Evaluation of a revision of the BSPcast decision support system for control of brown spot of pear

Abstract

Control of brown spot of pear requires fungicide treatments of pear trees during the growing season. Scheduling fungicide sprays with the Brown spot of pear forecasting system (BSPcast) provides signifcant fungicide savings but does not increase the effcacy of disease control. Modifcations in BSPcast were introduced in order to increase system performance. The changes consisted of: (1) the use of a daily infection risk (Rm≥0.2) instead of the 3-day cumulative risk (CR≥0.4) to guide the fungicide scheduling, and (2) the inclusion of the effect of relative humidity during interrupted wetness periods. Trials were performed during 2 years in an experimental pear orchard in Spain. The modifications introduced did not result in increased disease control efficacy, compared with the original BSPcast system. In one year, no reduction in the number of fungicide applications was obtained using the modified BSPcast system in comparison to the original system, but in the second year the number of treatments was reduced from 15 to 13. The original BSPcast model overestimated the daily infection risk in 6.5% of days with wetness periods with low relative humidity during the wetness interruption, and in these cases the modified version was more adequate.