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A factorial arrangement of four replications of ethephon (0, 25, 50, 100, or 150 mg·liter-1) and GA3 (0, 25, or 50 mg·liter-1) treatments in a Randomized Complete Block Design were applied to `Redhaven' peach trees in mid-September. Each tree received the same treatment in 1987-1990. Development of flower buds (after endodormancy completion) was significantly delayed by GA3 and ethephon. The date of 50% bloom was significantly delayed by GA3 (approximately 1 day) and by ethephon (4.7 days with 150 mg·liter-1 treatment). Increasing the concentration of each chemical resulted in more delay of bloom. There was no interaction of the effects of the two chemicals on bloom date. Application of 50 mg·liter-1 GA3 plus 150 mg·liter-1 ethephon caused the greatest bloom delay (6.5 days compared to untreated trees). Gummosis on scaffolds was evident in the fall and following spring on trees treated with the 2 highest rates of ethephon. During the summer and following fall, little gummosis was evident. By September 1991, evidence of gummosis was insignificant and no tree mortality occurred.
One-year-old peach trees in nurseries at McMinnville, Tenn., were exposed to –11C on 5 Nov. 1991 before digging. The nursery owners were concerned about the relationship of tree cambium browning to potential tree performance after planting. A color scale [0 = nondamage (white) to 6 = severely damaged (brown)] showing discolored cambium of peach nursery trees was developed to rate damage. Browning was rated at 8 cm above graft union. Five trees each of nine cultivars with chill hour requirements ranging from 175 to 1050 were rated. Cultivars with <500 chill hour requirement had higher ratings. Ten `Harbite' trees from each of six size grades were rated. Trees in grades of 30- to 90-cm height had less cambium browning than trees in grades of 90 to 152 cm height. In Dec. 1992, 1-year-old `Red Globe' trees were exposed to –6 (minimum field temperature), –15, –18, –24, –30, or –35C in a programmable freezer. A subsample of five trees per treatment was rated for browning 1 day after treatment and a second subsample rated in mid February. Trees in a third subsample were grown in a nursery the following summer. Slight browning (rating = 1.6) was evident soon after exposure to –24C; however, severe browning was evident on trees exposed to –30 or –35C. Trees exposed to temperature more than –24C did not differ in height, trunk diameter, or dry weight at the end of the growing season, however trees exposed to –30 or –35C did differ. In a similar experiment, `Juneprince' trees exposed to –18C had slight cambium browning (rating = 1.2) but trees died.
Abstract
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.