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  • Author or Editor: J. Thomas Raese x
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The effect of combinations of soil-applied paraquat and simazine and 3 levels of supplemental ammonium nitrate on leaf calcium and sorbitol was determined in ‘Delicious’ apple trees (Malus domestica Borkh.). Levels of leaf calcium were significantly lower in plots treated with simazine + paraquat than with paraquat alone for all levels of nitrogen. Leaf size was significantly related to levels of sorbitol in the wood and bark, and sorbitol content of 2-year-old shoots was significantly related to leaf calcium levels.

Open Access
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The temperature of spurs and trunks of misted ‘Delicious’ apple trees, Malus domestica Borkh., was reduced by as much as 12.5° and 18°C, respectively, by evaporative cooling in mid-September and October. Freeze tests during early autumn and winter indicated that the misted 2-year-old apple shoots were up to 6° hardier in October than the unmisted trees.

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Mono-ammonium phosphate applications to apple trees, ‘Oregon Spur’ seedling root (Malus domestica Borkh.), grown in a low P soil resulted in greater regrowth than the controls or other N or P soil treatments in the greenhouse. The high rate (12 g/tree) of mono-ammonium phosphate resulted in the most leaves per tree, the lowest percentage of leaves with purple margin, the highest level of leaf P and Mn, and relatively high levels of leaf N, K, Ca, and Mg. The 4 sources of N fertilizer (ammonium sulfate, ammonium nitrate, calcium nitrate, and urea) reduced the levels of leaf P in the trees. Trees treated with calcium nitrate had the highest level of leaf Ca.

Open Access
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Naphthaleneacetic acid (NAA) was applied in the spring to pruned apple (Malus domestica Borkh.) and pear (Pyrus communis L.) trees for control of sprouting on trunks and scaffold limbs. After one growing season, sprouting was completely controlled on trunks and scaffold limbs of ‘Delicious’ apple and ‘Bartlett’ and ‘d’Anjou’ pear trees. After two growing seasons, about 80 to 90% of the sprouts were inhibited on the scaffold limbs of ‘Delicious’ and ‘Winesap’ apple trees. NAA controlled sprouting at 1% with no added benefit at 2%; 0.5% NAA was least effective.

Open Access
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Potassium gibberellate (KGA) increased plant height, trunk diameter, and width and number of leaves of tung seedlings, Aleurites fordii, in the greenhouse. Growth response to KGA was greater under the high level of nutrition than under the lower level. Placement of KGA on the terminal buds or on mature leaves stimulated more growth than when it was applied to the stem or to the roots. KGA stimulated more growth when it was applied to the lower surface of leaves than when it was applied to upper surfaces. On mature trees in the orchard, KGA increased linear shoot growth, duration of vegetative growth period, and number of terminals whereas N-dimethylaminosuccinamic acid reduced shoot extension.

Open Access
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Growth regulators were applied in early autumn to evaluate their effects on induction of cold hardiness in 2-year-old apple shoots, as determined by the conductivity test. Mid-October applications of 500 ppm (2-chloroethyl)phosphonic acid (ethephon), followed 11 days later by 100 ppm of naphthaleneacetic acid (NAA), increased cold hardiness up to 5°C by early November in 1974 and to a lesser extent in 1976. Two annual sprays of succinic acid-2,2-dimethylhydrazide (daminozide, SADH) in June increased cold hardiness slightly (2 to 3°C) in late fall of 1974, 1975, and 1976. However, in 1974 treated trees were no hardier than the controls later in the winter and fruit set on ethephon-treated trees was severely reduced. In most cases, the combined content of fructose, glucose, sucrose, and sorbitol in the 2-year-old wood was slightly higher in treatments that induced cold hardiness in November or December, 1974 than in the controls. Techniques are described for screening growth regulators for induction of cold hardiness and estimating relative cold protection.

Open Access
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Abstract

Weed control and supplemental N markedly increased vigor and yield of pear trees (Pyrus communis L. cv. d’Anjou). Under conditions of low soil N, simazine enhanced N uptake. Consequently, simazine increased tree vigor, leaf N, shoot growth, and fruit size in the absence of supplemental N. Fruit from the control (no N or simazine) treatment was denser, yellower, higher in soluble solids, and had less scald and rot than fruit from trees treated with simazine but no N. Amitrole plus simazine (A + S) produced the highest yield in trees receiving no N, and resulted in as much tree vigor as the other treatments with supplemental N. The data suggest that certain triazine and triazole herbicides may partially substitute for N fertilizer on young ’d’Anjou’ trees.

Open Access
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Abstract

Chemical growth regulators were applied in early fall to 1-year-old ‘Delicious’ apple trees (Malus domestica Borkh.) to evaluate cold hardiness and cold injury during late fall to late winter. Evaluations were made by the conductivity test and expressed as the percentage of electrolytes. Of the 18 chemicals tested, CGA-15281 (500 ppm) showed the most promise for increasing cold hardiness, especially in November. During freeze tests in November or February of 1976, AMO-1618 (1000 ppm), GA3 and GA3 + fluoridamid (500 and 6000 ppm, respectively), and Thidiazuron (100 ppm) induced significantly greater cold hardiness than the controls. When tested separately or in combination with other chemicals, ancymidol, CGA-15281, DEPEG, PP 528, and NIA-10637 produced slightly more cold hardiness relative to the controls in more than 50% of the tests. Daminozide, ethephon, GA3, glyphosine, and UBI-P293 were the least effective chemicals for inducing cold hardiness.

Open Access
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Abstract

Bearing 15-year-old ‘Oregon Spur’, ‘Redspur’, and ‘Wellspur Delicious’/seedling apple (Malus domestica Borkh.) trees in a low-P (2 to 4 ppm) soil were treated over 3 years with different forms and rates of N and N + P fertilizers to overcome a severe condition pf low vigor and low yields. Fruit size and leaf N were greater on trees receiving all forms of N fertilizer than on the untreated controls. Levels of leaf P were up to 2 times greater on NH4H2P04 [mono-ammonium phosphate (MAP)] treated trees than on the controls or N-only [(NH4)2S04, NH4NO3, Ca(NO3)2 or urea] treated trees. In most instances, the higher rates of MAP (applied in 1983 and 1984) resulted in greater shoot extension and leaf weight than the controls and most of the N-only treated trees. Yield (3-year mean) was greater on ‘Oregon Spur’ and ‘Redspur’ cultivars treated with the moderate rate of MAP than in the controls or in most of the N-only treated trees.

Open Access
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Abstract

Naphthenic oil with and without succinic acid-2,2-dimethylhydrazide (SADH) was applied to dormant tung trees in February or early March to delay bloom in the spring. A late frost occurred in March 1968; the only branches of the trees to flower and set fruit were those that were treated with napthenic oil and oil with SADH. By contrast, branches treated with aqueous SADH were not saved. In 1969, branch sprays of 10% oil with 1% SADH resulted in delaying bloom up to 5 days and in setting more fruit than the control. In 1970, sprays of 50% oil with 2% SADH delayed bloom on 5-year-old tung trees by approx 2 weeks.

Open Access