Trials with applying chemical agents other than bactericides to control fire blight in pear orchards

Trees of pear cultivars in mature Orchard A (in 2000) and Orchard B (in 2001) in SW Hungary and NE Hungary, respectively, located under different climatic conditions, were treated with the systemic acquired resistance inducers benzothiadiazole (BTH) as Bion 50WG and prohexadione-Ca as BAS 125 10W, and with the leaf fertiliser Biomit Plussz, either alone or in combination with the copper-oil Vektafid R. Streptomycin 20WP (0.5 kg/ha) was sprayed as obligatory treatment in all experimental plots, once in Orchard A and twice in Orchard B. As compared with the check, the incidence of shoot blight in Orchard A was significantly reduced by treatment with Bion 50WG (15 g/100 L), Biomit Plussz and Biomit Plussz + Vektafid R ('Williams') and by treatment with prohexadione-Ca ('Conference'). Prohexadione-Ca also proved more effective than Bion 50WG 15 g/100 L ('Beurre Bosc'). In Orchard B, only minor differences were found between the effects of the products used. In comparison with the check, a certain but not significant effects of Bion 50WG ('Conference' and 'Olivier de Serres'), prohexadione-Ca ('Conference' and 'Beurre Bosc') and Biomit Plussz + Vektafid R ('Beurre Bosc') were observed.