Efficacy of agricultural oil and fungicide combinations as a late dormant treatment for control of peach scab in Alabama, 2015

Authors: SIKORA, ED - Auburn University; PITTS, JAMES - Auburn University; BRANNEN, PHILIP - University Of Georgia; Bock, Clive; Hotchkiss, Michael - Mike

Submitted to: Plant Disease Management Reports
Publication Type: Trade Journal
Publication Acceptance Date: 2/2/2016
Publication Date: 3/7/2016
Citation: Sikora, E.J., Pitts, J., Brannen, P.M., Bock, C.H., Hotchkiss, M.W. 2016. Efficacy of agricultural oil and fungicide combinations as a late dormant treatment for control of peach scab in Alabama, 2015. Plant Disease Management Reports. 10:STF011.

Interpretive Summary: Fungicides were evaluated for control of scab in a mid-ripening peach experimental block (‘Julyprince’) located at Clanton, AL. Chemical formulations were applied at the late dormant stage. Treatment regimens included a non-treated control, a standard spray program of Bravo/Bravo/Sulfur, Bravo applied with and without oil, and a higher than labeled rate of Bravo with oil. Scab incidence (percent infected fruit) and severity (lesions per fruit) were recorded on the day of harvest. All treatments provided a statistically significant level of scab suppression, with the exception of the late dormant application of Bravo Weatherstik at the labeled high rate. The standard spray program of Bravo/Bravo/Sulfur provided the greatest scab suppression, but both rates of Bravo with oil performed better than the untreated control. This trial suggests that Bravo in combination with oil provided greater scab suppression than solo applications of Bravo, albeit with limited statistical significance.

Technical Abstract: Fungicides were evaluated for control of scab in a mid-ripening peach experimental block (‘Julyprince’) located at the Chilton Area Research and Extension Center located in Clanton, AL. Chemical formulations were applied with an airblast sprayer (100 gal/A spray volume) at the late dormant stage. Treatment regimens included a non-treated control, a standard spray program of Bravo/Bravo/Sulfur, Bravo applied with and without oil, and a higher than labeled rate of Bravo with oil. Five replications of each treatment were applied to a randomized complete block design, with each plot consisting of four trees; the outer two trees in each plot were not utilized for ratings. An unsprayed guard row was left between each treatment row. All orchard cultural management was in keeping with peach production methods commonly practiced throughout the Southeast. At full maturity, 40 fruit were harvested from each plot for scab assessments (13 July). Scab incidence (percent infected fruit) and severity (lesions per fruit) were recorded on the day of harvest. All treatments provided a statistically significant level of scab suppression, with the exception of the late dormant application of Bravo Weatherstik at the labeled high rate. The standard spray program of Bravo/Bravo/Sulfur provided the greatest scab suppression, but both rates of Bravo with oil performed better than the untreated control. Previous trials conducted on almonds in California between 2011 and 2014 concluded that single application late dormant sprays of Bravo (chlorothalonil) were more effective at suppressing inoculum in the spring when applied with oil. Additional research should be conducted to determine if this benefit could translate to peach orchards in the Southeast, but this trial suggests that Bravo in combination with oil provided greater scab suppression than solo applications of Bravo, albeit with limited statistical significance.