Variabilidade de resposta de diferentes populações de Digitaria insularis e estratégias de manejo de uma população resistente
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Data
2016-07-22
Autores
Gomes, Leonardo José Petean [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Algumas espécies têm sido selecionadas, devido às aplicações frequentes de herbicidas com o mesmo mecanismo, como é o caso de Digitaria insularis ao glyphosate. Assim, objetivou-se estudar (i) o controle de doze populações de D. insularis pelo herbicida glyphosate, isolado e em mistura com quizalofop-p-tefuryl, (ii) classificar as populações quanto à sensibilidade (suscetível, medianamente suscetível ou tolerante) ao glyphosate, (iii) correlacionar características morfoanatômicas das folhas das populações, além de (iv) avaliar a combinação dos métodos químico e cultural (sobressemeadura de Urochloa ruziziensis) no manejo de plantas adultas de D. insularis resistentes ao glyphosate, durante a cultura da soja e no período de entressafra (outono-inverno). Para o experimento de controle químico das populações, o delineamento foi o inteiramente casualizado, com quatro repetições, em esquema fatorial 12 x 4. Doze populações de D. insularis foram pulverizadas com glyphosate isolado (1,44 e 2,16 kg e.a. ha-1) e em associação (2,16 kg e.a. ha-1) com quizalofop-p-tefuryl (0,12 kg i.a. ha-1). Além disso, uma testemunha sem aplicação foi mantida para cada população. Em laboratório, foram realizadas análises morfoanatômicas e de quantificação de cerosidade das folhas. As populações 3, 5, 6 e 8 foram consideradas suscetíveis ao glyphosate; 9, 10 e 12 medianamente suscetíveis; 1, 2, 4, 7 e 11, tolerantes. Todas as populações apresentaram as mesmas características morfológicas, mas, diferiram nas anatômicas e quantidade de cera. Porém, as populações dentro de cada grupo (suscetíveis, medianamente suscetíveis ou tolerantes) não tiveram características semelhantes que justificassem a resposta diferencial ao herbicida glyphosate. Na etapa de campo, dois experimentos foram instalados no delineamento de blocos ao acaso, em esquema de parcela subdividida (6 x 2), com quatro repetições. Nas parcelas, foram estudados quatro tratamentos com herbicidas {glyphosate (1,44 e 2,16 kg e.a. ha-1) em associação com quizalofop-p-tefuryl (0,12 kg ha-1) ou clethodim (0,108 kg ha-1) pulverizados antes da semeadura da soja (dessecação) e complementados na pós-emergência da soja; e duas testemunhas sem herbicida, uma mantida infestada e outra capinada durante todo o período experimental. Nas subparcelas, foi avaliada à realização ou não da sobressemeadura da soja com Urochloa ruziziensis. A combinação da aplicação de herbicidas antes da semeadura da soja com a aplicação sequencial na pós-emergência da cultura foi eficaz no controle de plantas adultas de D. insularis. Além disso, a cobertura do solo com U. ruziziensis após a colheita da soja, na entressafra, reduziu o potencial de reinfestação da área pela planta daninha.
Some species have been selected because of frequent applications of herbicides with the same mechanism, such as Digitaria insularis to glyphosate. The objective of this paper was study: (i) control twelve populations of D. insularis the herbicide glyphosate, alone and mixed with quizalofop-p-tefuryl, (ii) classify the population in terms of sensitivity (susceptible, moderately susceptible or tolerant) glyphosate, (iii) correlate morphoanatomic characteristics of the leaves of the population, and (iv) evaluate the combination of chemical and cultural methods (oversowing of Urochloa ruziziensis) in the management of adult plants of D. insularis resistant to glyphosate during the soybean crop and the off-season (autumn winter). For chemical control experiment populations, the design was completely randomized with four replications, in a factorial 12 x 4. Twelve populations of D. insularis were sprayed with glyphosate alone (1.44 and 2.16 kg and ha- 1) and associate (2.16 kg ae ha-1) using quizalofop-p-tefuryl (0.12 kg ai ha-1). In addition, a control without application was kept for each population. In the laboratory, morphoanatomic and quantification waxy leaves analyzes were performed. Populations 3, 5, 6 and 8 were considered susceptible to glyphosate; 9, 10 and 12 moderately susceptible; 1, 2, 4, 7 and 11, tolerant. All populations showed the same morphological characteristics, but differ in anatomical and amount of wax. However, the populations within each group (susceptible, moderately susceptible or tolerant) had similar characteristics to justify the differential response to glyphosate. In the field stage, two experiments were conducted in the design of a randomized block design in a split plot design (6 x 2), with four replications. The plots were studied four treatments with herbicides {glyphosate (1.44 and 2.16 kg and ha-1) in combination with quizalofop-p-tefuryl (0.12 kg ha-1) or clethodim (0.108 kg ha-1 ) sprayed before soybean seeding (desiccation) and supplemented postemergence soybean; and two untreated controls, one kept infested and other weeded throughout the experimental period. In the subplots, it was assessed in the realization or not of soybean overseeded with Urochloa ruziziensis. The combination of herbicide application before soybean seeding with sequential application in post-emergence of the crop was effective in controlling adult plants of D. insularis. In addition, the soil cover with U. ruziziensis after soybean harvest, in the off season, reduced the potential for reinfestation of the area by the weed.
Some species have been selected because of frequent applications of herbicides with the same mechanism, such as Digitaria insularis to glyphosate. The objective of this paper was study: (i) control twelve populations of D. insularis the herbicide glyphosate, alone and mixed with quizalofop-p-tefuryl, (ii) classify the population in terms of sensitivity (susceptible, moderately susceptible or tolerant) glyphosate, (iii) correlate morphoanatomic characteristics of the leaves of the population, and (iv) evaluate the combination of chemical and cultural methods (oversowing of Urochloa ruziziensis) in the management of adult plants of D. insularis resistant to glyphosate during the soybean crop and the off-season (autumn winter). For chemical control experiment populations, the design was completely randomized with four replications, in a factorial 12 x 4. Twelve populations of D. insularis were sprayed with glyphosate alone (1.44 and 2.16 kg and ha- 1) and associate (2.16 kg ae ha-1) using quizalofop-p-tefuryl (0.12 kg ai ha-1). In addition, a control without application was kept for each population. In the laboratory, morphoanatomic and quantification waxy leaves analyzes were performed. Populations 3, 5, 6 and 8 were considered susceptible to glyphosate; 9, 10 and 12 moderately susceptible; 1, 2, 4, 7 and 11, tolerant. All populations showed the same morphological characteristics, but differ in anatomical and amount of wax. However, the populations within each group (susceptible, moderately susceptible or tolerant) had similar characteristics to justify the differential response to glyphosate. In the field stage, two experiments were conducted in the design of a randomized block design in a split plot design (6 x 2), with four replications. The plots were studied four treatments with herbicides {glyphosate (1.44 and 2.16 kg and ha-1) in combination with quizalofop-p-tefuryl (0.12 kg ha-1) or clethodim (0.108 kg ha-1 ) sprayed before soybean seeding (desiccation) and supplemented postemergence soybean; and two untreated controls, one kept infested and other weeded throughout the experimental period. In the subplots, it was assessed in the realization or not of soybean overseeded with Urochloa ruziziensis. The combination of herbicide application before soybean seeding with sequential application in post-emergence of the crop was effective in controlling adult plants of D. insularis. In addition, the soil cover with U. ruziziensis after soybean harvest, in the off season, reduced the potential for reinfestation of the area by the weed.
Descrição
Palavras-chave
Glyphosate, Sobressemeadura, Tolerância, Urochloa ruziziensis, Variabilidade genética, Oversowing, Tolerance, Urochloa ruziziensis, Genetic variability