Embrapa and Epamig launch publication on the nematode that causes crazy soybeans II

Embrapa Soja and the Agricultural Research Company of Minas Gerais (Epamig) have just launched a publication on the green stem nematode Aphelenchoides besseyi, causing Crazy Soy II. In soybean crops, the problem was identified more than ten years ago and there is a record that it can cause reductions of up to 100% in productivity. The disease causes flower and pod abortion, wrinkling and browning of leaves. The green stem nematode predominates in hot and rainy regions such as the states of Mato Grosso, Pará, Maranhão, Tocantins and Amapá. 

"A. besseyi, Known worldwide as a pathogen that affects rice, strawberry and some ornamental plants, it has never been a problem for soybeans and cotton and, due to its lower economic impact on agricultural crops when compared to root-knot nematodes, of cysts and root lesions, these nematodes were little studied”, say researchers Maurício Meyer, from Embrapa Soja, and Luciany Favoreto, from Epamig Oeste. “However, it is essential to generate research results to establish control strategies, in the shortest possible time, to minimize losses in soybean and cotton production”, they warn.

History of Soya Louca II 

For more than ten years, several Brazilian researchers have tried to identify the cause of Crazy Soy II (SL-II). Only in 2015, researchers from Embrapa and Epamig Oeste identified the soybean green stem nematode, Aphelenchoides besseyi, as the causal agent of Crazy Soy II.

Meyer says that the symptoms of SL-II are observed at the beginning of the reproductive phase of soybeans, which presents thinning of the leaves at the top of the plants, wrinkling of the leaves and thickening of their veins. Furthermore, leaves with symptoms have a darker color and less hairiness compared to normal leaves. It is also observed that the stems exhibit deformation and thickening of the nodes. The pods may present lesions, cracks, rot, reduced number of grains and reduced hairiness.

The researchers also reveal that the affected plants record a high rate of flower and pod abortion, often causing the induction of new flowering and symptoms of overbudding. “This abortion of flowers and pods prevents the natural maturation process of the plant, leaving the stems, petioles and leaves green, even after the application of desiccant herbicides”, they report.

Favoreto highlights the high capacity for multiplication of A. besseyi in soybeans, being able to complete a vital cycle in a period of eight to ten days. Furthermore, this nematode can also survive in some invasive plants (trapoeiraba, cress-do-pasto, cordon-de-frade and pigweed), or by feeding on fungi that decompose organic matter in crop residues.

The green stem nematode Aphelenchoides besseyi - Technical Circular 147 is available here for download.