Does biological product’s alternate use interfere in soybean diseases and yield?

Abstract

Soybean (Glycine max L.) is one of the most important crops for the global economy, with Brazil being the global leader in production. However, the crop suffers from various problems that cause productivity losses, such as weather-related issues, nutrition, genetic adaptability, and diseases, the latter being the essential factor post-planting. There are many diseases that affect the crop, such as white mold caused by Sclerotinia sclerotiorum, purple seed stain (Cercospora kikuchii), and Asian rust (Phakopsora pachyrhizi), all fungal diseases that cause significant damage. The challenge related to them is the selection of resistant pathogens caused by the recurrent use of chemicals with the same mechanism of action, decreasing their effectiveness. Thus, we conducted two experiments using biological product rotation: the first using Bacillus spp. to control rust (Phakopsora pachyrhizi) in soybean; and the second using Trichoderma spp. to control white mold (Sclerotinia sclerotiorum). In the first experiment, we found that in the first planting season, the combination of Twixx followed by Bioimune, although not showing differences in disease control, increased productivity and consequently higher profits. On the other hand, in the second season, there was no statistical difference in productivity for the Bioimune treatments; Twixx_Bioimune; and Bioimune_Twixx, although the first combination showed a higher absolute value for productivity and provided higher profits. In the second experiment, although there was an effect of Trichoderma application on yield compared to the control, Trichoderma rotation showed no difference among treatments; scleroid viability was reduced by biological control use, but parasitism was low, indicating the presence of other organisms that can be recruited by Trichoderma application. The experiments show us that each pathosystem suffers different types of interference from biological product management and in some cases the positioning of different biological products can be beneficial or neutral.