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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #307427
Title: Efficacy of Prophyt, a systemic phosphonate fungicide, when mixed with contact fungicides for control of peach scab in Georgia, 2013

Author
item Bock, Clive
item Hotchkiss, Michael - Mike
item BRANNEN, MICHAEL - University Of Georgia
item FALL, L - University Of Georgia

Submitted to: Plant Disease Management Reports
Publication Type: Other
Publication Acceptance Date: 8/5/2014
Publication Date: 8/12/2014
Citation: Bock, C.H., Hotchkiss, M.W., Brannen, M.W., Fall, L.A. 2014. Efficacy of Prophyt, a systemic phosphonate fungicide, when mixed with contact fungicides for control of peach scab in Georgia, 2013. Plant Disease Management Reports. Rep.8:STF017.

Interpretive Summary: Fungicides were evaluated for control of scab in a late-ripening peach experimental block (‘O’Henry’) located at the USDA-ARS Fruit and Tree Nut Research Laboratory (Byron, GA); the test was specifically designed to determine whether the combination of a systemic phosphonate fungicide with contact materials would provide the same or better efficacy to that of Abound (azoxystrobin). Chemical formulations were applied with an airblast sprayer (100 gal/A spray volume) on 10 Apr (petal fall to 1% shuck split) and 22 Apr (shuck split to 10% shuck off). Treatments included: (1) a non-treated control, (2) Abound, (3) a combination of Prophyt and Bravo, (4) a combination of Prophyt and Captan, and (5) a combination of Prophyt and Yellow Jacket Sulfur. 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. No additional fungicides were applied for the remainder of the season. 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 (18 Jul). Scab incidence and severity were recorded on the day of harvest. Scab was intense due to above-average rainfall during critical infection periods. In other field trials, when Abound (azoxystrobin) has been applied at petal fall and shuck split phenologies, it has generally provided better efficacy that Bravo (chlorothalonil), Captan, or sulfur, likely due to both the systemic and residual anti-sporulent activity of the active ingredient. In this trial, the addition of Prophyt to Captan significantly reduced disease incidence when compared with Abound, while disease was numerically reduced with the combination of Bravo and Prophyt. Likewise, disease severity was also numerically reduced for both Captan and Bravo when in combination with Prophyt. This was not observed with the sulfur and Prophyt combination, which essentially provided equivalent disease control to that of Abound. Although Prophyt alone has not been proven to be an efficacious material for scab management, it might augment control when added to contact fungicides, such as azoxystrobin and chlorothalonil; additional testing is needed to confirm this premise. No phytotoxicity was observed with any treatment.

Technical Abstract: Fungicides were evaluated for control of scab in a late-ripening peach experimental block (‘O’Henry’) located at the USDA-ARS Fruit and Tree Nut Research Laboratory (Byron, GA); the test was specifically designed to determine whether the combination of a systemic phosphonate fungicide with contact materials would provide the same or better efficacy to that of Abound (azoxystrobin). Chemical formulations were applied with an airblast sprayer (100 gal/A spray volume) on 10 Apr (petal fall to 1% shuck split) and 22 Apr (shuck split to 10% shuck off). Treatments included: (1) a non-treated control, (2) Abound, (3) a combination of Prophyt and Bravo, (4) a combination of Prophyt and Captan, and (5) a combination of Prophyt and Yellow Jacket Sulfur. 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. No additional fungicides were applied for the remainder of the season. 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 (18 Jul). Scab incidence and severity were recorded on the day of harvest. Scab was intense due to above-average rainfall during critical infection periods. In other field trials, when Abound (azoxystrobin) has been applied at petal fall and shuck split phenologies, it has generally provided better efficacy that Bravo (chlorothalonil), Captan, or sulfur, likely due to both the systemic and residual anti-sporulent activity of the active ingredient. In this trial, the addition of Prophyt to Captan significantly reduced disease incidence when compared with Abound, while disease was numerically reduced with the combination of Bravo and Prophyt. Likewise, disease severity was also numerically reduced for both Captan and Bravo when in combination with Prophyt. This was not observed with the sulfur and Prophyt combination, which essentially provided equivalent disease control to that of Abound. Although Prophyt alone has not been proven to be an efficacious material for scab management, it might augment control when added to contact fungicides, such as azoxystrobin and chlorothalonil; additional testing is needed to confirm this premise. No phytotoxicity was observed with any treatment.