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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #408829
Research Project: Healthy, Sustainable Pecan Nut Production

Location: Fruit and Tree Nut Research

Title: Using a Double-sided Volute Sprayer to Control Scab in Tall Pecan Trees

Author
item Bock, Clive
item Hotchkiss, Michael - Mike
item PAULK, BUCK - Shiloh Pecan Farms, Inc

Submitted to: Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 11/27/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary: Pecan is an important crop in the southern United States, but the disease scab (caused by a fungus, Venturia effusa) can cause sever yield loss. Control of scab relies on large orchard air-blast sprayers. Some have been adapted to include a volute on one side to project spray higher into the canopy due to a decline in coverage with height. A grower-designed double-voluted (DV) sprayer was assessed for spray coverage and scab control compared to a standard (S), non-voluted sprayer. Spray coverage studies showed that spray using the DV sprayer resulted in greater spray coverage at heights between 13 and19 m compared to the S. In three seasons, scab control was either equal too, or superior using the DV sprayer. Although the difference was not significant in 2017, scab severity was less using the DV in 2018 and 2019. Thus, the DV provided greater spray coverage at heights >13 m when compared to the S sprayer, and disease control was numerically or statistically improved overall when using the DV. DV sprayers may offer economical, superior scab control in pecan orchards with trees >13 m.

Technical Abstract: Pecan (Carya illinoinensis) is an important specialty crop in the southern United States. Scab (caused by Venturia effusa) is the major biotic constraint to pecan production in the southeastern region. Control of scab relies on large orchard air-blast sprayers. Some have been adapted to include a volute on one side to project spray higher into the canopy due to a decline in coverage with height. A grower-designed and engineered double-voluted (DV) sprayer was assessed for spray coverage and scab control compared to a standard (S), non-voluted sprayer. Spray coverage studies showed that spray using the DV sprayer resulted in significantly greater spray coverage at heights measured >13.8 m (up to 19.0 m), with DV coverage ranging from 18.4 to 14.1%, compared to coverage using the S, which ranged from 7.9 to 2.9%. The slope in decline of spray coverage with height was significantly shallower with the DV sprayer, and spray profiles reflected these differences. Over three seasons, scab control was either equal too, or superior using the DV sprayer. In 2017, mean scab severity for the control was 9.07, for the DV was 0.19, and for the S was 0.24%, respectively; in 2018 severity was 84.3, 18.4 and 29.1%, respectively; and in 2019 was 32.7, 7.0 and 11.6%, respectively. There were no discernable gradients in scab severity with either sprayer in 2017, but in 2018 the difference was significant, with the DV having a shallower gradient, and in 2019 the slope was numerically less steep with the DV compared to the S. Thus, the DV provided greater spray coverage at heights >13.8 m when compared to the S sprayer, and disease control was numerically or statistically greater overall when using the DV. DV sprayers may offer economical, superior scab control in pecan orchards with trees >13.8 m.