Effectiveness of agricultural oils alongside fungicides in the late dormant treatment for suppression of peach scab in Georgia, 2016

Authors: BRANNEN, PHILLIP - University Of Georgia; YOST, J. - University Of Georgia; Bock, Clive; Hotchkiss, Michael - Mike

Submitted to: Plant Disease Management Reports
Publication Type: Other
Publication Acceptance Date: 2/15/2017
Publication Date: 3/1/2017
Citation: Brannen, P.M., Yost, J.O., Bock, C.H., Hotchkiss, M.W. 2017. Effectiveness of agricultural oils alongside fungicides in the late dormant treatment for suppression of peach scab in Georgia, 2016. Plant Disease Management Reports. 11:STF003.

Interpretive Summary: The efficacy of different fungicide applications for control of peach scab was tested on cv Flameprince. The treatments included a non-treated control, a standard fungicidal spray program from petal fall through cover sprays, and a treatment regimen in which the shuck split application was removed. Shuck split is a critical period for infection, so unless previous applications (late dormant or petal fall) fungicides have significant and persistent activity, disease would be increased significantly over the standard treatment program. Remaining treatments included various combinations of Abound (azoxystrobin), Bravo (chlorothalonil), or Abound + Bravo applied with Superior oil during a late-dormant application. Peaches were assessed for scab incidence and severity. As compared to the standard spray program, Bravo at both petal fall and shuck split followed by sulfur cover sprays, no treatment regimen provided better disease control. Though oil is often sprayed for scale insect management, the addition of fungicides with the oil spray does not consistently provide a benefit that would be worthy of the added costs.

Technical Abstract: The efficacy of different fungicide applications for control of peach scab was tested on cv Flameprince. The fungicidal applications were applied with an airblast sprayer with a spray volume of 100 gal/A. Control treatment regimens included a non-treated control, a standard fungicidal spray program from petal fall through cover sprays, and a treatment regimen in which the shuck split application was removed; shuck split is a critical period for infection, so unless previous applications (late dormant or petal fall) fungicides have significant and persistent activity, disease would be increased significantly over the standard treatment program. Remaining treatments included various iterations of these regimens with Abound (azoxystrobin), Bravo (chlorothalonil), or Abound + Bravo applied with Superior oil during a late-dormant application. Treatments were applied to a randomized block design with five replications per treatment. Each treatment was administered to a plot of four trees, where the center two were utilized for harvest. Unsprayed rows were maintained between treated rows as buffer zones. Orchards were otherwise maintained with common cultural practices of the region. When the peaches were mature (11 Jul), 20 fruit were harvested from each of the two center trees to yield 40 from each plot. On the day of harvest, the peaches were assessed for scab incidence and severity. Disease was prevalent in this trial, and treatments were readily separated on the basis of disease control. As compared to the standard spray program, Bravo at both petal fall and shuck split followed by sulfur cover sprays, no treatment regimen provided better disease control. Though oil is often sprayed for scale insect management, the addition of fungicides with the oil spray does not consistently provide a benefit that would be worthy of the added costs.