Cultural Methods of Nematode Management

Rev 08/12/17

Strategies

Tactics

A. Reduction of the initial population.


(i) Fallow

6-18 months required for most plant-parasitic species; causes depletion of metabolic reserves; consider effect of increasing biological activity.

  • Heterodera and Globodera cysts - may remain viable for up to 14 years in an anhydrobiotic state or in the absence of a host cue.
  • Root survival may be an issue if root remnants are providing food for nematodes, e.g., surviving roots of grapevines may support survival of Xiphinema index for 4-5 years or longer.
  • For fallow to be effective, soil needs to be weed free. 
  • Fallow can be costly practice, in terms of land out of production and soil conservation - wind and water erosion can occur; soil structure may deteriorate.
A. Reduction of the initial population.
(ii) Flooding

Soil must remain flooded for 12-22 months to control root-knot nematodes. 

Need plentiful water supply, land must be level, or there will be engineering problems. 

Flooding is also expensive - land usually out of production.

In some cases, flooding can be an integral part of cultural practices.  Rice seeded in water has trace white tip infection by Aphelenchoides besseyi, but if sown and flooded later (usual practice in many areas), 60% of the crop may be infected. 

Celery grown in saturated soil (left) has lower nematode damage.

 

 

Jacq and Fortuner showed in Senegal that sulfur-reducing bacteria produced hydrogen sulfide in rice under anaerobic conditions and in the presence of high levels of organic matter, resulting in reduction of Hirschmanniella spinicaudata. They tested this tactic between rice crops and enhanced the effect by incorporating organic material and adding sulfur. Unfortunately, sulfides are also toxic to rice. 

Same beneficial effects of flooding are reported for banana plantations. 

Note the practical problem of keeping field flooded during the dry season in Africa.

A. Reduction of the initial population.

C. Increase in carrying capacity.

 

(iii) Cover crops

Nematode populations may decline due to several mechanisms

  • greater biological activity leading to population regulation through exploitation and antibiosis;
  • induced egg hatching;
  • increased soil manipulation and disturbance;
  • green manuring effect enhancing soil fertility and structure;
  • crop residues and breakdown products, organic acids, butyric acid;
  • trap crop effect - endoparasitic nematodes enter roots, but cannot complete their life cycle due to low temperatures;
  • note that non-target nematode species may increase under the cover crop.
A. Reduction of the initial population.

C. Increase in carrying capacity.

(iv) Crop rotation

Very effective, easy to select a candidate crop when host range is narrow and economic alternatives are plentiful, e.g., Globodera rostochiensis, Heterodera glycines, Ditylenchus dipsaci, etc.

However, 2-8 years of rotation to non-hosts may be necessary depending on survival of nematode and how low the population must be reduced to avoid economic crop loss.

Consult a host status list for nematodes known to be associated with a crop.

Consider: 

  • level of resistance of rotation crop to both target and non-target species;
  • host range of target nematode species
  • non-host survival of target nematode
  • economic value of rotated crop;
  • creation of new nematode or other pest problems;
  • potential benefits in soil fertility, structure and management of other soil pests and diseases.
B. Reduction of the rate of population increase. (v) Destruction of infested plants

Examples:

  • R-6-P program in tobacco production in North Carolina (F.A. Todd).  Designed to prevent another generation of root-knot nematodes by plowing out roots immediately after harvest.
  • Cotton plowdown in San Joaquin valley - prompt plowdown provides lower overwintering Meloidogyne incognita (and probably other) population levels - Goodell.
  • Cotton stalk destruction reduces post-harvest reproduction of Meloidogyne incognita in Georgia (Lu et al., 2010)
  • Roguing greenhouse plants to eliminate Aphelenchoides spp.
  • Roguing of coconut and other diseased palms to reduce sources of Bursaphlenchus (Rhadinaphelenchus) cocophilus.
  • Removal of infected pine trees to reduce pine wilt disease caused by Bursaphelenchus xylophilus.
  • Push and treat program in citrus in Florida to reduce movement of Spreading Decline and Radopholus similis infestations.
A. Reduction of the initial population.

B. Reduction of the rate of population increase.

(vi) Antagonistic crops, crop residues, biofumigation

Examples:

  • Some plants in the Compositae produce chemical products detrimental to nematodes - e.g., marigolds produce thienyl compounds. Usually effective against endoparasites and do
    not leach into soil - or perhaps must be ingested for effect, thus, interplanting and other approaches have not worked. Effect may be differential - marigold is a host of M. hapla.
  • Recent research directions by McKenry as a result of problems with nematicides - use of water extracts of plant residues involving plants in the Compositae; dripper application of extracts; development of soil drenchers.
  • Suggestion that thienyl compounds are more effective if light-activated, so possibly some misleading data from in vitro tests.
  • Asparagus - produces a glycoside toxic to nematodes - greater rate of population decline than under fallow soil or non-host crop.
  • Some grasses are thought to have toxic compounds, or perhaps create an unfavorable soil environment, e.g., low oxygen level - Eragrostis curvula.
  • Ferris and Zheng (1999) found effects on plant nematodes in about 30% of 150 plant sources of Chinese Herbal medicines;  some were also phytotoxic.
  • Current interests in biofumigants as nematicide replacements, including tarped applications.

 

A. Reduction of the initial population. (vii) Clean planting stock

Obvious reduction of initial population by not introducing nematodes into a clean field.

Consider:

  • Most of the pest nematode species in agriculture have been introduced.
  • Importance of certification, inspection and quarantine programs.
  • Sampling and detection problems.
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