Abstract

The development of resistance of Echinochloa colona biotypes is emerging as a major problem in upland rice production, particularly where there is an apparent over use of the propanil - and fenoxaprop-P-methyl herbicides. A series of field studies in a commercial rice production facility were conducted to screen a wide range of recommended herbicides for upland rice weeds and to assess its efficacy and the possible resistance of herbicides. The results indicated that fenoxaprop was not performing as anticipated in upland rice management. However, propanil in combination with oxadiaryl improved yield and weed control. Preliminary evidence suggests that there is E. colona biotype present in the population that is exhibiting some level of resistance, but not necessarily to Fenoxaprop-P.

Key words: Echinochloa colona, biotypes, propanil, fenoxaprop-p-methyl, oxadiaryl herbicides.