The Effect of Sample Height on Spray Coverage in Mature Pecan Trees
Open Access
- 1 July 2015
- journal article
- Published by Scientific Societies in Plant Disease
- Vol. 99 (7), 916-925
- https://doi.org/10.1094/pdis-11-14-1154-re
Abstract
Pecan scab (caused by Fusicladium effusum) is the most damaging disease of pecan in the southeastern United States. Large air-blast sprayers for orchards are used to apply fungicide to control the disease but little quantitative information exists on the spray coverage achieved in the canopy of these trees. A series of experiments using water-sensitive spray cards to record spray coverage (percent area) at different heights and locations up to 15 m in the canopy of pecan trees showed a significantly greater percentage of card area covered at the lowest sample height when compared with the highest sample height. At the lowest height (5 m), spray coverage on individual cards ranged from 4.7 to 73.5% and, at the highest sample height (15 m), spray coverage ranged from 0.02 to 9.5%. In general, there was little significant difference in spray card coverage up to at least 10 m but, at 12.5 and 15 m, there was significantly less spray coverage compared with the coverage at 5 m. Regression analysis indicated a consistent linear relationship between sample height in the tree and the percent area covered. When spray cards were positioned at different heights without possible interference from pecan limbs and foliage, similar effects of sample height on spray coverage were noted. Wind speed measurements showed that air movement declined rapidly with distance from the sprayer fan. Whereas, at 2 m from the fan, wind speeds were approximately 26 m s−1, by 10 m, speeds had declined to 2 to 4 m s−1. At distances >12 m, wind speed was approaching ambient air movement of about 1 to 3 m s−1. Although aerial application resulted in numerically greater spray coverage at sample heights >10 m, it was not significant even though a weak linear relationship (R2 = 0.21 to 0.25) suggested an effect of height. Characterizing and understanding pesticide spray coverage in pecan will allow us to discern limits imposed by existing technology, and provide the basis for improving spray application methods (or tree management) for more efficacious disease control.Keywords
This publication has 26 references indexed in Scilit:
- Field evaluation of a calibration method for air-assisted sprayers involving the use of a vertical patternatorCrop Protection, 2004
- PA—Precision Agriculture: Variation of Spray Deposit and Loss with Air-jet Directions applied in OrchardsJournal of Agricultural Engineering Research, 2000
- Effects of Host Resistance, Temperature, Leaf Wetness, and Leaf Age on Infection and Lesion Development of Pecan ScabPhytopathology®, 1998
- Sensitivity of Cladosporium caryigenum to Propiconazole and FenbuconazolePlant Disease, 1997
- Effects of an Abbreviated Pecan Disease Control Program on Pecan Scab Disease Increase and Crop YieldPlant Disease, 1988
- Effect of Canopy Density on Pesticide Deposition and Distribution in Apple TreesPlant Disease, 1987
- Effects of Travel Speed, Application Volume, and Nozzle Arrangement on Deposition and Distribution of Pesticides in Apple TreesPlant Disease, 1987
- Effect of Time of Inoculation withCladosporium caryigenumon Pecan Scab Development and Nut QualityPhytopathology®, 1983
- Spray retention and distribution on apple treesPesticide Science, 1981
- The relationships between air volume and pressure on spray distribution in fruit treesJournal of Agricultural Engineering Research, 1971