall treatment or 2.2 kg ai/ha glyphosate as a preharvest treatment in soybean at least 2 wk prior to frost. POST treatments were applied the following spring in no-tillage field corn 4 wk after planting (WAP) and included glyphosate, CGA 152005 plus primisulfuron plus dicamba, halosulfuron plus dicamba, atrazine plus dicamba, nicosulfuron plus rimsulfuron plus atrazine plus dicamba, or nicosulfuron plus dicamba. The fall glyphosate application delayed horsenettle shoot emergence in the spring and resulted in > 90% control at the time of POST in-crop applications. At 11 WAP, the highest horsenettle control was observed with a fall glyphosate application followed by POST in-crop treatments of CGA 152005 plus primisulfuron plus dicamba, halosulfuron plus dicamba, or nicosulfuron plus rimsulfuron plus dicamba and no fall treatment followed by CGA 152005 plus primisulfuron plus dicamba.
Nomenclature: Atrazine; CGA 152005, 1-(4-methoxy-6-methyl-triazin-2-yl)-3-[2-(3,3,3-trifluoropropyl)-phenylsulfonyl]-urea, proposed common name prosulfuron; dicamba; glyphosate; halosulfuron; nicosulfuron; primisulfuron; rimsulfuron; horsenettle, Solanum carolinense L. #3 SOLCA; corn, Zea mays L.; soybean, Glycine max (L.) Merr.
Additional index words: Integrated weed management, perennial weed control, preharvest herbicide application.
Abbreviations: COC, crop oil concentrate; NIS, nonionic surfactant; POST, postemergence; PRE, preemergence; UAN, urea ammonium nitrate; WAP, weeks after planting.