GROWTH AND COMPETITIVENESS OF SULFONYLUREA-RESISTANT AND SULFONYLUREA-SUSCEPTIBLE KOCHIA (KOCHIA-SCOPARIA)

Growth, competitiveness, and fecundity differences between resistant ( R) and susceptible (S) biotypes affect management strategies. This gre enhouse research examines growth, competitiveness, and fecundity of ch lorsulfuron-resistant (R) and -susceptible (S) kochia collected from N orth Dakota and Kansas. In noncompetitive studies, sulfonylurea R and S kochia biotypes from Kansas and North Dakota had similar growth rate s and seed production. AH biotypes produced about 12 000 seeds per pla nt. Competitiveness of R and S biotypes from Kansas was similar. Inter biotype competition reduced R and S plant biomass more than intrabioty pe competition. The relative competitiveness of the R and S biotypes w as 0.75 and 0.85, respectively. The resistance trait did not reduce gr owth, seed production, and competitiveness of R compared to S kochia i n greenhouse studies.