Quarantine problems: an analytical approach with special reference to palm weevils and phytonematodes

摘要

Regulatory control can prevent further spontaneous introduction of alien pests to Egypt or slow down the rate of spread of several recently introduced plant pests and diseases, limit their damage and/or allow time to develop alternative management strategies. The problem essentially is the impracticability of detecting the pest at its initial infestation site at a sufficiently early stage to have any chance of eradicating it. Pest spread to secondary foci within the country should be blocked through quarantine and certification programmes. Recognizing that zero tolerance requires sampling every unit in the lot, the default strategy is to define an acceptable tolerance limit for each pest sampled. The binomial probability distribution is presentedas a base for determining probabilities of detecting various infestation levels as increasing numbers of samples are collected. Such a method saves time, labour and money in the detection and ensures the relative proportional certainty emanating from theinspected sample to the actual matter. However, a zero tolerance is required for the palm weevils. Neither Poisson nor the negative binomial distributions can be applied to such a zero tolerance or for soil sampling size to solely prove that the nematode is absent. Eventually, the tolerance limit must be backed up by sound technical information and consequent judgements for each specific case. Therefore, comprehensive precautions should be implemented for complete protection against pests and diseasesas yet not found in Egypt.