Colletotrichum truncatum em sementes de soja: redução pelo uso de fertilizantes, produtos fitossanitários e inoculante bacteriano

Abstract

Soybeans are cultivated on more than 38.532 million hectares, sown almost entirely with treated seeds. The expansion of the crop caused an increase in diseases, with this, the damage caused by the pathogen Colletotrichum truncatum, causal agent of soybean anthracnose, seed treatment with fertilizers, phytosanitary products and bacterial inoculant can act in its control. Therefore, the objective of this work was to gather information about the control of Colletotrichum truncatum, the causal agent of anthracnose, from the application of phytosanitary products, fertilizers and bacterial inoculant. The works were divided into two studies, the first on the evaluation of the physiological and sanitary quality of soybean seeds, after the contamination of the lots with the three levels 5%, 10% 30% infection by C. truncatum, and the effect of treatments on physiological quality of these seeds. In the second study, evaluations of yield and health components were carried out through the "Blotter test" to evaluate the incidence of the pathogen in the seeds, and its transmissibility after the treatments, verifying if C. truncatum is transmitted from the infected seed to the plant, and from the plant to seed. After the treatments, physiological tests were carried out, using a completely randomized experimental design in a factorial scheme, taking into account the assumptions, analysis of variance was carried out, being significant, tests of averages were carried out, according to each objective, the variables analyzed were the first seedling count, abnormal seedlings and normal seedlings, dead seeds, dry mass, germination in sand, pod weight, number of pods, seed weight, number of seeds, in the lower and upper parts of the plant. The sanitary tests were evaluated through fungal incidences, relevant to the test. The results indicate that, lower percentages of seedlings in the first count, was the treatment T6 - Fludioxonil + Metalaxil-M + Nutritional complex; and the best treatment T10 - Mineral fertilizer based on Silicon with a percentage difference of 53%, and comparing the infection rates, with and without inoculant. For the germination variable – normal seedlings, most treatments obtained satisfactory results, except T6 and T2, which were responsible for the highest number of abnormal seedlings. Sanitary tests have shown that even the seeds passing through the seed treatments, if the level of infection is too high, the products cannot fully control the infection caused by C. truncatum in the percentages of 30%. However, in lots with 10% of infection, the incidence of the fungus is reduced by around 3%, reaching 0% of incidence in lots with 5% of incidence of the fungus. Treatment T11 Nutritional Complex + Silicon-based mineral fertilizer, has a satisfactory rate of fungus control. And the transmission rate of the fungus from seed-plant-seed is practically nil.