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  • Author or Editor: Gerard Krewer x
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Abstract

There was an inverse linear relationship between fruit set of ‘Bicentennial’ and ‘Redhaven’ peach trees [Prunus persica (L.) Batsch] and treatments of 0 − 4000 ppm of (2-chloroethyl)methylbis(phenylmethoxy) silane (CGA 15281) in 1980. Increases in fruit weight occurred at the highest rate of CGA 15281 when compared to lower rates with ‘Bicentennial’, but no significant increase was obtained with ‘Redhaven’. Terminal fruit were larger than basal and middle node position fruits in ‘Bicentennial’. In 1981, all applications of CGA 15281 (0 − 3000 ppm) to ‘Candor’ and ‘Jefferson’ thinned blossoms and resulted in an increase in fruit size, when compared to the hand-thinned control. Treatments of 2250, 2500, and 2750 ppm to ‘Candor’ resulted in adequate thinning and increased yields. Applications at 1500 and 1750 ppm resulted in overthinning and reduced yields in ‘Jefferson’.

Open Access

In a series of experiments, gibberellic acid (GA3) was applied to rabbiteye blueberries (Vaccinium ashei Reade) under field and greenhouse conditions to determine if fruit set could be improved following physical or freeze injury to flowers. In field experiments, physically damaged flowers (i.e., corollas and styles removed, styles only removed, or ovaries lanced) of `Climax' and `Tifblue' treated with GA3 (4% ProGib at 250 mg·liter–1) set substantially more fruit than nontreated, damaged flowers. Under green-house conditions, GA3 applied postfreeze to `Tifblue' and `Brightwell' resulted in increased fruit set compared to unsprayed control plants of the same cultivars. Freeze-damaged plants had substantially reduced fruit set overall but to a much lesser extent for GA3-treated plants than for those not treated with GA3. Individual fruit weight was reduced by GA3 applications, as was berry seediness. Results from these greenhouse and field trials suggest that GA3 can be used to salvage a blueberry crop following a moderate freeze during bloom.

Free access

Southeastern peach and pecan orchards weathered hurricanes in the 1980s and 1990s that left long-term effects on tree health and productivity. Pecan trees were affected the most, due to being blown down from strong winds and wet soils or suffering considerable damage to branches and immature nuts resulting in massive nut drops. Premature nut drop triggered or enhanced alternate bearing problems. Cultivar differences were evident in the ability of trees to withstand wind damage, with open-canopy trees being most resistant, but essentially all trees were damaged when they exceeded ≈17m in height. Hurricanes in older, alternate-bearing orchards sometimes broke enough limbs to induce sufficient vegetative regrowth to reestablish an equilibrium between sink (nuts) and source (foliage), thus enhancing yields in subsequent years. Peach trees which were less than 4.5 m tall and already harvested usually did not blow over unless the soil was very wet. However, peach trees were often twisted about the tree axis from the change in wind directions as the hurricane passed over. Afterwards, many trees leaned more than 30 °, especially trees less than 6 to 7 years of age. Root damage was significant and increased when trees were manually repositioned as additional root breakage occured from which these trees often later died. Trees not repositioned but instead retrained to vertical by pruning lived longer. Ambrosia beetles also attacked wind-stressed trees and caused a long-term decline. Slow moving hurricanes significantly damaged peach trees by waterlogging the soil, which killed roots and helped primary pathogens such as Phytophthora sp. to attack the tree crown. This was followed by secondary pathogens like Oxyporous sp., which attacked the internal woody cylinder. Initial trunk damage appeared localized; however, trees continued to die over a number of years. Experience showed that whole orchard removal on severe waterlogged sites was the best economical response.

Free access

Experiments were conducted during 1999 at the Univ. of Georgia Research Farm near Alapaha with the rabbiteye blueberry (Vaccinium ashei Reade) cultivar Brightwell to determine how various harvesting and handling tactics influenced firmness. The research was facilitated by availability of a mechanical harvester and a commercial packing line. Firmness was determined with a FirmTech II firmness tester on fruit samples before and after cold storage. Fruit harvesting methods included machine harvesting in bulk, hand harvesting in bulk, and hand harvesting directly into clam shell containers. Assessment of precooling effects were made by comparing firmness of fruit that were placed immediately over ice after harvest to fruit that remained at ambient temperatures for 24 hours after harvest. Additional measurements were made to discern the effects of grading and sorting on fruit firmness. The data overall indicated that `Brightwell' fruit firmness was “acceptable” regardless of the harvesting and handling methods experienced. However, there were considerable firmness losses caused by the various procedures. The greatest loss in fruit firmness (20% to 25%) was caused by machine harvesting. This was followed by a 15% to 18% loss of firmness due to grading and sorting. Immediate cooling of fruit after harvest resulted in only a 8% to 12% increase in firmness as compared to keeping fruit at ambient temperature for 24 hours. These findings should be useful to growers and packers in targeting segments of their operations that can be manipulated to improve berry firmness and quality for fresh market sales.

Free access

Since 2004, growers and scientists have observed a disorder described as “yellow twig” or “yellow stem” affecting a major selection of southern highbush blueberry, FL 86-19, in the south Georgia blueberry production region. The initial symptom observed was leaf marginal chlorosis and subsequent necrosis, which eventually progressed throughout the whole leaf resulting in early leaf fall. Thin, yellow twigs or yellow stems became evident on some cultivars. The described symptoms on blueberry were similar to those exhibited on grapes with Pierce's disease and on plum with leaf scald disease. This prompted the enzyme-linked immunosorbent assay (ELISA) tests and isolations of Xylella fastidiosa, which is the causal agent of the previously mentioned grape and plum diseases. Two leaf and two root tissue samples were collected from a diseased FL 86-19 plant for isolation and ELISA testing on 2 Mar. 2006. ELISA results indicated all four tissues tested positive for the bacterial pathogen, X. fastidiosa, whereas only the two root tissues provided positive isolations. One leaf and one root tissue sample were later collected from each of five additional diseased plants for isolation and ELISA testing. Both isolation and ELISA testing methods obtained positive results. Cultures were multiplied to inoculate seedlings of three cultivars: ‘Southern Belle’ (eight plants), ‘Premier’ (six), and ‘Powderblue’ (six) on 23 May 2006 and one selection, FL 86-19 (eight), on 31 May 2006. Two FL 86-19 plants started to show symptoms of marginal necrosis 54 days postinoculation, whereas one plant each of ‘Southern Belle’ and ‘Powderblue’ started to show symptoms of marginal necrosis 63 days postinoculation and ‘Premier’ stayed symptomless. All eight culture-inoculated FL 86-19 plants (100%) showed symptoms 72 days postinoculation, but no symptoms were observed on the control plants. One hundred twenty-six days postinoculation, two ‘Powderblue’ and four ‘Southern Belle’ plants showed mild symptoms, whereas all ‘Premier’ plants were asymptomatic. Positive reisolations of the bacteria from the inoculated symptomatic plants, not from asymptomatic plants, fulfilled Koch's postulates, which confirmed X. fastidiosa was the causal bacterium of the new blueberry disorder, the bacterial leaf scorch of blueberry.

Free access

Bananas (Musa spp.) are a popular ornamental plant in the southern United States; however, only a few cultivars, such as Lady's Finger and Orinoco, are grown in Georgia. Thirty-three primarily commercial cultivars of bananas were grown for 2 years near Savannah, Georgia, to determine their suitability for ornamental and nursery production, and for 3 years for fruit observations. Most plants were grown from tissue culture plugs. They were given rates of fertilization used for commercial banana fruit production. Most cultivars produced 10 to 14 leaves and grew to heights of 1.5 to 2.0 m. Some displayed desirable ornamental characteristics such as pink-tinted pseudostems, colorful flowers, and large graceful leaves. Some of the most attractive tall-growing cultivars were Belle, Ice Cream, Kandarian, Manzano, Saba, and 1780. Some of the most attractive medium-height cultivars were Dwarf Namwah, Dwarf Orinoco, Goldfinger, Raja Puri, and Super Plantain. In the short category, the cultivars Dwarf Nino, Gran Nain, Kru, and Sum X Cross were among the most attractive ornamentals. Many of the cultivars flowered and began producing fruit in late summer, although only ‘Raja Puri’, ‘Sweetheart’, and ‘1780’ produced palatable fruit before frost in November. Cultivars were also rated for their ability to produce suckers that could be used for nursery production. In year 2, ‘Manzano’ and ‘1780’ produced more than six high-quality suckers for nursery propagation. Potential income for these cultivars was over $60 per plant. For the planting as a whole, sales of suckers at a field day averaged $7 per plant in year 2, and $17 per plant in year 3.

Full access

Mechanical harvesting systems for processed blueberries (Vaccinium spp.) are available. However, low harvest efficiency and high fruit damage have limited the use of mechanical harvesters for picking blueberries for fresh market to specific cultivars under good weather conditions. New harvesting technology for fresh-market blueberries is needed. The V45 harvester was developed by the U.S. Department of Agriculture in 1994 to harvest fresh-market-quality northern highbush (V. corymbosum) blueberries in Michigan. The current study was performed in Georgia to evaluate the V45 harvester on specially pruned rabbiteye blueberry [V. virgatum (syn. V. ashei)] and southern highbush blueberry (V. darrowi × V. corymbosum) and included analysis of harvest efficiency and fruit quality (percent blue fruit, percent bloom, percent split skin, and internal bruise damage). Six-year-old, 6- to 8-ft-tall ‘Brightwell’ and ‘Powderblue’ rabbiteye blueberry plants were winter pruned to remove vertically growing and overarching canes in the center of the bush in Jan. 2004 and Feb. 2005 respectively. Three-year-old, 3- to 5-ft-tall ‘FL 86-19’ and ‘Star’ southern highbush blueberry plants were similarly pruned in summer (June 2004) or in winter (Feb. 2005). Pruning removed an estimated 30% to 50% of the canopy and opened the middle, resulting in V-shaped plants in both rabbiteye and southern highbush blueberries. Yield of winter-pruned ‘Brightwell’ rabbiteye blueberry was lower compared with unpruned plants during both years, but winter-pruned ‘Powderblue’ rabbiteye blueberry plants produced as much as unpruned plants in 2005. In ‘FL 86-19’ southern highbush blueberry, plants that were summer pruned in June 2004 produced as much as unpruned plants in 2005, but plants that were winter pruned in Feb. 2005 had lower yields than unpruned plants in 2005. The V45 harvester caused little cane damage on pruned blueberry plants. In rabbiteye blueberries, internal fruit damage and skin splitting was less in V45-harvested fruit than in fruit harvested by a sway harvester and nearly that of hand-harvested fruit. However, in ‘FL 86-19’ southern highbush blueberry, the V45 harvester detached a lower percentage of blue fruit and excessive amounts of immature and stemmed fruit. These findings suggest that the V45 harvester has the potential to harvest some rabbiteye blueberry cultivars mechanically with fruit quality approaching that of hand-harvested fruit.

Full access

Abstract

Fruit tissue only was treated with concentrations of 0, 240, 360, 480, 600, 720, 840, and 960 ppm of (2-chloroethyl)methyl bis (phenyl methoxy) silane (CGA 15281) applied to 1/3, 1/2, and 2/3 of the fruit surface. Increased abscission of fruit occurred as ovule length increased from 3.5 mm to 13.3 mm when fruit alone were treated. Foliage sprays of the same concentrations with the fruit protected generally had no effect on fruit or leaf abscission. Application of 0.01 ml droplet of CGA 15281 to the abscission zone, peduncle, and fruit cheek caused little fruit removal, but produced chlorosis of the treated area on the fruit. The data suggest that fruit contact with CGA 15281 is necessary for fruit thinning.

Open Access