Soybean Cyst Nematode


The soybean cyst nematode, a microscopic roundworm, is the most destructive soybean pest in the United States. Early in their growing stages, they look like small, white or yellow spheres in the soil. These spheres are the bodies of female nematodes. Approximately 0.6 mm in length and about 10 mm in width, the nematodes are difficult to see with the naked eye.


The soybean cyst nematode has been found in most soybean-producing areas around the world. The nematodes were first discovered in Japan in 1915. Its first North American sighting was in North Carolina in 1954, and since then it has spread to more than 31 soybean-producing states. It is believed the nematodes were introduced when soybean seeds were imported into the United States from Asia.


Nematodes rely on host plants to reproduce. The nematodes complete one life cycle in 25 to 30 days and each female produces up to 500 eggs. Nematodes go through three stages: egg, juvenile and adult. As an egg begins to feed, it becomes yellowish in color and remains attached to the root. When the female dies, her body becomes a brown, lemon-shaped cyst, which allows her to protect her eggs for several years.


The yellowing or stunting of plants in soybean-producing areas is one of the most common signs of an infestation. If not given adequate soil moisture, some plants may wilt and others may die. Heavy infestations can cause root distortion. 

Soybean cyst nematode infestations can be confirmed by sightings of white females or lemon-shaped cysts on soybean roots. These sightings require that the soil around the soybean roots be gently removed and the plants dug up. Not seeing any visible females does not mean they are not present – it is impossible to determine the size of the infestation without digging up an entire crop. A soil sample is required to more accurately diagnose an infestation. 


No known method exists to completely eradicate nematode infestations from the soil. However, a number of suggested methods can help manage or reduce the populations to a controllable level for soybean crop production. Suggested practices include crop rotation or use of nematicides. Providing sufficient water through irrigation can help reduce the nematode population. Rotating soybeans is a simple method to reduce the impact of nematodes. For the best results, plant a non-host crop every few years.

The soybean cyst nematode is known to spread Sudden Death Syndrome (SDS) in soybean plants. The fungus that causes Sudden Death Syndrome lives in the soil with nematodes. Soybean pathogens generally require specific environmental conditions to transmit the disease, but once a plant is infected, other nearby plants can be impacted.