Symptoms

• When root knot infects your tomatoes, the roots can't take up nutrients as well from the soil. The plant has weak growth, the leaves may fade in color and fruit production is minimal. These symptoms are also signs of nutrient deficiency from poor soil or the wrong fertilizer, so the problem may go unrecognized until the plant dies. When the plant does die, the entire root system contains galls and appears swollen.
  
  

Cause

• The root knot nematode (Meliodogyne sp.) is the parasite that causes root knot in tomatoes and several other plants. While some nematodes are beneficial in the garden, the root knot nematode only survives as a parasite to plants. The nematodes aren't host specific, so even if you remove the tomatoes, the nematodes can move to another plant. When you plant tomatoes again, the root will be infected again.
  
  

Control

• Because the root knot nematodes can infect other plants, the best way to eradicate them is to remove all plants from the ground and leave the soil fallow for at least six months. Because the nematodes have no food source, they will eventually die. The next best option is to rotate crops each year with a root-knot-resistant species or variety. Other methods of control include repeated tilling the soil and leaving it exposed to the sun to kill the nematodes prior to planting or covering the area with plastic to use the trapped heat to kill the nematodes.
  
  

Resistant Tomato Varieties

• Tomato breeders continually work toward developing tomatoes that resist a wide variety of the most common tomato diseases. The Heatmaster tomato is reported to be very resistant to root knot. A few other root-knot resistant tomatoes include Better Boy, Lemon Boy, Enchantment, Beefmaster and Small Fry. When shopping for tomato seeds or plants, look for those whose label reads "VFN" or "VFNT."