Optimising import phytosanitary inspection

Keywords: quarantine pest, plant health policy, optimization, import phytosanitary inspection, ‘reduced checks’, optimal allocation of resources, multinomial logistic regression, the Netherlands World trade is a major vector of spread of quarantine plant pests. Border phytosanitary inspection is a major barrier against introductions of quarantine pests through imported commodities, although the inspection resources are limited. This thesis provides conceptual and empirical insights that may help optimise import inspection under limited resources. The developed conceptual models analysed inspection policies under capacity constraints and in the absence of capacity constraints. The empirical models focused on finding the optimal inspection policies of propagating materials imported in the Netherlands. The results indicate that inspection effort should focus on commodities, whose inspection yields ceteris paribus greater marginal reduction in the expected costs of pest introduction. The results show that under binding capacity constraints, inspection of chrysanthemum cuttings in the Netherlands has a high marginal benefit, ranging from 8 to 49 euros for every marginal euro of inspection cost. The results further indicate that in the presence of fixed inspection costs, attaining the unconstrained allocation of inspection effort from the current, capacity constrained levels, is relatively inexpensive and greatly reduces costs to society. To expand current inspection capacities, the costs and likelihoods of pest introduction should be carefully estimated. Using the developed models for optimal allocation of inspection resources, the efficacy of the ‘reduced checks’ import inspection system in the EU was analysed. The results indicate that the expected costs of pest introduction in the EU under reduced checks could further be reduced if the economic impacts of pest introduction through various commodities are accounted for when calculating the frequencies of reduced checks. Finally, a multinomial logistic model was developed to analyse factors that determine the likelihoods of rejecting imported commodities due to phytosanitary and non-phytosanitary reasons. The results suggest that the geographical position of the exporting country, the characteristics of the importing company, the size of imported shipments, and the intended use of the commodity, among others, are significant factors based on which shipments of plant commodities can be targeted for inspection. Inspecting agencies can considerably facilitate the design of optimal inspection frameworks for the management of import phytosanitary risks by sound data-recording procedures that enable scientific analysis and provide a solid basis for reliable and applicable results.