In general nectarines & peaches harvested at a mature stage will ripen properly without an eternal ethylene application. Ethylene application to fruit harvested at a lower, minimum maturity will help to ripen the fruit more uniformly but without speeding up the rate of ripening.
Apply 100 ppm ethylene 68°F (20°C) for a minimum of 24 hours (actual time of exposure to ethylene is determined by the maturity of the fruit; a decrease in fruit firmness indicates that the fruit is producing ethylene and the external ethylene source is no longer needed).
For more details on nectarine & peach ripening, please see "Recommendations for Maintaining Postharvest Quality: Peaches and Nectarines" at this web page
of UC Davis. The specialists at UC Davis can assist with more detail on the ripening of specific cultivars or any other questions.These recommendations were amassed from a diverse number of sources for use by clients of Catalytic Generators, LLC. While we have made great effort to provide accurate and current ripening techniques, Catalytic Generators makes no warranties regarding these recommendations or the applicability of such information to a particular ripening operation. Please note that we do not provide these recommendations as a replacement for technical ripening experts; if having ripening problems or starting a ripening program, we suggest that professionals be consulted.