INFLUÊNCIA DE NOVAS MOLÉCULAS QUÍMICAS NA PENETRAÇÃO, DESENVOLVIMENTO E REPRODUÇÃO DE Pratylenchus brachyurus e Meloidogyne javanica NA CULTURA DA SOJA

Abstract

The nematodes Pratylenchus brachyurus and Meloidogyne javanica cause damage to the soybean crop, causing economic losses on the scale of 27.7 billion reais annually. To reduce this damage, chemical control is a viable alternative for the management of nematodes in this crop. This research aimed to evaluate new chemical molecules, with nematicidal potential, in the penetration, development and reproduction of the nematodes P. brachyurus and M. javanica in the soybean crop. The trials were conducted under greenhouse conditions, with four treatments, three replications and ten evaluation times to evaluate penetration and six replications to evaluate reproduction, with the previously mentioned nematode species. The treatments used were: T1- Control (without nematicide), T2- Abamectin, T3- Fluopyram, T4- Cyclobutrifluram, applied in seed treatment or in planting furrows, following recommendations from patent holders. To evaluate the penetration of the nematodes, the roots were stained with acid fucinia and the nematodes were visualized inside the plant tissue with the aid of an optical microscope. Coloring evaluations were performed at 4, 6, 8, 10, 12, 15, 18, 21, 24 and 30 days after inoculation (DAI). In the reproduction evaluation, root nematodes were extracted at 45 and 60 DAI for M. javanica and P. brachyurus, respectively. The cycle of M. javanica in treatments with fluopyram and abamectin was delayed in relation to the control and cyclobutrifluram, which presented females in the root system at 10 DAI. The number of J2, J3, J4 and females from all treatments were smaller than the control. Root fresh mass was influenced by treatments, with cyclobutrifluran treatment reducing the nematode population per gram of root. For P. brachyurus, the average number of nematodes in the treatments that received the chemical molecules was smaller than the control. From 15 DAI, the number of nematodes in the control was higher than in the other treatments. Among treatments that received nematicides, the number of nematodes between 18 and 30 DAI was lower for the chemical molecules fluopyram and cyclobutrifluram. In reproduction, cyclobutrifluram caused a greater reduction in the number of nematodes in 10 g of root, when compared to the other treatments. With the development of this project, it was possible to understand the influence of these new chemical molecules on the biology of nematodes, as well as the protection that they conferred on the soybean crop.