FIRE BLIGHT SUSCEPTIBILITY OF SOME PEAR VARIETIES (ERWINIA AMYLOVORA, BURILL)

At Bistriţa Fruit Research and Development Station, in a pear collection, planted with 44 varieties, there has been studied the susceptibility to fire blight (Erwinia amylovora,Burill). During the vegetation period, phytosanitary treatments to control the disease have been applied using copper based products (copper sulfate, Champion, Funguran, Kocide). Erwinia amylovora infections have been influenced by the rainfall registered in April (70.9 mm) and May (104.7 mm) and the temperature fluctuations in April-May. The field observations on Erwinia amylvora attack demonstrate that the pear varieties have a different susceptibility to this dangerous bacterium. Evaluation of attack level in the pear collection was done using an evaluation scale with 9 scores using a reference resistance scale for : ‘Highly resistant’ , ‘Moderately resistant’, ‘Susceptible’, ‘Very susceptible’ cultivars . The most sensitive pear varieties in the collection were: ‘De Noiembrie’, ‘Abatele Fetel’, ’Daciana’, ’Triumf’, ’Williams Boway’, ’Margareta Marillat’, ’Beauty Tomme’, ‘Williams rosu’, ’Aromata de Bistrita’, ’Jeanne d`Arc’, ’Aramiu de Somes’, ’Belle des Arbres’, ’Zorka’ representing 13.64% of the total pear varieties. In several cultivars there have been observed increased symptoms, a very high susceptibility of infections leading to complete scorching of trees: Jeanne d`Arc’, Williams rosu’, ‘Triumf’, ‘Aromata de Bistrita’, ‘Zorka’. Strong attack symtoms were observed at the pear cultivars ‘Cure’, ‘Euras, ’Ciuda’ ‘Highland’, ‘Precoce Morettini’, ’Monica’, ’Cadillac’, ’Juliana’, ’Somesan’, ’Beurré Hardenpont’ these cultivars being susceptible to Erwinia amylovora , representing 40.91 % of total genotypes . Cultivars ‘Untoasa Geoagiu’, ‘Beurre Hardy’, ‘Trivale’ manifested a certain tolerance to Erwinia amylovora , no attack symptoms being observable at these varieties, in 6,82 % of total studied cultivars scores ranged between 8.0-8.22. Notably amount of genotypes were included in the “Moderately resistant” category (34.04 %) ‘Untoasa de Transilvania’, ‘Starkrimson’, ‘Josephine des Malignes’, `Untoasa Bosc`, ‘Magnes’, ‘Contesa de Paris’, ’Doina’, ‘Napoca’, ‘Carpica’, ‘Karamanka’, ‘Williams’, ’Expozitie’, ’ Ina Estival’, ‘Passe Crassagne’, ‘Conference’.