INTERACTING EFFECTS OF MON-12000 AND CGA-152005 WITH OTHER HERBICIDESIN VELVETLEAF (ABUTILON-THEOPHRASTI)

Greenhouse and laboratory studies were conducted to determine the effe cts of dicamba, atrazine, and bentazon on efficacy, foliar absorption, and translocation of MON 12000 or CGA-152005 applied to velvetleaf. T he efficacy of MON 12000, CGA-152005, and a combination of CGA-152005 plus primisulfuron applied at 4.5 g ai ha(-1) was similar when applied alone or with 140 g ha(-1) of dicamba. However, applying these herbic ides in combination with 840 or 560 g ha(-1) of atrazine or bentazon, respectively, reduced velvetleaf control. Increasing the rate of MON 1 2000, CGA-152005, or the combination of CGA-152005 plus primisulfuron to 3 g ai ha(-1) or replacing crop oil concentrate (COG) with methylat ed seed oil (MSG) increased velvetleaf control of the atrazine and ben tazon combinations but not to levels equal to these herbicides applied alone. Dicamba had no effect on the foliar absorption and translocati on of C-14 from MON 12000 or CGA-152005. Atrazine had little effect on foliar absorption of C-14 from MON 12000 or CGA-152005, but bentazon reduced the foliar absorption of C-14 from MON 12000. Replacing COC wi th MSO increased the foliar absorption of C-14 from MON 12000 or CGA-1 52005 applied alone or with dicamba or atrazine, bur not with bentazon . Translocation of C-14 from MON 12000 or CGA-152005 out of the treate d leaves was 11 and 12%, respectively, averaged across adjuvants and s ampling times. These values were reduced to an average of 3 to 4% for both MON 12000 and CGA-152005 when applied in combination with atrazin e or bentazon. The majority of C-14 from MON 12000 or CGA-152005 was t ranslocated acropetally. Atrazine and bentazon significantly reduced t he acropetal translocation of C-14 from MON 12000 at 24 and 72 h and f or CGA-152005 at 12, 24, and 72 h. The physiological basis for the obs erved antagonism of MON 12000 and CGA-152005 by atrazine and bentazon appears to be due to reductions in acropetal translocation of MON 1200 0 and CGA-152005 to velvetleaf meristems.