Ethephon has been used to advance maturity and promote uniform processing tomato ripening since the 1970s, Previous research focused on mid- or late-season applications. However, early-season applications would allow additional production during a limited growing season, permit processors to operate their facilities over a longer period, and advance crop maturities when adverse weather or other factors jeopardize delivery schedules. Replicated ethephon field evaluations have recently been conducted in the lower Sacramento Valley commercial production fields. The focus of these early-season tests was to determine the appropriate chemical rate and to evaluate varietal responses to ethephon. Ethephon effects on fruit maturity were determined. Fruit quality and yields were measured at harvest. The optimal product rate was identified as 280-420 grams (g) of ethephon, applied in 280 liters (1) of water, per hectare (ha). This rate results in a solution concentration of 1,0001,500 parts per million (ppm). Higher rates caused additional maturity advances, but resulted in unacceptable crop phytotoxicity when air temperatures exceeded 35degreesC for extended periods. There were variable cultivar responses to similar ethephon rates, with an average increased maturity of 3-10 days. There were no significant differences in fruit quality (soluble solids and color) or yields observed resulting from ethephon effects in either test reported here.
