Controlling vegetative growth resulting from a long growing season in the southeast is difficult while trying to promote early fruiting. This study was initiated in 1990 to evaluate higher density leader training techniques, cultivar interactions, and the benefits of pre-plant fumigation on apple replant sites. Another objective was to evaluate these management parameters in four regions with very different climates and elevations. The training techniques evaluated were, weak leader renewal, bending of the leader during the growing season, and partial terminal leaf removal every 10 inches of leader growth (without injuring the apical meristem). The cultivars used were Jonagored, Spur Gala, and Red Fuji, all on Mark rootstock. First and second year branching was not significantly different between the various training techniques. Yields during the third year did not appear to differ between the leader training techniques. Pre-plant fumigation appeared to be beneficial in increasing tree growth in only two of the four sites.
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.
Many of the apples (Malus ×domestica) grown in the southeastern United States are sold to consumers through direct farm markets and roadside stands. Fruit in these markets may be exposed to high temperatures (>68 °F), which cause the fruit to ripen quickly, limiting their shelf life and consumer appeal and increasing their susceptibility to decay pathogens. Studies were undertaken in 2009 and 2010 to determine the effects of a 1-μL·L−1 postharvest 1-methylcyclopropene (1-MCP) treatment on the maintenance of flesh firmness and the incidence of rots in fruit held at elevated temperatures for up to 8 weeks. 1-MCP-treated fruit of three apple cultivars (Ginger Gold, Gala, and Golden Delicious) held in three retail farm markets in the southeastern United States maintained their firmness for 3 to 5 weeks. The firmness of non-treated ‘Ginger Gold’ fruit declined to less than 12 lbf after 1 week in each market, whereas the firmness of treated fruit remained greater than 16 lbf after 3 weeks. Treated ‘Gala’ fruit maintained their firmness at 14 lbf during 4 weeks in each farm market, whereas the firmness of non-treated fruit declined to less than 12 lbf after 2 weeks. The firmness of non-treated ‘Golden Delicious’ fruit declined to less than 12 lbf after 1 week in each farm market, whereas treated fruit maintained their firmness for up to 4 weeks. ‘Golden Delicious’ fruit treated with 1-MCP exhibited almost no loss of firmness during 4 weeks at 32, 50, or 70 °F, or even up to 8 weeks at 32 or 50 °F. The incidence of fruit rots increased with temperature, and 1-MCP reduced the incidence of fruit rots after 4 weeks at 70 °F in 2009 or after 8 weeks at 70 °F in 2010. These data show that 1-MCP may be of great benefit to producers who sell their fruit directly to the consumer by delaying the loss in firmness and reducing the incidence of rots in fruit kept at elevated temperatures.