Green stem nematode can cause losses of up to 60% in soybean and other crops

The green stem nematode (Aphelenchoides besseyi) has been causing significant losses in Brazilian soybean crops, with damages that can reach up to 60% in affected areas. 

This information comes from Embrapa Soybean (Brazilian Agricultural Research Corporation) researchers Maurício Meyer and Luciane Favoretto, who highlighted the severity of the problem and management strategies to address it.

The experts pointed out that the area infested by the green stem nematode is estimated at 6.3 million hectares, covering regions in the Brazilian states of northern Mato Grosso, Pará, Maranhão, Tocantins, Rondônia, and Amapá. According to them, warm and rainy weather conditions are particularly favorable for the pest's development.

"In some cases, the loss is total, forcing the farmer to destroy the crop and opt for another culture," Meyer emphasized. This situation requires increased attention to prevent pest dissemination and mitigate its impacts.

Unlike other nematodes that concentrate on the roots, Aphelenchoides besseyi prefers tender plant tissues, such as inflorescences. This characteristic makes management both a challenge and an opportunity. "Since it is located in more exposed parts of the plant, chemical or biological control can be more effective," Favoretto explained.

Symptoms include leaf deformations, inflorescence necrosis, and retention of stem and pod maturation, resulting in green or rotten grains. These signs help producers identify the nematode's presence, but confirmation must be made through specific laboratory analyses, requiring aerial plant part collection, especially during flowering.

Experts emphasized three fundamental actions to combat the nematode. The first is entry prevention, which ensures that seeds, especially forage crops, are free of the nematode by sending samples for analysis before planting.

Next, they stated that interrupting feeding, meaning alternating host crops like cotton and soybeans with grasses that don't feed the nematode, is vital. This reduces its population over time.

Finally, the experts advocated for the need for environmental and chemical control. Early desiccation and the use of chemical or biological products are fundamental. However, the positioning of these tools still requires more studies to ensure field efficacy.

The researchers emphasized that nematode dissemination can occur through contaminated seeds, wind, or straw. Therefore, collective actions among producers are crucial to control its expansion and protect pest-free areas.

(Editing by Leonardo Gottems, reporter for AgroPages)