Efficacy of dormant and late dormant applications of mineral oil and chlorothalonil for peach scab control in Georgia, 2018

Authors: WILLIAMSON, Z - University Of Georgia; BALDINO, K - University Of Georgia; GLENN, T - University Of Georgia; BRANNEN, PHILLIP - University Of Georgia; Bock, Clive; Hotchkiss, Michael - Mike

Submitted to: Plant Disease Management Reports
Publication Type: Other
Publication Acceptance Date: 6/10/2019
Publication Date: 7/1/2019
Citation: Williamson, Z., Baldino, K., Glenn, T., Brannen, P.M., Bock, C.H., Hotchkiss, M.W. 2019. Efficacy of dormant and late dormant applications of mineral oil and chlorothalonil for peach scab control in Georgia, 2018. Plant Disease Management Reports. 13:PF035.

Interpretive Summary: Efficacy of treatment regimens were tested for their ability to control peach scab on an experimental block of peach trees (‘O’Henry’) located at Watkinsville, GA. Treatments included 1) an untreated control 2) Bravo Weather Stik (chlorothalonil) applied at petal fall (PF) and shuck split (SS), with cover sprays (CS) of Yellow Jacket Sulfur (the chemical standard regimen), 3) Bravo Weather Stik applied at PF, no SS application, with CS of Yellow Jacket Sulfur, 4) Bravo Weather Stik + Superior Oil applied at late dormant (LD), Bravo Weather Stik applied at PF, no SS application, with CS of Yellow Jacket Sulfur, 5) Bravo Weather Stik + Superior Oil applied at LD, Bravo Weather Stik (chlorothalonil) applied at PF and SS, with CS of Yellow Jacket Sulfur, 6) Bravo Weather Stik + Superior Oil applied at dormant (D) and LD, Bravo Weather Stik applied at PF, no SS application, with CS of Yellow Jacket Sulfur, and 7) Bravo Weather Stik + Superior Oil applied at D and LD, Bravo Weather Stik applied at PF and SS, with CS of Yellow Jacket Sulfur. Scab incidence (number of infected fruit) as well as scab severity (number of lesions per fruit) were recorded. Due to exterem rainfall scab pressure was overwhelming. Most notably, the chemical standard failed to suppress disease. However, the dual dormant applications of Bravo Weatherstik + Superior (mineral) Oil provided significant scab suppression, even under these conditions.

Technical Abstract: Efficacy of treatment regimens were tested for their ability to control peach scab on an experimental block of peach trees (‘O’Henry’) located at Watkinsville, GA. Treatments were applied with an airblast sprayer at a rate of 100 gal per acre and included 1) an untreated control 2) Bravo Weather Stik (chlorothalonil) applied at petal fall (PF) and shuck split (SS), with cover sprays (CS) of Yellow Jacket Sulfur (the chemical standard regimen), 3) Bravo Weather Stik applied at PF, no SS application, with CS of Yellow Jacket Sulfur, 4) Bravo Weather Stik + Superior Oil applied at late dormant (LD), Bravo Weather Stik applied at PF, no SS application, with CS of Yellow Jacket Sulfur, 5) Bravo Weather Stik + Superior Oil applied at LD, Bravo Weather Stik (chlorothalonil) applied at PF and SS, with CS of Yellow Jacket Sulfur, 6) Bravo Weather Stik + Superior Oil applied at dormant (D) and LD, Bravo Weather Stik applied at PF, no SS application, with CS of Yellow Jacket Sulfur, and 7) Bravo Weather Stik + Superior Oil applied at D and LD, Bravo Weather Stik applied at PF and SS, with CS of Yellow Jacket Sulfur. Scab incidence (number of infected fruit) as well as scab severity (number of lesions per fruit) were recorded. Scab pressure was overwhelming for most treatment regimens in this trial. Most notably, the chemical standard failed to suppress disease. Rainfall was prevalent in 2018, and affected spray timing. In addition, it rained 0.2 and 0.6 in on the date of the PF and SS applications, respectively, and there were five additional days with rainfall between these sprays. For all of these reasons, pressure was extreme. However, the dual dormant applications of Bravo Weatherstik + Superior (mineral) Oil provided significant scab suppression, even under these conditions.