A technological economic assessment of Spodoptera littoralis (boisd) : a pest of irrigated crops in Cyprus

Abstract

Appraisals of investment in pest control are complicated by the problems of predicting events in biological systems. In this study, an attempt is made to estimate the two necessary components of pest control investment appraisal, namely: the production function (decreases 1n crop losses with unit increases in pest control investment), and the pest damage function (relating crop damage to changing infestation variables), for attacks of the lepidopterous larvae of Spodoptera I1ttoralis (Boisd.), on Cypriot lucerne pastures. It is suggested that at present the best technique available to farmers for controlling S. littoralis infestations is the single application of one of three insecticides of proven efficacy. Consequently, the cost of successful pest control is represented by one value for a wide range of larval densities. The pest damage function is described as a dynamic relationship between a number of changing environmental and crop variab1es and is presented in the form of a computer simulation. This incorporates some of the existing empirical data on pest consumption and pest and crop interaction as well as much of the additional data collected by the author. The damage and production functions are compared, and estimates are made of the minimum larval density at various timings in the crop growth cycle, which is sufficient to cause losses equal to the treatment costs (the economic threshold of treatment). These estimates are offered as a basis for decision making on the economic control of S. littoralis in Cypriot lucerne fields.