SPRAYCHECK - A MODEL FOR EVALUATING GROWER TIMING OF BLACK SPOT (VENTURIA-INAEQUALIS) FUNGICIDES IN APPLE ORCHARDS

A computer program, SPRAYCHECK, was developed to analyse grower black spot fungicide spray programs during the period of primary inoculum re lease. The program, consisting of a series of models, uses weather dat a, infection periods and information from growers' spray diaries to an alyse grower black spot control decision-making, It also provides a re commended spray schedule for the season in question. Central to the pr ogram is a cover decay model which assesses whether or not the crop is protected from ascospore infection by previous fungicide applications . This model includes the effect of rainfall. Constructing the model r evealed a lack of quantitative information regarding behaviour of fung icides and the levels required to fully protect against black spot on apple foliage in the field. A sensitivity analysis revealed the rate o f cover decay to be very important in determining the number of fungic ides a grower would need to apply to fully protect his crop. (C) 1998 Elsevier Science Ltd. All rights reserved.