Nematode Control in Home Vegetable Gardens - ACES.edu

ANR-0030 A labama A & M and A uburn U niversities

Most gardeners are Nematode Control
familiar with problems in the Home
caused by diseases and Vegetable Garden
insects because such problems
are easily recognized. Few Figure 1. Most plant-parasitic nema- Figure 4. Watermelon plants in a root-
gardeners, however, are aware of todes are microscopic, wormlike ani- knot nematode-infested field displaying
the damage nematodes can cause. mals that live in the soil and damage yellowed foliage, a common aboveg-
plants by feeding on their roots. round symptom of nematode damage.
Nematodes are microscopic
(less than 1 mm long), wormlike Figure 2. Left, severe root damage Figure 5. Tomato plants infected with
animals too small to be seen from needle nematodes to a corn root-knot nematodes often exhibit yel-
with the unaided eye (Figure 1). plant’s root system (right, healthy root lowed foliage and a loss of plant vigor.
The majority of plant parasitic system) can impair the plant’s ability to
nematodes live in the soil and take up water and nutrients. Though there are at least 10
damage plants by feeding in different genera of plant parasitic
large numbers on the roots, Figure 3. Left, stunting of strawberry nematodes found in Alabama,
impairing the plant’s ability to plant (right, healthy plant) resulting the most important is the root-
take up water and nutrients. from severe root damage caused by knot nematode. Root-knot
Severe root damage (Figure 2) dagger nematodes. nematodes have a wide host
caused by nematodes typically range, but the most serious
results in aboveground symp- www.aces.edu problems occur on broadleaf
toms that may include stunting crops. Root- knot nematodes
(Figure 3), yellowing of leaves attack the roots of plants causing
(Figure 4), loss of plant vigor distinct knots, swellings, or galls
and/or an overall general decline to form on the infected roots
in plant performance (Figure 5). (Figures 6 and 7). Galls may
Damage is often more grow as large as one inch in
pronounced when plants are diameter where they merge, but
under other stresses such as lack usually they are not much larger
of water or nutrients or when than a pea. There are several
damaged by other diseases or different species of root-knot
insects. Although nematodes nematodes in Alabama and
rarely kill plants, they can drasti- several species may be present
cally reduce plant growth and
yields. Nematodes are usually
confined to localized areas in
the garden spreading very slowly
under their own power;
however, nematodes may be
dispersed more rapidly by
movement of infested soil
through cultivation, on soil
clinging to garden tools and
tillers, in water, or on roots
of transplants.

Figure 6. Distinct knots, swellings, or
galls visible on the root system of a to-
mato plant infected with root-knot
nematodes.

Figure 8. White to yellow adult females of soybean cyst nematodes visible on the
outside of a bean root.

Figure 7. Root-knot nematode galls Figure 9. Distinctive egg-containing brown cyst (dead soybean cyst nematode fe-
on tubers of Irish potatoes. male) may be seen on carefully removed and examined bean roots.

in any one location depending Site Selection Extension publication ANR-0114,
on which crops were grown “Collecting Soil and Root
previously (different species Consider nematodes when Samples for Nematode Analysis.”
have different host ranges), selecting a site for a vegetable
sources of contamination, and garden. Have the soil from the Sanitation
geographical region in the state. proposed area tested for nema-
Nematode species other than todes before planting. If possible, Sanitation aids in reducing
root-knot nematodes can cause collect soil in the fall when plant parasitic nematode popula-
damage to vegetables. These nematode populations are highest. tions. Nematode infected plants
species include dagger, reniform, The worst time to sample is in (including roots) should be
ring, stubby root, stunt, sting, root late winter or early spring. removed from the garden and
lesion, and cyst nematodes. With Nematode populations are at destroyed as soon as the vegeta-
the exception of the cyst nema- their lowest during this period bles have been harvested. This
tode, which produces distinctive and may not be detected in the practice can be particularly
egg-containing cysts on roots sample. Take samples with a soil effective in small gardens. Plow
(Figures 8 and 9), identification probe or hand shovel in a the garden immediately after the
of these other nematode species zigzag pattern across the garden final harvest to bring plant roots
requires laboratory analysis. area from the top 8 to 10 inches to the surface. Work the soil in
of soil. Mix samples thoroughly this manner two to four times
Nematode management and remove 1 pint of soil for during the winter. The drying
requires long-term planning. No laboratory analysis. Refer to action of the wind and sun will
current control practice will
permanently eradicate nematodes
from the garden. Nematodes can
be effectively managed in the
home garden by the use of one
or more of the following practices.

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Figure 10. Left, soybean cultivars resistant to soybean cyst nematode compared Use of Resistant
to various susceptible cultivars, center and right. Varieties

destroy many nematodes and should never be grown in the Resistant varieties offer the
their eggs, thus preventing same location more than once easiest, least expensive, and most
further buildup. Vegetable roots every three years. If space is effective method of controlling
left in the soil through the winter available, it is a good practice to nematodes in the home garden
serve as hosts on which nematodes rotate garden sites. Where garden (Figure 10). Unfortunately, resis-
can maintain or increase their space is limited, rotate related tant vegetable varieties are only
population for the following year. vegetables in one family group available for root-knot nema-
with vegetables in an unrelated todes and only for a limited
Crop Rotation family group. For specific family number of crops. Nematodes are
groupings, refer to Table 1. Crop unable to feed on a resistant
Rotating crops from year to rotation is not always an effective variety, resulting in a population
year can be an effective means strategy for controlling root-knot decline over time due to starva-
of controlling plant parasitic nema- nematodes because of their wide tion (as long as weed hosts of the
todes. Closely related crops are host range. However, rotating nematodes are also eliminated).
more likely to support the same crops in combination with Asparagus, onion, and strawberry
nematodes, diseases, and other fallowing or soil solarization can are resistant to most root-knot
pests than unrelated plants. A be used to manage most nema- nematode populations in Alabama.
particular vegetable or vegetables tode problems. Refer to Table 2 for vegetable vari-
belonging to the same family eties resistant to root-knot
nematodes. Also check seed cata-
Table 1. Plant Families logs each year to identify newly
released vegetable varieties with
Family Name Members resistance to nematodes.

Goosefoot Beets, Swiss chard, spinach Fallowing

Daisy Chicory, dandelion, endive, lettuce, marigolds, The practice of fallowing
sunflowers prevents any vegetation from
growing in the garden area, thus
Cabbage (crucifers) Alyssum, Bok choy, broccoli, Brussels sprouts, cabbage, starving the nematode popula-
cauliflower, collards, cress, kale, many oriental greens, tion. The target area must be kept
mustard, radishes, rutabagas, turnips completely weed free to prevent
nematodes from surviving on
Squash (cucurbits) Cucumbers, gourds, cantaloupes, pumpkins, squash, alternate hosts. One year of
watermelons fallowing will lower the nema-
tode population to a level where
Grass Barley, corn, oats, rice, rye, wheat an annual crop can be grown
successfully. The longer an area is
Pea or bean Alfalfa, beans (lima, pole, snap), lupines, peanuts, fallowed, the greater the decrease
(legumes) English peas, southern or field peas, soybeans in the nematode population.
Fall­owed soil should be roto-
Lily Asparagus, chives, garlic, leeks, onions, shallots (green tilled every two weeks to reduce
onions, bunching onions) weeds and to expose nematodes
to the sun.
Buckwheat Buckwheat, rhubarb, sorrel
Plant Stress Reduction
Mallow Okra, cotton
The less stress plants are
Morningglory Sweetpotato under, the better able they are to
withstand nematode attack.
Rose Brambles or caneberries, strawberries, apples, peaches Watering plants deeply and less
frequently will encourage the
Nightshade Eggplant, nicotiana, peppers, petunias, Irish potatoes, development of a deep root
tomatoes system that will reduce stress on
plants and can help minimize
Carrot Carrots, celery, chervil, dill, parsley, parsnips

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Table 2. Vegetable Varieties Resistant to Root-Knot Nematodes following a nematode suppres-
sive crop. Nevertheless, the use of
Crop Variety* a nematode suppressive crop has
been shown to be as effective as
Sweetpotato Cordner, Georgia Red (P), Heartogold (SPJ), Hernandez, or somewhat better than fallowing
Jasper (S), Jewel (S), Nugget, Red Jewel ( J), Resisto, an area to reduce the nematode
Southern Delite population. Refer to Extension
publication ANR-856, “Nematode
Southernpea California Blackeye #5 (S), Colossus 80 (SJ), Pinkeye Suppressive Crops,” for more
Purple Hull, Magnolia Blackeye, Mississippi Pinkeye, information on this technique.
Mississippi Purple (SJ), Mississippi Shipper (SJ),
Mississippi Silver (S), Zipper Cream (S) Organic Control

Beans (lima) Nemagreen Clandosan 618 produced by
Igene Biotechnology in Columbia,
Bean (snap) Alabama No. 1 (pole) Maryland, is an example of an
organic nematicide made of chitin
English pea Wando extracted from shellfish waste,
soybean meal, and urea. The
Pimento pepper Mississippi Nemaheart material works by increasing the
soil microorganisms that feed on
Tomato Beefeater VFN, Beafsteak Super VFN, Better Boy VFN, chitin. Chitin is one of the primary
Burpee’s Supersteak, Carnival, Celebrity, Early Girl, components in the body wall of
Hastings Red Chief, Jack Pot, Roma II, Lemon Boy, nematodes. The feeding activities
Monte Carlo, Patio Prize, President, Quick Pick, Red of the chitin-loving microorganisms
Express, Royal Flush, Small Fry, Sunripe, Sweet Chelsea have been shown to reduce the
(cherry), Sweet Million, Terrific VFN, Ultra Boy VFN, number of nematodes for two
Viva Italia cropping sequences. Control is
sporadic, however, and requires
*S = variety is resistant to the southern root-knot nematode; P = variety is resistant to large quantities of an expensive
peanut root-knot nematode; J = variety is resistant to the Javanese root-knot nematode. product. Chitin products should
be incorporated into the soil
nematode problems. Proper Suppressive Crops about two weeks before planting.
management of diseases and
insects can also reduce stress and Nematode suppressive crops Chemical Control
help reduce damage from nema- combat nematodes naturally.
todes. Nutrient deficiencies and Several plants minimize nematode There are no nematicides on
soil compaction can inhibit root damage in vegetable crops (Table the market that can be used by
development and increase plant 3). These plants produce nemati- homeowners. Currently, licensed
sensitivity to nematode damage. cidal (killing) and nemastatic pesticide applicators can still use
Nematode damage is more severe (suppressive) organic compounds metam sodium, a preplant fumi-
in sandy soils than in heavy soils. that are toxic to nematodes. These gant, on home gardens, but this
compounds are released from the chemical requires important safety
Addition of Organic roots of living plants or by plant’s precautions and may carry signifi-
Soil Matter being incorporated into the soil as cant legal liabilities. Therefore,
a green manure. Some plants may chemical control is not a viable
Organic soil amendments can act as trap crops that prevent option in home vegetable gardens.
improve plant health and vigor, nematodes from maturing and
but they must be incorporated reproducing once they invade the Soil Solarization
before seeding or transplanting. roots. Some marigolds, a few vari-
Amendments that improve the soil eties of chrysanthemums, Soil solarization is a simple,
composition, moisture retention, castorbeans, partridge peas, safe, and effective method of
or physical characteristics will several Crotalaris spp., velvet- nematode control. It allows the
help produce healthier plants. beans, and rapeseed are grower to bypass lengthy crop
Compost and pine bark are two considered nematode suppressive rotations and gives the added
amendments that can improve soil plants. Growing a nematode benefit of controlling other soil
conditions and plant health. Pine suppressive crop will not elimi- pests such as insects and weeds.
bark, which works best if fresh nate nematodes from the soil; Radiant heat from the sun is the
and ground into small pieces, has however, it may reduce nema-
been reported to help suppress tode numbers enough to allow
damage from root-knot nema- production of a crop in a nema-
todes. This should be done a tode infested area. Nematode
month or more before planting. populations often rebound to
pretreatment levels when a
susceptible vegetable is grown

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Table 3. Reaction of Nematode Suppressive Crops to Root-Knot Nematode many soil pests. Long, hot sunny
Species days are needed to reach the soil
temperatures required to kill soil
Root-knot Species pests and weed seed. The longer
the soil is heated, the better and
Suppressive Crop Southern Peanut Northern Javanese deeper the control of nematodes
and other soil pests will be. In
French Marigold ** ** ** — Alabama, a tarping period of 4 to 6
Tangerine — — — ** weeks in the summer should be
Happy Days ** — — — sufficient to kill nematodes and
Lemondrop — — — — soilborne plant pathogens. For
French Dwarf Double ** — — — effective spring or fall solarization,
** — — — a 6- to 8-week period is required
Chrysanthemum — ** — — to ensure good pest control. Refer
Escapade — ** — — to Extension publication
** ** — ** ANR-0713, “Soil Solarization for
Castor Bean ** ** — ** the Control of Nematodes and
Bronze King ** ** — ** Soilborne Diseases,” for more
Hale — ** — ** information on this technique.
— ** — **
Partridge Pea
Crotalaria ** — — **

Showy Crotalaria
Florida Velvetbean
Common Vetch

Cahaba White
Vantage, Nova II
Vanguard, Warrior
Rapeseed
Jupiter, Cascade, Elena
Indore, Humus,
Bridger, Dwarf Essex

** indicates a high level of suppression
— indicates no suppression or no available data

lethal agent involved in soil solar- ture zone. As a result, some
ization. A clear polyethylene damage may be seen on deep-
mulch or tarp is used to trap solar rooted crops, but those with
heat in the soil (Figure 11). Over a shallow root systems should
period of several weeks to a few escape serious injury.
months, soil temperatures become
high enough to kill nematodes, as The soil to be solarized must
well as many other soil pests and be cultivated until it is loose and
weed seed to a depth of 8 friable with no large soil clods or
inches. None of the pests will be debris. A roto-tiller will eliminate
completely eradicated, but their clods or other debris creating air
numbers will be greatly reduced, pockets that reduce heating of
allowing successful production of the soil or keep the tarp from
a crop. In sandy or sandy-loam fitting tightly over the soil
soils, nematodes may survive at surface. Make sure moisture
depths below the lethal tempera- levels are adequate for working
Figure 11.A clear polyethylene mulch the soil before laying the plastic
or tarp is used to trap solar heat in tarp. Use a clear, UV-stabilized
the soil. plastic tarp or sheeting 1 to 4
millimeters thick. The edges of
the tarp must be buried to a
depth of 6 inches in the soil to
prevent blowing or tearing by the
wind. White or black plastic
usually does not transmit enough
solar radiation to raise soil
temperatures to lethal levels for

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ANR-0030 Edward Sikora, Extension Plant Pathologist, Professor, Austin Hagan, Extension
Plant Pathologist, Professor, both in Entomology and Plant Pathology; Joseph Kemble,
Extension Horticulturist, Associate Professor, Horticulture; and William Gazaway,
former Extension Plant Pathologist, all with Auburn University

Use pesticides only according to the directions on the label. Follow all directions, precautions, and restrictions that are listed.
Do not use pesticides on plants that are not listed on the label.

The pesticide rates in this publication are recommended only if they are registered with the Environmental Protection Agency
and the Alabama Department of Agriculture and Industries. If a registration is changed or cancelled, the rate listed here is no
longer recommended. Before you apply any pesticide, check with your county Extension agent for the latest information.

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the number.

Published by the Alabama Cooperative Extension System (Alabama A&M University and Auburn University), an equal oppor-
tunity educator and employer.

4M, Reprinted May 2009, ANR-0030
© 2009 by the Alabama Cooperative Extension System.