GUIDANCE ON THE USE OF BILLING'S INTEGRATED SYSTEM (BIS) FOR FIRE BLIGHT RISK ASSESSMENT

Billing’s integrated system (BIS) was designed for use with all host plants throughout the growing season. It can be used for optimal timing of applications of protective agents and searches for early signs of disease following infection. Weather forecasts can be used if desired. The methods for use of BIS have been clarified and suggestions are made regarding appropriate adaptations that do not undermine the basic principles of the system. These include the use of degree hour sums in some climatic areas and of wetness recorders to supplement dewfall observations. BIS graphics show patterns of weather and events and are a valuable aid for following risks throughout the growing season and for exploring possible reasons why some cases failed to fit the predictions. Users of BIS should be warned that BIS, and two earlier systems that it replaced, have sometimes been misquoted, misrepresented or modified. Evaluations were confined to blossom periods; infection risk scores were omitted or wrongly considered to be guides to disease incidence; incubation (disease development) periods following an infection risk day were confused with infection periods; the pathogen population associated with symptom expression was wrongly stated as the dose necessary for blossom infection; daily rainfall records were replaced by wetness records. BIS requires further testing alongside other models and systems. Risk assessment systems are working hypotheses and need continual critical testing by users. It remains to be seen how far fire blight management can be improved by including the assessment of risks outside the primary blossom period.