ACETOLACTATE SYNTHASE-RESISTANT AND SYNTHASE-SUSCEPTIBLE CORN (ZEA-MAYS) RESPONSE TO IMAZETHAPYR, IMAZAQUIN, CHLORIMURON, AND CGA-L52005

Field experiments were conducted from 1993 to 1995 to evaluate the res ponse of ALS-resistant and ALS-susceptible corn to imazethapyr, imazaq uin, chlorimuron, and CGA-152005 at label and twice label rates applie d preplant incorporated (PPI) and postmergence (POST). The susceptible hybrid (P3245) and the resistant hybrid (P3245IR) grain yield were no t different where weeds were removed by hand-weeding alone. Alachlor p lus atrazine alone plus hand-weeding reduced grain yield by 5% compare d to hand-weeding only. Imazethapyr applied PPI and POST reduced heigh t of the susceptible hybrid 11 and 6%, respectively, averaged across i mazethapyr rates. Imazaquin reduced the final height of the susceptibl e hybrid by 30 to 75% and reduced corn density by 62 to 78%. Chlorimur on applied PPI reduced final corn height of the susceptible hybrid by 26 to 36% and density by 27%. Chlorimuron applied PPI and imazaquin ap plied PPI and POST reduced grain yield of the susceptible hybrid. Imaz ethapyr did not reduce grain yield of the susceptible hybrid, regardle ss of application timing or rate. Imazethapyr, imazaquin, and chlorimu ron did not reduce height, density, or grain yield of the resistant hy brid, regardless of application timing or rate, CGA-152005 applied PPI reduced grain yield of the susceptible and resistant hybrid. CGA-1520 05 applied POST did not reduce grain yield, regardless of hybrid or ra te.