Tratamento de sementes florestais com inseticidas visando a semeadura direta

Abstract

Forest degradation has increased, making it necessary to develop techniques that are viable and effective. Among the viable techniques, direct seeding stands out, with low cost and greater accessibility. However, for the technique to be effective, some points must be developed, such as reducing seed predation. Therefore, it is nessary to develop solutions that minimize this problem. The objective was to evaluate the phytotoxicity and the bioactivating effect of the insecticides thiamethoxam and cyantraniliprole, in seeds of forest species. Therefore, three experiments were installed, with the first one aimed to evaluate the effect of seed treatment with insecticides on germination and initial development of seedlings of native species. The second experimente aimed to analyze the efficiency of the insecticide thiamethoxam in the field against seed predation by insects and its bioactivator effect on five forest species. The third experimente aimed to evaluate the influence of thiamethoxam on the physiological performance of seeds of two forest species during storage. It was found that under laboratory conditions positive effect of the use of thiamethoxam and cyantraniliprole in P. dubium. when analysed the seed vigor and seedling development. In E. contortisiliquum there were positive effects, with the exception of IVG, when thiamethoxam was used. In G. ulmifolia, H. courbaril and Bowdichia virgiioides, phytotoxic effects were observed when both insecticides were used. Under field conditions, thiamethoxam had a positive effect when analysed seedling shoot length for E. contortisiliquum and leaf number for G. ulmifolia. For the primary root length in E. contortisiliquum, a negative effect was observed in treated seeds. There was observed seed predation 30 days after sowing only in S. multijuga, where all individuals were attacked by ants, regardless of seed treatment. Germination of S. multijuga seeds was higher in when treated with thiamethoxam, when the seeds stored in nylon bags, kept under a thin layer of soil in the field. For stored seeds, seed treatment with thiamethoxam did not negatively alter the physiological quality of P. dubium and E. contortisiliquum seeds. Tiamentoxam does not affect the physiological quality of stored P. dubium seeds and has a bioactivating effect on seedlings.