Differential vegetable crop responses to mesotrione soil residues a year after application

Field experiments were conducted in 2002 and 2003 at Fremont and Wooster, Ohio to characterize the effect of mesotrione herbicide soil residues 12 months after application to field maize on rotational snapbean, cabbage, bell pepper, processing tomato, pickling cucumber, and red clover. Mesotrione was applied either pre-emergence or post-emergence to field maize in 2002 at 0, 210, 420, and 840 or 0, 105, 210, and 420 (0, 1×, 2×, 4× rate), respectively. The response of rotational vegetable crops to mesotrione soil residues varied by site with plants at Fremont displaying greater injury. Snapbean was the most affected, and the yield was lowest at Fremont ranging from 0 to 0.18 T/ha for 4× rate to 0.27 and 0.9 T/ha for 1×, pre-emergence and post-emergence, respectively. Snapbean yield was reduced by 60% and 31% when grown in residues of mesotrione 4× rate, pre-emergence and post-emergence, respectively, when compared to the untreated treatment (14.24 T/ha). Cabbage injury was very high at Fremont regardless of the use rate, but there was no reduction in yield at Wooster. When grown in soil residues from 2× to 4× rates, processing tomato yield was reduced to 32% and 33%, and 28% and 23% compared to untreated control (85 T/ha). A similar trend was observed for bell peppers growing at Wooster. Similarly, the yield for pickling cucumber was reduced 18% when grown in 4× rate mesotrione soil residues at Wooster compared to the untreated control (30 T/ha). At Fremont, the pickling cucumber yield was reduced regardless of the application timing and rate. The levels of injury are too high for growers to rotate vegetables 12 months following application of mesotrione to field maize.