Interação entre herbicidas e cultivares de soja sobre o desenvolvimento populacional de Heterodera glycines em campo

Abstract

This study evaluated the effect of herbicides on the population density of H. glycines in soybean cultivars, (one resistant and three susceptible) in natural infestation conditions. Experiments were done in Campo Alegre de Goiás and Gameleira de Goiás, agricultural year 2006/07, using randomized blocks, with three repetitions. The treatments were arranged in a factorial design 4 x 4 + 1, with four cultivars (BRSGO Ipameri, BRSGO Luziânia, BRSGO Jataí BRS Silvânia RR), four forms of weed control (hand weeding, chlorimuron-ethyl + lactofen, chlorimuron-ethyl and haloxyfop-methyl), and additional treatment represented by the combination of transgenic cultivar BRS Silvânia RR and herbicide glyphosate. In agricultural year 2009/2010, another test was conducted in Gameleira de Goiás, with four repetitions, in a factorial design 2 x 4 + 2, involving two cultivars (BRSGO Chapadões and BRSGO 8360), four forms of weed control (hand weeding, lactofen, chlorimuron-ethyl; haloxifop-r), and two additional treatments represented by the combination of transgenic cultivar BRS Valiosa RR with control manual weed and chemical control via herbicide glyphosate. In the agricultural year 2006/07, in Campo Alegre de Goiás, eighty days after planting, there was less formation of viable cysts in cultivar BRS Silvânia RR associated with the application of clorimuron + lactofen, compared to manual control. In Gameleira de Goias, it was found, forty days after planting, increase in the number of viable cysts using herbicides, compared with manual control, in cultivar susceptible BRSGO Luziânia, BRSGO Ipameri, resistant to H. glycines, the number of viable cysts was lower when applied herbicides clorimuron+lactofen or haloxyfop, compared the application of clorimuron. The herbicides had no effect on the number of females in susceptible and resistant cultivars in the year 2009/10. In cultivar susceptible BRSGO 8360, the herbicide haloxifop led to a smaller number of females, in comparison with clorimuron, 45 days after sowing. The herbicide lactofen, in the cultivar BRSGO Chapadões (resistant) was associated with increase in the number of viable cysts 45 days after sowing. This herbicide affects negatively the biomass of leaves, fresh green beans and dry bean in the cultivars BRSGO Chapadões and BRSGO 8360.