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Poster: Biology & Disease Mgmt: Chemical Control


Reducing initial infections of apple scab and black rot with salicylic acid and Actigard applied as trunk injections or sprays.
P. ABBASI (1), G. Braun (2), E. Bevis (2), S. Fillmore (2) (1) Agriculture and Agri-Food Canada, Canada; (2) Agriculture and agri-Food Canada, Canada

Apple scab [Venturia inaequalis] and black rot [Botryosphaeria obtusa] are two fungal diseases that affect apple leaves early in the growing season and also make fruit unmarketable at harvest. Salicylic acid has been found to induce plant defense mechanisms to reduce initial disease infections. In this study, salicylic acid and Actigard were applied as trunk injections and spray treatments to measure their effects on the development of apple scab and black rot on established apple trees (‘Honeycrisp’ and ‘Cortland’) in the field during 2014 and 2015. Treatments were applied at the tight cluster stage of bud development and again near bloom. Incidence of leaf infections was assessed in planta 7, 14, and 21 days after the second treatment and disease incidence on fruit was assessed at harvest. For injection treatments, the branch directly above the injection site was assessed. In 2014, salicylic acid and Actigard applied as trunk injection or spray treatments resulted in lowest black rot and apple scab incidences on leaves and fruit compared to the control treatment. In 2015, salicyclic acid and Actigard again showed a lower incidence of apple scab in the early stages of leaf infections only. No reduction in fruit infection was observed in 2015. Although salicylic acid and Actigard treatments showed a reduction in early leaf infections, apple trees must also be protected from secondary infections.