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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #393008

Research Project: Healthy, Sustainable Pecan Nut Production

Location: Fruit and Tree Nut Research

Title: Spraying tall pecan trees: characteristics of coverage at different speeds and volumes, and with and without a volute

item Bock, Clive
item HOTCHKISS, MICHAEL - Retired ARS Employee
item Cottrell, Ted

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 5/20/2022
Publication Date: 11/1/2022
Citation: Bock, C.H., Hotchkiss, M.W., Cottrell, T.E. 2022. Spraying tall pecan trees: characteristics of coverage at different speeds and volumes, and with and without a volute. Phytopathology. Vol 112:S3.80.

Interpretive Summary:

Technical Abstract: Pecan (Carya iliinoinensis) trees grow tall and obtaining adequate spray coverage high in the canopy using air-blast sprayers is challenging, but desirable to control pecan diseases (particularly scab, caused by Venturia effusa) and insect pests. As a result, gradients of disease occur in trees that affect fruit size and yield in the upper canopy. To study the effects of height on spray coverage in the absence of a tree canopy, we positioned spray cards on a 20 m pole at heights of 5.0, 7.2, 9.4, 11.6, 13.8, 15.0, 17.2, and 19.0 m. Spray was applied without a volute at 2.4 or 3.2 km/h and 470 L/ha, 940 L/ha, and 1870 L/ha, and with a volute at 2.4 km/h or 3.2 km/h and 470 L/ha and 940 L/ha. Spray coverage on cards was measured using image analysis. Results showed that without a volute there was more coverage at 5 m compared to 19 m, and although greater volumes resulted in more coverage at 5 m, the differences declined with height, and at 19 m there was negligible and inconsistent difference between treatments. The differences between speeds were small and inconsistent. In contrast, the volute-based treatments had more coverage at 19 m compared to 5 m, but the effect was minimal with 470 L/ha. At 940 L/ha spray coverage was greater, particularly at heights >13.8 m. It is likely that using a volute at spray volumes <940 L/ha will be marginal. With a volute, speed effects were minor and inconsistent. The results confirm previous studies of spray coverage in pecan canopies and illustrate the limitations of orchard air-blast sprayers for spraying tall pecan trees.