Nematode causes losses of nearly 100% of cotton lint

Date:06-16-2022

It is not just the soybean producer who should be concerned about the attack of Aphelenchoides besseyi, a nematode that feeds on fungi present in the soil and crop residues and that parasitizes the aerial part of the plant.

In soybeans, it causes the Green Stem and Leaf Retention Syndrome (“Crazy Soybean II”), which leads to more than 60% of inflorescence abortion. But it is not restricted to the oilseed. Researchers Rosangela Silva, a nematologist from the Mato Grosso Agricultural Research Support Foundation, Fundação MT, and Santino Aleandro, from Agronema, a nematological consultancy, have seen immense damage in the field of the phytonematode in cotton crops, with losses in some cases of 80 to 100% of the fruits.

The rainfall regime is a crucial factor in quantifying the level of infestation and multiplication of this nematode. If, according to Santino, there has been a lot of precipitation since the beginning of the planting of the crop and until flowering, there are situations in which the losses range from 80 to 100% of the fruit production. “The producer will not harvest anything in this area that was attacked. It is a concern that one must have with soybeans and cotton,” he highlighted. One of the aggravating factors he pointed out are the regions under pivot because, even if the rain stops, it is possible to create favorable conditions “because of the humidity offered by irrigation.”

Situation in Mato Grosso

According to the Mato Grosso Institute of Agricultural Economics (Imea), Mato Grosso, a reference in cotton production, planted around 1.12 million hectares in the 2021-2022 harvest. In the State, sowing begins from December to February and the harvest from June, when the crops planted earlier are possibly already being harvested. “It is from there, the producer will check the losses, even visualizing the presence of plants that continue to vegetate when they should start senescence. Although he can use the chemical desiccant, these plants can continue to vegetate,” the researcher from Agronema pointed out.

This year, January, February and March had rain, but within the expected average, with the monthly accumulation being around 200 millimeters (mm). However, in April, rainfall dropped significantly, below 80mm.

“This reduction influences the presence of Aphelenchoides symptoms because it no longer offers an ideal condition for the development of the pathogen,” said Santino. Even so, it cannot be neglected, since year after year, according to the weather conditions, there is a greater or lesser incidence of the problem.

Recent Identification

Soybean green stem syndrome is relatively new. Its causal agent was identified almost a decade ago, and, only in 2017, was the presence of the disease observed in cotton, specifically in the municipality of Sapezal-MT. “We already know that in areas where there is the pathogen without weed management, the problem tends to be more aggravated because most of them, especially legumes and dicots, multiply this nematode more, allowing it to be not only present in the field, but also in greater quantity,” Rosangela explained.

Santino said that no-till brings a series of improvements to the soil and production. On the other hand, it also offers conditions for maintaining this nematode, because of the humidity and the straw, which allow the multiplication of fungi. These, in turn, feed Aphelenchoides besseyi in the off-season. The introduction of this nematode in areas where it is not yet present can also happen through planting forage seeds, especially Brachiaria, “which has not been properly processed, has clod remains and has no nematicide treatment.”

The recommendation of both researchers is to avoid, whenever possible, the sequence of planting cotton in areas that had soybeans with a history of Green Stem Syndrome. They also advise that, in plantations with heavy infestation, the soil should be turned over. The practice, even without technical, scientific data to prove it, is observed with good results combined with using nematicides in seed treatment and/or application of some foliar product.

“We are at an early stage of research. Several chemical and biological tests are being conducted. However, we still do not have a technical position that offers management with the certainty of a satisfactory level of control. The MT Foundation has experiments in progress, and we hope to have results soon. For this reason, there is an alert for maximum attention to crops, whether soybean or cotton,” researcher Rosangela added.

Fundação MT: Created in 1993, the institution plays an essential role in the development of agriculture, serving as a support to the agricultural class in the mission of bringing results to life through the development of technologies applied to agriculture. The head office is located in Rondonópolis-MT, with three laboratories and greenhouses, a local research center and six other Advanced Research Centers (CAD) distributed throughout the State in the cities of Sorriso, Nova Mutum, Sapezal, Itiquira, Primavera do East and Serra da Petrovina.