Field evaluation of a brown spot disease predictor as a system for scheduling fungicide sprays for control of Stemphylium vesicarium on pear
2002
Llorente, I. | Moragrega, C. | Vilardell, P. | Montesinos, E. | Bugiani, R. | Govoni, P. | Gherardi, I.
A forecasting model for prediction of brown spot of pear was developed from previous research (BSPcast/STREP). The objective of our study was to evaluate this model for scheduling fungicide sprays in pear orchard plots naturally affected by brown spot. The BPScast model quantifies the relationship between wetness duration and mean temperature on disease severity. Every 24 hours the model generates a daily risk (R) and a 3-day cumulative risk index (CR). Values of CR were used as thresholds for spraying fungicides. Eleven trials were performed during 1995, 1996, and 1997 in five pear orchards of two different climatic areas in Girona (Spain) and Emilia-Romagna (Italy). Fungicides used were thiram, procymidone and kresoxim-methyl and the thresholds tested were CR:0.4, CR:0.5 or CR:0.6. Field evaluation of the forecasting model consisted of comparing disease control levels for fungicides applied according to the model with those from the standard commercial schedule. Disease control on fruits with the fungicide thiram and CR:0.4 or CR:0.5 thresholds was similar to the fixed spray schedule, but saving 25-50% of fungicide sprays. The use of a CR:0.6 threshold showed a lower efficacy than fixed sprays but it saved about 50-70% of applications. The efficacy using procymidone or kresoxim-methyl with CR:0.4 was similar to fixed sprays but saving 70-75% and 20% of procymidone or kresoxim-methyl fixed sprays, respectively.
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