Ethephon Sprays Research Articles

613 Mitigation of Ethephon Injury to Tomato Plants by a Natural Lipid Lysophosphatidylethanolamine (LPE): Influence on the Activity of Phospholipase D (PLD)

Ethephon [2-(chloroethyl) phoshonic acid] is used widely to maximize the yield of ripe tomato fruits. However, ethephon causes rapid and extensive defoliation, overripening, and promotes sunscald damage to the fruit. Recent studies from our laboratory have provided evidence that lysophosphatidylethanolamine (LPE) can reduce leaf senescence. We investigated the potential use of LPE to reduce damaging effect of ethephon on tomato foliage and influence on the activity of phospholipase D (PLD). Disruption of membrane integrity has been suggested as a primary cause of senescence in plants. PLD is known to be a key enzyme, which initiates the selective degradation of membrane phospholipids in senescing tissues. Two-month-old tomato plants (`Mountain Spring') grown in greenhouse condition were sprayed with water, 200 ppm LPE, and 1000 ppm ethephon. In addition, LPE spray prior to ethephon or mixture with ethephon were also tested. Leaves were sampled after 0, 2, 5, 24, 72, and 168 h of spray application, for PLD activity measurements. Spray of LPE prior to ethephon spray or inclusion of LPE in the ethephon spray reduced foliar injury by ethephon. Activity of soluble PLD was increased dramatically in leaves sprayed with ethephon initially and than dropped by 7 days. We also found that LPE-treated leaves had lower PLD activity than the ethephon-treated leaves. Plants treated with LPE-ethephon mixture also showed significantly lower PLD activity. These results suggest that LPE treatments mitigate ethephon injury to tomato plants. Furthermore, it appears that this mitigation involves modulation of the activity of PLD.

165 Ethephon, Foliar Nutrient, and Gibberellin Sprays on Subsequent Season(s) Return Bloom and Fruit Set

Heavily cropping `York'/M.27 trees sprayed with seven multiple low doses of ethephon (135 mg/L each) did not cause greater return bloom in 1999 unless foliar fertilizers (either 18–18–18 or Ca N03) were added to the ethephon sprays. Foliar fertilizer sprays alone did not promote return bloom. `York'/M.7 trees selected for very little bloom in 1997 (“off year” of the biennial bearing cycle) and sprayed with 160 mg/L GA3 or 320 mg/L GA3 had significantly less return bloom in the 1998 (“on year”) (61% and 46% spurs flowering, respectively, compared to control trees that had 99% of spurs flowering). Trees sprayed in 1997 (“off year”) with GA3 return bloom and cropped in 1999; but trees in the “off year” in 1997 that were not sprayed with GA3, did not crop in 1999. Sprays of GA3 provided some control of alternate bearing of `York'/M.7 trees when applied in the “off year” of the biennial bearing cycle. Leaves taken from `Braeburn'/M.27 trees in 70 °F rooms evolved ethylene through out the 12 days of the test. A moderate ethylene peak occurred on about days 5 and 6. Leaves from trees in the 40 °F room did not evolve detectable ethylene levels until trees were put in another 70 °F room on day 6. Ethylene levels were about the same from day 6 through day 12 for all treated trees at 70 °F. Nontreated control trees in rooms at 40 or 70 °F did not produce detectable ethylene levels during the experiment (except for a very small amount detected only on day 2 from leaves seal for 24 h at 70 °F.

122 Processing Tomato Fruit Firmness, Color Uniformity, and Peeling Response to Ethephon Sprays

Ethephon (2-chloroethyl phosphonic acid) has been widely used under field conditions as a growth regulator to trigger the ripening of processing tomatoes prior to mechanical harvesting. Recent interest in whole-peeled and diced tomato products has raised questions about ethephon rates, and possible split applications for top quality. This 3-year field study tested two commercial cultivars of processing tomatoes (`OH8245' and `P696') and the effect of various ethephon applications on fruit firmness, color uniformity, and peeling variables. Transplants were established in mid to late May of 1996–1998 on raised beds in single rows at the OSU/OARDC Veg. Crops Branch in Fremont, Ohio. Ethrel applications for each cultivar were: 0, 0.58, 0.58 × 2 applications, 1.17, 1.17 × 2 applications, 1.75, 2.34, 4.68, and 7.02 L·ha–1. Fruit were tested for firmness, color uniformity, pH, titratable acids, and soluble solids. Samples from ethephon treatments of 0, 1.17 × 2 applications, 2.34, 4.68, and 7.02 L·ha–1 were peeled and canned for color inspection and firmness after 18 months storage. Three-year data for red fruit yield showed a typical response to increasing amounts (0 to 7.0 L·ha–1) of applied ethephon. While high rates (4.7 or 7.0 L·ha–1) gave some of the highest red fruit yields, and the greatest percent red fruit values, high rates were also linked with among the lowest fruit solids values. Split application comparisons showed little influence on quality variables examined in this study. However, chroma values were improved (more vivid color) when 2.3 L·ha–1 was applied vs. 1.17 L·ha–1 applied twice. Split applications also tended to produce softer fruit. Our results suggest that single ethephon applications of 1.17 to 2.34 L·ha–1 provide optimal fruit ripening and quality under midwestern U.S. conditions.

Growth Retardants Affect Growth and Flowering of Scaevola

The effects of concentration and method of application of uniconazole on growth and flowering of Scaevola aemula R. Br. `New Wonder', `Mini Pink Fan', `Purple Fan', and `Royal Fan', Scaevola albida (Sm.) Druce. `White Fan', and Scaevola striata `Colonial Fan' were studied, as was the efficacy of four other growth retardants on S. aemula `New Wonder'. Variables measured included plant width, flower stem number, flower stem length, flower number per stem, flower number per cm stem length, and days to flower. Uniconazole (1.0 mg·L–1) applied as a medium drench to S. aemula `New Wonder' reduced plant width and flower stem length without affecting flower stem number or time to flower. Flower number per stem and number of flowers per cm of stem length were increased, resulting in attractive, compact clusters of flowers. Paclobutrazol medium drench at 4.0 mg·L–1 gave similar results. Daminozide and ethephon sprays reduced plant width; however, flower number was reduced and ethephon delayed flowering. Ancymidol did not affect the parameters measured. When uniconazole drenches were applied to the other cultivars, plant width and flower stem length in all cultivars except `White Fan' decreased as rate increased. Spray applications reduced plant width of all cultivars except `Mini Pink Fan'. Flower stem length was not affected in any cultivar. Flowering habit was improved more in S. aemula `New Wonder', `Purple Fan', and `Royal Fan' than in the other cultivars. Chemical names used: α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol); butanedioic acid mono (2,2-dimethylhydrazide) (daminozide); (2-chloroethyl)phosphonic acid (ethephon); β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol); (E)-(s)-1-(4-chlorophenyl)-4,4-dimethy-2-(1,2,4-triazol-1-yl)-pent-1-ene-3-ol (uniconazole).

Efeito do ethephon e da frigoconservação na maturação de pêras cv. Packham's Triumph

Este trabalho, realizado em 1996 na Estação Experimental Agronômica da Universidade Federal do Rio Grande do Sul, em Eldorado do Sul, RS, e na Embrapa-Centro de Pesquisa Agropecuária de Clima Temperado (CPACT), em Pelotas, RS, objetivou avaliar o efeito do ethephon aplicado em pré-colheita e da frigoconservação na maturação da pêra (Pyrus communis L.) cv. Packham's Triumph. O ethephon foi pulverizado nas concentrações de 0, 12,5, 25, 50 e 100 ppm, e as pêras frigorificadas a -1,0ºC e 92-96% de umidade relativa por 0, 10, 20, 40 e 80 dias. Após os períodos de armazenamento refrigerado, os frutos foram conservados em temperatura ambiente por dois ou oito dias. A firmeza da polpa apresentou uma tendência de diminuição com o aumento das concentrações de ethephon, do período de frigorificação e dos dias à temperatura ambiente. O comportamento da relação sólidos solúveis totais (SST)/acidez titulável (AT) variou mais em função da AT do que dos valores de SST. A relação SST/AT aumentou desde a aplicação dos tratamentos até a colheita. A produção de etileno aumentou com o aumento do período de frigorificação e do número de dias em temperatura ambiente; mas não foi influenciada pela concentração de ethephon.

側枝２本仕立て一段果房栽培と房どり収穫による生食用トマトの省力・機械化栽培様式の開発

For the purpose of developing labor saving cultivation system of the fresh market tomato, the following were examined: multi-shoots training and whole truss-harvesting in single-truss tomato plants.1. To keep the high uniformity of shoot growth and flowering between lateral shoots regardless of the cultivation time, the double shoot-training method which used two lateral shoots developed from first and second node of primary shoot of seedlings was suitable.2. The occurrence of malformed fruit increased, when number of trained lateral shoots were increased.3. By topping and transplanting of seedlings at the same time, it was possible to raise uniformity of the flowering on suppressing the generation of the malformed fruit.4. By utilization of cultivar which did not became soft easily even if ripening and ethephon spraying of 400ppm for the truss before the harvesting, simultaneity harvesting by the bunch take was possible.5. We proposed the laber saving cutivation system of fresh market tomatoes which consisted of main element techniques such as mechanical transplanting of plug seedlings, double-shoots training of single-truss plants, whole-truss harvesting and fruit selection with color sencer.

296 Chemical Thinning of `Fuji' Apple with Ethephon, NAA, MCPB-ethyl, and Carbaryl

We propose that return flowering of `Fuji' apple can be improved if sufficient flower clusters are removed during or shortly after bloom. In this study conducted at Corvallis, Ore., we evaluated two synthetic auxins, MCPB-ethyl and the Na salt of NAA, each at 0, 4, 8 and 16 ppm, as blossom cluster thinners. Each auxin treatment was applied alone or with 100 ppm ethephon as a tank mix. Six-year-old `Fuji'/M.26 trees were sprayed at full bloom of the king flowers (≈85% of whole-tree full bloom). A follow-up treatment of Sevin XLR (800 ppm carbaryl) was made at 11-mm fruit diameter to determine if carbaryl's known effectiveness as a fruitlet thinner was influenced by the bloom-time auxin or auxin + ethephon treatments. MCPB-ethyl proved ineffective as a bloom-time thinner, whereas the NAA effect on cluster removal was linear with concentration, 16 ppm NAA completely defruiting 33% of initial flower clusters. On control trees fewer than 12% of flowering clusters failed to set fruit. Ethephon alone defruited 25% of the clusters and NAA+ethephon defruited 51% of clusters. It is notable that the NAA and ethephon + NAA treatments did not reduce fruit set on the remaining clusters, resulting in considerable need for hand-thinning. Carbaryl effectively reduced total crop load by increasing the number of defruited clusters and reducing the incidence of doubles and triples. There was evidence to suggest that its effectiveness was compromised by the bloom-time NAA and/or ethephon sprays.

Potential Role of Apple Peel Phenolics in Superficial Scald Development

Cuticle scraped from apple peel contained both free and bound phenolics, and cuticle enzymatically isolated from peel contained much greater amounts of them. Both free and bound phenolics inhibited linoleic acid oxidation, but free forms had ≈50% higher activity. Free and bound phenolics had ≈75% and 50%, respectively, of diphenylamine's antioxidant activity on a molar basis. Cuticle possessed little lipid-soluble antioxidant activity, but surface cells contained four to seven times the activity of cuticle. In a model system, free cuticular phenolics strongly inhibited farnesene oxidation in hexane during 4 months at 25 °C, but lipid-soluble antioxidants did not. Both free and bound cuticular phenolics increased during maturation. During 0 °C storage, free forms doubled during 15 weeks, then remained constant, while bound forms did not change. Cellular phenolics fell during maturation and storage, reducing browning potential in the cells. These changes all correlated with changes in C2H4 production. When C2H4 was inhibited by AVG spray and low-C2H4 storage, little or no change occurred; when promoted by ethephon spray or high-C2H4 storage, phenolic changes were accelerated. Farnesene and cuticular phenolics were positively correlated but conjugated trienes, cellular phenolics, and scald negatively correlated with C2H4. We believe that C2H4 effects on phenolics may be closely related to scald development.

Effects of Aminoethoxyvinylglycine (AVG) on Preharvest Fruit Drop and Maturity of ‘Delicious’ Apples

Abstract Aminoethoxyvinylglycine (AVG) applied 2 to 6 weeks before the optimum harvest date dramatically reduced preharvest drop of ‘Delicious’ apples (Malus domestica Borkh). The loss of fruit firmness, starch, and water core was reduced by AVG sprays particularly when harvest was delayed beyond the optimum harvest date. Color development and soluble solids concentration (SSC) generally was unaffected. Equivalent dilute airblast concentration (EDAC) of 44 mg·L−1 AVG was no more effective than a standard rate of napthalene acetic acid (NAA), but a rate of 44 mg·L−1 AVG EDAC + a silicone surfactant ABG 7011 or 88 mg·L−1 AVG EDAC was more effective than NAA. When fruit were left on the tree for periods of 3 to 5 weeks after the optimum harvest date, NAA enhanced softening and loss of starch and increased water core of ‘Delicious’. Soluble solids and red color generally were unchanged by NAA. Ethephon sprays hastened the rate of fruit drop. When NAA was tank mixed with ethephon, it delayed fruit drop caused ...

AVG Effects on Preharvest Apple Fruit Drop and Maturity in Virginia

AVG applied 2 to 6 weeks before the optimum harvest date for several cultivars dramatically reduced pre-harvest fruit drop. The loss of fruit firmness and starch loss after the optimum harvest date was reduced by AVG sprays. The development of watercore in `Starkrimson Delicious' and `York' and maturity cracking in `Rome' and `Golden Delicious' were delayed and/or prevented by AVG. Color development was slightly delayed for most red cultivars and `Golden Delicious'. Soluble solids concentration was generally unchanged. Airblast applications of 123 g·ha–1 AVG was no more effective than a standard rate of NAA (28 to 56 g·ha–1), but rates of 248 g·ha–1 AVG and above were more effective than NAA for most cultivars. When fruit were left on the tree for periods of 3 to 5 weeks after the optimum harvest date, NAA hastened the loss of fruit firmness and starch and NAA increased watercore of `Delicious' and maturity cracking of `Golden Delicious' and `Law Rome'. Soluble solids and red color were generally unaffected by NAA. Ethephon sprays hastened the rate of fruit drop. When NAA was tank mixed with ethephon, NAA delayed fruit drop caused by ethephon, but AVG did not. The use of superior oil or Regulaid surfactant did not affect NAA or AVG responses; however, the silicone surfactant Silwet L-77, in one experiment, promoted the effectiveness of AVG. Tank mixing NAA or AVG with pesticides (Guthion + Lannate + Captan) did not affect the responses of AVG or NAA on fruit drop.

Effect of Ethephon Spray Treatments on Mechanical Harvesting and Oil Composition of `Arbequina' Olives

Ethephon was applied at 0, 625, 1250, 1875, and 2500 m·gliter-1 in 2 consecutive years to `Arbequina' olive trees to determine its effect on fruit removal with mechanical harvesting and on fruit oil composition. Ethephon increased the mechanical harvesting efficiency by 20%. Ethephon at 1250 and 1875 mg·liter-1 were the optimum treatments, resulting in 63% and 66% of the olives being mechanically harvested, respectively, with a preharvest olive drop of 10% and 11%. Leaf drop (4.6 and 4.8 kg/tree fresh weight, respectively) at these concentrations did not reduce flowering the following year. Oil acidity, peroxide value, and fatty acid composition were affected little by ethephon and the values observed were within the range of normal annual variation. These results suggest that ethephon did not modify oil quality and that its use on traditionally pruned `Arbequina' trees is not economically justifiable. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).

Cultivar, Planting Density, and Plant Growth Regulator Effects on Growth and Fruiting of Tissue-cultured Apple Trees

Tissue-culture (TC)-propagated `Gala' and Triple Red `Delicious' apple trees grown at three planting densities were not treated (CON) or treated with plant growth regulators (PGRs) starting the third or fourth season to control tree size and maximize fruiting. `Gala' and `Delicious' trees budded on M.7a rootstock (BUD) were also included as controls. `Gala' trees were larger than `Delicious' after the first three growing seasons but `Delicious' were larger than `Gala' at the end of 9 years. BUD trees were larger than CON trees the first few seasons hut final trunk cross-sectional area (TCSA) of CON trees averaged 43% greater than BUD trees. Paclobutrazol and uniconazole treatments more readily controlled the growth of `Gala' than `Delicious' and uniconazole was more effective than paclobutrazol in controlling tree size. Daminozide + ethephon sprays (D+E-S) did not influence tree size. Tree size of both cultivars was inversely related to planting density and both triazole PGRs were more effective in controlling tree size as planting density increased. The trees had fewer flowers as planting density increased and BUD trees generally had more Bowers than CON. Triazole PGRs had little effect on the flowering pattern of `Gala' trees but tended to stimulate flowering of young `Delicious' TC trees, although the increases were not sustained. The D+E-S treatment increased flowering of `Gala' trees the last 3 years of the experiment and consistently increased flowering of `Delicious' TC trees. Fruit yields were higher for young `Gala' compared to `Delicious' trees and the final cumulative yield per tree for `Gala' was also greater. Yield per tree decreased as tree density increased and was the same for BUD and CON trees. D+E-S increased cumulative per tree yield of `Delicious' but not of `Gala'. Cumulative yields per tree for triazole-treated TC trees were the same as, or significantly lower than, CON trees. Increasing tree density did not increase yield/ha. Yield efficiency of `Gala' trees was increased by three, and of `Delicious' trees by one, of the triazole treatments, because they reduced TCSA proportionally more than they reduced per tree yield. There was less bienniality with `Gala' than `Delicious' and no difference between BUD and CON trees. Bienniality indices were higher for paclobutrazol-treated `Gala' trees compared with CON `Gala' but only uniconazole applied as a trunk paint increased the bienniality index of `Delicious' trees. Chemical names used: succinic acid-2,2-dimethyl hydrazide (daminozide), (2-chloroethyl) phosphonic acid (ethephon), (2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)pentan-3-01 (paclobutrazol), (E)-(l-chlorophenyl)-4,4-dimethyl-2-(I,2,4-triazol-l-yl)-1-penten-3-ol (uniconazole).

Response of `Reliance' Table Grapes to Canopy Management and Ethephon Application

Canopy management and ethephon application (100 mg·liter-1 2 weeks after veraison) were investigated for 2 years as possible ways to improve color and overall quality of `Reliance' grapes (Vitis spp.). Canopy management consisted of leaf removal, shoot positioning, and cluster thinning. Grapevines were subjected to one of two levels of leaf removal and one of two levels of preharvest ethephon spray and were either thinned to a basal cluster or nonthinned. Thinning and ethephon advanced harvest dates by 5 to 8 days and 2 to 3 days, respectively. In 1989, berry weight was increased by thinning but was not affected by leaf removal or ethephon. Leaf removal (direct sun exposure) of thinned and nonthinned treatments increased “L” values (lighter colored fruit) in 1989. In 1990, leaf removal, ethephon, and thinning resulted in higher “L” values. The “a” values were significantly increased by leaf removal in 1989 and 1990 and by thinning in 1989, a result indicating increased skin redness. Exposed clusters of nonthinned treatments had significantly higher “b” values due to more yellow fruit in 1989 than in 1990. Ethephon increased “b” values in thinned and nonthinned treatments. In 1990, leaf removal increased “b” values. Thinning resulted in more evenly colored, redder fruit. Leaf removal caused a lightening and yellowing of the skin. Juice from leaf removal treatments in 1990 had significantly higher “L”, “a”, and “b” values. Ethephon significantly increased the “a” value of juice in 1989, and leaf removal significantly increased the “b” value in 1989. The percent soluble solids of juice was generally decreased by ethephon and increased by leaf removal and thinning. Titratable acidity was decreased by leaf removal and ethephon and increased by thinning in both years. Leaf removal decreased berry pH in 1990. Thinning increased coloration, and direct exposure to light decreased coloration. The results with ethephon were not conclusive. Chemical name used: 2-chloro-ethyl-phosphonic acid (ethephon).

Calcium and Ethephon Effects on Paprika Pepper Fruit Retention and Fruit Color Development

Ethephon has increased yields of red fruit, but its use as a pepper (Capsicum annuum L.) fruit ripening agent has been limited by premature fruit abscission and defoliation. We tested ethephon solutions of 0,1500,3000,4500, and 6000 μl·liter-1 with or without 0.1 m Ca(OH)2 as a onetime foliar application to field-grown paprika pepper in southwestern Oklahoma. There was a linear increase in fruit abscission with increasing ethephon rates in 2 of 3 years, with or without added Ca. Marketable fruit as a percentage of total harvested fruit weight was improved by ethephon at 6000 μl·liter-1 in 2 of 3 years, primarily due to a decrease in weight of harvested green fruit. However, ethephon never significantly increased the dry weight of harvested marketable fruit over that obtained from the control. There also was no effect of ethephon on the intensity of red pigment extracted from dehydrated marketable fruit. The only consistently significant effect of Ca(OH)2 was an undesirable increase in the retention of green fruit on the plants. Ethephon had little value as a fruit-ripening agent for paprika pepper under the conditions of our studies, and Ca(OH)2 was not useful as an additive to ethephon sprays. Chemical name used: (2-chloroethyl) phosphoric acid (ethephon).

Combining ethephon and naphthalene acetic acid (NAA) in one spray to thin ‘Golden Delicious’ apples

Abstract A trial examined the effects of using ethephon or naphthalene acetic acid (NAA) alone or in combination to thin ‘Golden Delicious’ apples. All sprays were applied only at full bloom (FB). A factorial design was used with ethephon sprays of 0, 50, 100, and 200 mg/litre and NAA at 0, 5, 10, and 20 mg/litre with an additional treatment hand thinned just after FB. Ethephon applied alone thinned effectively at 100 or 200 mg/litre. NAA applied alone did not thin at any concentration. The three concentrations of NAA with ethephon at 50 mg/ litre improved thinning over the untreated control but not enough to significantly improve fruit weight and size. Ethephon alone at 100 mg/litre thinned very effectively and as well as any combination with NAA. Fruit weight and size were improved by all treatments using ethephon at 100 mg/litre. There was no advantage using ethephon at 200 mg/litre when compared to 100 mg/litre. Although there was some evidence that the combination of ethephon and NAA at the highest concentrations removed more fruit than ethephon alone at 200 mg/litre this was not reflected in better fruit weight or size. There is no advantage in adding NAA to ethephon to thin ‘Golden Delicious’ at FB and ethephon at 100 mg/litre would be the thinning spray of choice.

Relationships of antioxidants in apple peel to changes in α-farnesene and conjugated trienes during storage, and to superficial scald development after storage

Three experiments were conducted: (1) ‘Cortland’ and ‘Delicious’ apples were harvested at four weekly intervals; (2) ‘Cortland’ apples were induced to ripen prematurely with ethephon sprays; (3) ‘Cortland’ apples were enclosed in brown bags for six weeks before harvest. At harvest and after intervals of storage at 0°C, concentrations of α-farnesene and conjugated trienes, estimates of total lipid-soluble and total water-soluble antioxidant activity, and concentrations of α-tocopherol, carotenes, ascorbic acid, glutathione, anthocyanins and flavonols in fruit peel were measured. The objective was to determine if differences in antioxidants at harvest persisted through storage, and if changes in antioxidants corresponded to accumulations of conjugated trienes and development of scald. Treatments resulted in significant differences in antioxidant and pigment concentrations at harvest. Water-soluble antioxidants and anthocyanins declined during storage, but lipid-soluble antioxidants generally increased. In general, antioxidant concentrations at harvest were inversely related to maximum conjugated triene concentrations at the end of storage, and to scald development. However, no individual antioxidant was associated consistently with conjugated triene accumulation or scald development, and as conjugated triene concentrations increased, total lipid-soluble antioxidant activity also increased. Water-soluble antioxidants generally decreased during storage. Possible involvements of antioxidants with scald development is discussed.

Preharvest applications of ethephon on ‘Jaffa’ oranges (Citrus sinensis L. Osbeck) in Martínez de la Torre, Ver. México

Sprays of ethephon (2-chloroethyl phosphonic acid) applied at 0, 100, 300 and 500 mg.litro^-1 were done in September 23^rd. and 30 th. In 1989, on ‘Jaffa’ orange trees, when fruits initiated to change color from green to yellow (color break), to evaluate its effect on fruit characteristics and injury to trees. Results showed no significative effects on internal quality characteristics as total soluble solids (TSS), acid TSS/acid ratio, juice percent; neither on size (polar and equatorial diameter), weight, fruit firmess and chlorophyll content, although in this last it was noted a tendency to decrease as rate of ethephon increased. An evident difference was obtained in fruit coor. Ethephon at 500 mg·litro^-1applied September 30 th. Was the best treatment to promote yellow color. Injury to trees was noted in drop leaf and drop fruits. Leaf drop percent and fruit drop number increased when ethephon rates were increased. Doses of 300 and 500 mg·litro^-1 were the ones causing more leaf and fruit abscission.

Enhancing abscission of mature macadamia nuts with ethephon

Abstract The effect of (2‐chloroethyl)phosphoric acid (ethephon) on the abscission of mature ‘Beaumont’ macadamia nuts (Macadamia integri‐folia × M. tetraphylla) was investigated in two experiments. In 1988, 6‐year‐old trees were treated with 200 or 400 mg/litre of ethephon, with and without pH neutralisation or a surfactant, 2 weeks after nut maturity. Nut abscission increased from 6% on untreated trees to a maximum of 87% on trees treated with a 400 mg/litre neutralised solution of ethephon which included a surfactant. Trees treated with 400 mg/litre ethephon sprays showed a large but nonsignificant reduction in yield in the following season. A second experiment in 1990 determined the effects of three ethephon rates (400, 500, and 600 mg/litre) applied on three separate dates (nut maturity, nut maturity +2 weeks, and nut maturity +4 weeks). In this study 70% of nuts abscissed after the final application compared to only 7% on untreated trees. However ethephon applied 2 or 4 weeks after the nuts matured ...

Auxin-induced Ethylene Synthesis during Rooting and Inhibition of Budbreak of `Royalty' Rose Cuttings

Single-node `Royalty' rose (Rosa hybrida L.) cuttings were used to examine the relationship between adventitious root formation, budbreak, and ethylene synthesis following IBA treatment. IBA was applied as a lo-second basal quick dip before rooting, and AIB, GA3, STS, and ethephon were applied either as basal dips or foliar sprays. IBA application increased rooting and inhibited budbreak of cuttings. IBA 2 600 mg·liter-1 greatly inhibited budbreak during 4 weeks of rooting. IBA treatment stimulated ethylene synthesis, which was inversely correlated with budbreak of cuttings. Ethephon also significantly inhibited budbreak. Budbreak of rose cuttings was completely prevented by repeated ethephon sprays used to maintain high endogenous ethylene levels during the first 10 days. Treatment with STS, an ethylene-action inhibitor, improved budbreak. The inhibition of budbreak by IBA treatment resulted primarily from elevated ethylene levels. Root initiation and root elongation of cuttings initially inhibited budbreak, but later promoted budbreak. Chemical names used: indole-3-butyric acid (IBA); gibberellic acid (GA3); silver thiosulfate (STS); AIB, aminoisobutyric acid (AIB); (2-chloroethyl)-phosphoric acid (ethephon).

MANAGING HIGH VIGOR IN BEARING ORCHARDS: CONTROLLING GROWTH WITH ETHEPHON

Ethephon application at rates of 1000 ppm to 1500 ppm substantially inhibited tree growth but also caused fruit abscission. Application of gibberellin plus ethephon did not prevent fruit abscission. Low weekly doses of ethephon did not cause fruit abscission but gave good control of tree growth. Ethephon increased soluble solids and substantially reduced starch in the year of application. Flowering and fruit set were greatly increased by ethephon sprays the previous season. Fruit diameter or length:diameter ratios (L/D ratio) were not altered by the previous seasons' low weekly doses of ethephon.Complete or partial loss of fruit in high density apple plantings can result in excessive shoot growth that is normally controlled by cropping. Spot spraying with ethephon in the top part of `Redchief Delicious'/MM. 26 trees for tree training purposes increased the number of shoots over 10 cm in the lower part of the tree, but also caused fruit abscission in the unsprayed parts of the tree. Summer training of high density plantings of fireblight susceptible varieties with spot sprays of ethephon would reduce the need for cutting or pinching branches during the tree growth period.