Resistance of barnyardgrass biotypes (Echinochloa crus-galli) to ACCase-inhibiting herbicides in the main rice-growing regions of the state of Santa Catarina, Brazil

ABSTRACT: The resistance of Echinochloa crus-galli (barnyardgrass) to cyhalofop-p-butyl has already been confirmed in rice fields Santa Catarina, Brazil. However, it is not known if this affects other ACCase inhibitors. This study evaluated the occurrence cross-resistance biotypes from main rice-growing regions Catarina research was conducted a greenhouse, using completely randomized design with factorial scheme that included three ACCase-inhibiting herbicides (cyhalofop-p-butyl, quizalofop-p-ethyl, and profoxydim) belonging two chemical groups (aryl-oxifenoxi-propionates cyclohexanediones), eight herbicide doses, four F1 generation F2 generation. These were selected based on results preliminary trial 21 populations. applied when plants presented true leaves. After control evaluations, lethal dose required 50% 80% population (LD50 LD80) factor (RF) determined by nonlinear regression. showed only one biotype Tubarão, met all statistical agronomic criteria had inhibitors confirmed. In both generations, RF greater than 1.0, achieve exceeded maximum recommended label. Resistance levels higher for aryl-oxifenoxi-propionate group, 7.0. For cyclohexanedione less 5.0.