EFFECTS OF TEMPERATURE ON THE LENGTH OF THE INCUBATION PERIOD OF FIRE BLIGHT ON APPLE, PEAR AND HAWTHORN

The effects of temperature on the length of the incubation period of fire blight following infection on apple, pear and hawthorn were studied using data from 61 historic cases, of which 19 were for apple blossom.
The length of the incubation period ranged from 2 to 66 days and was usually well estimated.
Hourly temperatures were estimated using a sine-curve from daily maximum and minimum temperatures.
Models of both linear and non-linear types were fitted to the hourly temperature data (not to the average temperature of an entire incubation period or to daily average temperatures) using a rate summation method to relate the rate of disease development during the incubation period to temperature.
Non-linear models failed to fit the data because of a very low frequency of maximum temperatures that were greater than 25°C. Linear models fitted the data best only when hourly temperatures greater than 12 or 13°C were included, i.e. the rate of disease development was assumed to be zero for temperatures below the threshold.
The results showed that the rate of disease development was usually much slower on apple blossoms (15 out of 19 cases) than pear and hawthorn blossoms and shoots.

VIII International Workshop on Fire Blight

X.-M. Xu, E. Billing

Erwinia amylovora

https://doi.org/10.17660/ActaHortic.1999.489.81