A problem facing the peach industry is the ability to harvest field-ripened peaches and get them to market without significant softening or damage. However, getting mature peaches into marketing channels before significant softening occurs is a challenge. Our objectives were to evaluate two growth regulators to determine the effect on fruit quality and softening at harvest and after 1, 2, or 3 weeks in cold storage and to evaluate the effect on harvest date. The two products evaluated in this study were ReTain (aminoethoxyvinylglycine (AVG)—Abbott Labs) and EthylBloc (1-methylcyclopropene (MCP)—Biotechnologies for Horticulture). ReTain is a growth regulator that inhibits ethylene production and is used in commercial apple production to delay harvest. EthylBloc is applied as a gas and attaches to ethylene receptor sites which inhibits ethylene effects. A trial with preharvest foliar applications of ReTain and postharvest gassing with EthylBloc was initiated in July 1998 on `Contender' peaches. ReTain applications were made at 3-day intervals beginning 19 days before first harvest at the rate of 50 g a.i./acre. Applications 3 days before harvest resulted in increased flesh firmness at harvest and decreased ethylene evolution, which continued for up to 3 weeks in cold storage. Fruit were also gassed with 1 μl•L-1 (1ppm) EthylBloc in the laboratory the day following harvest for 24 h. Fruit treated with ReTain and EthylBloc had twice the flesh firmness of peaches that were not treated after 1 week in storage. ReTain applied 3 days before harvest delayed maturity. Further evaluation will be conducted in 1999.
Apple (Malus domestica Borkh.) cultivars Spur Galagored (#42) (`Gala'), Jonagored (`Morren's'), and Red Fuji (B.C. #2) (`Fuji') on Mark rootstock and `Gala' on Malling 26 EMLA (M.26) and Malling 9 EMLA (M.9) were planted in the four major apple-production regions of western North Carolina. Three leader management techniques, weak leader renewal, snaked leader, and heading with partial terminal leaf removal (H + PTLR), were applied to five-tree plots beginning the spring after planting. Leader management techniques, weak leader renewal or H + PTLR, which involved dormant pruning or vegetation removal and an interruption in vegetative vigor, reduced total branching and yield during the third year. Fumigation with methyl bromide increased lateral branching and yield in the third year. No significant yield differences were detected for `Gala' grown on M.9, M.26, or Mark rootstocks. Trees grown in the most western region of the state, Haywood County, had smaller trees and reduced yields compared to the other three regions due to a shorter growing season.
Peach (Prunus persica L. Batsch. `Biscoe'/Lovell) trees were grown in a sandy loam soil under six orchard floor management systems, including five vegetative covers (continuous under the tree) and a vegetation-free control (bare ground). At the end of the fifth year, trees grown in bare ground and nimblewill grass (Muhlenbergia schreberi J.F. Gmel.) had a significantly larger trunk cross-sectional area (TCSA) than trees grown in weedy plots, centipedegrass [Eremochloa ophiuroides (Munro) Hack.], or bahiagrass (Paspalum notatum Flugge). Trees grown in brome (Bromus mollis L.) did not differ significantly in TCSA from any other treatment. Soil profile excavations of the root system revealed that trees grown in bare ground or with nimblewill had significantly higher root densities than those in the weedy plots or grown with bahiagrass. Vector analysis of root distribution indicated that trees grown in bare ground or nimblewill rooted deeper than trees in all other treatments. The greatest reduction in deep rooting occurred with bahiagrass.
Managing vegetative growth in higher density apple systems in the Southeast can be difficult due to the longer growing season. This study was initiated in 1990 to evaluate leader management techniques that have commercial potential for high-density systems in the Southeast. `Spur Galagored', `Jonagored', and `Red Fuji' apples on Mark root-stock were planted in the four major apple production regions of western North Carolina. The three leader management techniques evaluated were weak leader renewal, banding of the leader during the growing season (snaked leader), and leader heading with partial terminal leaf removal (H + PTLR) every 25 cm of leader growth. In the third year, branching was greatest for the snaked leader. In the fifth year, no differences in trunk cross-sectional area were detected between the leader management techniques. However, yields were significantly greater for trees managed with the snaked leader. Trees with the snaked leader yielded 44 kg/tree compared to 35 and 34 kg/tree for the H + PTLR and weak leader renewal, respectively. This illustrates that leader management techniques that use pruning or vegetation removal reduce the early production required of profitable high-density systems.
Peach trees (`Biscoe'/Lovell) were planted in March, 1988 in ten different ground cover management systems. The trees were planted at the Sandhills Research Station in Southeastern North Carolina on a Candor sand and Eunola sandy loam. In December, 1991 the trench profile method was used to evaluate root distribution under the six orchard floor management systems of nimblewill, bare ground control, centipedegrass, brome, bahiagrass, and weedy control. Trenches were dug parallel to the tree row 60 cm from the center of the row on both sides of the tree. Grids 1 meter square, sectioned into 10 cm squares, were placed on the profile walls and root distribution (in three size categories) was recorded for 1 meter on each side of the tree in each trench. Root numbers were greatly reduced under the vegetative covers that provided the greatest suppression of vegetative tree growth. Total root densities under the trees in the vegetative covers were ranked into three size categories which were correlated with the amount of vegetative tree growth.
Peach tree short life (PTSL), a major disease complex impacting peach culture in the southeastern United States for decades, accounts for millions of dollars of losses annually. In spite of the overwhelming amount of research that has been conducted on PTSL, many uncertainties still exist regarding the factors involved in the syndrome and the true cause of tree death. As a consequence, we examined the wood structure and anatomy of 6-year-old peach trees, some showing the initial visible symptoms of PTSL, and others that appeared unaffected and healthy. Very dramatic differences in wood anatomy were observed between healthy and stricken trees. Stricken trees showed a total lack of vessel formation in some earlywood zones, a decrease in vessel formation in latewood, and a marked increase in ray parenchyma cells. Healthy trees showed normal vessel and ray formation. Preliminary results indicate that in some way PTSL may be associated with increased gum production in the xylem and decreased earlywood vessel production, thereby significantly reducing water conduction, leading to tree death. Results of studies currently in progress to further investigate this hypothesis will also be presented.
Western flower thrips (WFT), green peach aphid (GPA) and sweet potato whitefly (SPWF) are major pests of the greenhouse industry. Chemical control of these pests is not desirable. Alternative approaches to pest management need to be developed.
Entomopathogenic fungi hold great promise as sustainable biological control options. A broad range of indigenous fungal isolates have been screened for activity vs. WFT and GPA. Strains of Metarhizium anisopliae, Beauveria bassiana and Verticillium lecanii have been shown to be particularly effective. Plant and soil trials vs. WFT are now underway to permit selection of the best strains for further development. To date, assays vs. SPWF indicate that strains of Paecilomyces farinosus and B. bassiana are the most pathogenic.
A study was initiated in 1994 to evaluate the performance of the recently released peach rootstock Guardian TM (BY-5209-9), compared to Lovell, the commercial standard in North Carolina. `Redhaven' was the scion for both rootstocks. Guardian&™ is reported to be tolerant to root-knot nematodes and not affected by ring nematodes, which contribute to the incidence of peach tree short life (PTSL). The site of this study has a history of poor peach tree survival. Six-year-old trees were removed because of tree mortality from PTSL in Spring 1993. After tree removal, one-half of each existing row was pre-plant fumigated and trees were replanted over the rows of the previous orchard in Feb. 1994. In Spring 1996, tree mortality for the trees planted on Lovell was 30%, compared to 10% for the trees planted on GuardianTM. Trunk cross-sectional area for trees grown in the fumigated soil was approximately double that of trees grown in the unfumigated soil for both GuardianTM and Lovell. The 1996 fruit crop was eliminated from frost/freeze conditions and 1997 yields will be discussed. In Fall 1996, one-half of the trees were treated with a post-plant nematicide to determine if such treatments are necessary or beneficial with the GuardianTM rootstock.
Orchard floor vegetation competes with peach trees for water and nutrients and may harbor pathogens and insects. Tree growth, fruit yield, and fruit size can be optimized through management of vegetation in the tree row and irrigation. Under-tree vegetation-free strip widths (0, 0.6, 1.2, 2.4, 3.0, and 3.6 m) and irrigation were studied in years four through eight of a young peach orchard to determine their effects on peach tree growth and fruit yield, harvest maturity, and fruit size. Immature fruit samples were collected during thinning in years four through six to determine the effect of the treatments on the incidence of hemipteran (catfacing) insect damage. Trunk cross-sectional area (TCSA), as a measure of tree growth, increased with increasing vegetation-free strip width; trees grown in the 3.6-m vegetation-free strip had TCSAs 2.2 times greater, on average, than trees grown in the 0-m vegetation-free strip. TCSA also increased with irrigation; trees grown with irrigation had TCSAs 1.2 times greater, on average, than trees grown without irrigation. Yield increased with increasing vegetation-free strip width, from 9.6 kg per tree in the 0-m plot to 26.5 kg per tree in the 3.6-m plot in year four, to 24.3 kg per tree in the 0-m plot and 39.6 kg per tree in the 3.6-m plot in year eight, for a total yield over years 4–8 per tree of 100 kg in the 0-m plot compared with 210 kg per tree in the 3.6-m plot. Yield, average fruit weight, and average fruit diameter increased with irrigation in three of 5 years; the other 2 years had higher than average rainfall reducing the need for supplemental irrigation. In 3 out of 5 years fruit in irrigated plots matured earlier than fruit in nonirrigated plots. In all years, fruit grown in the 0-m strip matured earliest and had the smallest diameter. Establishing a vegetation-free strip of as narrow as 0.6 m reduced the incidence of catfacing damage compared with the 0-m treatment, even though the orchard was on a commercial pesticide spray schedule. The least damage was seen with the industry standard vegetation-free strip widths greater than 3.0 m with or without irrigation.
With the current situation facing land grant universities of declining resources and a portion of federal funding being dependent upon multistate activities, the search for means to successfully address clientele needs may be handled through multistate activity. In the Southeast, the tree fruit programs, both research and extension, have been evaluating areas that could be addressed with multistate programming. To date, most of the tree fruit multistate activities have been informal in nature. The apple program was the first to look at multistate activity because of the heavy concentration of the industry in the mountains of NC, SC, GA, and TN. The formation of the Southeastern Apple Growers Meeting, which combined the annual educational meeting for apple growers in NC, GA, SC, and TN, was the first initiative. It proved to be very successful with the completion of the eighth joint meeting. In addition, the pest management guides for both apple and peach have been combined for many of the southeastern (five states) and southern states (11 states), respectively. Numerous working groups, workshops, tours, and field days are held on a regional scale as well. However, in order for multistate programming to succeed, our experience suggest the need for several key components. The technical competence in the program to be addressed, a supportive university administration, backing of the industry groups, and personnel that are neither territorial nor resistant to change must be present. From our experience multistate programming can be very successful!