Imidazolinone-tolerant maize as a tool for weed control in flooded rice production systems

Abstract

This study aimed to (1) evaluate the optimal dose of the herbicide [imazapic + imazapyr], for control of red rice, as well as its selectivity to imidazolinone-tolerant maize; (2) to identify the most suitable adjuvant to be added to the optimal dose for maximizing red rice and barnyardgrass control; and (3) to evaluate its carryover effect on winter species commonly planted after maize in Southern Brazil. Three studies were carried out (two under field conditions, one under greenhouse) in completely randiomized blocks design. Experiment one consisted of ap¬plication of [Imazapic + Imazapyr] and nicosulfuron, at increasing rates, on OnDuty® maize crop; experiment two consisted of application of the optimal dose of [Imazapic + Imazapyr] determined in experiment 1, plus atrazine, with distinct adjuvants, and experiment 3 consisted of planting rapeseed (Brassica napus), tall fescue (Festuca arundinacea), birdsfoot trefoil (Lotus corniculatus), ryegrass (Lolium multiflorum), white clover (Trifolium repens) and vetch (Vicia sativa) after applying [Imazapic + Imazapyr] at 1x and 2x the label dose in order to verify its toxic¬ity effects. Application of [imazapic + imazapyr] at dose of 0.100 kg c.p. ha-1 (equivalent to 52.5 + 17.5 g a.i. ha-1) on imidazolinone-tolerant maize was effective in controlling red rice and barnyardgrass when using Cicol or Dash as adjuvants, being also selective to the crop cv C 909 CL. Residues of these herbicides can affect winter crops in succession. Further studies should be conducted to evaluate the use of vetch in phytoremediation following imidazolinone-tolerant maize.