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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #375532

Research Project: Healthy, Sustainable Pecan Nut Production

Location: Fruit and Tree Nut Research

Title: The Effect of Tractor Speed and Spray Application Volume on Severity of Scab at Different Heights in Tall Pecan Trees

item Bock, Clive
item Hotchkiss, Michael - Mike

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/13/2020
Publication Date: 12/1/2020
Citation: Bock, C.H., Hotchkiss, M.W. 2020. The Effect of Tractor Speed and Spray Application Volume on Severity of Scab at Different Heights in Tall Pecan Trees. Meeting Abstract. Page 1-206.

Interpretive Summary: Abstract Only,

Technical Abstract: Scab (caused by Venturia effusa) is the most yield-limiting disease of pecan in the southeastern USA. On susceptible cultivars, the disease is managed using fungicides, but spray coverage is an issue in tall trees. We used an air-blast sprayer to compare scab severity on fruit at 5 – 15 m height in trees receiving the same dose of fungicide at 468, 935 and 1871 L/ha at 2.4 and 3.2 kph. An air-blast sprayer was used for the applications, which included a typical series of active ingredients (a.i.). Nozzles were selected to provide similar proportions of spray to the upper and lower canopy. The treatments (or subsets thereof) were repeated 2015-17 on cv Schley, and in 2017 and 2019 on cv Desirable. All treatments reduced scab compared to the control. But overall there was little difference among the treatments on severity of scab on mature fruit. Fungicide applied in 468 L/ha at 2.4 or 3.2 kph was as effective at reducing disease in most seasons as were the higher volumes (sometimes more so). There were height effects related to volume: higher volumes generally had slightly better control higher in the canopy. The scab epidemic severity appeared to affect control efficacy. These preliminary observations indicate no single volume or speed was consistently superior; this suggests in most seasons’ low volumes (high concentration of a.i.) may be similarly efficacious as high volumes (low concentration of a.i.) for controlling scab in tall pecan trees.