Determination of application time for chemical control of fire blight disease in pear varieties

Fire blight, caused by the bacterium Erwinia amylovora, is a serious disease of pear, apple, and other plants of the Rosaceae family. In this study, from the point of view of continuousness of protection of fire blight disease and shoot growth in growing season, application times and effectiveness of host resistance inducers, harpin protein, benzothiadiazole, prohexadione-Ca as alternatives to conventional products, streptomycin, copper and maneb+copper were evaluated on susceptible pear varieties in greenhouse and field conditions. Type 1 and Type 2 applications for prevention of the disease and Type 3 and Type 4 applications for evaluation of shoot growth were performed. Type 2 application of harpin protein gave remarkable effectiveness on prevention of the disease about 49% and 65% in greenhouse and field, respectively. After Type 1 and 2 applications by prohexadione-Ca and benzothiadiazole, disease severity significantly decreased comparing to applications of copper and maneb+copper and, controls. Only prohexadione-Ca applications significantly reduced shoot lengths and plants were highly affected by the application Type 4 of this chemical. According to findings, applications of Type 2 provided better results than Type 1 on all of pear varieties in greenhouse and field conditions and use of resistance inducing substances during the production season is proposed in managing of shoot blight phase of fire blight disease.