Field Scouting Guide: Root-Knot Nematode

By Karli Petrovic|Updated: March 05, 2024

This edition of Field Scouting Guide concentrates on Meloidogyne (root-knot nematode). Johan Desaeger, University of Florida, shares insights into how to spot and treat this pest.

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Root galls clearly indicate root-knot nematodes.
Photo by Johan Desaeger
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Aboveground damage is not enough to identify root-knot nematodes.
Photo by Johan Desaeger
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Root-knot on a yam (left) compared to an undamaged yam.
Photo by Johan Desaeger

THE BASICS

Scientific name: Meloidogyne
Common name: Root-knot nematode
Geographical Range: Global
Crops affected: Almost all

PEST IMPACT

This pest affects the entire state of Florida. It is difficult to say the economic impact of root-knot nematode, as crop loss can range from just a small percentage to total crop loss. Typically, hot spots will occur in a field, showing clusters of unthrifty, stunted plants. Root-knot is one of the major pests for vegetable and strawberry growers.

The pest is a problem from the get-go. Under favorable conditions (soil temperature and moisture), root-knot can severely stunt newly seeded/planted crops. Double-cropped vegetables especially are at risk.

IDENTIFICATION

Root-knot nematode can be mistaken for many pests and problems, ranging from other soilborne diseases, to fertility issues, to drought (plugged drip tapes), etc.

The aboveground symptoms are not very specific, but below-ground symptoms are. Root galls and swellings on the root system can range from very small spherical knots to large, swollen, deformed roots — tell-tale signs of root-knot nematode.

RECOMMENDED TREATMENT

The most effective treatment is soil fumigation, nematicides, crop rotation, and resistance when available.

Traditional chemistries

Name	Company	Active Ingredient	IRAC Nematicides	Classification
Telone	Corteva	1,3-dichloropropene	Group N-UNX	Presumed multi-site inhibitor – Halogenated hydrocarbon
Kpam	AMVAC	metam	Group N-UNX	Presumed multi-site inhibitor – Methyl Islthiocyanate generator
Pic	Corteva	chloropicrin	Group N-UNX	Presumed multi-site inhibitor – Chloropicrin
Vydate	Corteva	oxamyl	Group N-1A	Carbamates
Nimitz	Adama	fluensulfone	N-UN	Unknown
Velum	Bayer CropScience	fluopyram	Group N-3	Mitochondrial complex II electron transport inhibitors. Succinate-coenzyme Q reductase

Organic controls

Name: Majestene, Melocon, and several thyme oil-based products, azadirachtin-based products, mustard meal
Active ingredient: Burkholderia rinojensis, Purpureocillium lilacanus
Mode of action: unknown

The IPM recommendations are to integrate cover crops/rotation. Florida sunn hemp is a good cover crop that is a poor host to root-knot, as are certain cowpea cv’s. When available, resistant cv’s (for tomato), and increase soil organic matter.

Other practices that can be used when appropriate are flooding, solarization, steaming, and fallowing.

Karli Petrovic is a former associate editor for Greenhouse Grower^® magazine, a Meister Media Worldwide publication, and current freelance writer/content creator in Austin, TX. See all author stories here.