Biological Nitrogen Fixation reduces sugarcane foliar diseases by up to 16%

A study by Embrapa Meio Ambiente (SP) showed that the use of inoculants for Biological Nitrogen Fixation (BNF) in sugarcane reduced the severity of foliar diseases that affect this crop by up to 16%. This conservation practice is already used successfully in soybean crops in Brazil, covering an area of ​​more than 33 million hectares and generating annual savings of around US$8 billion, but it was the first time that its efficiency was proven with the sugar cane. The research can benefit the integrated management of emerging diseases and open new markets for inoculants in the country. To read the full work, click here. 

According to Embrapa Environment researcher Katia Nechet, the research evaluated the effects of conservation practices in controlling two emerging foliar diseases, ring spot and red rot, capable of reducing the dry biomass of sugar cane, which harms production (see more details in the table below). In addition to FBN, which showed greater efficiency in reducing the severity of these diseases, minimum tillage, conventional tillage and the Direct Planting System (SPD) were also tested. “The good performance with sugarcane adds even more value to the FBN technology, developed by Embrapa Agrobiologia”, she highlights.

She explains that some control mechanisms may be involved in the interaction between pathogens and diazotrophic bacteria (capable of fixing soil nitrogen) used in FBN, such as antagonism, induction of resistance and competition. These reactions have been reported during host adaptation to bacteria under conditions of environmental stress.  

“Monitoring the incidence and severity of diseases can help understand how conservation practices in sugarcane can change the importance of foliar pathogens over time”, points out Nechet. Another point to be considered is the effect of fertilizers on leaf nitrogen content and its relationship with disease severity.

Study may benefit integrated management of emerging diseases

Changes in crop management practices can lead to the prevalence of diseases previously considered of minor importance. In the first experimental period, three months after planting, no root rot or leaf disease was observed. In the following evaluations, the occurrence of diseases, regardless of the evaluation period, was restricted to ring spot, caused by the fungus Leptosphaeria sacchari, and red rot, caused by the fungus Colletotrichum falcatum. The first symptoms of foliar diseases were observed six months after planting in the rainy season. 

There were no significant differences in the severity of diseases when sugarcane was planted in the dry season or in the rainy season. The depth of the straw layer also did not impact the severity, which is only influenced by the precipitation accumulated in the month. In Brazil, sugarcane is affected by stem and root rot and foliar diseases. The occurrence and economic importance of each one depend on the genotypes and production systems adopted, as well as the environmental conditions of each growing region.

Interestingly, these foliar diseases appeared more frequently after the implementation of mechanized systems, explains the researcher.  

According to her, ring spot is very common, but is not considered one of the main diseases in Brazil, although it is used as a selection parameter in breeding programs to eliminate susceptible genotypes.

Red rot occurs at various stages of the plant, with different symptoms, causing death of buds, spots on leaves and rotting of the stem. The colonization of the stems by the pathogen leads to rot, which is the most serious form of the disease and is generally associated with injuries caused by the sugarcane borer.

According to researcher Nilza Patrícia Ramos, two experiments were carried out in the Guaíra region (SP), one during the sugarcane-plant cycle (18 months) and the other between the first and second ratoons (2 years). “The simultaneous occurrences of ring spot and red rot, associated with leaf spot, were the only diseases observed, regardless of the conservation practices used in the experiments,” she explains.