What's Attacking my Tomatoes?

Root-knot and stubby-root nematodes are the two major species of nematodes present throughout the tomato-producing states. Fusarium wilt and Verticillium wilt – which gain access to tomatoes through entry ways created by nematodes – also can result in significant damage.

Root-knot nematodes can cause severe damage to tomato plants in California.

• Root-knot nematodes are named for the galls created on plant roots by the nematode. These nematodes are some of the most dangerous nematodes and can be found in nearly any field, but are most commonly found in sandy soils. The density of root-knot nematodes is typically scattered within an infested field.
  
  The occurrence and severity of Fusarium wilt and Verticillium wilt are increased significantly in fields with root-knot nematodes. Infected plants can be easily identified by digging up stunted plants and checking for swollen knots on the roots.
  
  Potential host weeds: prickly sida, smallflower, morningglory, ivyleaf morningglory, bermudagrass, johnsongrass, cocklebur, goosegrass, red-root pigweed, purple nutgrass, yellow nutsedge, purple nutsedge, smartweed, teaweed, lambsquarters, groundcherry, crotalaria, sicklepod

• Fusarium wilt can be identified by yellowing foliage that begins with the lower leaves and progresses up the plant. Infected leaves start curling downward, turning brown and eventually dying. Wilting of the vine becomes progressively worse as time passes until becoming permanently wilted. Fusarium wilt can greatly reduce yields and can survive many years within the soil.

• Verticillium wilt symptoms start with yellow blemishes on the lower leaves, followed by brown veins and dead spots, with the leaves eventually dying and falling off the plant. These symptoms climb the stem, stunting the growth of tomatoes in the process. All of this is made possible by nematodes feeding on the root system, thereby opening entrances in the roots for the fungus to enter.