The 2010 ASHS Annual Conference

Fire blight caused by Erwinia amylovora, one of the most destructive bacteria, affects pome fruits and other rosaceaous plants. Growing shoots are a major site of the disease infection, that can be more difficult to control than bloom infection because the susceptible period is long and conditions favoring the disease are not well defined. Prohexadione Calcium (PC) is a plant growth regulator that reduces longitudinal shoot growth by inhibiting gibberellin biosynthesis without affecting fruit set or yield. PC represents an alternative to antibiotics or heavy metal for the control of fire blight. The growth response to PC treatment is dependent on several factors, including total dosage applied, application timing, crop load, cultivar treated, and geographic region. PC allows growers of pome fruits that have experienced excess vigor problems to limit shoot elongation, reduce pruning needs, reduce the incidence of fire blight disease, and maintain light penetration into the lower canopy for good flower and fruit development. PC gives only a transient effect because it disintegrates relatively rapidly and is effective only in young shoots. The strategy described provides a safe and effective control of secondary fire blight. In our researches on apple, pear, quince and loquat, hopeful results were obtained on control of fire blight disease.