Associação de produtos biológicos e químicos no controle de doenças foliares do trigo e mofo-branco em soja

Abstract

Wheat [Triticum aestivum (L.)] and soybean [Glycine max (L.) Merrill], are crops of great importance for the Brazilian agribusiness, during cultivation, both are subject to attack by diseases caused by fungi, bacteria and viruses, in which we can highlight powdery mildew (Blumeria graminis f. sp. tritici ). The main method of control of these diseases is the chemical control with the application of fungicides, in which the biological control presents itself as an additional tool to the integrated management. In this sense, research was conducted on the association of chemical fungicides and different species of Bacillus applied to two wheat cultivars, TBIO Sinuelo (susceptible to leaf rust) and 'TBIO Sonic (susceptible to powdery mildew), in order to verify the effect on the control of leaf rust (Puccinia triticina) and powdery mildew (Blumeria graminis f. sp. tritici). In the laboratory, biological compatibility tests were performed between chemical fungicides and different Bacillus species. In the soy culture, products based on Trichoderma and Bacillus were evaluated in the control of white mold in field conditions, in which there were different moments of application. For the experiments carried out in wheat, the results showed that all the treatments where there was a mixture of fungicides with B. amyloliquefaciens or B. subtilis there was a greater reduction of the Area Under the Curve of Disease Progress (AACPD) of leaf rust, even differing from treatments where only fungicides were used, in experiment 1 the average reduction with respect to the control was 60% for fungicides and 76% for fungicides in mixture with Bacillus, In experiment 2, this reduction was 38% for fungicides and 52% for the mixtures, when analyzed the AACPD variable for oidium disease, the reductions were 46% for fungicides and 56% for fungicides in mixture with Bacillus, in experiment 2 the reduction was 52% for fungicides and 64% for the mixtures. The greater reduction of disease progress in treatments with mixtures of Bacillus-based products associated with chemical fungicides resulted in higher yields, the average between the two experiments resulted in an increase of 7 bags per hectare for the cultivar TBIO Sinuelo and 2.5 bags for the cultivar TBIO Sonic, when compared to treatments where only chemical fungicides were used. The biological compatibility tests demonstrated that the mixtures between the chemical fungicides and the strains of B. amyloliquefaciens and B. subtilis are compatible, that is, none of the fungicides used totally inhibited the growth of the bacteria, although there was a reduction in the number of colonies. The results of the soy experiment for the control of white mold showed that there was no statistical difference between treatments for the variable Area under the incidence progress curve (AACPI). However, when the productivity variable was analyzed, it was identified that the application of Bacillus amyloliquefaciens BGB124 + B. subtilis BGB137 applied in the stages V9, R4 and R5 provided an increase in the soybean productivity, when compared to the other treatments that did not receive the application of Bacillus. The results discussed above demonstrate the potential of biological products in the control of wheat and soybean diseases, as well as the increase in productivity, thus highlighting its importance in the integrated management of diseases.