SUSCEPTIBILITY OF THREE JOINTVETCH SPECIES (Aeschynomene spp.) TO THE HERBICIDE ONLY

Jointvetch species is an important weed in rice production, with an relatively high importance in the Clearfield system, where the herbicide Only (imazapic + imazethapyr) is not consistent in control. A greenhouse experiment, was carried out aiming of evaluating the efficacy of the Only herbicide on jointvetch control, and jointvetch susceptibility to the herbicide treatments. The study was located at in Porto Alegre, Rio Grande do Sul State, Brazil, from November 2005 to January 2006. The growth media was soil from a rice field. The experimental design was a randomly complete block, using a 3 x 6 factorial scheme, with five replications. The jointvetch species composed the A factor ( denticulata, indica , and sensitiva ); and the treatments of the herbicide Only was the B factor. The parameters evaluated included weed control in percentage and dry shoot weight. The results demonstrate that A. sensitiva showed greater susceptibility to the herbicides Only and Ally than the species A. denticulata and A. indica ; whereas, A. indica presents greater tolerance. The herbicide Only performed variable activity on jointvetch species, depending on rate and time of application. When Only is applied at the rate of 1,0 L ha -1 , on