Dec. 17, 2018
By Leonardo Gottems, reporter for AgroPages
There has been a marked increase in cases of Asian rust in soybeans in Brazil during the 2018/2019 harvest. The Antiferrugem Consortium has already registered 69 occurrences this season, which corresponds to 331% more than in the same period of the 2017/2018 harvest.
Paraná leads in the records of the disease this season, with 37 occurrences, 311% more than in the previous cycle. The states that also recorded the presence of Asian rust, to date, include: Rio Grande do Sul (13 cases), Santa Catarina (7 cases), São Paulo (6 cases), Minas Gerais (3 cases) and Mato Grosso do Sul 3 cases).
The anticipation of seeding, favorable climate for fungus development and the presence of volunteer soybean in the off season are the main reasons for this. Asian rust is considered the primary disease of soybean cultivation in Brazil. According to Embrapa, losses vary from 10% to 90% of production. The nation's humid and mild climate favors the development of the fungus Phakopsora pachyrhizi, which propagates easily in the wind.
"Preventive management is indicated to delay the appearance of the fungus and reduce the symptoms of the disease in the plantation. There are products indicated for each phase of the crop and the development of the disease," according to Helio Cabral, BASF's Marketing Manager Soja.
The initial symptoms of the disease are small leaf lesions, from brown to dark brown. On the underside of the leaf, lesions that rupture and release spores are seen. Severely infected plants exhibit early defoliation, which compromises the formation, filling of pods and final grain weight.
"In regions where rust is recorded, farmers should tighten controls to prevent fungal growth. To maximize results, we recommend using Versatilis (fenpropimorph), in combination with multisite fungicides, such as the Status (copper oxychloride) or other products recommended for disease control, as well as rotating with products of different modes of action to prevent the resistance of fungus," said Cabral.