Bloom or postbloom sprays of 2-chloroethylphosphonic acid (Ethrel) thinned peaches. Applications at full bloom did not produce consistent thinning in ‘Cardinal’. Postbloom sprays applied approximately at endosperm cytokinesis produced consistent thinning of 3 cultivars. Degree of thinning was related to time of Ethrel application. Most thinning was obtained when Ethrel was applied near the end of Stage I or during Stage II. Ethrel sprays within a month after full bloom caused significant fruit size reduction that persisted 2 months or more after treatment. Ethrel sprays within 50 days of harvest accelerated maturity of several cultivars.

No abstract

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.

Several peach varieties were sprayed with 3-chlorophenoxy-α-propionamide (3-CPA) at different stages of fruit development. The timing of the application was critical, and varieties differed greatly in their thinning response. The ‘Ranger’ variety was thinned with ease, but attempts to thin ‘Cardinal’ with 3-CPA were unsuccessful. Fruit thinning apparently increased the cold hardiness of the flowers during the following bloom period. Several spray additives were found to increase the thinning effectiveness of 3-CPA.

Effects of 8 peach seedling rootstocks on tree growth, survival, and fruit yield of ‘Redhaven’ and ‘Loring’ peach scion cultivars were tested in Alabama, Arkansas, Georgia, North Carolina, and South Carolina. Lovell seedling rootstock was a standard for comparison. Six years of data indicated that Siberian C was not an acceptable rootstock because tree survival and fruit yield were low. Halford was equivalent to Lovell for tree growth, fruit yield, and survival. Fruit size was unaffected by rootstock. Nemaguard and 2 North Carolina selections were resistant to root-knot nematodes (Meloidogyne spp.) but they were not resistant to ring nematodes [Criconemella xenoplax (Raski) Luc and Raski]. Soil fumigation improved tree survival in nematode-infested soil.