What are Nematodes? 

Nematodes are microscopic worm-like animals that feed on alfalfa plants and cause yield or stand losses. Nematodes feed on root hairs, feeder roots, tap roots and the nitrogen fixing nodules on alfalfa plants. They can kill seedlings, mature plants and reduce yield by limiting the plants ability to take up soil nutrients and fix nitrogen. Nematodes are spread with the movement of soil and/or plant residue. 

How do I know if nematodes are in my field?

• Uneven plant growth
• Circular stunted areas
• Yield reduction
• Stand reduction 

 
Stem Nematodes

Stem Nematodes cause economic losses each year in the dark shaded areas to susceptible varieties. Stem Nematodes are more common in Western states where sandier soils, irrigation and host crops produce optimum conditions for this alfalfa pest. Sainfoin and potatoes are common host crops for Stem Nematodes. Symptoms are most common during cool and moist periods of the year or under sprinkler irrigation. 

Common Symptoms 
   

 
Root & Lesion Nematodes  

Root Knot Nematodes - Southern, Northern and Columbia Root Knot Nematodes are generally a problem where alfalfa potatoes, sugarbeets, bean and tomato are produced.

Lesion Nematodes - are more common on Eastern soils where corn serves as the host crop.  

Map areas shaded blue indicate area of disease distribution
 

Symptoms: Root Knot Nematodes

• Small oval galls seen on roots
• Stunting of plant and tap roots with increased lateral growth
• Symptoms: Lesion Nematodes
• Black or brown lesions on the outside of the root. Lesions can become so severe the entire tap root darkens
• Stunted tap roots with reduced lateral root growth 

Prevention and control

• Take soil and plant samples to lab to confirm type and number of nematodes
• Plant a non-host crop in rotation to reduce population build-up
• Chemical control is generally too costly
• Best control is resistant varieties.