Researchers warn of losses of up to 100% of cotton plumes due to attack by Aphelenchoides

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 green stem and leaf retention syndrome (“Crazy Soy II”), which leads to more than 60% of inflorescences aborting. But it is not restricted to oilseeds, researchers - nematologist Rosangela Silva, from the Mato Grosso Agricultural Research Support Foundation, MT Foundation, and Santino Aleandro, from Agronema, a nematological consultancy, have seen in the field great damage caused by the phytonematode in crops. of cotton, with loss in some cases of 80% to 100% of the fruits, that is, the plumes.

A very important factor in quantifying the level of infestation and multiplication of this nematode is the rainfall regime. If from the beginning of planting the crop there was a lot of rainfall and was constant until flowering, according to Santino, situations are observed in which losses range from 80 to 100% of fruit production. “The producer will not harvest anything in this area that was attacked. It’s a concern that should be had with soybeans, but also with cotton,” he highlights. One of the aggravating factors he points out are the regions under pivot, because even if the rain stops, it is possible to create favorable conditions “due to the humidity offered by irrigation”.

Situation in Mato Grosso

A reference in cotton production, Mato Grosso planted in the 2021/22 harvest, according to the Mato Grosso Institute of Agricultural Economics (Imea), an area of ​​around 1,18 million hectares. In the State, sowing begins from December to February and harvest begins in June, when crops planted earlier are possibly already being harvested. “It is from there that the producer will check losses, even visualizing the presence of plants that continue to vegetate when they should begin to senescence. Even though he can use the chemical desiccant, these plants can continue to vegetate”, points out the Agronema researcher.

This year, the months of January, February and March were rainy, but within the expected average, with the monthly accumulation of around 200 millimeters. However, in April, the amount of rain fell significantly, falling below 80 millimeters. “This reduction influences the presence of symptoms of Aphelenchoides because it no longer offers ideal conditions for the development of the pathogen”, says Santino. Still, we cannot be careless, as year after year, depending on 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, the presence of the disease was observed in cotton, specifically in the municipality of Sapezal-MT. “We already know that in areas where the pathogen exists without weed management, the problem tends to be more aggravated because many of them, especially legumes and dicotyledons, multiply this nematode more, allowing it to be not only present in the field, but in greater quantities”, explains Rosangela.

Santino says that direct planting brings a series of improvements to the soil and production, but, on the other hand, it also offers conditions for maintaining this phytonematode, due to the humidity and straw, which allow fungi to multiply. 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 the planting of forage seeds, especially brachiaria, “which has not been properly processed, has the remains of clods and has not been treated with nematicides”.

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

“We are at an early stage in research. There are several tests with chemical and biological products being conducted. We still do not have a technical position that offers handling with the certainty of a satisfactory level of control. The MT Foundation has experiments underway and we hope to have results soon. Therefore, it is important to pay maximum attention to crops, whether soy or cotton”, adds researcher Rosangela.