Abstract

BRAZ, G.B.P. et al. Selectivity of ammonium-glufosinate applied alone or in mixture with pyrithiobac sodium in transgenic LL^® cotton. Planta daninha [online]. 2012, vol.30, n.4, pp. 853-860. ISSN 0100-8358.  http://dx.doi.org/10.1590/S0100-83582012000400020.

Due to the recent introduction of transgenic cotton varities with resistance to ammonium-glufosinate (LL^®) in Brazil, there is a lack of information related both to the selectivity of sequential reapplications of ammonium-glufosinate and to tank mixture with other herbicides. This work aimed to evaluate the selectivity of sequential applications of ammonium-glufosinate isolated or in associations with pyrithiobac-sodium in LL^® cotton. A field experiment was installed in a randomized block design with eight replicates. Treatments were arranged in a factorial scheme (3x3)+1. The first factor consisted of herbicide treatments as follows: ammonium-glufosinate (500 g ha^-1), ammonium-glufosinate + pyrithiobac-sodium (500 + 42 g ha^-1 and 500 + 56 g ha^-1). The second factor was the number of sequential post-emergence applications (one, two, or three), and the additional treatment was a non-applied check. All treatments were manually kept free of weeds throughout the crop cycle. Associating pyrithiobac-sodium to ammonium-glufosinate increased initial crop injury although no significant injury differences were found two weeks after application. Cotton fiber quality was not affected by any herbicidal treatment. Use of isolated ammonium-glufosinate was selective to LL^® cotton up to three sequential post-emergence applications. LL^® Cotton yield was also sustained after one application of ammonium-glufosinate + pyrithiobac-sodium, with no effects on crop yield.

Keywords : Gossypium hirsutum; crop injury; GS inhibitor; ALS-inhibitor; tank mixture.