Field evaluation of plant resistance bioactivators on the control of the coffee leaf rust

Abstract

This work aimed to evaluate in the field the spraying effects of three plant defense bioactivators or PRIs [plant resistance inducers] (labeled as PF14-50, PF5, and PSD; non-commercially available and subjected to patent registration), 85% copper oxychloride (chemical fungicide) and water (control) on severity of coffee leaf rust (Hemileia vastatrix) in coffee plants (Coffea arabica L. var Bourbon), expressed as Infection Index (II), area under disease progress curve (audpc) and delay on the disease progress (factor ∆t). The coffee plants were sprayed every 15 days from July 25th to December 9th, 2018. Our results showed that PF5-treated plants registered the lowest value of audpc (8559.0) in comparison to control plants (11937.5) but was similar to audpc of copper oxychloride (9298.1), PF14-50 (9924.0) and PSD (11247.5). Nevertheless, at the end of the experiment the chemical fungicide delayed the disease progress by 42 days, while PF5, PF14-50, and PSD caused a delay of 27, 22 and 15 days, respectively, and in comparison to the control. It is concluded that PF5 and copper oxychloride were the most effective treatments, in addition to making evident the potential of the three PRIs tested, to reduce the severity levels of the coffee leaf rust.