TILLERS DO NOT INFLUENCE PHYTOTOXICITY OF IMAZAMETHABENZ IN WILD OAT (AVENA-FATUA)

The response of wild oat to imazamethabenz varies with the growth stag e, but the role of tillers in this regard is unclear. Removal of tille rs at the three-leaf stage before spraying with imazamethabenz did not significantly affect the total shoot fresh weight measured 3 weeks la ter. The leaf area and dry weight of intact plants at the three-leaf s tage were 17-21% greater than for plants with coleoptilar and first le af main shoot tillers (TO and TI) removed. The greater leaf area may h ave increased herbicide interception per plant. Similar fresh weight r eductions in main shoot, total tillers, and total shoots were found wh ether imazamethabenz was applied to the plant at the two-leaf without tillers or the three-leaf with two tillers stage. Imazamethabenz appli ed only to the main shoot reduced total shoot dry weight more than an equivalent amount of imazamethabenz applied only to tiller TI or appli ed over the whole shoot. Imazamethabenz had the least inhibitory effec t on whole plant growth when applied only to T1. When C-14-herbicide w as applied to the first main shoot leaf of plants at the three-leaf st age with two tillers, the C-14 translocated 38% to roots, 33% to the m ain shoot, and nearly 30% to all tillers. When C-14-herbicide was appl ied to the first leaf of T1 then the C-14 translocated 50% to T1, 25% to the main shoot, 20% to roots, and 5% to all other tillers. The tran slocation pattern and fresh weight values suggested that the presence of early tillers during herbicide application neither increased nor de creased imazamethabenz efficacy in wild oat.