Efficacy of fungicides for control of peach scab in middle Georgia, 2013

Authors: BRANNEN, P - University Of Georgia; FALL, L - University Of Georgia; Bock, Clive; Hotchkiss, Michael - Mike

Submitted to: Plant Disease Management Reports
Publication Type: Other
Publication Acceptance Date: 8/5/2014
Publication Date: 8/12/2014
Citation: Brannen, P.M., Fall, L.A., Bock, C.H., Hotchkiss, M.W. 2014. Efficacy of fungicides for control of peach scab in middle Georgia, 2013. Plant Disease Management Reports. Rep.8:STF016.

Interpretive Summary: Fungicides were evaluated for control of scab in a mid-ripening peach experimental block (‘Julyprince’) located at the USDA-ARS Fruit and Tree Nut Research Laboratory (Byron, GA). Chemical formulations were applied with an airblast sprayer (100 gal/A spray volume) at each application date: 5 Apr (petal fall to 1% shuck split), 15-16 Apr (shuck split to 10% shuck off), 22 Apr, 3 May, 10 May, 17 May, 24 May, 31 May, 7 Jun, 14 Jun, 21 Jun, 28 Jun, (cover sprays). Treatment regimens included a 1) non-treated control; 2) Bravo at petal fall and shuck split followed by Yellow Jacket Sulfur cover sprays; 3) Bravo at petal fall and shuck split; 4) Abound at petal fall and shuck split; 5) Yellow Jacket Sulfur at petal fall and shuck split; 6) Abound at petal fall and Bravo at shuck split; 7) Bravo at petal fall and Abound at shuck split. Four 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 cultural management adhered to standard peach production methods commonly practiced throughout the Southeast. At full maturity, 40 fruit were harvested from each plot for scab assessments (1 Jul). Scab incidence and severity were recorded on the day of harvest. Though scab infections can occur throughout much of the growing season, a critical peak in spore production and dispersal occurs during the petal fall and shuck split phenologies; fungicides applied during this timeframe must have excellent activity. When applied independently at petal fall and shuck split, Abound and Bravo provided similar efficacy, although Abound was numerically superior to Bravo and statistically better than sulfur as measured by severity. Abound followed by Bravo provided better disease control than Bravo followed by Abound. One might speculate that contact materials, such as Bravo, are confined to the exterior of the shuck (which is removed with fruit expansion), whereas the systemic nature of Abound may allow for penetration to the fruit (and thus added protection). Development of good fungicidal regimens for scab management continues to be an important endeavor; furthermore, fungicide resistance management, such as rotation of fungicide classes, likewise requires careful attention.

Technical Abstract: Fungicides were evaluated for control of scab in a mid-ripening peach experimental block (‘Julyprince’) located at the USDA-ARS Fruit and Tree Nut Research Laboratory (Byron, GA). Chemical formulations were applied with an airblast sprayer (100 gal/A spray volume) at each application date: 5 Apr (petal fall to 1% shuck split), 15-16 Apr (shuck split to 10% shuck off), 22 Apr, 3 May, 10 May, 17 May, 24 May, 31 May, 7 Jun, 14 Jun, 21 Jun, 28 Jun, (cover sprays). Treatment regimens included a 1) non-treated control; 2) Bravo at petal fall and shuck split followed by Yellow Jacket Sulfur cover sprays; 3) Bravo at petal fall and shuck split; 4) Abound at petal fall and shuck split; 5) Yellow Jacket Sulfur at petal fall and shuck split; 6) Abound at petal fall and Bravo at shuck split; 7) Bravo at petal fall and Abound at shuck split. Four 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 cultural management adhered to standard peach production methods commonly practiced throughout the Southeast. At full maturity, 40 fruit were harvested from each plot for scab assessments (1 Jul). Scab incidence and severity were recorded on the day of harvest. Though scab infections can occur throughout much of the growing season, a critical peak in spore production and dispersal occurs during the petal fall and shuck split phenologies; fungicides applied during this timeframe must have excellent activity. When applied independently at petal fall and shuck split, Abound and Bravo provided similar efficacy, although Abound was numerically superior to Bravo and statistically better than sulfur as measured by severity. Abound followed by Bravo provided better disease control than Bravo followed by Abound. One might speculate that contact materials, such as Bravo, are confined to the exterior of the shuck (which is removed with fruit expansion), whereas the systemic nature of Abound may allow for penetration to the fruit (and thus added protection). Development of good fungicidal regimens for scab management continues to be an important endeavor; furthermore, fungicide resistance management, such as rotation of fungicide classes, likewise requires careful attention.