“Technology controls Corynespora cassiicola fungus in soybean, cotton” – Interview with Nédio Tormen (Technical Director of the Phytus Group)

By Leonardo Gottems, Reporter for AgroPages

Soybean and cotton crops are among the most affected by the fungus, Corynespora cassiicola, which causes a disease called “target spot” in Brazil. AgroPages interviewed Nédio Rodrigo Tormen, who is a doctor of Phytopathology and the Technical Director at the Phytus Group, on how technology can control this threat.

What is target spot and how does it affect crops?

Target spot is a disease caused by the fungus, Corynespora cassiicola, which attacks over 500 species of plants worldwide, especially in the tropics. Among cultivated species, it is one of the main diseases of soybean and cotton crops today. The fungus is disseminated through seeds and survives in cultural remains in the off-season, which are the main sources of the inoculum of the pathogen. After the planting of new crops and under favorable environmental conditions, the fungus can infect practically all parts of the plant. However, the most important symptoms occur in the leaves, with the presence of necrotic lesions with a darker center similar to a “target,” but the symptoms will vary between cultivars and especially between plant species.

What damage has this disease been causing?

The disease can evolve quickly when it attacks susceptible cultivars and causes early defoliation in plants, drastically reducing their photosynthetic capacity and consequently their ability to produce photoassimilates for production. In experimental conditions and under natural infection, the disease has caused productivity reductions of up to 30%, meaning around 15 to 25 bags of soybeans per hectare in current productivity standards. In commercial areas, we estimate that the reduction in productivity has reached up to 15 bags per hectare due to inadequate handling.

What are the current control alternatives?

The control alternatives with the greatest impact on the disease are the use of pathogen-free seeds, seed treatment, crop rotation with grasses, the use of less sensitive cultivars and the application of fungicides in the aerial part. However, it is difficult for producers to use all these practices, which has made the application of fungicides an indispensable component in protecting the productive potential of crops.

How was the response of the fungicide, Aumenax (Basf), in controlling this target?

The fungicide, Aumenax, has been shown to be a good tool for managing target spot in soybean and cotton crops. This fungicide contains the active ingredients, fluxpyroxade and copper oxychloride, and has shown good levels of efficiency in experiments aimed at controlling target spot in the state of Goiás.

Talk more about the subject of your master's degree and any other point you want to add to that theme in relation to target spot.

With regards to target spot, it is very important to monitor the progress of the efficiency of fungicides over many years, as the fungus, Corynespora cassiicola, has already developed resistance against the fungicides of the benzimidazoles group and also to carboxamides. However, the frequency of populations crops varies between soybean and cotton growing regions. As fungus population changes, the efficiency of fungicides can vary widely, reinforcing the importance of monitoring this evolution by technical teams responsible for management.