This document discusses various cultural strategies for nematode management using plants, including using non-host crop rotations, green manure cover crops, antagonistic plants, trap crops, and resistant cultivars. It provides examples of different plants used in each strategy and their effects on nematode populations, such as marigolds and cruciferous plants which can reduce populations through nematicidal compounds in root exudates. Trap crops are discussed as a way to attract and trap sedentary nematodes before they can reproduce. Early planting and harvest is also summarized as a strategy to avoid nematode damage by escaping high nematode activity periods.

1. Cultural Strategies for Nematode Management
Nematode Management With Plants
- No plants – fallow
- Nonhosts – crop rotation
- Green manure cover crops
- Antagonistic plants
- Trap crops
- Resistant cultivars
- Timing of planting and harvest to avoid damage
= “escaping in time”

2. ANTAGONISTIC PLANTS
A number of plants are antagonistic to nematodes.
Mechanism of “antagonism” is not always clear.
Need more study as potential sources of suppression.
Used as a rotation crop, cover crop, or an intercrop.
Some are simply “nonhosts” due to some
biochemical or physical incompatibility between the
nematode and the plant.

3. ANTAGONISTIC PLANTS
However, others appear to produce some kind of
chemical exudate that acts nematicidal.
In other cases, the growing plant is not particularly
nematicidal, but the decomposing plant, when
incorporated as a green manure, displays nematicidal
properties.
Rapeseed is a host for Pratylenchus penetrans but a
green manure amendment of rapeseed tops can reduce
P. penetrans populations.
It may also be possible that the growing or
decomposing plant encourages microbial antagonists.

4. ANTAGONISTIC PLANTS
“Antagonistic plants” have not been studied
extensively in developed countries but are commonly
studied in developing countries.
Interest has increased as nematicides are lost.
Information often comes from anecdotal observations.
Literature often hard to retrieve since most research is
done and published in undeveloped countries.
Will go through the more prominent examples.

5. Marigolds - Tagetes
Few nematodes reproduce well on marigolds.
Apparently does not affect the eggs of cyst nematodes.
French marigolds - growth period of 3-4 months (16
varieties tested) necessary to reduce Pp populations.
African marigolds reduced Pratylenchus penetrans;
yield of the following crop of Daffodil was doubled.
Population decline is due to nematicidal action of
root-diffusates (terthienyl and bithienyl compounds)
Minimum lethal dose = 0.2-5 ppm! Kill in soil?
Have to be careful! Sap and diffusates can burn skin,
can also be phytotoxic.

6. EFFECTS OF GREEN MANURE COVER CROPS
ON PRATYLENCHUS PENETRANS
Population Densities 16 weeks after Planting
NEMATODES/POT
4500
Plants were clipped to 10 cm at 8
and 12 weeks to simulate mowing
4000
3500
3000
Unclipped
Clipped
2500
2000
**
1500
Initial Density
1000
500
0
D-ESSEX
TRUDAN
STEPTOE
SAIA
TANGIA
Marigold

7. Cruciferae
Sinapsis alba = white mustard
Brassica hirta = white mustard, called yellow mustard
Brassica nigra = black mustard
Lepidium sativum = cress
All inhibited emergence of Globodera rostochiensis J2,
Suppress Meloidogyne chitwoodi, Stubby-root?
Attributed to isothiocyanate (remember MIT?) from
glucosinolates in root diffusate.

8. Asparagus
Produces glycoside “aspargic acid”
Inhibits juvenile emergence from cyst eggs and is
toxic to several nematodes.
Reduced numbers of Paratrichodorus minor and had
systemic nematicidal properties when sprayed on
tomato roots.

9. Crotalaria
Crotalaria juncea – Sunn Hemp
Being used as a cover crop in tropical and subtropics
Crotalaria spectabilis (Rattlebox) = suppress nematodes
when used in various cropping sequences.
May be due to the alkaloid monocrotaline =
pyrrolizidine ester
- Inhibited mobility of Meloidogyne incognita.
However, other plants with this compound are
susceptible.

10. Neem
= many medicinal properties = “Nature’s Drugstore”
Parts of the plant as well as seed-cakes (seed remnants
after oil is removed) are highly nematicidal. .

11. Neem
Intercropped seedlings suppress Meloidogyne
incognita and Rotylenchulus reniformis on tomato as
well as Tylenchorhynchus brassicae on cabbage and
cauliflower but free-living nematodes remained high.
Root exudates seem to be toxic to many nematodes.
Inhibit hatching of M. incognita.

12. Neem
Mixed cropping with neem is often impractical.
An organic amendment with neem seed-cakes is a
little more practical.
Neem may serve as a model for developing new
control strategies and new nematicidal compounds
that could be commercially produced.
This stresses the importance of plant diversity and
looking for naturally occurring compounds.
Often nematode control with an antagonistic plant can
be enhanced by incorporating it as a green manure.

13. Cultural Strategies for Nematode Management
Nematode Management With Plants
- No plants – fallow
- Nonhosts – crop rotation
- Green manure cover crops
- Antagonistic plants
- Trap crops
- Resistant cultivars
- Timing of planting and harvest to avoid damage
= “escaping in time”

14. Trap Crops
Plants which are good hosts for sedentary parasites.
Nematodes are allowed to infect the plants, and then
the plants are killed, trapping the nematodes inside
where they die before they can lay eggs.
Particularly effective for species that require a host
exudate to hatch (i.e. cyst nematodes)
Does not work for ectoparasites or migratory
endoparasites that are not “trapped” in roots.
Initial concept was to use susceptible commercial
cultivars, which could result in population increase
if the plants were not killed before females laid eggs.

15. Trap Crops
Recently, cultivars have been developed specifically
as trap crops (radish for sugar beet cyst nematode).
These cultivars may be attractive to the nematode
for invasion but may lack nutritional requirements
for females to develop and lay eggs.
This allows the plant to be grown longer and
provide some of the other benefits from cover crop
such as building organic matter, weed suppression
and increasing beneficial microbial populations.
Practiced more in developing countries.

16. Susceptible Tobacco as a Trap Crop
to Reduce Tobacco Cyst Nematode
% of Starting Density
140
120
100
80
60
40
20
0
3 WKS
4 WKS
5 WKS
6 WKS
13 WKS
Period of Growth Before Plant Destruction
P
LaMondia, 1996

17. Tobacco as a Trap Crop
to Reduce Tobacco Cyst Nematode
% of Starting Density
140
Susceptible
Resistant
120
100
80
60
40
20
0
3 WKS
4 WKS
5 WKS
6 WKS
13 WKS
Period of Growth Before Plant Destruction
P
LaMondia, 1996

18. Cultural Strategies for Nematode Management
Nematode Management With Plants
- No plants – fallow
- Nonhosts – crop rotation
- Green manure cover crops
- Antagonistic plants
- Trap crops
- Resistant cultivars
- Timing of planting and harvest to avoid damage
= “escaping in time”

19. Nematode Management by
Early Planting and Harvest
Nematodes are limited by cool soil temperatures.
For crops that tolerate cool temperatures
planting early can give the crop a “head start” before
temperatures allow nematode activity to cause
substantial damage.
Once the crop develops a sufficient root system it can
tolerate a moderate density of nematodes when they
do become active.
Earlier planting can also result in an earlier harvest
and crops can be removed before damage can occur.

20. Examples
Sugarbeet seed germinates at cool spring
temperatures before sugar beet cyst nematode
(Heterodera schachtii) becomes active.
Planting early when it is cool allows the plant to
develop a robust root system that can tolerate a larger
nematode population when soils warm later.

21. Examples
Cereal cyst nematode (Heterodera avenae) hatch and
infect roots in the spring.
Fall-planted cereals are larger than spring-planted
cereals when nematodes begin infecting roots so
plants tolerate nematodes better, are not as stressed,
and yield reduction is less.

22. Examples
The first generation J2 of Northern root-knot
nematode (Meloidogyne hapla) infect roots of potato
when soil temperature is warm enough.
Second and later generations infect tubers as well as
roots. If potato is planted and harvested early, you
can avoid most or all nematode infection of tubers.
Any nematodes in tubers will not develop in storage
because temperatures are too cool, symptoms will not
be expressed.

23. Examples
This will not work for Columbia root-knot nematode
which becomes active at cooler temperatures and
infects potato roots much earlier.
Therefore, second generation J2 emerge earlier and
infect tubers before they are large enough to harvest.
Columbia root-knot nematode also can continue to
develop under some storage temperatures so
symptoms can be expressed in storage.