Abstract Pecan [Carya illinoensis (Wangenh.) C. Koch] faces serious problem of alternate bearing producing large number of fruits of low quality in one year, followed by small number of fruits in next year with low total fruit production. As a consequence, the farmers get low income over years. Ethephon application in the form of foliar is considered as an alternative method for fruit thinning, however, limited published information is available on pecan. Effect of different levels of ethephon as source of ethylene on pecan fruit thinning, yield and quality was evaluated in this research. Foliar ethephon; 200, 400, 600 ppm, water spray and control (No spray) were sprayed on 27 year old pecan cultivar ‘Wichita’ at New Mexico State University, Las Cruces, USA. The ethephon was used as a source of ethylene. The increase in leaf defoliation, chlorosis, and kernel quality with decrease in total kernel weight were significant. However, total number of nuts at harvest remained the same. Foliar ethephon applied at 600 ppm performed better compared with other treatments. In conclusion, the ethephon at the rate of 600 ppm as foliar spray produced good quality by reducing number of nuts in the excessive fruit loading year, which had resulted in greater fruit set in the following year. This may increase profit of the pecan growers on a regular basis.
Keywords Ethephon, ethylene, fruit thinning, yield, quality, pecan.