Effect of soybean seed treatment on the population dynamics of Pratylenchus brachyurus under water stress conditions = Efeito do tratamento de sementes de soja na dinâmica populacional de Pratylenchus brachyurus sob condições de restrição hídrica

The aim of the study was to evaluate the efficacy of seed treatment in the Pratylenchus brachyurus control and on the development parameters of soybean plants subjected to two water regimes. Seeds of the cultivar MSoy 7639 were treated with products containing imidacloprid + thiodicarb, pyraclostrobin + thiophanate-methyl + fipronil and abamectin + azoxystrobin + mefenoxam + fludioxonil + thiamethoxam. The plants were also subjected to two water regimes (absence and presence of water stress), maintaining 40 and 60% field capacity 15 days after nematode inoculation. At 60 days after inoculation, the aerial part and root fresh and dry weight were evaluated, together with the number of nematodes per gram of root and total nematodes (soil + root). Treating the seeds significantly reduced the population of P. brachyurus, irrespective of the water regime. Water stress also significantly reduced the total number of nematodes. In general, for a given water regime, the treatments did not affect vegetative development. However, plant development was significantly reduced under water stress, except for the treatment containing pyraclostrobin + thiophanate-methyl + fipronil. The conclusions were that seed treatment helped reduce populations of P. brachyurus and treatment with pyraclostrobin + thiophanate-methyl + fipronil resulted in beneficial changes in the soybean plants, increasing tolerance to water stress.