Comparative assessment of phosphite formulations for apple scab (Venturia inaequalis) control

Abstract

Potassium phosphite is a widely used plant protection agent. However, a suite of phosphite formulations with alternative cation attachments (calcium, copper, silicon, zinc) are commercially available. The plant protective properties of these formulations have received little attention. This study evaluated five phosphite formulations for plant protection purposes against the foliar pathogen apple scab (Venturia inaequalis) under field conditions. In addition, a comparative analysis against the synthetic fungicide penconazole, which is widely used for apple scab control, was conducted. Greatest reductions in leaf and fruit scab severity were achieved by sprays of the synthetic fungicide penconazole. However, all phosphite formulations evaluated significantly reduced leaf and fruit scab severity at the cessation of the growing season. Within the phosphites tested, the greatest reductions in leaf and fruit scab severity were achieved in the order: copper phosphite> silicon phosphite> zinc phosphite> calcium phosphite> potassium phosphite> control. The advantages and disadvantages of these phosphite formulations for scab control are discussed. © 2014 International Society of Arboriculture.