FIRE BLIGHT RISK ASSESSMENT DURING BLOOM IN AN EXPERIMENTAL ORCHARD USING BIS (BILLING INTEGRATED SYSTEM)

The value of BIS for blossom blight risk assessment was studied from d ata collected in an experimental orchard in south-west France. Trees o bserved included mature commercial pear and apple trees and some young trees in experimental plots. There was a weather station in the orcha rd and beehives were present. Field records included flowering times o f the pear and apple cultivars studied (mostly Passe-Crassane and Beur re Hardy, Royal Gala and Golden Delicious) and dates when blossom blig ht was first seen on each cultivar. Between 1980 and 1991, records of blight were available for 25 cases. In most cases, one or more infecti on risk (IR) days, as defined for BIS, could be found during bloom. DD 13 mean sums (sums of degree days above a mean temperature of 13 degre es C) gave good guidance on times when early signs of blossom blight w ere present in 14 cases. There was only a slight divergence from BIS g uides in a further five cases. Possible reasons for divergence and for non-fit in the remaining six cases are discussed. It is concluded fro m this study that BIS should give useful guidance on optimal times for protective spray applications and for timing of searches for signs of early blossom blight in south-west of France. Graphical presentations of data provide additional information.