• Korean Journal of Organic Agriculture
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• v.23 no.2
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• pp.267-280
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• 2015

The study was conducted to evaluate effects of time and degree of defoliation on growth of 'Wonhwang' pear (Pyrus pyrifolia Nakai) trees managing with low pesticides as well as regrowth of cuttings in vitro. Treatments included degree of defoliation (20% and 60%) with time of defoliation (Early-Aug, End-Aug, and Early-Sep); Early-Aug (20%), Early-Aug (60%), End-Aug (20%), End-Aug (60%), Early-Sep (20%), Early-Sep (60%), and No defoliation. No defoliation and Early-Sep (20%) defoliation increased growth of water sprouts and new shoots, which were improved by delayed defoliation or 20% of defoliation. Total-C, total-N, B, and free sugar contents increased in No defoliation-shoots but decreased in End-Aug (60%)-shoots. Delayed defoliation increased total-C, total-N, and free sugar in shoots, with high contents of C, K, Ca, Mg, and B observed for 20% of defoliation-trees. Fruit yield and weight or fruit length increased in No defoliation, End-Aug (20%) defoliation, and Early-Sep (20%) defoliation, but reduced in End-Aug (60%). Fruit soluble solids content reduced in defoliation in August. Time of defoliation did not affect the fruit yield and fruit quality, while degree of defoliation influenced yield and fruit weight and length. Defoliation at End-Aug (60%) mostly increased the leakage rates of the stem cuttings at $-18^{\circ}C$ and $-21^{\circ}C$ in vitro and reduced the germination rates at $-24^{\circ}C$ and $-27^{\circ}C$. Under comparison of time and degree of defoliation, the Early-Sep defoliation increased germination rates of the stem cuttings at $-27^{\circ}C$ in vitro, and 60% of defoliation decreased the germination rates compared to the 20% of defoliation.

• Korean Journal of Organic Agriculture
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• v.23 no.3
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• pp.469-480
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• 2015

The study was conducted on the effects of time of defoliation on fruit quality of pear (Pyrus pyrifolia Nakai) trees, managing with low-pesticides, and regrowth of stem cuttings in vitro. Treatments included for 40% of uniform defoliation at early-August, end-August, and early-September, as well as control (no defoliation). Defoliation at early-September and control increased growth of water sprouts as well as concentrations of carbohydrates, total nitrogen, and free sugar in one-year old shoots. Defoliation at early-September and control increased fruit yield and mean fruit weight, with high soluble solids content and fruit surface color of $a^*$ observed for both defoliation at end-August and early-September. Defoliation at early-August increased rates of electrolyte leakage in stem cuttings at $-18^{\circ}C$ in vitro. There were no significantly different for germination rates of the cuttings between the treatments at -18 and $-21^{\circ}C$ in vitro, with the highest germination of the cuttings observed for defoliation at early-September and control at $-27^{\circ}C$. Therefore, orchard management should be performed to be minimized for defoliation of the spur leaves until end-August, causing from precipitation and pests.

• Journal of The Korean Society of Grassland and Forage Science
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• v.13 no.2
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• pp.132-138
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• 1993

Yield and plant constituent responses of forage sorghum cultivars have usually been compared in uniform defoliation management test. However the influence of harvest time on differential response of cultivars needs more precise definition. Therefore this study with sorghum-sorgo-sudan hybrid cv. NC+Sweet Leaf, and Super Su 22 and Sorghum-Sorghum hybrid cv. Pioneer 931 was carried out under two defoliation regimes, namely defoliation at heading stage of each variety and defoliation on the same calendar date in response to heading stage of early variety. The results are summarized as follows; 1. Three harvests were taken by early variety with 80 days and two harvests by late variety with 94 days from sowing to heading. 2. Dry matter and TDN yield tend to be higher when the plants are cut at ear emergence stage of late variety. 3. Crude protein content was similar for the same growth growth stage of 1st growth and 1st regrowth, and rather big different between varieties. 4. Considering only dry matter and TDN yield, it is recommendable to cut two times at ear emergence stage of late variety and also three times at ear emergence stage of early variety in view point of utilization period extension and distribution of forage products.

• Horticultural Science & Technology
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• v.35 no.4
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• pp.410-417
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• 2017

We compared the quality of 'Fuji' apples (Malus ${\times}$ domestica) from trees whose leaves were not removed (no artificial defoliation; NAD) with apples from trees that underwent early defoliation (ED, treated in mid September and early October) and conventional defoliation (CD, treated in early and mid October). The experiment was conducted in three consecutive years using 15-year-old 'Fuji' apple grafted on Malus prunifolia. Fruits were harvested on November 7, 16 or 12 in 2011, 2012 and 2013, respectively. Compared to NAD treatment, ED and CD treatment reduced the fresh weight by 4.7% and 0.6%, respectively. The soluble solids content of NAD apples ($14.4^{\circ}Brix$) was slightly higher than that of CD ($14.1^{\circ}Brix$) and ED ($14.0^{\circ}Brix$) apples. Soluble sugar content, flesh firmness, water-core index, and titratable acidity were not affected by defoliation treatment regardless of treatment timing. The skin blush index of NAD apples (2.3) was inferior to that of CD (3.3) and ED (3.4)- treated apples. Furthermore, artificial defoliation treatments increased skin redness ($a^*$) and yellowness ($b^*$) and significantly improved the degree of skin blush compared to NAD fruits.

• Korean Journal of Environmental Agriculture
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• v.34 no.4
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• pp.288-293
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• 2015

BACKGROUND: This study was conducted to investigate the effect of the unexpected early loss of leaves on a newly-bred kiwifruit on the regrowth of axillary buds the current season and the early growth and development the following year.METHODS AND RESULTS: The vines were defoliated on Jul. 18, Aug. 16, and Sep. 17 in 2012 and on Jul. 16, Aug. 13, and Sep. 12 in 2013. The vines were defoliated 0 (control), 50, and 100% of the total number of leaves on a vine. The regrowth of axillary buds at 30 days after defoliation increased in proportion to defoliation degrees regardless of the defoliated time. Defoliation the previous season did not influence percent budbreak the next season. Percentage of floral shoots of the control vines was 27.4%, each bearing 2-3 flowers. In those vines defoliated 100% in August and September, however, percent floral shoots and number of flowers significantly reduced.CONCLUSION(S): Defoliation in July, August, and September didnot affect percent budbreak the following year regardless of degrees of defoliation. A 100% defoliation in August and September significantly reduced flowering the following year compared to the control; that in August resulted in no floral buds at all.

• Journal of Bio-Environment Control
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• v.26 no.4
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• pp.291-296
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• 2017

This study was conducted to evaluate the influence of early defoliation on photosynthesis and carbohydrate reserves when the source leaves of 'Fuji'/M9 apple (Malus domestica Borkh.) trees were removed during the growing period. Bud regrowth rates of 80%, 50% defoliation and non-defoliation treatments were significantly different 82.7%, 45.9% and 2.1% respectively at 30 days after treatment. In all treatments, sucrose and starch concentrations in remaining leaves decreased non-significantly during the 14-day period. No significant changes were observed for total soluble carbohydrates in non-defoliation and 50% defoliation. However, in 80% defoliated treatments, concentrations of sorbitol and total soluble carbohydrates in remaining leaves declined steadily during the 14-day period. It is thought that high sink strength increases the requirements of carbohydrate from remaining leaves more than non-defoliated. The concentrations of starch in the roots tend to decrease non-significantly as percentage of defoliation increased. Photosynthesis of remaining leaves was monitored during the 14-day period after partial defoliation treatments. Net photosynthetic rates (Pn) and stomatal conductance were significantly enhanced in the 80% defoliation. The observed photosynthetic enhancement following partial defoliation may have been due to the enhancement of osmotic potential in leaves. These results were estimated that increasing of photosynthetic rate in the partial defoliation is due to the sink carbohydrate requirements for the current year's secondary growth of buds.

• Korean Journal of Environmental Agriculture
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• v.31 no.3
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• pp.229-234
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• 2012

BACKGROUND: The fruit quality and flowering characteristics of Kiwifruit (A. deliciosa cv. Hayward) in the following year is known to be affected by the extent and timing of defoliation of the current year. In korea, the production of kiwi, which is a perennial, straggling deciduous warm-temperate fruit, is often restricted by wind damage due to typhoons resulting to defoliation at the middle season of its growing period. In this paper, we report the effect of the different timing of defoliation and severities at the current season to the kiwifruit quality. METHODS AND RESULTS: Twenty seven-year-old 'Hayward' trees grown under polyethylene film rain-shelter were defoliated in different days from August to September at seven day-intervals. In each day, 0, 25, 50, 75 and 100% of leaves were removed from the trees. Fruits from each treatment were classified into four floating types (L: lying in bottom, S: standing on bottom, F: floating and SF: floating at the surface of water) by submerging them into tap water. Defoliation of kiwifruit trees in August and September caused air holes in locules of inner pericarp. Increased number of air hole in locules of a fruit was observed in floating types F and SF, and most of the air holes were located in stem end. The defoliation of trees in August significantly reduced the ratio of L-floating type fruits, which have the least number of locule air holes. The extent of defoliation also affected the distribution of the four types, the more leaves removed, the less L-floating type fruits harvested. The weight of fruits from trees defoliated in August was lower than that of fruits from September. Soluble solids content decreased as the number of locule air holes increased. Negative correlations were observed between the extent of defoliation and the weight and soluble solids content of fruits. CONCLUSION: Early defoliation effect on kiwifruit locule air hole occurrence and fruit quality were more severe in August than in September. And also if the defoliation severity is over 25%, severe fruit quality reduction expected to happen due to increase of fruit locule air hole in the inner pericarp.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.34 no.4
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• pp.390-395
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• 1989

This experiment was conducted to study the effect of different defoliation methods on the same leaf characters and grain yields of perilla. Transplanting dates were from June 20, July 20, to August 20, 1989, and defoliated 30, 40, 50, 60 days after transplanting, respectively. The results obtained are summerized as follows: In the case that the fully developed leaves were defoliated, the number of total leaves were increased by more defoliations and by the later defoliation, Leaf length, width and area, fresh leaf weight, defoliated leaves per plant and grain yeidls were significantly influenced by the defoliation methods, Grain yields of the defoliation plots were lower than that of non-defoliation plot, As the above results, considering the grain yield, defoliation may be available in the case of one or two times of defoliation at the early growing stage. The profits from any type of defoliation were higher than that for grain yield only.

• Korean Journal of Environmental Agriculture
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• v.32 no.3
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• pp.201-206
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• 2013

BACKGROUND: Kiwifruit, which was introduced to Korea in late 1970s, is a warm-temperate fruit tree, whose leaves are easily damaged by wind because of their large size. To produce high quality fruits, efficient windbreak is necessary to protect leaves until harvest. In Korea, typhoons from July onwards usually influence the production of kiwifruit. Damages from typhoons include low fruit quality in the current year and low flowering ratio the following year. This study was conducted to investigate the effect of early defoliation of kiwifruit vines from July to October on the regrowth of shoot axillary buds the current year and bud break and flowering the following year. METHODS AND RESULTS: Scions of kiwifruit cultivar 'Goldrush' were veneer grafted onto five-year-old Actinidia deliciosa rootstocks, planted in Wagner pots (13L) and grown in a rain shelter. Kiwifruit leaves in the proximity of leaf stalk were cut by lopping shears to simulate mechanical damage from typhoon since only leaf stalks were left when kiwifruit vines were damaged by typhoons. Kiwifruit vines were defoliated from July 15 to October 14 with one monthintervals and degrees of defoliation were 0, 25, 50, 75 and 100%. All experiments were conducted in the rain shelter and replicated at least five times. Defoliation in July 15 resulted in a high regrowth ratio of 20-40% regardless of degree of defoliation but that in August 16 showed only 5.8% of regrowth ratio in the no defoliation treatment; however, more than 25% of defoliation in August 16 showed 17-23% of regrowth ratio. In September 15, regrowth ratio decreased further to less than 10% in all treatments and no regrowth was observed in October 14. Percent bud break of all defoliation treatments were not significant in comparison to 64.7% in no defoliation except for 42.1% and 42.9% in 100% defoliation in July 15 and August 16, respectively. Floral shoot in the no defoliation treatment was 70.2% and defoliation of 50% or less resulted in the same or increased floral shoot ratio in July 15, August 16, and September 15; however, defoliation in October 14 showed no difference in all treatments. In flower number per floral shoot, 2-3 flowers appeared in no defoliation and only 1 flower was observed when the vines were defoliated more than 50% in July 15 and September 15. In October 14, contrary to the floral shoot ratio, flower number decreased with increased defoliation. CONCLUSION(S): Therefore, it is suggested that dormancy of 'Goldrush' axillary buds, was started in August and completed in October. The effect of defoliation on bud break of axillary buds the following year was insignificant, except for 100% defoliation in July 15 and August 16. From July 15 to September 15, floral bud ratio was significantly reduced when more than 50% of leaves were defoliated compared to no defoliation. Also, the number of flowers per flower-bearing shoot the following year decreased by less than 50% when compared to no defoliation, and this decrease was more prominent in September 15 than July 15 and August 16.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.682-689
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• 2019

The Korean flowering cherry is a popular tree. However, the trees have started to defoliate early, including those in Gurye. Thus, it is necessary to identify the causes of the early defoliation and how to manage them. Therefore, the purpose of this study was threefold: 1) to investigate the early defoliation of flowering cherry trees, 2) to identify the differences in growth and flowering of the trees in response to treatment, and 3) to suggest an optimal treatment for the trees. The experiment was conducted in Gurye at a site 3km long with 102 flowering cherry trees along a street. There were three treatments: control, an environmentally friendly insecticide and a disinfectant(treatment 1), and an environmentally friendly insecticide, a disinfectant, and irrigation (treatment 2). The trees in Gurye were compared to trees on Jeju Island. The defoliation rates of the flowering cherry in Gurye were significantly higher than those on Jeju Island at each measurement time. Within Gurye, the defoliation rate was significantly higher in the trees of the control than in the two treatments and only the trees in the control from Gurye had shot-hole disease. Post-treatment, twigs collected from the control during April showed significantly poorer growth, lower numbers of flowering buds per twig, and lower numbers of foliar buds. The trees given treatment 1 showed significantly greater growth, number of total buds, flowering buds per twig, and density of buds than the trees given treatment 2. After analyzing the correlations, it was established that early defoliation led to poorer growth, affecting the flowering of the trees.