Efficacy of a new chemical fungicides for peach scab control in Georgia, 2018

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

Submitted to: Plant Disease Management Reports
Publication Type: Other
Publication Acceptance Date: 6/10/2019
Publication Date: 7/1/2019
Citation: Brannen, P.M., Baldino, K., Williamson, Z., Bock, C.H., Stokes, U.L., Hotchkiss, M.W. 2019. Efficacy of a new chemical fungicides for peach scab control in Georgia, 2018. Plant Disease Management Reports. 13:PF033.

Interpretive Summary: Efficacy of four fungicides applied at petal fall (27 Mar), shuck split (5 Apr), and first cover (13 Apr) were compared for peach scab control on an experimental block of peach trees in Byron, GA and applied with an airblast sprayer at 100 gal per acre. Treatments were an untreated control [no fungicides applied], Bravo Weather Stik (chlorothalonil), and numbered Syngenta experimental products A19649, A20560, and A20259. Scab incidence (number of infected fruit) as well as scab severity (number of lesions per fruit) were recorded. All treatments provided a significant level of scab suppression. Indeed, fungicide applications at petal fall, shuck split and first cover resulted in substantive disease control, even ~3 months later. The experimental materials were particularly effective, with all providing better control than the protective contact chlorothalonil product. The A20560 experimental fungicide was particularly impressive in its control of scab, with virtually no scab observed at fruit maturity.

Technical Abstract: Efficacy of four fungicides applied at petal fall (27 Mar), shuck split (5 Apr), and first cover (13 Apr) were compared for peach scab control on an experimental block of peach trees in Byron, GA. All treatments were applied with an airblast sprayer at a rate of 100 gal per acre. Treatment regimens included: an untreated control [no fungicides applied], Bravo Weather Stik (chlorothalonil), and numbered Syngenta experimental products A19649, A20560, and A20259. At commercial maturity (5 Jul), 40 peaches were randomly collected from the two center trees in every plot. Scab incidence (number of infected fruit) as well as scab severity (number of lesions per fruit) were recorded. Early-season scab sprays are essential to management of scab, and only three applications during this timeframe can provide good efficacy data, though commercial recommendations would require application of captan or sulfur through remaining cover sprays. There were 43 recorded days with precipitation from petal fall till fruit harvest, resulting in significant disease levels. All treatments provided a significant level of scab suppression. Indeed, fungicide applications at petal fall, shuck split and first cover resulted in substantive disease control, even ~3 months later. The experimental materials were particularly effective, with all providing better control than the protective contact chlorothalonil product. The A20560 experimental fungicide was particularly impressive in its control of scab, with virtually no scab observed at fruit maturity. No phytotoxicity was observed with any treatment.