Mechanical Pruning Research Articles

The Influence of Mechanical Pruning in Cost Reduction, Production of Fruit, and Biomass Waste in Citrus Orchards

In this work the suitability of mechanical pruning to reduce costs and increase profits in citrus orchards has been analyzed. Six different types of solely mechanical pruning were assessed, another six of mechanical pruning combined with subsequent manual pruning, and these were compared with traditional pruning. The most suitable method of cutting was determined as well as its influence on production, the quality of the fruit, and the biomass waste obtained. The results obtained indicate that the practice of mechanical pruning combined with manual pruning improves production, the cost being similar to traditional pruning. This means that profits are increased. The cost of combined pruning (mechanical + manual) is 800 € ha-1, reaching an increase in production of 30 kg per tree, which is equal to 18 t of fruit/ha. With a sale price of 192.3 € t-1 of fruit, an extra profit of 2,661.4 € ha-1 is obtained with respect to conventional manual pruning.

Application Interval and Concentration Affect Nursery Crop Response to Cyclanilide

Abstract Cyclanilide (CYC) is a bioregulator that promotes the development of lateral shoots in ornamental and fruit tree crops, potentially reducing the need for mechanical pruning during nursery production. In 2006, three foliar applications of 200 ppm CYC applied at a 1, 2, or 3 week application interval increased shoot counts of ‘Diana’ sasanqua camellia, ‘Sky Pencil’ holly, and ‘Snow White’ Indian hawthorn when compared to pruned and unpruned controls. However, application interval had no effect on shoots counts in holly or camellia and minimal effect in Indian hawthorn. Foliar injury to Indian hawthorn was severe, regardless of application interval. In 2007, three applications of 50 or 100 ppm CYC were applied at a 1, 3, or 6 week interval to ‘Sky Pencil’ holly and ‘Snow White’ Indian hawthorn. At 120 to 150 days after initial treatment (DAIT), shoot counts in both species increased with application interval, and all CYC-treated plants formed more new shoots than controls. Transitory injury to new growth of Indian hawthorn, although not quantified, appeared to increase as application interval decreased. At 120 DAIT foliar injury was no longer evident in Indian hawthorn. At 180 DAIT quality rating of both cultivars increased with CYC application interval and was greater than that of controls, and CYC-treated plants were visibly more dense and compact.

EVALUATION OF THE CUTTING FORCE ON VINE BRANCHES IN WINTER PRUNING

Mechanical pruning, usually integrated with manual finishing, still excites some doubts regarding the quality of the cut which appears not to be the best as precision and cleanliness. This aspect, probably conditioned by the model and the application of pruning machines, might also be affected by the characteristics of the vine branches in particular by their cutting force. In order to evaluate the cutting force on different vine type, laboratory and field trails were carried out. The experiments were set in order to evaluate this parameter during winter pruning in relation to three variables: vine type; branch size; pruning time. The results show how the cutting resistance of vine branches during vegetative rest depends on vine variety (Trebbiano 675 N Cabernet 1175 N), on the diameter of the canes (increase of force from 56 % to 86 % between the classes of diameter) and on the pruning date (26% decrease of the cutting force in the latest period for Trebbiano and Sangiovese, and 32 % for Cabernet Sauvignon). Such variations, which can be considerable, affect directly the pruning results. High values of cutting force can generate tiring of operator in manual pruning or cutting damages on the vegetation during mechanical pruning.

Mechanical Cane Pruning and Crop Adjustment Decreases Labor Costs and Maintains Fruit Quality in New York ‘Concord’ Grape Production

Four pruning techniques were evaluated from 1999 to 2003 in a commercial ‘Concord’ (Vitis labruscana) vineyard in Westfield, NY. Manual pruning, mechanical pruning with manual pruning follow-up, mechanical pruning with fruit thinning, and minimal pruning with fruit thinning averaged a 2.4-fold difference in retained nodes per vine. Treatments with crop adjustment required fruit thinning in 3 of 5 years to maintain an acceptable crop size. Manually pruned vines, mechanically pruned vines with manual follow-up pruning, and mechanically pruned vines with crop adjustment had similar yields, juice soluble solids, lignified periderm, juice color, juice titratable acidity, and juice pH in 4 of 5 years. Minimally pruned vines tended to have slightly higher yield and lower juice soluble solids, color, and titratable acidity in 3 of 5 years. Pruning system cost estimates indicated a 56% and 80% cost reduction per acre when comparing manual pruning with mechanical pruning plus manual follow-up or mechanical pruning plus mechanical fruit thinning, respectively. These results support two commercially acceptable and sustainable pruning management options for New York ‘Concord’ grape production.

Neoformed growth responses to dormant pruning in mature and immature pistachio trees grown on different rootstocks

SummaryThe relationship between pruning and the production of neoformed growth in ‘Kerman’ pistachio (Pistacia vera L.) trees on different rootstocks was investigated to determine if the increased neoformed growth common in trees on more vigourous rootstocks was related solely to rootstock vigour, or was an artifact of pruning practices. While some neoformed growth was inherent in mature trees, pruning increased the amount produced on each tree regardless of rootstock or crop load. However, regardless of pruning severity, the least vigourous rootstock never produced as much neoformed growth as the two more vigourous rootstocks. Pruning cuts made into 2-year-old wood were the most stimulatory, while pruning cuts into 1-year-old wood resulted in growth similar to unpruned controls. The data presented indicate that the invigorating response to pruning in young trees is highly localised, and that pruning can be varied depending on the stage of tree development and the desired growth response. Overall, the data suggest that hand-pruning, while more costly in the short-term than mechanical pruning, may be useful in creating a more desirable canopy architecture, thereby potentially reducing long-term pruning needs and overall management costs.

Cyclanilide Spray Increases Branching in Containerized Whip Production

Abstract A major goal in the production of tree whips is to produce appropriately sized, well-branched liners with a crown form similar to that of a mature tree. Pruning is used to induce lateral branching. This can result in poor tree quality, reduced growth and the practice is labor intensive. An alternative to mechanical pruning, foliar Cyclanilide® (CYC) sprays at 0, 56, 1 12 and 223 ppm were applied to container grown whips to determine its effect on branching of Amelanchier; Cercis, Malus and Tilia whips. Most species responded to CYC sprays with increased lateral branching if treated during active shoot elongation. Cyclanilide® sprays of 1 12 ppm produced the greatest number of branches. Sprays at 56 ppm resulted in reduced branching (relative to 112 ppm), while sprays of 223 ppm did not increase the number of branches, relative to sprays of 112 ppm, but reduced growth. Cyclanilide® sprays reduced height growth, relative to untreated whips, but did not alter height diameter growth. Cyclanilide® foliar applications to container -grown whips during periods of active shoot elongation increased branching in one-year-old whips that normally do not branch until the second year of production. Further, the origin of lateral branching can be controlled by timing of CYC application. The results indicate that CYC foliar sprays can be an important tool in the production of one-year-old branched whips.

A influência da poda mecânica na produção e na eficiência da colheita da azeitona por vibração

In Portugal, olive farmers, particularly those with orchards of around 100 trees per hectare, are facing increasing pruning costs every year. As a result they tend to lengthen pruning intervals. With the purpose of studying a mechanised alternative to the labour intensive manual pruning practice, the authors established in 1997 field trials with the following three treatments: T1 -manual pruning cutting with a chain saw; T2 - mechanical pruning, performed by a tractor mounted cutting bar provided with 6 circular disc-saws; T3 -mechanical pruning, as in T2, followed by a manual pruning complement. In each test site, olives were harvested using a trunk shaker. Total production per tree, as well as the shaker efficiency was also evaluated. This paper, updating the research work previously presented at the 5th International Symposium on Olive Growing (Dias et al., 2004), shows the following major results: In both olive orchards tested, the cumulative results in yield in the subsequent four harvesting campaigns from the date of pruning, reveal no significant differences (P>0,1) between pruning treatments. In one of the olive orchards, shaker performance was not influenced by the way trees had been pruned. However, in other orchard, shaker efficiency was observed to be significantly lower on trees that had been pruned mechanically.

One-Time Pruning of Pecan Trees Induced Limited and Short-Term Benefits in Canopy Light Penetration, Yield, and Nut Quality

Twenty-five-year-old `Cape Fear', `Desirable', and `Kiowa' pecan [Carya illinoinensis (Wangenh.) C. Koch] trees were either not pruned, or subjected to single selective or mechanical pruning using a mechanical hedger [or hedge pruning (HP)] in the dormant season 2003. Canopy light interception, yield, and nut quality were monitored during a period of three years. Leaf area index and light interception were significantly affected during the first growing season after treatment application, but after three years canopies grew back to control levels. In general, there were small positive effects observed on yield and nut quality after pruning. Minor improvements were recorded for `Desirable', in which yield was affected positively by both pruning strategies in 2004. However, most effects disappeared by the third year. `Desirable' responded better than `Cape Fear', whereas no beneficial effects were recorded on `Kiowa'. In 2005, yield was significantly reduced in HP trees of `Cape Fear' and `Kiowa'. Alternate bearing index was unaffected by pruning treatment or cultivar. Kernel percentage increased only in HP `Desirable' trees in 2003 and 2004. Kernel quality was improved in HP `Cape Fear' and `Desirable' in the first growing season after treatment application, but not in 2004. In 2005, quality was again improved in HP `Desirable'. The results of the current study indicate that one-time pruning of pecan trees induce positive short-term effect on light, but not necessarily an increase in productivity and nut quality.

The Use of Cyclanilide to Promote Lateral Branching in Container-grown Whips

In nursery production, increased branching is desirable, especially when growing stock that will be marketed at smaller sizes. Typically, branching is increased by pruning, which reduces growth potential. As an alternative to mechanical pruning, a chemical branching agent, Cyclanilide, has been evaluated for its ability to increase branching in container-grown whip production systems. Cyclanilide sprays of 0, 50, 100, and 200 mg·L-1 were applied to elongating shoots of Acer ×freemanii `Jeffsred', Cercis canadensis, Diospyros virginiana, Eucommia ulmoides, Malus ×`Prairie Fire', Malus ×`Harvest Gold', and Quercus rubra whips. Branching was increased in all taxa except Eucommia at concentrations >100 mg·L-1, without significantly reducing plant dry weight. For Diospyros, branching was increased when combined with pruning before Cyclanilide application.

BA Application Frequency and Concentration Effects on Two Indian Hawthorn Cultivars

Abstract Benzyladenine (BA) is a synthetic cytokinin that promotes lateral shoot development in herbaceous and woody ornamentals and may be a viable alternative to mechanical pruning in nursery production. A study was conducted to determine the effects of BA application number, interval and concentration on two Indian hawthorn [Rhaphiolepis Lindl. Cor. Poir. indica (L.) Lindl. (Crataegus indica L.)] cultivars. In spring 2002, actively growing ‘Olivia’ and ‘Eleanor Taber’ received three applications of 2500 or 5000 ppm BA at a one-, two-, or three-week interval. Data collected four weeks after initial treatment (WAT) reflected the effects of one, two, or three BA applications at each concentration. At this time new shoot counts in both cultivars and foliar injury in ‘Olivia’, but not in ‘Eleanor Taber’, increased with increasing number of applications and BA concentration. Data collected 12 WAT reflected the effects of BA application interval and concentration. At this time new shoot counts increased with decreasing application interval in ‘Olivia’, while ‘Eleanor Taber’ formed the most new shoots when BA was applied at a two-week interval. All treated plants sustained minimal to moderate injury to immature foliage. The experiment was repeated in 2003 using 1750 ppm and 3500 ppm BA on ‘Olivia’ Indian hawthorn. Applications were halted at the first sign of foliar injury resulting in plants treated at one, two, and three-week intervals receiving three, two, and two applications, respectively. New shoot counts on ‘Olivia’ treated at the three application intervals were similar, but greater than those on untreated plants. Control plants had a foliar injury rating similar to that of plants treated at a two or three-week interval, but less than that of plants treated at a one-week interval. Growth index was not affected by treatment in either year.

Effect of training-pruning regimes on Eutypa dieback and performance of ‘Cabernet Sauvignon’ grapevines

SummaryThe effects of training-pruning regimes on Eutypa dieback, vigour, yield and fruit composition were evaluated in ‘Cabernet Sauvignon’ grapevines from 1991 to 2004 in Galt, California, USA. Mechanical pruning at bud swell, and minimal pruning (trimming only in Summer) gave the least dieback. In contrast, pruning of dormant vines trained on either a bilateral cordon or a Sylvoz system increased wounding and dieback. Hand pruning of head-trained vines gave fewer cuts and less dieback, compared with vines trained as bilateral cordons or Sylvoz. Dieback reduced the extension of fruiting arms on bilateral cordon- and Sylvoz-trained vines with dormant season pruning, whereas arms were healthy after mechanical and minimal pruning. Hand-pruned vines (bilateral cordon, Sylvoz or head) had greater pruning weights, fewer shoots and clusters, heavier clusters, and lower yields than vines pruned mechanically or minimally. Despite the presence of dieback, yields did not decline over 14 years (except for Sylvoz-trained vines from 2002, and bilateral cordon-trained vines from 2003). Fruit had lower °Brix and pH, and higher titratable acidity in some years, suggesting possible delays in fruit ripening on minimally-pruned vines. Mechanical pruning at bud swell and Summer trimming can minimise Eutypa dieback while maintaining yield and fruit quality. Training-pruning regimes that require early pruning and that generate large numbers of wounds when vines are dormant should be avoided where Eutypa is a concern.

Adaptation of olive (Olea europaea L.) to water-limited environments

Olive has been widely grown around the Mediterranean Basin for around 5000 years, where productivity and survival of this long-lived evergreen tree in environments of low and variable rainfall depend on physiological characteristics but also on management. The tree exercises effective control of water loss by transpiration and can also withstand intense internal water deficit that in turn increases extraction of water from soil. Critical aspects of management that maintain, albeit limited, transpiration and metabolic activity during hot dry summer months, are directed at both crop and understorey. Strategic decisions are selection of cultivar, tree density, and canopy size, together with surface management as tilled soil or as cover crop of selected species. Tactical adjustments are seen in extra pruning of olives and timing of tillage, or of grazing, mowing, or herbicides to restrict growth and water use of the understorey, especially following dry winters and during dry summers. Survival of olive orchards in low-rainfall climates requires that canopies intercept a small proportion of incident radiation, depending upon rainfall amount, distribution, and soil water storage capacity. Crop water balance models can assist in defining optimum canopy size for productivity and survival. New olive production in the Mediterranean and now extending widely in the ‘New World’, including in Australia, deviates widely from traditional practice. Orchards are planted at higher density, are generally irrigated, and trees are formed to suit mechanical pruning and harvesting. The environmental adaptation and understanding of water relations of olive in traditional systems are of limited applicability to these new production systems. Rather, there are now new emphases on nutrition, irrigation, canopy management, assimilate relationships, and fruiting performance to add to the existing questions of the suitability of cultivars to new environments in terms of productivity and oil quality.

Integrated Control of Grape Black Rot: Influence of Host Phenology, Inoculum Availability, Sanitation, and Spray Timing

ABSTRACT The epidemiology and control of black rot (Guignardia bidwellii) was studied from 1995 to 1999 in vineyards in Dresden and Naples, NY, where disease pressure was moderate and extreme, respectively. The efficacy of serial applications of myclobutanil, provided at 2-week intervals and varied with respect to their number and time of initiation, was examined within the context of host phenology, inoculum availability, and sanitation. At Dresden, sprays applied over 4 weeks through the immediate prebloom stage provided only 13 to 91% control of diseased clusters, despite the release of 95% of the season's ascosporic inoculum during the period of fungicidal protection. However, applications immediately prior to bloom plus 2 and 4 weeks later, which afforded protection while fruit are highly susceptible to infection, provided virtually complete control. At Naples, where mummified berries were retained in the canopy after mechanical pruning, this same regime provided only approximately 80% disease control, but applying a fourth spray 2 weeks prebloom generally improved control. Hand-pruning mummies to the ground in selected plots significantly (P </= 0.05) improved control in some spray regimes. Although this sanitation practice did not affect inoculum dynamics through bloom, very few spores were recovered thereafter from mummies collected from the ground, whereas abundant ascospores and conidia were recovered from mummies in the trellis for an additional 6 to 8 weeks.

Crop Load Management in Concord Grapes Using Different Pruning Techniques

Effects of mechanical pruning and crop adjustment on Concord vine productivity were studied over a five-year period (1997 to 2001) in two mature vineyards in eastern Washington. Data showed that vines could sustain considerably higher yields than are achieved by balance pruning. Balance-pruned vines consistently produced relatively low yields with only marginally improved fruit composition, but fruit could be harvested somewhat earlier. Large, mechanically pruned single-wire or double-curtain-trained vines produced heavy crops and attained satisfactory fruit composition and shoot lignification in both warm and cool seasons. On average, mechanically pruned vines produced over 9 t/ha more fruit than balance-pruned vines. Yields of vines with fixed-node pruning (130 nodes) or mechanical pruning with crop adjustment were similar and 4.6 t/ha greater than yields of balance-pruned vines. Crop adjustment following mechanical pruning reduced yields but did not improve yield variation, fruit composition, and shoot lignification and therefore was unnecessary in all but the heaviest cropping season (1997). Yields for all pruning treatments varied almost in parallel from season to season, and the influence of pruning method on yield, fruit composition, and shoot lignification was less important than seasonal effects. There was no evidence of vine decline and alternate or biennial bearing due to overcropping of lightly pruned vines.

Performance of Croatina under Short-Cane Mechanical Hedging: A Successful Case of Adaptation

The hypothesis that short mechanical hedging can be successfully applied even on cultivars with low fruitfulness of basal buds was tested over four years (2000 to 2003) on <i>Vitis vinifera</i> L. cv. Croatina. Yield per vine increased from 23 to 49% on hedged vines as compared to short-cane hand-pruned vines; up to a 30% increase (equivalent to ∼60 nodes per vine) there was no detriment to grape quality, and labor demand was cut by 55 to 60%. Yield compensation in the hedged vines mostly occurred as reduced budbreak; weak or no compensation effects were seen for cluster weight and bud fruitfulness, respectively. A tendency for impaired quality was seen only at the highest node number per vine (∼75), while the linear relationship found between yield and node number per vine suggests that short-cane hand-pruning can also be feasible provided that at least 30 nodes per meter of row are retained. These findings indicate that mechanical pruning can be an excellent tool for converting traditionally long-cane pruned cultivars into short-cane pruned with related advantages in terms of more balanced growth and ripening and adaptability to full mechanization.

Economic Evaluation of Mechanized Pruning of Coffee in Hawaii

Marketable coffee (Coffea arabica) yield and cost of production under two systems of mechanized pruning—hedging and stumping— were investigated. Data were collected from 1997 to 2001—a single pruning cycle—on three cultivars on three farms on Kauai, Maui, and Molokai. Treatments were variations of hedging and stumping, including time of pruning, methods of re-growth control, and tree in-row spacing were applied to each coffee cultivar. Economic evaluation was based on a partial budget analysis of the actual costs per year of the different pruning systems used on each farm. Mechanical pruning costs per acre for best hedging and stumping treatments across cultivars were 90% and 83% less, respectively, than the current practice of manual pruning. Response to pruning system varied according to coffee cultivar, tree in-row spacing and farm location. The tall cultivar Mokka had higher yields when hedged at 5 ft (1.5 m) tall and 5 ft wide, and the semi-dwarf cultivar Yellow Catuai had higher yields when stumped at 2 ft (0.6 m) tall. Hedge pruning should be done early in the year, January to February, for the semi-dwarfs, `Yellow Catuai' and `Red Catuai', but can be delayed until May for `Mokka'. Annual topping in the hedging systems should be done January to May for `Yellow Catuai' but maybe delayed until May for `Mokka' and `Red Catuai' without yield loss. The economic evaluation revealed that the cost of stumping was higher than hedging. For `Yellow Catuai' on Kauai the economic evaluation indicated that although the cost of stumping was higher, the accompanying higher yields resulted in a higher gross margin for this system. When stumping, verti- cal branches can be set with a contact herbicide spray to avoid higher hand pruning costs without lowering yields. Stumps should be narrowed after stumping if spaced, 2.5 ft (0.75 m) the current standard in-row spacing for mechanical harvesting. Wide in-row spacing (5 ft) should be considered by growers when planting or re-planting.

EUROPEAN PEAR ARCHITECTURE AND FRUITING-BRANCH MANAGEMENT: OVERVIEW OF AN INRA RESEARCH PROGRAM

Tree architecture traits are often described in relation to planting densities, tree height or adaptation of the tree to mechanical pruning. The need to reduce both pruning costs and the use of plant growth regulators (PGRs), notably in a context of integrated fruit production (IFP), lends further support to the development of architectural analysis as an aim in itself. A research program at the Institut National de la Recherche Agronomique (INRA), France, is currently focusing on two main objectives: the optimisation of training methods based on natural tree habit and the definition of new morphological criteria to better meet the needs of breeders. Resistance to pests and diseases, along with fruit quality, is also a major consideration. Observations are being carried out on trees of four cultivars in order to determine and compare their branching and fruiting patterns. Natural tree behavior is being investigated at two different development stages. The development of laterals along the trunk and their number and location during the earliest years of growth have been studied as the main determinants of tree architecture. A relationship is highlighted for differences in sylleptic branching between the first and second year shoots and the onset of bloom in the third spring. Observations were then carried out on fruiting branches once the adult stage had been reached. A relationship is shown between high-return bloom and the physiological abortion, called extinction, of a certain number of young spurs. On the other hand 'Angelys,' a newly released INRA cultivar, shows that a high alternation ratio at the individual spurs may be offset by an improved balance between vegetative and flowering spurs, resulting in more regular flowering over subsequent years (desynchronization phenomenon).

Evaluation of Strategies for Pruning and Crop Control of Concord Grapevines in Southwest Michigan

Seven strategies for pruning and adjusting the crop level of Concord vines were evaluated over a six-year period in a commercial vineyard in southwest Michigan to determine their long-term influence on vine productivity, vine structure, and fruit quality. Manual balance pruning retained 44 nodes per kilogram of cane prunings. Commercial manual pruning resulted in 25% more live nodes per vine and a 19% larger yield than manual balance pruning. Commercial manual pruning resulted in more clusters per meter of canopy but less yield per node, smaller clusters, and lower Brix than vines managed with manual balance pruning. Nevertheless, commercial manual pruning did produce acceptable fruit soluble solids in five out of six years of the experiment. Three severities of mechanical pruning resulted in yields that were comparable to commercial manual pruning at approximately 13 t/ha. As the severity of mechanical pruning treatments decreased, the number of live nodes and clusters per meter of canopy increased while yield per node and average cluster weight decreased. Moreover, the range of annual yields and fruit soluble solids for these treatments became greater as pruning severity decreased. Crop adjustment, applied in combination with mechanical pruning by spraying ammonium nitrate solutions on a portion of the vine at bloom, resulted in lower yields and higher fruit soluble solids than mechanical pruning alone. Fruit soluble solids from treatments involving crop control were greater than the commercially acceptable minimum standard of 15 Brix in five out of six years. Distribution analysis revealed that approximately 90% of the live nodes and clusters for all treatments were situated within the top 60 cm of the trellis. Moderate or minimal mechanical pruning, whether used alone or in combination with chemical crop adjustment, did not provide consistently comparable fruit quality to manual pruning. Severe mechanical pruning produced yields and fruit soluble solids that were similar to commercial manual pruning. The comparable response of these two treatments was due to the compensating factors of a 45% reduction in node fruitfulness and a 75% increase in the number of live nodes for severe hedging when compared to commercial manual pruning. Severe mechanical pruning, when used in combination with cane positioning, manual follow-up pruning after hedging, and shoot positioning, was an acceptable, sustainable practice for managing Concord vines.

Effect of feeding by larvae of Inopus rubriceps (Diptera: Stratiomyidae) on development and growth of sugarcane.

Pot experiments were used to investigate the effect of root-feeding larvae of the soldier fly Inopus rubriceps (Macquart) on shoot production from sugarcane planting pieces (setts) and on growth and ratooning of sugarcane plants. Shoot elongation was inhibited while setts were exposed to larvae, and it resumed when larvae were removed. Infested setts produced a greater weight of roots than uninfested setts. Similar symptoms were induced by mechanical root pruning, suggesting that the effect of soldier fly larvae on setts may be a redirection of growth from the shoot to roots due to root damage. Larvae had a greater effect on shoot production at lower temperature, particularly in cultivar 'Q151', which had a higher temperature threshold than 'CP44-101'. Temperature and cultivar may influence the harmful effect of soldier fly larvae on sett germination by changing the differential rates of plant growth and larval feeding. When growing plants were exposed to larvae, the infested plants were slightly smaller at harvest and subsequently produced many fewer ratoon shoots from underground buds than uninfested plants. Shoot elongation from buds was also inhibited in setts cut from the above-ground stalks of infested plants. Analysis of nutrient levels in plants did not indicate the mechanism for ratooning inhibition, because levels of time 10 elements analyzed were at least as high or higher in infested plants. Infestation was associated with an increased level of sucrose and a reduced level of fructose in stalks. The inhibitory effect of larval feeding on ratooning was not reversed when larvae were removed from pots 10 wk before harvest. However, new stubble produced from infested plants then ratooned normally after a second harvest, provided the new roots were not attacked. The symptoms of larval feeding in growing plants are unexplained, but may be caused by the prolonged withdrawal of sap from roots or the injection of some inhibitory substance by larvae.

Response of Five Woody Landscape Plants to Primo and Pruning

Abstract The use of Primo (trinexapac-ethyl) was investigated as an alternative to pruning of container-grown woody ornamental species. A foliar spray of 469, 938, or 1407 ppm (0.5, 1.0 or 1.5 oz/gal) was applied to pruned plants. A nontreated control (water) and an industry control [Atrimmec (dikegulac-sodium)] were also included for comparison. Monthly mechanical pruning or no pruning treatments were imposed during the production period. Monthly pruning alone reduced the height of euonymus, forsythia, Chinese privet, waxleaf privet, and azalea. Efficacy of plant growth regulator treatments differed among the five species. Primo was not effective in suppressing the height or trimming dry weight of forsythia, Chinese privet, or waxleaf privet and provided only a transient suppression of euonymus and azalea.