Abstract

ORTIZ, Aída et al. Resistance and herbicide control of imazapir+imazetapir-resistant fimbry (Fimbristylis littoralis Gaudich.) in rice. Bioagro [online]. 2017, vol.29, n.1, pp.15-22. ISSN 1316-3361.

The grass-like weed fimbry [Fimbristylis littoralis Gaudich] has evolved resistant to pyrazosulfuron-ethyl (sulfonylurea herbicide inhibitor of the enzyme acetolactate synthase, ALS) in rice crops of Guárico, Venezuela. The resistance of F. littoralis to other ALS-inhibiting herbicides (imazapyr+imazethapyr) currently used in the Clearfield System to control weedy rice in other countries was assessed using a dose response experiment.  Also, responses to alternative herbicides to control this weed were explored. For the dose response experiment, the accessions FM58G (susceptible, S) and FM9G (resistant, R) were treated with increasing doses of imazapyr + imazethapyr from 0 to 4.81+14.44 g·ha^-1 a.i. and 0 to 308+924 g·ha^-1 a.i., respectively.  In the other experiment, the R y S accessions were treated with 25, 40, 154, 60, 1200, 1200+150, 40 y 540 g·ha^-1 a.i. of: pyrazosulfuron-ethyl, byspiribac-sodium, imazapyr+imazetapyr, penoxsulam, bentazona,  bentazona+MCPA, carfentrazone-ethyl y  2,4 D-amine, respectively. We proved that the accession FM9G, resistant to pyrazosulfuron-ethyl, has also evolved resistance to imazapyr + imazethapyr (imidazolinone) and to bispyribac-sodium (pyrimidinyl thiobenzoate). Both, R and S plants were not controlled by penoxsulam, but they were effectively controlled with bentazon, bentazon+MCPA, carfentrazone-ethyl and 2,4 D-Amine herbicides. The resistance patterns observed reflects the intensive use of ALS-inhibiting herbicides in Venezuelan rice, and may indicate that success of Clearfield system in Venezuela may be compromised when applied to weeds different to the weedy rice.

Keywords : ALS inhibitor; herbicide resistance; imidazolinone.

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