Paclobutrazol Sprays Research Articles

The influence of foliar sprays of tetcyclasis or paclobutrazol on the growth and water use of transplantedMalus, TiliaandBetulastocks

SummaryFoliar sprays of tetcyclasis or paclobutrazol at 50 or 500 mg l_l reduced shoot extension growth and total leaf area of young transplants of Malus, Tilia and Betula. Paclobutrazol produced the stronger effects on both Malus and Tilia whilst tetcyclasis was the more potent on Betula. The treatments had no significant effect upon root growth, stem girth increment, or the numbers of shoots or leaves formed. Root: shoot dry weight ratios were significantly increased. All treatments reduced total water use by the three species in the four weeks following treatment, although the effect was not statistically significant for Betula. These responses were mainly attributable to the effect of the growth retardants in reducing individual and total leaf area. Treatment effects on rate of transpiration and stomatal conductance were small.

Use of paclobutrazol sprays at mid-anthesis for increasing fruit size and yield of avocado (Persea americanaMill. cv. Hass)

SummaryMid-anthesis foliar sprays of paclobutrazol (PB) at 2.5, 1.25 and 0.62 g a.i. I-1 reduced spring growth and altered dry-matter distribution in fruiting spring shoots of ‘Hass’ avocado.(Persea americana Mill.) trees. There was a decrease in dry matter allocation to vegetative components and an increase in allocation to fruit. The starch concentration in the wood of spring shoots on trees treated with 2.5 g a.i. I-1 foliar PB was increased by ca. 70% compared with spring shoots from trees of other treatments. The mid-anthesis foliar treatments also reduced summer growth by ca. 20%. Trunk injection of PB at 0.2 g a.i. m~2 of canopy silhouette area when the spring growth matured, in addition to a mid- anthesis foliar spray of 1.25 g a.i. I-1, reduced the length of summer shoots by 36% when compared with untreated trees. The spray treatments of 2.5 and 1.25 g a.i. T1 PB at mid- anthesis increased the mean fruit size at harvest by 16 and 11% respectively. Fruit yield was not significantly affected by PB ...

Effects of paclobutrazol and carbaryl on the yield of Hi-Early red ‘Delicious’ apples

SummaryA trial at Spreyton in north-western Tasmania compared the effects of paclobutrazol and carbaryl sprays on fruit thinning of apples. Untreated control and hand thinned trees were compared with trees treated with paclobutrazol or carbaryl alone or combinations of both. Paclobutrazol was applied 28 and 49 days after full bloom (AFB). The 28 day AFB paclobutrazol sprays were at rates of either 62.5 or 125 ppm of active ingredient followed by 62.5 ppm 49 days AFB. Carbaryl was applied at 1000 ppm at 10,17 or 24 days AFB. Although several treatments removed more fruit than the controls, only two treatments thinned to less than the desired crop load, represented by the hand thinned treatment. These overthinned treatments were combinations of paclobutrazol applications and carbaryl sprayed 24 days AFB. It is recommended that if paclobutrazol programmes are to be initiated 28 days AFB, that carbaryl should not be sprayed later than 17 days AFB. Also, if carbaryl is sprayed late it is preferable to use pacl...

Shoot Length Control of Tree Peony (Paeonia suffruticosa) with Uniconazole and Paclobutrazol

Potted plants of `Taiyoh' and `Hanakisoi' tree peony (Paeonia suffruticosa Andr.) were treated with a foliar spray of uniconazole or paclobutrazol for shoot length control. Uniconazole sprays at 25 or 50 ppm upon sprouting effectively reduced shoot length in both cultivars. The retarding effect was greater in `Taiyoh' than in `Hanakisoi' at 25 ppm. Uniconazole treatment did not influence flower diameter or days to flowering in either cultivar. Paclobutrazol sprays at 500 and 1000 ppm were less effective in reducing `Hanakisoi' shoot length than uniconazole sprays at 25 and 50 ppm. Chemical names used: E-1-(4-chlorophenyl)-4,4-dimethyl-2-(l,2,4-triazol-l-yl)-l-pentan-3-ol (uniconazole); (1RS, 3RS)-1-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-l-yl)-l-pentan-3-ol (paclobutrazol).

Chemical control of tree growth of plum(.Prunus domesticaL.) II. Comparisons between foliar and soil treatments and different dose rates of paclobutrazol on growth and cropping of three cultivars

Sprays of paclobutrazol, when applied to the soil beneath European plum trees prior to bud break in early spring significantly reduced mean extension shoot length. Foliar sprays applied later, in late May and mid-June, had similar effects. Proportionally, effects were greatest on the vigorous cvs Opal and Cambridge Gage, and less on River’s Early Prolific, which has a more compact habit. In the season of treatment, growth inhibition was apparent earlier on the soil-treated trees and was slightly more pronounced than that produced by foliar sprays. Addition of a spray additive, Sunspray oil, to the foliar sprays gave no significant benefit. Extension shoot lengths were severely reduced in the year following a single paclobutrazol treatment to ‘Cambridge Gage’ and ‘River’s Early Prolific’, whilst residual effects on ‘Opal’ shoot growth were, in contrast, minimal. In the third and fourth seasons following treatment no residual effects on shoot growth were recorded and the trees grew at rates similar to, or s...

Adjuvant Addition Increases Paclobutrazol Spray Efficacy on ‘Delicious’ Apple

Abstract The objective of this study was to determine the effect of various adjuvants in a foliar paclobutrazol (PB) spray on vegetative growth and fruit characteristics of apple (Malus domestica Borkh.) trees.

Growth and Development of Young ‘Loring’ Peach Trees after Foliar Sprays of Paclobutrazol and GA3

Abstract Container-grown ‘Loring’/Lovell seedling peach trees [Prunus persica (L.) Batsch] trained to four current-season extension shoots (ES) were treated with 60, 240, or 960 mg of foliar-applied paclobutrazol (PBZ)/liter 8 weeks after shoot growth began, followed 2 weeks later by a 50-mg spray of gibberellic acid (GA3)/liter. PBZ reduced both the post-treatment increment in trunk cross-sectional area (𝚫TCA) and current-season shoot length (𝚫ES) by up to 26% and 43%, respectively, as compared to control. GA3 increased 𝚫TCA by 45% and stimulated an increase in 𝚫ES, especially on the trees treated with PBZ at 0 and 60 mg·liter-1. PBZ had reduced the total length of lateral shoots (LS) developing on the ES by up to 48% and 38% as compared to control by 2 and 14 weeks, respectively, after PBZ application. However, the GA3 application increased the total LS length by 38%. The ES positioned at the two most basal locations on the tree trunk produced a 31% increase in LS length per ES, but there was no interaction between ES location and PBZ or GA3 influence on the final growth parameters. Total plant dry weight and root: shoot ratio were not affected by PBZ, but GA3 increased plant dry weight 38% and decreased the root: shoot ratio. Chemical name used: β -[(4-chlorophenyl) methyl]- α-(1,1-dimethylethyl)-l-H-l,2,4-triazole-1-ethanol (paclobutrazol).

Growth and Development of Young Peach Trees as Influenced by Foliar Sprays of Paclobutrazol or XE-1019

Abstract A single or four sequential foliar sprays of paclobutrazol (PBZ) and XE-1019 (Valent Corp., Walnut Creek, Calif.) to peach [Prunus persica (L.) Batsch.] supplied, respectively, 7.5 to 480 mg a.i. and 0.75 to 48 mg a.i. doses per tree. These treatments reduced the net change in total shoot length (current-season extension shoots plus lateral shoots) occurring over the 15-week period after the sprays were applied by up to 80% and 69%, compared to the control, for each compound, respectively. The average number of lateral shoots was decreased 85% and 81% by the highest dose of each material. The shoot and whole plant dry weight at the end of the growing season (15 weeks after treatment) were ≍22% and 27% lower than the control for PBZ and XE-1019, respectively. Trunk cross-sectional area, leaf area, and dry weight of leaves and roots were also smaller on the trees treated by either compound. Root : shoot ratios were not influenced by any treatment. Chemical names used: β-[(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazole-1-ethanol (paclobutrazol); (E)-1-(p-chlorophenyl)-4-,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol (Valent XE-1019).

Cranberry growth and yield response to fertilizer and paclobutrazol

In glasshouse studies with cranberry, paclobutrazol (PP333) ((2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pentan-3-ol) applied twice as a foliar spray at 75, 150, 300, 600 or 1200 mg 1 −1 decreased shoot and root growth, and the shoot: root ratio. Paclobutrazol decreased shoot elongation within 3 weeks of application and increased the number of branches on primary shoots. Buds were formed within 7 weeks of treatment and some contained flowers. In a second experiment, flower-bud formation was greater when plants were treated with paclobutrazol at 1.25, 2.50 or 5.00 mg pot −1 as a soil drench and grown for a longer period. Plants grew more with high NPK than with low NPK but growth was diminished still by paclobutrazol. High NPK decreased floral induction. Paclobutrazol was still detected in the soil 50 weeks after application. In a cranberry field study, foliar sprays of paclobutrazol at 75 or 150 mg 1 −1 at full bloom and 2 weeks later decreased fruit set, fruit size and yield, but increassed bud set and flower-bud set on uprights. Shoot growth was decreased the following year but the number of flowers per upright was increased. Fruit set was the most important contributor to yield variation, followed by fruit size and flowers per upright. The effects of paclobutrazol upon adjusted yield components accounted for a substantial amount of yield variation. No effect of cultivar on yield was apparent as the higher proportion of adjusted number of uprights flowering in cultivar ‘McFarlin’ was offset by an increased adjusted number of flowers per upright in cultivar ‘Bergman’. Bud set and flower-bud set were greater in uprights that did not flower in the current season.

Effect of the plant growth regulators paclobutrazol and chlormequat chloride on pear psyllid (Cacopsylla pyricola(Foerster)) and pear rust mite (Epitrimerus piri(Nal.))

SummaryFollowing programmes of four to six sprays of paclobutrazol and chlormequat chloride on pear cv. Conference, population densities of pear rust mite (Epitrimerus piri) were reduced by ca. 60% compared with unsprayed trees. Population densities of pear psylla (Cacopsylla pyricola) on paclobutrazol-treated trees were about half those on untreated ones, but were not affected by chlormequat chloride. In laboratory bioassays, chlormequat chloride was toxic to pear rust mite at concentrations well below field rates. Chlormequat chloride was not toxic to pear psylla larvae, and adults were affected only at rates well above those used in the field. Paclobutrazol showed no acute toxicity to either pest species.

Effect of paclobutrazol on vegetative growth in citrus nursery trees

Two foliar sprays of paclobutrazol applied at four different concentrations, viz. 50,100, 200 and 500 mg a.i. l−1 on Citrus volkameriana (Ten. & Parq.) under greenhouse conditions, showed that concentrations of 100 mg l−1and above are suitable for reducing undesirable spindly growth of citrus rootstocks under crowded nursery conditions. Paclobutrazol at 200 and 500 mg l−1 resulted in the greatest growth check and there was no significant difference between these two treatments. At these higher concentrations, however, there seemed to be a residual effect on the subsequent growth of the scions. The growth check on the rootstock at 100 mg l−1 was significantly less than 200 and 500 mg l−1 but still of practical benefit to nurserymen, besides having no residual effect on the growing scions. The treatments did not cause any significant differences in stem diameter and bud take.

Growth Response of Selected Container-grown Bedding Plants to Paclobutrazol, Uniconizole, and Daminozide

A study was conducted to compare the growth-retarding effects of paclobutrazol (Bonzi), uniconizole (XE-1019, Sumagic), and daminozide (B-Nine) on container-grown bedding plants. Seedlings of Begonia semperflorens ‘Olympia’, ‘Scarletta’, and ‘Vodka’, Catharanthus roseus ‘Little Bright Eye’, Impatiens sultani ‘Blitz Orange’, and Zinnia elegans ‘Yellow Marvel’ were treated with a paclobutrazol spray at 0.15, 0.3 or 0.45 mg ai/plant, or a drench of 0.15 mg ai/pot. Uniconizole was applied as a spray at 0.025, 0.05, or 0.075 mg ai/plant, or a drench of 0.025 mg ai/pot. The daminozide was applied only as a 5000 ppm spray. Paclobutrazol and uniconizole were very effective in controlling the height of begonia, catharanthus (vinca), and impatiens at relatively low rates compared to daminozide. The height of zinnia was controlled by daminozide, but not by the other compounds at the rates tested.

Paclobutrazol Inhibits Growth of Zinnia and Geranium

Abstract ‘Scarlet Ruffles’ zinnia (Zinnia elegans Jacq.) and ‘Smash Hit’ geranium (Pelargonium × hortorum L.H. Bailey) were treated with soil drenches and foliar sprays of paclobutrazol for height control. Single drench applications of 0.5 or 1.0 mg a.i./pot and single spray applications of 250, 500, or 1000 ppm were effective in reducing the height of zinnia. Geranium height was reduced by single drenches of 0.0075 or 0.015 mg a.i./pot and single sprays of 20 or 40 ppm. Higher drench or spray rates resulted in excessive reductions in height and leaf size. Chemical name used: (±)-(R*, R*)-β([4-chlorophenyl]methyl)-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

Comparison of Paclobutrazol Tablets, Drenches, Gels, Capsules, and Sprays on Chrysanthemum Growth

Abstract Paclobutrazol drenches were more effective in retarding chrysanthemum (Chrysanthemum × morifolium ‘Charm’) plant height than paclobutrazol incorporated in plaster-of-paris tablets, injected hydrogels, and gelatin capsules applied at the same rate (0.5 mg a.i./15-cm pot) in three experiments. Capsules containing paclobutrazol also controlled plant height effectively in all three experiments. Drenches consistently reduced plant area, whereas a 50-ppm paclobutrazol spray did not. Paclobutrazol tablets, gels, and capsules reduced plant area in two of three experiments. Drenches were the only treatment to reduce flower number per plant. Chemical name used: β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

Preliminary studies on the use of (2RS, 3RS)-paclobutrazol for fruitlet thinning and growth control of ‘Conference’ pear

SummarySingle foliar sprays of paclobutrazol (PP333) at 300, 1000 or 3000 mg H applied at three different stages from full bloom to petal-fall in a year of average initial sets . and fruit size were equally effective in thinning ‘Conference’ pear, increasing the proportion of large fruits at harvest, but decreasing their absolute numbers. Sprays applied nine days after petal-fall reduced initial sets less effectively and, applied 21 days after petal-fall, were ineffective. Thinning was completed within 25 days after petal-fall. Shoot extension was initially retarded at all three concentrations, but later increased, so that the total growth made during the season was not reduced. Single foliar sprays at 300 or 1000 mg l−1 applied at 70% full bloom in a year of heavy set and small fruit size increased the numbers of large fruits in the >55 mm size category by 66% and decreased those of fruits <55 mm by a similar amount. The increase in the yield of fruits >55 mm and decrease of unsaleable <45 mm fruits was equivalent to about 3 and 2 t ha−1 respectively from a total average yield of about 17.5 t ha−1. In the same experiment, similar sprays counteracted the stimulation in the production of small fruits by sprays of gibberellic acid (GA) applied on the same day, but did not increase the harvest of large fruits. Sprays of paclobutrazol at 30 or 100 mg l−1 applied two weeks after petal-fall and then on three successive occasions at two-week intervals inhibited total extension growth per shoot during the season without affecting initial or final sets, fruit size or flower bud production. Single sprays applied at 100 mg l−1 in July reduced total extension per shoot almost as effectively as the repeated sprays. For more effective control of ‘Conference’ shoot growth, paclobutrazol may have to be sprayed later in the season than commercially recommended. Applied as a blossom thinner, paclobutrazol may increase the yield of large fruits only in years of heavy set and small fruit size, requiring that applications be delayed until set can be judged.

The mechanism of the effect of (2RS, 3RS)-paclobutrazol on flower initiation of pear cvs Doyenne du Comice and Conference

SummaryThe mechanism of action of paclobutrazol in promoting flower initiation in two cultivars of pear was studied by comparing responses to overall sprays, localized treatment of shoot tips and shoot tipping by hand, and by monitoring bud development in ‘Doyenne du Comice’. Flower initiation was promoted as effectively by localized shoot tip applications as by overall sprays. Shoot tipping did not promote flower initiation, and did not affect the stimulation of flower bud production by overall sprays. Shoot extension in both varieties was inhibited equally by shoot-tip applications, but not by overall sprays, the effects of which on ‘Comice’ were followed by a compensatory promotion of growth. In the season after overall spraying, ‘Comice’ produced many more new, mostly “bourse” shoots. This effect was not produced by shoot tipping or by paclobutrazol treatment of shoot tips or fruitlets. Repeated sprays of paclobutrazol at 250 mg l−1, but not a single spray at 1 g l−1 in July, delayed flower initiation...

Restructuring and cropping large ‘Red Delicious’ apple trees with paclobutrazol and daminozide

SummaryApplications of paclobutrazol to the soil in 1983 did not affect shoot length in either the first year (1983-4), or in the following year. In trials in 1983-4 and 1985-6, foliar sprays of paclobutrazol or daminozide reduced shoot length. Sequential sprays were mostly similar to one high-concentration spray of the same quantity of chemical applied in November. With appropriate concentrations, paclobutrazol and daminozide increased fruit numbers/unit trunk area and increased the number of flower clusters per unit limb area, but did not affect fruit shape. Mean fruit weight was decreased by daminozide. Fruit shape, measured by length-diameter ratios was unaffected by any treatment in these trials. After the 1984 treatments, where vegetative growth was retarded, more flowers were initated.

Effect of Fertilizer, Paclobutrazol, and Chlormequat on Strawberry

Abstract In a greenhouse study with strawberry (Fragaria × ananassa Duchesne), foliar sprays of paclobutrazol (PP333) at 10, 46, 215, or 1000 ppm and chlormequat chloride (CCC) at 215 or 1000 ppm decreased runnering, but PP333 was most effective. PP333 inhibited runnering more for ‘Totem’ than ‘Shuksan’, with the reverse true for CCC. Biweekly fertilization with 20N-4.3P-8.3K at 180 mg/pot increased leaf area and runnering relative to 45 mg/pot. PP333 at equal rates produced larger decreases in leaf area than CCC. Both high fertilizer and PP333 in a rate-dependent manner delayed leaf senescence and berry ripening. CCC increased yield in ‘Shuksan’ only, and while berry fresh weight was increased by PP333, no increase in yield occurred, as it was offset with a decreased number of berries that ripened over the period of our study. PP333 decreased pollen germination. Soil residues of PP333 were evident 11 weeks after application. Chemical names used: β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H- - 1,2,4-triazole-1-ethanol (paclobutrazol); 2-chloro-N, N, N-trimethylethanaminium chloride (chlormequat chloride).

Uptake and translocation of paclobutrazol by shoots of M.26 apple rootstock

When 14C-paclobutrazol, a gibberellin synthesis inhibitor, was applied to different parts of actively-growing M.26 apple rootstock shoots it was translocated acropetally when applied to the young stem and, to a lesser extent, from the youngest unrolled leaf. Paclobutrazol was not translocated out of leaf laminae, shoot tips or from one-year-old wood but translocation occurred out of a treated petiole into the attached leaf. No basipetal translocation was detected. This translocation pattern suggested movement through the xylem. Localised application of paclobutrazol caused a reduction in shoot extension and leaf production when the young stem or shoot tip were treated; the effect decreased as older parts of the stem were treated. Treatment of laminae or petioles had only a slight effect on shoot extension and treatment of one-year-old wood was ineffective. Combined treatment of the shoot tip plus young stem was similar in effect to treatment of the complete shoot. It is suggested that paclobutrazol exerts its effects on shoot growth by inhibiting gibberellin biosynthesis in the shoot tip and the expanding leaves. The findings contribute to an understanding of the requirements for efficient orchard application of foliar sprays of paclobutrazol.

Effects of paclobutrazol and A-Rest on growth, flowering, leaf carbohydrate and leaf senescence in ‘Nellie White’ Easter lily ( Lilium longiflorum Thunb.)

The influence of paclobutrazol and A-Rest treatment on plant height, flowering, leaf senescence and leaf carbohydrates in ‘Nellie White’ Easter lily were examined. Soil incorporation of granular paclobutrazol was most effective in reducing plant height, followed by soil drench and a top dressing of granular paclobutrazol. The relationship between paclobutrazol concentration and height reduction was linear. However, paclobutrazol spray had no effect on height. A-Rest soil drench was more effective than foliar spray. Paclobutrazol and A-Rest treatments hastened lower leaf senescence. During flower bud development, leaf total soluble sugars were reduced by paclobutrazol incorporation and drench, and A-Rest drench.