Pest Surveillance and Forecasting

Survey and Sampling

  • Survey: Survey is a planned activity to collect some data.
  • Surveillance: When survey of the same area/ plot or locality is carried out at regular intervals to record some observation or to ascertain the changes in the subject of study, it is called as surveillance. In other words pest surveillance is the close and constant vigil on insect population in a particular area.
Objectives of survey and surveillance:
  • To monitor the pest population and /or damage regularly to arrive at a decision whether control measures are required or not, if required when to initiate the control measures.
  • Pest forecasting with reasonable precision.
  • Endemic areas of various pests may also be marked
  • To predict future population trends or the corresponding potential damage to the crops or both
Types of survey:
  • Qualitative: To identify the different insect species present over an area or their density whether abundant, common, rare, in traces, etc
  • Quantitative: To estimate the exact number of one or more species of insects in time and space.
Sampling insect populations:
  • In quantitative survey a count of insects is required.
  • Due to large number and/or secretive nature it is not possible or even desirable to count each and every individual in a population.
  • Hence more efficient method is by sampling.
  • Randomization and the choice of sampling unit are the fundamentals of sampling.
  • The total number of samples to be taken depends upon the degree of precision required
Sampling unit:
  • Sampling unit is a portion of the habitat from which insect counts are to be made e.g. a plant, branch, leaves or fruiting bodies, a clump, a micro plot of 1 m2, etc.
  • Sampling unit must be distinct and should not overlap.
Sample: A group of sampling units from which an estimate is made.

Sampling technique: It is the method used to collect information form a single sampling unit.

Sampling programme: Sampling programme is the procedure that employs the sampling technique to obtain sample and make a density estimate.

Sampling programmes:

Extensive programmes:

  • Conducted over a large area to determine information like species distribution, status of injurious insect stages.
  • Usually a single insect stage is sampled.
  • Only one or few samples are taken per season.
  • Only moderate levels of precision are required and emphasis on low cost.
Intensive programmes:
  • Conducted as part of research in population ecology.
  • Here sampling is done frequently, in a small area
  • All or most stages in the life cycle are sampled
  • High degree of precision in sought

Last modified: Saturday, 3 March 2012, 9:28 AM