Selectivity of ammonium-glufosinate applied alone or in mixture with pyrithiobac sodium in transgenic LL® cotton

G.B.P. Braz R.S. Oliveira Jr J. Constantin M.A. Raimondi L.H.M. Franchini D.F. Biffe J.G.Z. Arantes H.K. Takano About the authors

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 gha-1 and 500 + 56gha-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.

Gossypium hirsutum; crop injury; GS inhibitor; ALS-inhibitor; tank mixture

Sociedade Brasileira da Ciência das Plantas Daninhas Departamento de Fitotecnia - DFT, Universidade Federal de Viçosa - UFV, 36570-000 - Viçosa-MG - Brasil, Tel./Fax::(+55 31) 3899-2611 - Viçosa - MG - Brazil