Tomato Root Knot Nematodes

Meloidogyne incognita in warm climates, M. hapla where winters are cold

Root knot nematodes on a tomato plant [Credit: Scot Nelson]

Nodules on roots caused by Southern root knot nematode [Credit: Gerald Holmes, California Polytechnic State University at San Luis Obispo, Bugwood.org]

Host Plants:

On Crops: Tomatoes, peppers, okra, carrots and many other vegetable crops. Tomatoes are moderately susceptible to root knot nematodes.

Where Found:

Worldwide, in warm temperate climates

Description:

Root knot nematodes are tiny 'eelworms' that live in soil and become plant parasites when they use tomato roots as their nurseries. Often nematodes enter tomato roots through small injuries. As their numbers multiply, small feeder roots are destroyed, and irregular galls take their place.

Damage:

Plants grow slowly, in erratic spurts, and are generally dwarfed in size. When you dig up a troubled tomato or pepper plant, numerous swellings and galls are evident on the roots. Because root knot nematodes don’t move far in the soil without human help, neighbouring plants may be infected while those at the end of the row remain healthy.

Preventing Problems:

Tomatoes and peppers are moderately susceptible to root knot nematodes, in part because they thrive in the same hot summer conditions that please nematodes. Good crop rotations prevent nematode buildup in many gardens, but root knot nematodes may be unavoidable in sandy soils in warm climates. Numerous resistant varieties are available in both tomato and pepper. Regularly amend soil with materials that contain chitin, such as seafood meal, eggshells, or shrimp hulls. In the soil, these materials feed microorganisms that chow down on chitin, including nematode eggs.

Managing Outbreaks:

Pull up badly infected tomato plants, lop off the roots, and dispose of the roots in the trash. Compost the rest. Mark the area where the troubled plants grew, and do not grow tomatoes, peppers, okra or carrots there again. If tomato or pepper plants are only slightly infected, they may make a crop if a deep mulch is used to keep the root zone cool and moist.

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