Researchers point out low incidence of cotton diseases in the 21/22 harvest

A low incidence of cotton diseases marked the 2021/2022 harvest compared to past harvests. This was the conclusion of the researchers, technicians and producers present at the XIV Cotton Technical Meeting, promoted by the Mato Grosso Agricultural Research Support Foundation (Fundação MT), at the end of August, in Cuiabá. One of the factors that contributed to this result was the unfavorable climate for diseases, with a reduction in the rainy season in the main cotton-producing regions.

During the panel “Cotton Crop Disease Management”, coordinated by researcher João Paulo Ascari, from Fundação MT, with the participation of phytopathologists Fabiano Perina and Luiz Chitarra, from Embrapa Algodão, and phytopathologists Mônica Müller and Karla Kudlawiec, from Fundação MT , a retrospective of the last harvest was carried out.

According to Ascari, in a survey carried out on cotton crops in the state of Mato Grosso by Fundação MT, in the 2021/22 harvest there was almost no occurrence of target spot (1%) and ramularia spot remained at around 30% of severity. In the previous harvest, the scenario was of greater pressure from the target spot (7%) and the ramularia spot reached a severity of 40%. In the 2019/20 harvest, water was available during the crop cycle, with a favorable microclimate for the development of both diseases, reaching a 50% incidence of target spot and 32% of Ramularia.

Perina and Chitarra presented research results regarding the occurrence of diseases in cotton cultivation in Western Bahia and Mato Grosso, respectively. They also presented data from the Ramulária Network, coordinated by Embrapa Algodão, as well as guidelines for controlling the main diseases of cotton crops for the next harvest.

“This harvest, in general, was calm in relation to ramularia, the main disease of cotton. Environmental conditions were not favorable for the development of the disease. It highlighted some areas with a higher occurrence of the target spot and initial problems with the fungus Rhizoctonia solani, causing plants to fall at the beginning of planting and 'cotton blight' in the aerial part”, reported Perina.

“Rhizoctonia drew attention due to excessive rainfall at the beginning of the cycle, causing a reduction in the stand and the need for replanting in some areas”, commented Perina. According to Chitarra, it was possible to evaluate and identify, in cotton crops in the north of Mato Grosso, the susceptibility of some cultivars to target spot.

Search recommendations

Among the guidelines for the next harvest, the researchers emphasized the need for producers to use the main control strategies, from correct monitoring of the crop to make more effective decisions, to the use of chemical products with proven efficiency for controlling leaf spot. -ramularia and target spot, as well as cultural techniques such as adapting the plant population, managing plant height, with a growth regulator and the adoption of cultivars resistant to ramularia or with less susceptibility to the target spot. For rhizoctonia, the recommendation is to use a seed treatment with products proven to be effective against the fungus and registered with the Ministry of Agriculture, Livestock and Supply.

Ramular Network

Perina highlights that data from the Ramulária Network has contributed to greater control of the disease. “The network launches each year the isolated efficiency of each fungicide and chemical groups, giving the producer the opportunity to choose chemical products, always with an emphasis on the rotation of active ingredients and the use of multi-site fungicides to contribute to control efficiency and reduce chance of the emergence of fungal resistance to the active ingredients of the products”, he stated.

west of Bahia

On September 2, Fundação Bahia also held the 2021-2022 Cotton Crop Research Results Workshop, bringing together producers, consultants, farm managers, companies and other links in the agricultural sector. The event was attended by Fabiano Perina, as well as researcher Alexandre Cunha de Barcellos, who presented research results both on the control of target and ramular weeds, and on the “low carbon” cotton and grain production system. Results from the soil health and health survey were also presented, with nematological, soil fungus and soil health samples.

“We have been carrying out these samplings in western Bahia for two years, where we want to have a diagnosis not only of nematode infestation in cotton areas in rotation with soybean crops, but also to infer how the soil is healthy and what the relationship between soil health (with active microbiology) and plant health”, said Perina.

Alexandre presented the results of the work carried out in recent harvests and long-term work on several projects involving cotton production and management systems. “These works aim to achieve high productivity, not only of cotton, but of the crops that make up the system and also to improve soil quality,” he stated.