An assessment of the potential economic impact of Thrips palmi on horticulture in England and the significance of a successful eradication campaign

Abstract

Thrips palmi has not become established in England, yet its potential introduction represents a continuous threat to glasshouse ornamental and vegetable crops. The first outbreak of T. palmi in England occurred at a site of chrysanthemum production in southern England during 2000. The statutory eradication of the pest imposed significant financial costs on both the producer and Defra Plant Health Service. The use of additional insecticides, methyl bromide soil sterilisation, imidacloprid-treated compost, plastic sheeting to cover the growing media and associated additional labour costs during the eradication campaign resulted in a six-fold increase of expenditure on pest control. The estimated eradication costs for the grower exceeded £56,000 for the period April 2000 to July 2001. If eradication had not been achieved, T. palmi may have spread to establish in protected cultivation throughout England. The net present value of the economic impact of T. palmi over 10 years is estimated to be between £16.9 and £19.6 M depending upon the rate of pest spread. Impacts include yield and quality losses, additional research, plant health certification costs and loss of exports. Although there is uncertainty as to whether revenue from exports liable to carry T. palmi would be lost, if they were lost they would be the most significant contributor to the overall economic impact. Without loss of exports, impacts fall to between £0.6 and £3.3 M over 10 years. Benefit:cost ratios for eradicating the outbreak and maintaining an exclusion policy towards T. palmi range from 4:1 to 19:1 if there is no loss of exports, and from 95:1 to 110:1 if significant export losses did result from T. palmi establishment.