Biological Insecticides contra Insect Growth Regulators in Polish Forestry — a Financial Cost-Benefit Analysis

Abstract

Strategic decision-making within integrated forest pest management is often mistakenly based on a short-term treatment cost evaluation. A modelling framework is presented having a long-term perspective focused on the environmental impact associated with two groups of control agents — insect growth regulators and biological insecticides. The analysis is linked to the dynamical ecophysiological processes in a pine forest soil, based on the decomposing role of the soil fauna biomass in the ecological system. A considerable part of the soil fauna biomass depends on chitin formation and deposition which is halted by the presence of an effective insect growth regulator on the litter. The persistency of Dimilin (an insect growth regulator) on leaf surfaces has been reported to be up to 12 months, as opposed to biological insecticides having a short persistency of up to two weeks. Therefore, a subsequent mortality of elements of the soil fauna may block the release of nutrients associated with decomposition of litter and lead to a reduction of the growth and yield of the stand. A sensitivity analysis of the incremental cost is performed by use of a long-term dynamic linear programming model for the state forest area of Poland, leading to a financial cost-benefit analysis. Based on historical Polish data on treatment of defoliating forest pests it is found that a possible yield reduction of approximately six per cent of the treated forest area seems to make a biological insecticide more profitable than an insect growth regulator, in despite of the annual treatment cost per ha of the former being considerably lower.KeywordsIntegrated forest pest managementeconomic result evaluationbiological pesticidesinsect growth regulatorslinear programming