ECONOMICS OF FORECASTING FOR CHEMICAL CONTROL OF BLACK BEAN APHID, APHIS-FABAE, ON FIELD BEAN, VICIA-FABA

The economics of a forecasting scheme for predicting the need for chemical control of the black bean aphid, A. fabae Scop., on spring-sown field beans, V. faba, are compared with alternative control strategies, namely no treatment, eradicant treatment and routine preventive treatment. Two criteria are assessed: the risk of lost revenue from wrong control decisions and the overall profitability of the strategy. A wrong decision is made when a profitable treatment is not applied or when an unprofitable one is applied. These constitute risk for the grower. The forecasting scheme involves least risk of monetary loss and the most acceptable alternative strategy is the routine preventive treatment. Relative to the routine treatment, a gain averaging .pnd.3.78/ha of bean crop would have been made between the years 1970-75 by adopting control based on the forecasting scheme. There was considerable year-by-year and area-to-area variation in monetary benefits, with the largest gains in areas where economic damage occurred least frequently and where relatively large areas of beans are grown, as in East Anglia [England]. Other benefits of using the forecasting scheme, e.g., correct timing of chemical application, are discussed but not evaluated.