Chile peppers have extensive morphological diversity, especially for leaf and fruit color and shape as well as plant habit. This diversity has led to the development of chile pepper plants for ornamental applications (Stommel and Bosland, 2006). Ornamental chile peppers are extensively used as potted or bedding plants, and are popular in Europe and the United States (Bosland, 1999).
Although considered a self-pollinating crop, chile peppers can have outcrossing rates at sufficient levels to impede progress in breeding programs (Bosland, 1993; Tanksley, 1984). Bosland (1993) developed a simple and effective method of caging chile pepper plants for seed increase ensuring self-pollination for breeder seed, through the exclusion of pollinating insects. However, before caging can be implemented, all open flowers and possibly cross-pollinated fruit on the chile pepper plants must be removed. This is currently accomplished through laborious and time-consuming hand removal, which is exacerbated in ornamental chile peppers because of their short stature and prolific flowering. To hasten the caging process, and more efficiently produce self-pollinated seed, a more efficient method of flower and fruit removal is needed and would be welcomed.
Ethephon (2-chloroethylphosphonic acid) is an ethylene-releasing compound and is labeled for many crops, including chile peppers. Ethephon has numerous horticultural applications, including limiting stem elongation, increasing lateral branching, and manipulating flowering date (Hayashi et al., 2001). In addition, ethephon has long been reported as a flower- and fruit-thinning agent on fruit crops such as citrus (Citrus sp.) and apple (Malus ×domestica) (Davis et al., 2004). In olive (Olea europaea), ethephon treatments initiate abscission of flowers and peduncles of mature inflorescences (Weis et al., 1991).
Kahn et al. (1997) evaluated the effect of fall ethephon applications at concentrations of 0, 1000, 2000, 3000, and 4000 ppm to control fruit abscission in paprika-type chile peppers. The authors recommended ethephon applications of 2000 to 3000 ppm during the growing season for the removal of immature fruit of paprika-type chile pepper. However, they stated that application time will vary due to genotype and environmental differences. In ornamental chile peppers, ethephon has been used to control plant height and increase lateral branching; however, this practice also delayed flowering and reduced fruit production (Khademi and Khosh-Khui, 1977). Santos et al. (2013) found that ethylene sensitivity was genotype specific in ornamental chile peppers.
Much of the work with ethephon on chile peppers is for increased uniformity in fruit maturity, facilitating cost-effective once-over mechanical harvest. Paprika-type chile peppers treated with ethephon before harvest have an increased ratio of red to green pods (Cantliffe and Goodwin, 1975). Ethephon has been shown to cause immature fruit and flower abscission in paprika and cayenne chile pepper in mid- to late-season applications (Kahn et al., 1997; Tripp and Wien, 1989; Uchanski and Blalock, 2013). There is no information on the effect of early season foliar applications of ethephon on chile peppers for flower and fruit abscission. Our objective was to determine the efficacy of early season ethephon foliar applications for floral and fruit abscission in ornamental chile peppers.
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