Severe Pruning Research Articles

Effects of crown-pruning on seed and pollen cone production in two lodgepole pine seed orchards in British Columbia

The effects of top pruning on subsequent seed and pollen cone production in lodgepole pine (Pinus contorta Dougl.) grafted clones in two seed orchards were evaluated. In the older orchard (14 years old), three pruning regimes were applied: an untreated control, a moderate pruning where 25% of the crown was removed and a severe pruning where 40% of the crown was removed. In the younger orchard (ten years old), only a control pruning and a severe pruning (50% of crown removed) were applied. Five-year seed cone production was lower in treated ramets compared to controls in both orchards. However, when cumulative seed cone yields were adjusted for reduced tree heights after pruning, differences were no longer significant in the older orchard. Strong clonal variation was observed in seed cone yields in both orchards. Pollen cone development was less variable among treatments in the older orchard. In the younger orchard, controls consistently produced heavier pollen crops. Pruning recommendations for similar orchards are made and results discussed for reducing the impacts of losses in seed cone yields.

Rootstock, severity of dormant pruning, and summer pruning influences on peach tree size, yield, and fruit quality

Peach trees in British Columbia are pruned heavily during the dormant season with some potentially detrimental effects. Summer pruning has been used to control fruit tree vigor and improve fruit quality. The objective of this study was to reduce tree size, increase yield, and improve fruit color by using a less severe dormant pruning system and summer pruning prior to harvest. Over 4 yr, mature, self-rooted (micropropagated) Fairhaven peach trees and Fairhaven on Siberian C rootstock were subjected to two different dormant pruning regimes, with or without summer pruning. Yield, tree growth, pruning weights (dormant and summer) and fruit quality (size and color) measurements were recorded annually. There were no differences in yields per tree for the two rootstocks or for the summer pruning treatments. The lighter ("long") dormant pruning increased yields but average fruit weight was higher in the heavier ("short") dormant pruning treatment. Summer pruning increased the amount of red color on the fruit but only slightly. Own-rooted trees were larger (tree height and ground area covered) than trees budded on Siberian C. Tree height was also increased by the lighter dormant pruning treatment. The partitioning index was higher for trees on Siberian C rootstock, "long" dormant pruned, or non- summer pruned trees. Key words:Prunus persica, fruit color, fruit size, partitioning index

Effect of repeated severe pruning on endogenous polyamine content in hazelnut trees

Effect of repeated severe pruning on endogenous polyamine content in hazelnut trees

Effect of repeated severe pruning on endogenous polyamine content in hazelnut trees

Endogenous polyamine content was determined in leaves and buds of adult and repeatedly severe pruned hazelnut trees (Corvlus avellana L.). Polyamine content in leaves from shoots obtained by forced outgrowth of branches taken from adult and pruned trees was also determined. Variations of polyamine levels in relation to pruning treatments were observed in all the analysed, tissues. Free polyamines increased in response to pruning treatments, mostly due to an increase in free putrescine. Free spermidine and spermine seemed to decrease with pruning intensity, whereas bound polyamines did not seem to correlate with treatments. Significantly, in all the analysed tissues the putrescine to spermidine plus spermine ratio increased in the free polyamine fraction. The results indicate that polyamine metabolism could play a role as a physiological marker for juvenility and rejuvenation in relation to cloning of woody plants. The possible role of polyamines in mediating and/or regulating phase change and reinvigoration is discussed.

Infestation dynamics of Dioryctria sylvestrella (Ratz.) (Lepidoptera: Pyralidae) in pruned maritime pine ( Pinus pinaster Ait.)

The infestation dynamics of Dioryctria sylvestrella were studied for 2 consecutive years, in both pruned and unpruned maritime pine. In comparing four levels of pruning severity, the percentage of attacked trees and the location of attacks on the trunks were recorded. The level of attack of pruned trees strongly increased with the intensity of pruning, showing a significant positive correlation with the number of pruning wounds. The removal of dead branches did not result in any increase of infestation. The infestation of pruned trees had no contagious effect towards neighbouring unpruned trees. The location of attacks did not differ between either unpruned or any pruned tree treatments. The majority of the attacks were located in the vicinity of the branch insertion, and in 2-to 3-year-old internodes. In the second year, the percentage of pruned re-attacked trees continued to show a significant positive correlation with the severity of pruning. A model of infestation behaviour was hypothesised which involved two distinct phases. First, a primary attraction, mediated by components of oleoresin exuding from the pruning wounds, might allow the selection of an individual host tree. This attraction would be also quantitative and occur for at least 2 years. Second, female moths would select oviposition sites which would improve brood survival, providing easier access to suitable food resources.

068 EFFECT OF PRUNING SEVERITY ON APPLE TREE GROWTH, YIELD AND YIELD EFFICIENCY

`Empire'/M.26 apple trees which were planted in 1978 and trained to a Y-trellis were pruned differentially from 1989-1993. Trees were dormant pruned by removing from 1-4 scaffold limbs. The annual increase in trunk cross-sectional area (TCA), and the number and length of shoots removed during summer pruning increased linearly as the severity of pruning increased. The number of shoots removed during summer pruning from the most severe pruning treatment was more than double that of the least severe treatment Cumulative fruit number and yield were reduced linearly with increasing severity of pruning while average fruit size was increased only slightly by severity of pruning. Light interception was reduced with increasing severity of pruning. Tree efficiency of converting light energy into fruit (g fruit/MJ PAR intercepted) was linearly reduced with increasing pruning severity. Most of the reduction in conversion efficiency appeared to be due to reduced partitioning of resources into fruit since partitioning index (g fruit/unit increase in TCA) was more highly correlated to pruning severity than to conversion efficiency. Conversion efficiency and partitioning index accounted for a greater portion of the yield variation than did light interception indicating that the influence of pruning on yield was more a function of changing internal physiology than reduced light interception.

158 Effects of supplemental lighting and cluster pruning on yield, photosynthesis, and sugar accumulation of greenhouse tomato plants

Tomato plants were submitted to three photosynthetic photon fluxes (PPF) of 50, 100, and 150 μmol. m-2s-1 and cluster-pruned according to different scenarios. The highest PPF combined with severe cluster pruning produced the highest yield and the best fruit quality. The highest PPF increased growth, photosynthesis and leaf sugar content. Severe cluster pruning increased the average fruit weight, leaf sucrose and glucose content, but reduced photosynthesis. Data will be discussed in relation to crop management and efficiency.

Periodic orbit expansions for the Lorentz gas

We apply the periodic orbit expansion to the calculation of transport, thermodynamic, and chaotic properties of the finite-horizon triangular Lorentz gas. We show numerically that the inverse of the normalized Lyapunov number is a good estimate of the probability of an individual periodic orbit. We investigate the convergence of the periodic orbit expansion and compare it with the convergence of the cycle expansions obtained from the Ruelle dynamical σ-function. For this system with severe pruning we find that applying standard convergence acceleration schemes to the periodic orbit expansion is superior to the dynamical σ-function approach. The averages obtained from the periodic orbit expansion are within 8% of the values obtained from direct numerical time and ensemble averaging. None of the periodic orbit expansions used here is computationally competitive with the standard simulation approaches for calculating averages. However, we believe that these expansion methods are of fundamental importance, because they give a direct route to the phase space distribution function.

USING MECHANICAL PRUNING TO MITIGATE ALTERNATE BEARING OF PISTACHIOS

A single severe mechanical pruning done January, 1985, with the following treatments, hand pruned control, hedging, topping and topping and hedging, successfully reduced the alternate bearing of pistachios. The respective alternate bearing indexes are as follows; control, 0.88; hedged, 0.79, topped. 0.55, hedged and topped, 0.36. All treatments produced approximately equal cumulative yield over the 7 year experimental period. However, the most severely pruned trees demonstrated yield loss in the first 2 years after pruning.The severe mechanical pruning, done prior to the low crop year, produced its effects by forcing trees to produce less fruiting wood during the off-crop year. The effects of a single severe mechanical pruning persisted 7 years.

Management of the flat‐headed borer,Sphenoptera dadkhaniObenberger on peach in India

Abstract In management studies on the flat‐headed borer, Sphenoptera dadkhani Obenberger (Buprestidae: Coleoptera) on peach, spraying of lindane 20 EC at 500 g a.i./ha in June and September was most effective in controlling the borer. With a mild level of pruning, the reduction in the carryover of the borer population was 46.6% (branches destroyed/burnt) and 35.5% (branches left in the orchard). A reduction of 61.1% was recorded when severely pruned branches were destroyed, whereas this reduction was only 43.2% when pruned branches were left in the. orchard. Integration of severe pruning of infested trees, followed by their destruction and application of recommended doses of farmyard manure and NPK fertilizers in January followed by three sprayings of lindane (500 g a.i./ha), at the times of adult emergence in April, June and September most effectively managed the borer. Integration of these practices resulted in up to 91.5% control of the borer.

QUANTITATIVE MEASUREMENT OF CLUSTER COMPACTNESS IN SEVERAL TABLE GRAPE CULTIVARS.

Cluster compactness can affect fruit quality by influencing pesticide spray penetration into clusters and by predisposing berries to cracking and subsequent decay. Compactness of clusters can be altered through gibberellic acid sprays, flower cluster thinning and pruning severity. Assessment of cluster compactness has often been performed using a visual rating system which may not provide adequate quantitative measurement. Evaluation of cluster compactness by insertion of wedges between randomly chosen pairs of berries on a cluster revealed a high correlation with a visual rating system and a more sensitive measure of cluster compactness than the visual rating system. Several pruning severity treatments were applied to table grape cultivars to determine their influence on cluster compactness. It was possible to measure statistically significant differences in cluster compactness among these treatment using this wedge measurement technique.

COMPARISON OF PRUNING TECHNIQUES TO INVIGORATE LOW-VIGOR ALMOND TREES

Some precocious almond varieties often produce little vegetative growth once they reach full maturity. A pruning trial was established using 11 year old `Harvey' trees that were healthy but making little or no new growth. The four treatments were: 1) severe heading or dehorning trees to six foot in height (first year only), 2) heading one third of the tree for three years, 3) making 20 small heading cuts all over the tree each year, and 4) normal thinning cuts (or control). All heading treatments caused more shoot growth than did the conventional thinning cuts (or control). The dehorning treatment (#1) responded with the most vigorous growth but much lower yields during the next two years compared to the control (#4). Yields were comparable between the two treatments during years three to five however. The heading treatments #2 and #3 had comparable yields with the control by the second year. They also showed more shoot growth. Tree yields from treatment #2 tended to lag below treatment #3 and the control, even though they were statistically the same. This trend may indicate that three years of moderately severe pruning is too much. Treatment #3 may be the best technique for invigorating healthy low vigor trees while minimizing yield losses, but will be the most expensive.

PRUNING VS. TREE REMOVAL OF CROWDED `HARTLEY' (JUGLANS REGIA) TREE

Two management systems were initiated in a 10 year old Juglans regia cv. Hartley orchard planted 8 m. × 8 m. in 1977. Annual dormant selective pruning was practiced for the next 8 years on all trees within one treatment (pruning) compared to dormant severe pruning on alternate temporary trees with no pruning on adjacent permanent trees (thinning). Temporary trees were removed in the thinning treatment in 1985. Yield, trunk cross sectional area, pruning weight and nut quality factors were evaluated each year from the 5 replicate, completely randomized trial. Yield and nut quality factors did not differ between the two treatments during the 15 years. In 1990 the pruned trial was again pruned causing a 20% drop in production (p=.06). With no additional pruning yield returned to slightly above the thinned treatment in 1991. This trial demonstrates that Hartley walnut trees (terminal bearing habit) continue to produce satisfactory crops under crowded canopy management but a tree thinning program offers other advantages which also should be considered.

Pruning of nodal root axes to simulate feeding by corn rootworm (coleoptera: chrysomelidae) on grain corn

Mechanical root pruning was examined as a technique to simulate damage by northern and western corn rootworm to corn plants in a 3-year study. Nodal root axes of corn were pruned with steel blades of 4, 6, 8, 10 and 12-cm widths on each inter-row side of plants. Roots were pruned each week for 1 to 6 weeks during the normal period of rootworm infestation to simulate continuous larval feeding. For evaluation of the technique, plants in some treatment plots and in nontreated checks were retrieved immediately after pruning and 1 week later to determine amount of root pruning. In other plots the effect of mechanical root pruning on corn plant growth and yield was determined to compare with descriptions of actual rootworm damage. The effect of soil moisture on plant growth and lateral root development on nodal root axes after root pruning was determined by experiments in controlled environmental chambers. The results indicated that moderate and severe pruning of adventious roots with mechanical devices resulted in a decrease in initiation of nodal root axes and that for each cm width of the tool ca. 3% of the roots in the most recent two nodes were severed. Comparisons between effects of mechanical root pruning and reports in the literature on effects of rootworm feeding on corn revealed similar results for compensatory root growth and plant growth and development. Significant increases in lateral root development on nodal root axes were observed after mechanical root pruning and the amount of compensatory root growth was affected by soil moisture conditions. Field experiments were conducted over 2 years employing the techique. In 1987 seasonal rainfall was nearly normal and there were significant differences in plant growth and yield among both the various root pruning treatments and for the different periods of 1 to 6 weeks of consecutive pruning. In 1988 drought conditions resulted in a large soil moisture deficit and there were significant differences in grain yield among the different root pruning treatments but number of weeks of consecutive root pruning did not affect yield. In both years the lowest root pruning treatment of 25% nodal root axes removal resulted in less than a 10% reduction in yield even when the pruning was repeated in each week for 6 weeks. Mechanical root pruning was shown to be an effective technique for causing damage to corn roots in the field similar to that caused by corn rootworms in removing a consistent proportion of roots at a designated time.

Timing and Severity of Pruning Effects on Cranberry Yield Components and Fruit Anthocyanin

Timing and severity of pruning in a 30-year-old commercial `McFarlin' cranberry (Vaccinium macrocarpon Ait.) bed were studied. Treatments in 1989 and 1990 consisted of early or late pruning and heavy, moderate, light, or no pruning. Yield component data were collected in Fall 1989 and 1990, just before harvest. Time of pruning did not affect yield components. In 1989, the unpruned and lightly pruned vines had a higher total plant fresh weight, fewer berries, higher berry yield, longer and more fruiting uprights, and fewer nonfruiting uprights (U,) compared with moderately or heavily pruned vines. Average length of UN and anthocyanin content of berries in 1989 were not influenced by pruning. In 1990, the effects of pruning severity were similar to 1989. In 1990, unpruned vines had a lower percent fruit set and berries contained less anthocyanin than pruned vines. Annual pruning with conventional systems in use decreases yield.

Effect of pruning on fruitset and shoot growth of ‘Packham's Triumph’ pear trees

The severity of dormant pruning of two-year-old shoot units on young bearing Pyrus communis L. cultivar ‘Packham's Triumph’ pear trees was varied. The location of new shoot growth was manipulated by removing new shoots from various sections of 2-year-old shoot units. Shoot units were pruned at intervals before and after anthesis. The number of styles pollinated per flower on pruned and unpruned shoot units was varied. Percentage fruitset increased with pruning. Poor correlation between percentage fruitset and the number of new shoots indicated that competition between shoots and fruits alone could not explain the variable fruitset. The location of new shoots relative to fruits was important. Pruning delayed 3 weeks or longer after anthesis failed to improve fruitset. Pruning increased the set of true parthenocarpic fruit.

Influence of Training System and Pruning Severity on Yield, Vine Size, and Fruit Composition of Vignoles Grapevines

Vignoles grapevines were trained to four training systems: (1) high cordon - a bilateral cordon at the top wire (1.8 m); (2) low cordon - a bilateral cordon at the bottom wire (1.0 m); (3) high head - a head with the trunk maintained at or just below the top wire; and (4) low head - a low head with the trunk maintained at or just above the bottom wire. In addition, three pruning severities were applied (15 + 15, 20 + 20, and 25 + 25). Data were collected over a seven-year period from 1983 through 989. The vines were evaluated for yield, vine size maintenance, fruit quality, winter damage, and vine canopy characteristics. Vines trained to the high cordon system were superior to other training systems in yield and the equivalent or better than other systems with relation to vine size and fruit maturity indices. Tentatively, we propose that crop may be controlled via a linear pruning severity of 15 + 15.

ブドウ‘巨峰’の結実と小花中の内生植物ホルモンとの関係

The effects of dipping flower clusters before bloom in solutions of various plant growth regulators (GR) on the setting of parthenocarpic and seeded berries in 'Kyoho' grape were studied. The effects of a) dipping immature rachis in 2, 500 ppm succinic acid-2, 2-dimethyl hydrazide (SADH) and b) severe winter pruning on the content of endogenous plant growth substances in florets were also examined. The 'Kyoho' vines were trained to a vertical espalier and the pergola trellis systems.1. Dipping flower clusters in plant growth retardants, ((2-chloro-ethyl) trimethyl ammonium chloride) (CCC) and SADH significantly increased the set of seeded berries as compared to the control clusters. Among different dosages of GR, 2, 500 ppm SADH was most effective, independent of the training system; applications of growth promoters were ineffective in setting seeded berries. SADH also increased the number of seeds per berry, especially on vines trained to an espalier system.2. Severe pruning resulted in a high percentage set of seedless berries.3. An application of SADH decreased gibberellin (GA) and increased abscisic acid (ABA) contents in florets. Contrarily, severe pruning resulted in a rapid increase in GA level at bloom and a decrease in ABA content. The amount of cytokinins and indole-3-acetic acid (IAA) in florets also changed with these treatments. The amount of cytokinins increased with SADH treatment, but the relationship between the setting of seeded berries and the level of cytokinins and IAA in florets could not be established.These results suggest that poor berry setting in 'Kyoho' can not be explained by the theory of nutritional competition between cluster development and shoot growth. That endogenous plant growth substances, especially GA and ABA, in the florets are closely associated with the setting of seeded berries became evident in this study.

The Relationship between Maturity Level and Splitting in Poinsettia

The relationship between poinsettia (Euphorbia pulcherrima Willd. ex Kl.) maturity and premature flower bud initiation (splitting) was evaluated. Changes in root growth, phyllotaxy, and heterophylly of `Annette Hegg Dark Red' poinsettia stock plants and cuttings in response to repeated severe pruning (hedging) and the chemical growth regulators gibberellic acid (GA4+7), PBA, or ethephon were evaluated. Cuttings taken from hedged stock plants exhibited a phyllotaxy of 1/3 to 2/5, extensive root growth (characteristics of juvenility in poinsettia), and a low level of splitting (34%). Cuttings taken from nonhedged stock plants exhibited a phyllotaxy of 3/8, reduced root growth (characteristics of maturity in poinsettia), and a high level of splitting 177%). There was a moderate negative correlation (-0.75) between root growth and splitting and a strong positive correlation (0.94) between splitting and phyllotaxy. Cuttings treated with gibberellic acid or PBA exhibited elliptic to ovate leaves (a juvenile characteristic) and levels of splitting ranging from 20% to 90%, depending on concentration and application timing. Untreated cuttings and those treated with ethephon exhibited lobed leaves (an adult characteristic) and levels of splitting ranging from 82% to 100%. Names of the chemical growth regulators were: trihydroxy-1-methyl-8-methylenegibb-3-ene-1,10-dicarboxylic acid 1,-4a-lactone (GA4+7); N-(phenylmethyl)-9-)tetrahydro-2H-pyran-2-yl)-9H-purin-6-amine (PBA); (2-chloroethyl) phosphonic acid (ethephon).

Regrowth and Palatability of Acacia Shoots Following Pruning by African Savanna Browsers

Stands of two species of African Acacia were monitored for 1 yr in a natural savanna ecosystem, to compare shoot regrowth and leaf chemistry in lightly browsed and heavily browsed trees. Where ungulates concentrated at a seasonal waterhole, A. nigrescens was more severely browsed than the thornier and finer leafed A. tortilis. Shoot regrowth in heavily browsed A. nigrescens more than compensated for herbivory, as net annual shoot extension was not significantly different from that in light browsed trees. Foliage of heavily browsed A. nigrescens was higher in nutrients and lower in condensed tannins than foliage of light browsed trees. We propose that severe pruning by browsing ungulates reduces intershoot competition for nutrients, promoting rapid shoot regrowth. Carbohydrate demands of rapid regrowth reduce carbon—based secondary metabolite synthesis. This results in patches of highly palatable browse that attract further browsing, generating a browsing regrowth feedback loop. Such patches may be considered analogous to grazing lawns.