NEMATODE CONTROL IN FRESH MARKET TOMATOES
» Root-knot nematodes and sting nematodes can cause significant yield losses in fresh market tomatoes.
» Testing soils for nematode levels is useful in selecting the appropriate management strategies.
» Successful nematode management requires integration of variety selection, cultural practices, and the use of nematicides.
Root-knot nematode is the most important nematode pest
on tomatoes in the United States, and the sting nematode is
damaging to tomatoes in some areas.1,2 There are several
species of root-knot nematode (RKN). Meloidogyne incognita
(southern RKN) is the most widely distributed species. This
species does best in areas with moderate soil temperatures,
and it becomes inactive at temperatures below 66°F.
Meloidogyne hapla (northern RKN), does best with moderate to
low soil temperatures. At least four other species of
Meloidogyne occur in the U. S., and they are typically found in
southern, more tropical regions. The sting nematode
(Belonolaimus longicaudatus) is found mostly in areas with
course, sandy soils.1,2
RKN and the sting nematode both survive in the soil and in
root debris as eggs and juveniles (larvae). Nematodes are
spread by anything that moves soil or infested plant
material, including field equipment, water running through
fields, and infected transplants. These nematodes have wide
host ranges, including many vegetable, ornamental, and
weed plant species.
These nematodes feed on roots, resulting in dysfunctional
root systems with reduced water and nutrient absorption.
Poor root function results in above ground symptoms that
include plant stunting, wilting, and leaf chlorosis. Affected
plants often occur in patches in the field.1.2
Root symptoms of RKN include the development of swollen
roots areas, called root galls. These galls can be spherical to
elongated in shape (Figure 1) and vary in size depending on
the specific species of Meloidogyne present. Symptoms of
sting nematode infection include short, stubby roots, and
the formation of tight mats of short roots.1.2
Once introduced, RKN and sting nematodes are almost
impossible to eliminate from the soil. Management is based
on an integrated approach involving cultural practices to
reduce nematode populations, the use of resistant varieties,
and the use of nematicides. It is important to lower
populations before planting, as there are few effective postplanting
Soil population levels of nematodes are estimated by
collecting soil samples from the field and having them
assayed for nematodes. Estimates of the population size
and distribution will help to determine the most appropriate
control strategies to use. Fields should be divided into 5-
acre sections and a zig-zag pattern used to collect 10 to 20
soil samples from each section. The 10 to 20 samples are
combined to create one bulk sample for each 5-acre section.
The samples are then immediately sent to a soil testing
laboratory for analysis. Nematode populations are highest at
the end of the growing season, so this is usually the best
time to collect samples for analysis. Consult local extension
or soil lab guidelines for the most appropriate time and
procedures for soil sample collection and submission.
Results are often reported as the average number of
juvenile nematodes detected in 100 grams of soil.
Nematode damage thresholds vary with the particular
species present and with the texture of the soil. Counts as
low as 2 juveniles per 100 g of soil can result in economically
significant levels of yield loss.2,3
The use of nematode resistant tomato varieties is an
important tool for managing nematode problems. The
designation VFN on a tomato variety indicates resistance to
Verticillium wilt, Fusarium wilt, and Nematode (RKN) damage.
Seminis uses the designations Fol for Fusarium wilt
resistance, Va/Vd for Verticillium wilt resistance, and Ma, Mi,
and Mj to indicate resistance to particular RKN species.
Some root infection by nematodes still occur on RKN
resistant varieties, but the nematodes fail to develop and
reproduce normally, and fruit yields are usually maintained
even though some root galls develop. This form of
resistance is conveyed by a single resistance gene (Mi), and it
is effective against M. incognita, M. arenaria, and M. javonica
but not against northern RNK (M. hapla). This resistance
does breakdown when soil temperatures rise above 80° to
90°F. So this resistance should only be used for cool season
plantings in areas where soil temperatures typically rise
above 80°F. In areas where resistant varieties have been
used repeatedly, nematode populations that are no longer
affected by this form of resistance can develop. Resistant
and susceptible cultivars should be alternated to prolong
the effectiveness of resistance by slowing the development
of resistance-breaking nematode populations.1,2 The use of
tomatoes grafted onto nematode resistant rootstocks is
another strategy that shows promise.
Plant parasitic nematodes do require the presence of a
susceptible host plant in order to feed and reproduce, so
rotating to non-host crops can reduce populations in some
situations. However, both RKN and sting nematodes have
very wide host ranges, including many vegetable and
agronomic crops, so finding a non-host can be difficult. It
may not be possible to find acceptable rotational crops that
are effective at reducing populations. A one- to two-year
rotation is usually effective, but the rotation may not be
economically justified. Careful weed management during the
rotation is also important, as many weed species are
susceptible hosts for these nematodes.1,2
Additional cultural practices that have been shown to be
effective for lowering nematode populations and yield losses
include the addition of organic soil amendments through
the use of cover crops and green manures, soil solarization,
soil flooding, avoiding the use of ditch and pond water for
irrigation, and the promotion of rapid decomposition of
plant root debris by discing fields shortly after harvest.1,2
In many situations, the use of chemical nematicides may be
required to adequately control nematodes on tomatoes.
Nematicides can be grouped into two general categories,
fumigants and non-fumigants. Fumigants are chemicals that
become volatile gasses when applied to the soil. They
disseminate through the soil and affect the target pests over
a period of time (weeks). Fumigants can be applied on a
whole-field basis, but it is more common to strip apply
fumigants under the plastic mulch in plasticulture-raised
bed systems (Figure 2). The fumigants are most effective
when applied to well-drained soils in seedbed condition at
temperatures above 60°F. Fumigants are most effective
against RKN when infested plant debris is removed or
allowed to decay prior to fumigation. All fumigants are
phytotoxic, so it is important to allow for a two to four week
plant-back period between application and the planting.
Longer periods may be needed when soil temperatures are
low. Fumigant products that are recommended for
controlling nematodes on tomato include those that contain
the active ingredients metam sodium or 1,3-
There are not many non-fumigant nematicides registered for
us on tomatoes, and they may not provide control that is as
effective and consistent as the do the fumigant nematicides.
Oxamyl (DuPontTM Vydate® L Insecticide/Nematicide) can be
applied as pre- and post-plant treatments on tomatoes
through soil treatment, foliar sprays, and through drip
irrigation systems. This product is not registered for use in
all states, and approved methods of application vary by
state, so it is important to consult up-to-date product labels
for information on where and how it can be used.1,2
1 Jones, J., Zitter, T., Momol, T., and Miller, S. 2014. Compendium of tomato diseases and pests, second edition. American Phytopathological Society, St. Paul, MN.
2 Noling, J. 2016. Nematode management in tomatoes, peppers, and eggplant. University of Florida IFAS extension, ENY-032.
3 Ploeg, A. 2013. Tomato: Root knot nematode. UC Pest Management Guidelines. University of California. http://ipm.ucanr.edu/PMG/r783200111.html.
For additional agronomic information, please contact your local seed
representative. Developed in partnership with Technology,
Development & Agronomy by Monsanto.
Individual results may vary, and performance may vary from location to location and from year to year. This result may not be an indicator of results you may obtain as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible. The recommendations in this article are based upon information obtained from the cited sources and should be used as a quick reference for information about nematode diseases of tomato. The content of this article should not be substituted for the professional opinion of a producer, grower, agronomist, pathologist and similar professional dealing with this specific crop. SEMINIS DOES NOT WARRANT THE ACCURACY OF ANY INFORMATION OR TECHNICAL ADVICE PROVIDED HEREIN AND DISCLAIMS ALL LIABILITY FOR ANY CLAIM INVOLVING SUCH INFORMATION OR ADVICE. 170808113844 100217DME
Seminis® is a registered trademark of Seminis Vegetable Seeds, Inc. © 2016 Seminis Vegetable Seeds, Inc.