Efficacy of dormant and late dormant applications of mineral oil and chlorothalonil for peach scab control in Alabama, 2018

Authors: BRANNEN, PHILLIP - University Of Georgia; SIKORA, EDWARD - University Of Georgia; PRICE, M - University Of Georgia; Bock, Clive; 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., Sikora, E.J., Price, M., Bock, C.H., Hotchkiss, M.W. 2019. Efficacy of dormant and late dormant applications of mineral oil and chlorothalonil for peach scab control in Alabama, 2018. Plant Disease Management Reports. 13:PF036.

Interpretive Summary: Efficacy of treatment regimens were tested for their ability to control peach scab on an experimental block of peach trees (‘Ruston red’) in Clanton, AL. Treatments were applied with an airblast sprayer at a rate of 100 gal per acre and included 1) an untreated control [no fungicides applied] 2) Bravo Weather Stik (chlorothalonil) applied at petal fall (PF) and shuck split (SS), with cover sprays (CS) of Yellow Jacket Sulfur [chemical standard], 3) Bravo Weather Stik applied at PF, no SS application, with CS of Yellow Jacket Sulfur, 4) Bravo Weather Stik + Superior Oil applied at late dormant (LD), Bravo Weather Stik applied at PF, no SS application, with CS of Yellow Jacket Sulfur, 5) Bravo Weather Stik + Superior Oil applied at LD, Bravo Weather Stik applied at PF and SS, with CS of Yellow Jacket Sulfur, 6) Bravo Weather Stik + Superior Oil applied at dormant (D) and LD, Bravo Weather Stik applied at PF, with CS of Yellow Jacket Sulfur, 7) Bravo Weather Stik + Superior Oil applied at D and LD, Bravo Weather Stik applied at PF and SS, with CS of Yellow Jacket Sulfur. All treatments provided a statistically significant level of scab suppression, and no fungicidal regimen was different than the other relative overall scab management. Shuck split is a critical application window for scab infection, and even though fungicides were not applied in some regimens at the shuck split timeframe, scab levels did not increase significantly as a result – indicating that conditions were not conducive at shuck split for scab development. There was no benefit from the addition of chlorothalonil + Superior Oil dormant and/or late-dormant applications under the low disease pressure observed in this trial.

Technical Abstract: Efficacy of treatment regimens were tested for their ability to control peach scab on an experimental block of peach trees (‘Ruston red’) in Clanton, AL. Treatments were applied with an airblast sprayer at a rate of 100 gal per acre and included 1) an untreated control [no fungicides applied] 2) Bravo Weather Stik (chlorothalonil) applied at petal fall (PF) and shuck split (SS), with cover sprays (CS) of Yellow Jacket Sulfur [chemical standard], 3) Bravo Weather Stik applied at PF, no SS application, with CS of Yellow Jacket Sulfur, 4) Bravo Weather Stik + Superior Oil applied at late dormant (LD), Bravo Weather Stik applied at PF, no SS application, with CS of Yellow Jacket Sulfur, 5) Bravo Weather Stik + Superior Oil applied at LD, Bravo Weather Stik applied at PF and SS, with CS of Yellow Jacket Sulfur, 6) Bravo Weather Stik + Superior Oil applied at dormant (D) and LD, Bravo Weather Stik applied at PF, with CS of Yellow Jacket Sulfur, 7) Bravo Weather Stik + Superior Oil applied at D and LD, Bravo Weather Stik applied at PF and SS, with CS of Yellow Jacket Sulfur. At maturity (2 Jul), 40 peaches were collected. Scab incidence (number of infected fruit) as well as scab severity (number of lesions per fruit) was recorded. All treatments provided a statistically significant level of scab suppression, and no fungicidal regimen was different than the other relative overall scab management. Shuck split is a critical application window for scab infection, and even though fungicides were not applied in some regimens at the shuck split timeframe, scab levels did not increase significantly as a result – indicating that conditions were not conducive at shuck split for scab development. There was no benefit from the addition of chlorothalonil + Superior Oil dormant and/or late-dormant applications under the low disease pressure observed in this trial.