How to combat target spot and anthracnose in soybeans

Target spot and anthracnose are among the main diseases that limit productivity and cause serious damage to soybean crops. To contain these two obstacles, the use of fungicides, combined with other management measures, constitutes an efficient and economically viable alternative.

To expand soybean production, technologies and innovations were added, basically by introducing genetic materials, improving management practices and consolidating the direct planting system on agricultural frontiers. However, this did not prevent the emergence of problems that reduce productivity, such as diseases caused by fungi, bacteria and nematodes. Among the diseases that concern farmers, in addition to Asian rust (Phakopsora pachyrhizi), the target spot stands out (Corynespora cassiicola) and anthracnose (Colletotrichum truncatum), which occur frequently in crops in the Midwest.

The application of fungicides in most cases is efficient and economically viable to guarantee the quality and productivity of crops. Thus, the effect of the fungicides azoxystrobin, trifloxystrobin + prothioconazole, pyraclostrobin + epoxiconazole, fluxapiroxad + pyraclostrobin, pyraclostrobin, picoxystrobin + cyproconazole, and tebuconazole on the control of anthracnose and target spot, and on the morphological characters of soybean in the north of Mato Grosso were evaluated. .

The trial was conducted at Fazenda Andorinha, in the municipality of Lucas do Rio Verde/Mato Grosso, using the cultivar BMX Desafio RR 8473 RSF, sown in the first half of October, in a direct planting system. The first application of fungicides (Table 1) was carried out at soybean flowering and the second, 15 days later.

In the anthracnose control (Figure 1), there was no significant difference between the treatments and this may have occurred due to the low severity of the disease in the experiment, probably due to the low concentration of the inoculum at the site.

Considering the area under the target stain progress curve (AACPMA) (Figure 2), treatments T2 - Azoxystrobin, T3 – Pyraclostrobin + Epoxiconazole and Fluxapyroxad + Pyraclostrobin, T4 - Pyraclostrobin and Pyraclostrobin + Epoxiconazole, T5 – Fluxapyroxad + Pyraclostrobin and T8 - Tebuconazole, presented the lowest AACPMA values, showing efficiency in target stain control. The best control of the disease was provided by T3 – Pyraclostrobin + Epoxiconazole (1st application) and Fluxapiroxad + Piraclostrobin, in the 2nd application.

Regarding morphological characteristics, there was no difference between treatments in plant height (cm), stem diameter (cm), first pod insertion height (cm), number of pods per plant and number of grains per plant (Table two). In general, the application of fungicides had no effect on these morphological characteristics evaluated, most likely due to the fact that they are influenced by the plant population. However, the application of T2 – Fluxapiroxad + Piraclostrobin and Fluxapiroxad + Piraclostrobin, T5 – Pyraclostrobin + Epoxiconazole and Fluxapiroxad + Piraclostrobin, T3 - Azoxystrobin and Azoxystrobin, and T2 – Trifloxystrobin + Prothioconazole and Trifloxystrobin + Prothioconazole, provided an increase in the mass of a thousand grains of 6%, 1,62%, 1,24% and 0,77%, respectively, in relation to the witness. The mass of a thousand grains is information that can be used to compare grain quality, despite being commonly used in trials, as a yield component for various crops. In addition to being a parameter used to calculate seeding density, it can also be used as a comparative factor for seed quality.

According to the conditions under which this work was established and conducted, the results allow us to conclude that there was no difference in plant height (cm), height (cm) of insertion of the first pod, number of pods per plant and number of grains per plant. Regarding anthracnose (C. truncatum), the treatments did not show a significant difference in the control of this disease, however, treatment with Pyraclostrobin + Epoxiconazole in the first application and Fluxapiroxad + Piraclostrobin in the second application demonstrated greater efficiency in controlling the target spot (C. cassiicola) and greater mass of a thousand grains. Furthermore, the farmer must adopt preventive measures to control these diseases, such as crop rotation, use of resistant cultivars, certified seed, seed treatment, plant population, fertilization and adequate spacing. If foliar application of fungicides is necessary, consult an agronomist and follow the technical recommendations of the products.

Soy in Brazil

Soybean cultivation has great prominence on the world stage, as it is a source of food products, both for animals and humans, in addition to the growing use of biofuels made from the grain, which is of great global interest in renewable and clean energy.

According to data from Conab, the last soybean harvest in Brazil, 2013/2014, reached a production record (86,12 thousand tons), with an increase in the area produced, totaling 30,17 thousand hectares, with Mato Grosso responsible for 28,55, XNUMX% of this area.

Pricila Basso, Solange Maria Bonaldo, Solenir Ruffato, Federal University of Mato Grosso

Article published in issue 190 of Cultivar Grandes Culturas.