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  • Author or Editor: Jeff W. Daniell x
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Abstract

Pruning dates as treatments were imposed on 4- to 6-year old peach trees [Prunus persica (L) Batsch], growing on new and old peach sites. May and July pruning reduced the number of blooms in 1971 but had no effect in 1972. Fruit set and yield resulting from spring pruning or non pruning averaged higher by an order of 2 than from winter pruning in 1971, a year when cold injury to blossoms reduced average peach yields in the area 50 percent. Time of pruning had no effect on fruit set in 1972, a year with no cold injury to blossoms. Therefore, the yields per hectare in 1972 reflected mostly the tree mortality where trees were growing on old peach sites. Significant increases in yield were obtained from February, March, and May pruning over November and January pruning. In addition, June pruning increased yields when compared to November, December, and January pruning. These data also provide further evidence that cold injury is involved at some point in the peach-tree decline process. The relationship of these findings to peach-tree decline is discussed.

Open Access
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Abstract

Pruning dates as treatments were imposed for a 4 or 5-year period on peach trees [Prunus persica (L.) Batsch] growing on old and new peach land. The trees were pruned during the middle of each month with an unpruned check in 1 test only. Trees growing on old peach land and pruned in fall or early winter generally had greater mortality than non-pruned or trees pruned in spring. Time of pruning, however, had little or no effect on longevity when trees were grown on new peach land. Also time of pruning had no consistent effect on tree growth.

Open Access

Abstract

Diuron at 2.2,4.4, and 8.9 kg/ha was ineffective in controlling grass and broadleaf weeds in a muscadine grape (Vitis rotundifolia Michx.) vineyard while diuron at 4.4 or 8.9 followed by dalapon at 5.5 kg/ha gave effective weed control with no visible phytotoxicity. Yields were significantly reduced at the 2.2 and 8.9 kg/ha diuron rates and by diuron at 8.9 in combination with dalapon at 5.5 kg/ha. A simazine, dalapon, and 2,4-D system also controlled weeds in the vineyard with no influence on yield. Herbicide treatments had no effect on soluble solids of the fruit.

Open Access

Abstract

Leaf water relations and soil-to-leaf resistance were studied in 3-month-old pecan [Carya illinoenis (Wangenh.) C. Koch] seedlings as soil dried progressively to minimum water potentials of −0.3, −0.6, and −1.1 MPa in three separate tests. Leaf conductance, transpiration, and predawn leaf water potential declined with increasing soil water deficits, and only predawn leaf water potential fully returned to pre-stress levels after rewatering. Reduced levels of leaf conductance following water stress were apparently caused by internal factors other than leaf water potential. Leaf conductance of well-watered seedlings decreased logarithmically and with increasing leaf-to-air vapor pressure gradient. Soil-to-leaf resistance to water flow varied diurnally and generally increased following water stress at minimum soil water potentials of −0.6 and −1.1 MPa. Osmotic adjustment and changes in the distribution of water between the apoplast and symplast in leaves did not occur in response to soil water potentials of −0.6 MPa.

Open Access

Abstract

Peach seedlings [Prunus persica (L) Batsch] were grown in liquid culture with 0,1,4, 7 and 10 Mg/ml Fe++. After 6 months, the plants were inoculated with Pseudomonas syringae van Hall, the causal agent for bacterial canker, or water, and cankers were measured over a 5 month period. Plants not receiving iron were chlorotic and smaller than those grown in 1,4, 7 μg/ml of iron. Ten μg/ml of Fe++ reduced plant weight when compared to the 1 μg/ml rate. Plants receiving no Fe++ developed the longest bacterial cankers. No significant differences in canker length occurred between treatments containing Fe. In the 0 and 1 μg/ml rate, P. syringae was recovered farther from the inoculation site and after a longer time following inoculation than in other rates of Fe++. P. syringae was not recovered from water inoculated seedlings. The possible relationship of these findings to peach tree short-life is discussed.

Open Access

Abstract

In a muscadine (Vitis rotundifolia Michx.) vineyaid, postemergence applications of glyphosate over a 2-year period at 4.5, 6.7 and 10.1 kg/ha were very effective in controlling weeds tolerant to yearly applications of simazine. There was no injury to 1-year-old or older vines if basal leaves were not contacted by glyphosate sprays. There were no significant effects on yield and soluble solids content of the free-run juice by glyphosate treatments.

Open Access

Abstract

Three-year-old peach trees [Prunus persica (L) Batsch. cv. Elberta] growing on old peach land where a high incidence of bacterial canker was suspected in previous plantings, were pruned or pruned and inoculated with Pseudomonas syringae van Hall in October, December, February, or April. All trees pruned and inoculated in October or December were either dead or dying by May. P. syringae was recovered from all of the October-inoculated and from 86% and 71% of the December- and February-inoculated trees, respectively. Also, 43% mortality occurred in February-pruned and inoculated trees. Uninoculated but early-pruned trees showed severe short life or decline symptoms with 43% mortality following October and December pruning. On the other hand, April-pruned trees, whether inoculated or not, showed less short life or decline symptoms than early-pruned trees and no deaths occurred in April-pruned and inoculated trees.

Open Access

Abstract

Freezing tests were conducted on 1-year-old ‘Elberta’ peach trees during the dormant season. The degree of injury was recognized by discolored cambial area, bud mortality, vegetative vigor of buds, and retardation of leaf development. Plants preconditioned at 70° until new tissue was evident and then subjected to low temperatures were injured more severely than those not preconditioned. The freezing rate had a greater effect on the degree of injury than the minimum temperature reached within the range tested. Severity of injury at a given temperature was associated with the physiological stage of the trees. Plants exhibited more injury when frozen just prior to a natural “leaf expansion” than at periods earlier in the dormant season, even though the plants were preconditioned to the same apparent growth state. These data along with data on natural temperature conditions in a region where peach-tree decline is severe are discussed in relation to peach-tree decline.

Open Access

Abstract

Mature peach trees (Prunus persica (L.) Batsch. cv. Southland) were treated with 0, 1.73, 2.42, and 3.11 Mmoles/1 of (2-chlorethyl)phosphonic acid (ethephon) and ethylene evolution was measured up to 9 days after treatment. Ethephon caused a marked increase in ethylene evolution, a sharp decrease in the breaking force of fruit abscission, and a pronounced increase in leaf abscission. Ethylene evolution was higher in leaves than fruits. In general, ethylene from tissue explants containing the abscission zone of fruits was higher than that of explants from the side of fruits from treated trees. However, it was postulated that ethylene has an overall affect on all tissue with subsequent abscission rather than a direct effect on the abscission zone of leaves and fruits of peaches.

Open Access

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