SIMULATIVE ANALYSES OF APPLE AND PEAR BLOOM RISKS IN BULGARIA WITH MARYBLYT 4.3

Fire blight is wide spread in Bulgaria and the forecast of the disease could be a valuable tool in optimizing control. So far, no predicting systems have been officially introduced and MARYBLYT 4.3 is one of the potential models. Using that system and the available meteorological and phenological data (1985-2007) from the region of Plovdiv, more than 120 analyses on apple and pear bloom epidemiology were done. Principle lack of information concerning the exact time of petal fall led to a simulative extension of the blooming periods with 7 (3+4) and 5 (3+2) days in apple and pear, respectively. Furthermore, fire blight risk was analyzed on the base of information registered in different regions of the Southern and Northern parts of the country for three consecutive years (2003–2005). The simulative extension seemed to be a valuable approach and helped to outline more precisely the bloom epidemiology itself. In general, the prediction signals from the system have had very good correlation with the fire blight damages observed in the region of Plovdiv. It was also established that about 70% of the years were risky and every third year could have infections in ‘Golden Delicious’ (23-year period) whereas the earlier blooming cultivar ‘Red Delicious’ (18 years) and the pear species (15 years) were less threatened. The predicted fire blight blossom strikes for the three-year period in different country regions were relatively similar, following mainly the global season’s characteristics. An exception in the epidemic years was the Black Sea coast strip where the bloom periods pass under lower temperatures and such attacks rarely take place. The promising results supposed a benefit once MARYBLYT is introduced into the practice of the country.