• Korean Journal of Weed Science
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• v.18 no.4
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• pp.304-313
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• 1998

Foliar retention of pyribenzoxim (1% EC) was measured using the fluorescent dye rhodamine B, and related to efficacy and phytotoxicity to barnyardgarss (Echinochloa crusgalli) and rice (Oryza sativa cv. Chucheong), respectively. Effects of nozzle types (8002E flat-fan and disk-type), addition of adjuvant, variation of herbicide concentration or spray volume were compared. In barnyardgrass, foliar retention of pyribenzoxim at a recommended condition (application rate : 30g ai/ha, spray volume : 1000 L/ha) was 2.3 to 2.7 or 1.4 to $1.5{\mu}g$ ai/g fresh foliage when sprayed using the disk-type nozzle with or without adjuvant, respectively, and 0.6 to 0.7 or 0.3 to $0.5{\mu}g$ ai/g fresh foliage when sprayed using the flat-fan nozzle with or without adjuvant, respectively. The slope of increase in foliar retention was 1.0 to 1.8 when application rates increased from 10 to 60g ai/ha at 1000 L/ha, while that was 1.6 to 2.4 when spray volume increased from 330 to 2000 L/ha at $30{\mu}g$ ai/L concentration. Foliar retention of pyribenzoxim had a close relationship with herbicidal activity; regardless of spray conditions, retention to provide 90% control was about $0.8{\mu}g$ ai/g fresh foliage, and below this retention amount, efficacy decreased almost linearly. In rice, foliar retention at the recommended condition was 1.9 to 2.3 or 1.2 to $1.3{\mu}g$ ai/g fresh foliage when sprayed using the disk-type nozzle with or without adjuvant, respectively, and 0.6 to 0.9 or $0.3{\mu}g$ ai/g fresh foliage when sprayed using the flat-fan nozzle with or without adjuvant, respectively. The slope of increase in foliar retention was 1.0 to 2.8 when application rates increased from 30 to 120g ai/ha at 1000 L/ha, while that was 1.3 to 4.4 when spray volume increased from 1000 to 4000 L/ha at $30{\mu}g$ ai/L concentration. Despite the great difference in retention, rice phytotoxicity was not observed in any of these spray conditions, suggesting retention differences within 4-fold increase of application rate or spray volume do not affect rice safety. When pyribenzoxim 1EC was sprayed in tank-mix with several other commercial pesticide formulations, its retention to rice foliage tended to increase by 30 to 50%.