Use of Ethephon and NAA for Inducing Early Shuck Dehiscence of Pecan

Abstract

Abstract Field observations indicate that conjunctive use of ethephon (Ethrel) and NAA (Fruitone-N) can induce early pecan [Carya illinoensis (Wangenh.) C. Koch] shuck (involucre) dehiscence, while greatly reducing undesirable leaflet abscission. Comparisons of the efficacy of 2,4-D and NAA in preventing undesirable leaflet abscission revealed that the comparative molar protective activity of 2,4-D greatly exceeds that of NAA, providing leaflets absolute protection against ethephon-induced abscission, but it was functionally inferior to NAA due to the induction of leaflet necrosis. Single ethephon treatments accelerated shuck dehiscence 3 to 6 weeks for several cultivars. Treatment of ‘Stuart’ and ‘Moneymaker’ pecan fruit and foliage, several weeks prior to the completion of natural shuck dehiscence, with a NAA-ethephon mixture accelerated shuck dehiscence by 5 and 3 weeks, respectively, without severe leaflet abscission or loss of nut quality. These data indicate possible development of harvest-aid technology for early harvesting of pecan without severe leaflet abscission. Chemical names used: (2-chloroethyl)phosphonic acid (ethephon); (2,4-dichlorophenoxy)acetic acid (2,4-D); and 1-naphthaleneacetic acid (NAA).