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Submitted to: Pecan Grower
Publication Type: Trade Journal Publication Acceptance Date: 5/4/2017 Publication Date: 6/1/2017 Citation: Bock, C.H., Hotchkiss, M.W., Cottrell, T.E. 2017. Characteristics of spray coverage from an air-blast sprayer, and why this is of concern for disease control in tall pecan trees. Pecan Grower. 31(3):28-40. Interpretive Summary: Application of fungicide sprays to pecan trees is challenging due to the height of the canopy above ground and the limitations of the ground-based spray application equipment (usually orchard air-blast sprayers). We describe results of experiments at the USDA, Byron, GA that were aimed to characterize spray coverage and the resulting distribution of the devastating fungal disease, pecan scab. Spray coverage declined with height, most dramatically at approximately 12 m. In contrast, disease severity increases in the canopy of large trees at heights greater than 12 m. Spray emitted from an air-blast sprayer occupies an increasing volume of air the further away from the sprayer it impacts a surface, thus coverage declined with distance. Furthermore, the wind of the air-blast sprayer declines too. Coupled with the screening effect of limbs and foliage, spray coverage inevitably declined rapidly with height in tall tree orchards. Aerial application is one method to that can help reduce disease severity high in the canopy. Technical Abstract: Application of fungicide sprays to pecan trees is challenging due to the height of the canopy above ground and the limitations of the ground-based spray application equipment (usually orchard air-blast sprayers). We describe results of experiments at the USDA, Byron, GA that were aimed to characterize spray coverage and the resulting distribution of the devastating fungal disease, pecan scab. Spray coverage declined with height, most dramatically at approximately 12 m. In contrast, disease severity increases in the canopy of large trees at heights greater than 12 m. Spray emitted from an air-blast sprayer occupies an increasing volume of air the further away from the sprayer it impacts a surface, thus coverage declined with distance. Furthermore, the wind of the air-blast sprayer declines too. Coupled with the screening effect of limbs and foliage, spray coverage inevitably declined rapidly with height in tall tree orchards. Aerial application is one method to that can help reduce disease severity high in the canopy. |
