Strategies

Tactics

(i)  Goodell (1983) showed that the population level of Meloidogyne incognita declined by about 40% each plowing after termination of a cotton crop in Kern County, CA.

(ii)  When nematode inoculum is incorporated with soil in a cement mixer for greenhouse experiments, many of the nematodes are killed by abrasion.  Parts of nematodes are recovered when nematodes are extracted from the mixed soil.

(iii) Rototilling of sandy soil killed 80% of a Paratrichodorus population within the rototilled zone in The Netherlands.  

(i)  Dry heat for sterilizing containers:  50 C for 30 minutes is effective.

(ii)  Flaming of metallic equipment - shovels, sampling tools, etc.

(iii)  Soil solarization.  Consider the energy cost of heating soil:

• 1 calorie is required to raise 1g water through 1C
• 1 acre of sand at 5% moisture contains 136,000,000 ml (=gm) soil solution - so 136,000,000 calories for each degree C elevation in temperature
• 1 acre of clay at 5% moisture contains 3.6 million liters soil solution (=3.6 billion calories per degree rise)

Therefore we need an inexpensive source of energy to heat soil sufficiently to kill nematodes.

Soil solarization may have potential (in the upper 12 inches of soil) where the following conditions occur:

• high solar output
• sandy soil
• low soil moisture
• shallow previous root depth
• limited areas (e.g., backyards)- consider tarp cost and disposal
• pots and soil in nurseries.

(iv) Burning brush or leaf litter has little effect  It may kill weed seeds and pathogens at the soil surface, but brush burning only killed Meloidogyne spp. in top 9 cm  of soil in Nigeria. Brush had to be burned on the soil surface for 45 hours to heat soil sufficiently to kill root-knot nematodes in the top 60 cm of soil (Caveness).

(i) soil for greenhouse use is often steamed.  The practice may have undesirable side effects.  These include toxic breakdown products of organic matter and release of minerals at toxic levels from organisms.

(ii)  The detrimental effects on beneficial organisms in the soil may create a biological vacuum and opportunities for colonizers, etc.  Consequently, the use of aerated steam is recommended (about 70 C), but not often used.
Penetration of soil with steam is a problem.  A permanent manifold for delivering steam may be installed in nursery beds.  This requires expensive infrastructure and preparation.

The use of hot water dips to eliminate nematodes from plant material is only effective when the thermal tolerance of the nematode is less than that of the plant material.

Usually there are specific temperature*time (thermal dosage) requirements to achieve lethal conditions for nematodes without causing damage to the plant material.

For example:

•  lesion nematode (Pratylenchus vulnus) can be killed by immersing grape roots in water at 51.5 C for 5 min
• Ditylenchus dipsaci can be killed in bulbs by immersion at 44 C for 1 hour.
  

any beneficial effects resulting from passing an electric current through soil are generally attributed to a heating effect.
e.g., work by Lear, Daulton and others in the 1950s.

(i) "The Zapper" was a large unit designed for delivering microwave energy to soil.  So far the results have been unconvincing.  The soil acts as a buffer; microwave energy does not penetrate well.