Ethephon ((2-chloroethyl)phosphonic acid) at 50 to 200 ppm hastened the maturation of peach fruit of the cvs. ‘Cardinal’, ‘Ranger’, ‘Redhaven’, ‘Blake’, and ‘Richhaven’ over a range of application times. Stimulation of maturation was not attributed solely to reduced fruit load, since an influence on maturation was found even when ethephon-treated trees bore no fewer fruits than hand-thinned controls. When treated and nontreated ‘Richhaven’ fruit were harvested at a comparable maturity based on firmness, ground and flesh color a and a/b values were increased by ethephon, as were soluble solids. No differences were found in b values for ground or flesh color or in total titratable acidity. Fruit treated with ethephon exhibited more uniformity in firmness and color than untreated fruit at shipping maturity, a characteristic which has potential value in facilitating once-over mechanical harvesting operations.

The ethylene-releasing agent CGA-15281 (2-chlorethyl-methylbis (phenylmethoxy) silane) effectively thinned fruit of several cultivars of peach [Prunus persica (L.) Batsch.]. Thinning varied with cultivar, stage of development, concentration, and application technique. Negligible (<1%) leaf injury and drop occurred even at the higher (720 ppm) concentration over the 8-year period.

CGA-15281 applied in the fall delayed bloom in peach (Prunus persica L. Batsch) by 4–9 days without damage to the trees. The length of the delay was cultivar and concentration dependent. Fall ethephon applications (500 ppm) damaged trees severely, but delayed bloom 10–18 days, whereas 125 or 250 ppm ethephon caused little tree damage and delayed bloom 3–5 days. Bloom delay from application of ethylene-generating compounds resulted from both prolonging rest and slow bud development once rest was complete. Daminozide applied in January caused bloom delay in 1983 but not in 1984. Silver nitrate had little effect on bloom delay or blossom density at any time of application. Dimethipin and merphos applications in late summer caused defoliation and reduced blossom density, but did not affect date of bloom. Thidiazuron did not induce defoliation or delay in bloom, but greatly reduced blossom density. Chemical names used: (2-chloroethyl)methylbis(phenylmethoxy)silane (CGA-15281); (2-chloroethyl) phosphonic acid (ethephon); butanedioic acid mono (2,2-dimethylhydrazide (daminozide); 2,3-dihydro-5,6-dimethyl-1,4-dithiin 1,1,4,4-tetraoxide (dimethipin); N-phenyl-N′-1,2,3-thiadiazol-5-ylurea (thidiazuron); Tributyl phosphorotrithioite (merphos).

No abstract

SADH, applied as postbloom sprays to 9 peach cultivars in a series of experiments from 1964 to 1969, accelerated maturation and reduced the number of pickings required for most cultivars. Although SADH did not affect the number of fruits per tree, yield, or fruit size, it advanced the maturity date of ‘Ranger’ as much as a week; that of ‘Blake’ 4 days. ‘Cardinal’, an early cultivar, was not noticeably affected by SADH applied at different stages of development. SADH caused fruit to abscise more readily from the stem and left less fruit remaining on the trees when harvested mechanically. SADH had no detrimental influence on ‘Redglobe’ peaches stored at 50°F for 3 weeks. These effects support the feasibility of using SADH as an aid in mechanically harvesting freestone peaches intended for fresh market.