Tomato Roots Infested with Nematodes (IMAGE) Boyce Thompson Institute Caption These tomato roots have been infected with southern root-knot nematodes (Meloidogyne incognita). The microscopic roundworms form galls or "knots" where they feed, ultimately stunting the plants and reducing yield. Credit BTI/Murli Manohar Usage Restrictions free to use with proper credit License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.