By carefully digging up affected plants and shaking the soil from the root system, you can check for swellings on the roots, a strong indication of root knot nematode. Galls may vary in size and shape. On heavily infected plants, galls tend to fuse together so that a large part or all of the root may be swollen. Lateral roots appear on root crops such as carrots, resulting in a condition known as hairy root. Infected potato tubers may have small, bumpy swellings on the surface.
Roots begin to swell within a day after infection.
The cells where the nematode is feeding are stimulated to multiply and swell. Changes occur in the vascular system which prevent it from functioning properly. Consequently, the flow of nutrients and water is inhibited and the top growth is affected. The heavier the infection and the more damage to the roots, the more severe the above ground symptoms will be. The root knot nematode is a soil-inhabiting parasite.