Mitigation of Hurricane Damage in Pecan Orchards

Abstract

Hurricanes make landfall in the southeastern United States, the center of the majority of worldwide pecan production, on an annual basis. Hurricanes cause severe damage to orchards and reduce yield dramatically for years following. Defoliating pecan trees may mitigate injury caused by excessive rainfall and wind speeds of hurricanes by reducing the drag coefficient (CD) of the tree crown. Chemical defoliation was first developed for the cotton industry; however, it may have application in protecting pecan trees by reducing the CD below the major damage threshold. To determine the effectiveness of defoliation for reduction of CD in pecans, wind force measurements were recorded at five hand defoliation percentages. Results showed 50% defoliation equated to 50% reduction in midpoint wind pressure to 7.92 lbs/ft2, enough to avoid major limb breakage and uprooting according to the Coder Wind Scale. After preliminary screening, the safest and most effective defoliants were evaluated at varying mixtures and concentrations to determine percent defoliation efficacy with time. Thidiazuron (6.4 oz/100 gallons of water) with ethephon (3.2 oz/100 gallons of water) and chelated copper with urea ammonium nitrate (UAN) and a nonionic surfactant showed the highest defoliation percentages at 67% in 72 hours and 88% in 96 hours respectively. This series of studies establishes defoliating pecan trees prior to hurricane conditions could prevent breakage of major scaffold branches and uprooting.