The symptoms seen on tobacco plants and the damage pattern in the field are important clues to be used in determining the cause of poor growth. Often the above-ground symptoms are related to root problems. For example, wilting and the death of leaves, usually beginning at the tips and extending to the base of the leaf, are symptoms of root problems. Plants to be examined for root problems should be dug rather than pulled from the soil. Many roots, particularly diseased or injured ones, may be left in the ground if a plant is pulled up.
Diseased roots are dark brown or black, healthy roots white.
Root-knot nematodes cause a characteristic swelling, which is easily identified, on parts of the roots. Damage to roots from fertilizer salts. The vascular system should also be examined. This is done by splitting the stalk lengthwise with a knife. Healthy tissue will be white, whereas diseased tissue is dark colored or black.