Potencial fungicida e inseticida de co-cultivos de Beauveria bassiana, Trichoderma harzianum e Metarhizium anisopliae para o manejo fitossanitário da cultura da soja

Abstract

The cultivation potential of soybean crop is constantly interfered by diseases and insect pests, mainly fungal diseases and stink bugs. The brown stink bug (Euschistus heros) is the most abundant in the crop, which causes damage directly to the grains, making them hollow, and to the embryo contained in the seed. Fungal diseases such as white mold caused by Sclerotinia sclerotiorum, black root rot caused by Macrophomina phaseolina and anthracnose caused by Colletotrichum spp. are difficult to eradicate. The chemical control of pests and diseases has generated residues and resistance of target insects and fungi. Otherwise, biological control has demonstrated to be efficient and has less environmental impact. In this study, co-cultures and paired cultures of entomopathogenic fungi Beuauveria bassiana, Trichoderma harzianum, and Metharizium anisopliae were carried out aiming at the development of a product with bioinsecticide and biofungicide effect as an increment to the sanitary management of the soybean crop. This research was based on evaluations of laboratory bioassays, including statistical experiments. Cultivations were carried out in submerged medium with the fungi using glucose, sucrose, hydrolyzed animal protein, hydrolyzed soybean meal plus organic phosphorus, and hydrolyzed feathers using Plackett-Burrman planning. The fermented broths were applied directly to the back of adult brown stink bugs to assess their mortality, which was compared with the positive control. The data obtained and compiled were submitted to analysis of normality and homogeneity, which they were significant. Thereafter, they were submitted to the comparison test of means by Tukey’s test at 95% confidence. The independent variables did not have significant effects on the biomass of the co-cultures. However, they were significant for the number of conidia. The co-cultures were promising in terms of insecticidal potential for the biological control of Euschistus heros, with emphasis on the cultivation of Trichoderma harzianum, which provided the highest percentage of insect mortality, between 70 and 100%. The paired cultivation indicated total control of Macrophomina phaseolina by the entomopathogenic fungus Metharizium anisopliae. The fungi Beauveria bassiana + Metharizium anisopliae were effective against the pathogens of Sclerotinia sclerotiorum and Colletotrichum gloesporioides, showing 70% inhibition. Trichoderma harzianum and Metharizium anisopliae showed control of Colletotricum truncatum, between 50 and 60% inhibition. The results are promising, showing effective alternatives to complement the biological control of soybean.