TEN YEAR SUMMARY OF FIRE BLIGHT PREDICTION IN SOUTH-WEST GERMANY (1994-2003)

Due to the heavy outbreak of fire blight in 1993 Plantomycin (streptomycin sulfate) is allowed to be sprayed during bloom according to the advice of the plant protection service since 1994. For timing of the applications the risk assessing system Billing’s Integrated System 95 (Billing, 1996) and the prediction model Maryblyt™ (Steiner, 1990; Steiner and Lightner, 1996) were transferred into a computer program.
In general, both systems indicated the same infection risk days.
The weather data during apple bloom from two locations, which are representative for the fruit growing region of South-West Germany, were evaluated by the Maryblyt™ model and summarized from 1993 to 2003 (Table 1 and 2). Fire blight has been widespread since 1993 in the district of Heuchlingen (Table 3). In Ailingen, near Lake Constance, fire blight has spread through the district during the last ten years (Table 4). The Maryblyt risk estimation of ‘high’ was separated into two classes, ‘H’ and ‘h’, depending on which requirements were fulfilled. ‘H’ represented cases where open blossoms and accumulation of degree days (temperature) were fulfilled, but not wetness or daily average temperature. ‘h’ represented cases where open blossoms, wetness, daily average temperature were fulfilled, but not accumulation of degree days (temperature). In many cases, wetness resulting from dew is judged subjectively.
In our analysis, leaf wetness lasting more than 2 hours was evaluated as heavy dew.
However, in several years infections occurred even without wetness measured by this method.
Therefore, the infection risk assessment of ‘H’ was considered to represent a similar risk of infection as the highest Maryblyt infection risk assessment of ‘I’.

X International Workshop on Fire Blight

E. Moltmann

Erwinia amylovora, prediction system, Maryblyt™, risk assessment system, Billing¿s Integrated System 95, control, streptomycin

https://doi.org/10.17660/ActaHortic.2006.704.22