title: Alternative herbicides to manage Italian ryegrass (Lolium multiflorum lam) resistant to glyphosate at different phenological stages.
abstract: During the growing season of 2002--2003, field and greenhouse experiments were conducted with the objective of evaluating the influence of Italian ryegrass phenological stages and management alternatives on the control of resistant biotypes to glyphosate. Three field experiments were conducted in Lagoa Vermelha, RS, Brazil and glyphosate was applied alone and in combinations with alternative herbicides. Two greenhouse experiments were also conducted at the Department of Crop Science, ESALQ/USP, Piracicaba, SP, Brazil. The Italian ryegrass resistant population was collected from Lagoa Vermelha, RS, Brazil. From the results it was possible to conclude that: (i) the more advanced the phenological stage of application, the more difficult the control of resistant Italian ryegrass by glyphosate, mainly by the rate of 960 g a.i. ha(-1); however, this rate applied at earlier phenological stage (five tillers), the control was higher than 90%; (ii) with the increment of glyphosate rate, it significant response was observed on the control at all stages of application; (iii) the mixture of glyphosate + clethodim (1440 + 72 g a.i. ha(-1)), paraquat + diuron (500 + 250 g a.i. ha(-1)), at all stages of application and clethodim (96 g a.i. ha(-1)) and paraquat + diuron (300 + 150 g a.i. ha(-1)) at the initial stages until pre-flowering were excellent alternatives for management of these populations; and (iv) the response of control was much faster for the mixture of glyphosate + clethodim, independently of growth stage.
authors.affiliation: Department of Crop Science, University of São Paulo, Piracicaba, São Paulo, Brazil. pjchrist@esalq.usp.br
authors.forename: Pedro Jacob
authors.initials: PJ
authors.lastname: Christoffoleti
authors.forename: Renato
authors.initials: R
authors.lastname: Trentin
authors.forename: Saulo
authors.initials: S
authors.lastname: Tocchetto
authors.forename: Aroldo
authors.initials: A
authors.lastname: Marochi
authors.forename: Antonio João Batista
authors.initials: AJ
authors.lastname: Galli
authors.forename: Ramiro Fernando
authors.initials: RF
authors.lastname: López-Ovejero
authors.forename: Marcelo
authors.initials: M
authors.lastname: Nicolai
mesh_terms: D000222:Adaptation, Physiological; D004351:Drug Resistance; D035264:Flowers; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006540:Herbicides / Q000494:pharmacology*; D008129:Lolium / Q000254:growth & development*; D010571:Pest Control; D012098:Reproduction; D013997:Time Factors; D000097797:Glyphosate
chemical_list: D005998:Glycine; D006540:Herbicides; D000097797:Glyphosate