Synchronizing Cayenne Chile Pepper Development for Mechanical Harvest

In the desert southwest cayenne chile is an important crop for the production of hot sauce base. The crop is currently harvested by hand to accommodate staggered, indeterminant crop development. However, there is evidence that a single, early application of ethylene as a controlled abscission agent can increase red yields of mechanically harvested chile pepper (Capsicum annuum L.). The present study was performed over two years in two locations with treatments arranged in a randomized complete block design (RCBD). Four spray application timings of Ethrel® (Ethephon) were evaluated for their potential to increase red cayenne cv. Mesilla yields and percentage of red and green pods. The spray treatments of ethylene were selected at four key cayenne growth stages based on heat units accumulated after planting (HUAP). Heat units are defined as the product of temperature and time within predetermined upper and lower temperature thresholds (30°C and 13°C). The HUAP are based on daily high and low temperatures and are a useful way of predicting crop growth and development in the climate of the desert southwest. The predetermined ethylene spray treatments were at 1400 HUAP (late June to early July), 1800 HUAP (mid July), 2800 HUAP (late August to early September), and 3100 HUAP (mid to late September), which corresponded to early bloom, peak bloom, late physiological maturity, and pre-harvest, respectively. A non-sprayed control treatment was also included. Fresh red, green and non-marketable weights were recorded for each treatment and analyzed for statistical differences. The 3100 HUAP treatment is the application timing directed by the label. However, this treatment timing resulted in no significant red cayenne yield increase or decrease, but was successful at increasing the percentage of red to green cayenne in some locations. The 2800 HUAP treatment did not significantly increase red cayenne yields, and actually caused a decrease in one location. The 1800 HUAP treatment increased red cayenne yield, and also the percentage of red to green pods, which is desirable for mechanical harvest. The earliest ethylene spray treatment at 1400 HUAP did not impact red cayenne yield, but showed variable effects on the percentage of red to green cayenne. The results of this study indicate potential for a new, early season spray application of ethylene to increase the yield and percentage of mechanically harvested red cayenne.