Aboveground symptoms usually involve stunt and chlorotic and seem to wilt during the heat of the day. These symptoms also can result from unfavorable growing conditions, but it is the swollen and distorted roots that are most typical of root knot. 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.