Meloidogyne chitwoodi Columbia Root-knot nematodes juvenile M. chitwoodi tails Damage to Potatoes.  Presence of the Columbia root knot nematode in potato growing areas preclude the export of potatoes to international markets due to the restrictions imposed by many countries against this pest.  Biology.  Juveniles penetrate host roots where they establish a feeding site, developing into swollen females (cysts). The female is usually pear-shaped, with a fragile white cuticle, and may be up to 2 mm in diameter.  Ecology.  Root-Knot nematodes are distributed world-wide. Symptoms.  Symptoms of Meloidogyne chitwoodi damage in potatoes include dark specks in the potato flesh and reduced potato quality.  Damage to other crops.  Meloidogyne species are also damaging pests of tomato and corn.  Control