Primary Objectives For Sampling
1. Detection and Survey
- Quarantine and phytosanitary regulations of many countries/states require that planting materials (root stocks, rhizomes etc) be produced on land certified to be free of certain nematodes.
- Sampling for certification requires extreme precision for detection and quarantine of pests.
Sampling must be intense but only requires presence/absence data = nonquantitative = qualitative. May require 20-100+ cores/5 acre section (combined into one composite sample).
- Important point - absence of detection does not necessarily indicate an absence of a pest but only suggests that the population is below some given density of detection, which may or may not be zero.
- Thus, detection sampling should be combined with good sanitation practices to reduce the chance of introducing nematodes into a new area.
2. Diagnosis of Disease Problems
- Without sampling, poor plant growth due to nematodes may be misinterpreted as nutrient deficiencies or other maladies or attributed to nematodes when nematodes are not the cause.
- This type of sampling is more limited and less intense, usually collect soil and roots from diseased plants and nearby healthy ones and look for differences in kinds or densities of nematodes = "qualitative".
- Nematode populations and therefore nematode damage often occurs in patches surrounded by acres of low nematode density and healthy plants.
- Best to sample at edge of area with symptoms rather than in the center of patch where symptoms are most severe.
3. Advice for IPM programs or Nematode Advisory Services
- Used to relate initial population densities with yield to develop advisory standards for making management decisions.
- Must sample sufficiently to get a reliable density estimate = "quantitative".
- Because of the importance of reliable detection, sampling is generally conducted when populations are near their maximum, often after harvest. This, of course, does little to aid the yield of the present crop just harvested but is intended for making management decisions for the following crop.
- With perennial crops periodic repeated sampling may be necessary since non-detectable levels may increase to damaging levels over the life of the crop.
4. Research Needs
- Much effort must be invested in collecting soil or plant tissues for experimentation or studying population dynamics.
- Design and intensity of sampling may need to be modified for specific types of experiments, often desire a precision of 10% or better so need to, and probably can afford to, take more samples.