Comparison between 6-benzyladenine and metamitron as thinning agents in ‘Royal Gala’, ‘Cripps Pink’ and ‘Red Delicious’ apple cultivars

Rosa, Nídia; Verjans, W.; Oliveira, Cristina M.; Bylemans, D.; Remy, Serge

doi:10.17660/actahortic.2018.1221.8

Cited by 13 publications

(8 citation statements)

References 20 publications

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“…Many authors have reported the day of maximum Brevis ® induced inhibition at between 2 and 6 days after application (Brunner, 2014;Rosa, 2016;Stern, 2015). Their results differ from the observations of this study, with maximum inhibition Qy(%) values observed 5-10 days after treatment.…”

contrasting

confidence: 99%

Effect of different application rates of metamitron as fruitlet chemical thinner on thinning efficacy and fluorescence inhibition in Gala and Fuji apple

González¹,

Torres²,

Carbó

et al. 2019

Plant Growth Regul

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Crop thinning is an important and difficult agricultural practice. Knowing the effect of the application dose of a product is a crucial element of any thinning program. The aims of this study were to investigate the effect of different metamitron doses on Gala and Fuji apples applied at fruit king diameters of between 8 and 10 mm and to determine fluorescence inhibition at the different application rates. Trials were conducted over two seasons from 2015 to 2016 in apple orchards in Lleida (Spain). Photosynthesis inhibition caused by metamitron was also analysed and measured, using chlorophyll fluorescence and biexponential pharmacokinetic models. Under the trial conditions, the application of metamitron reduced final fruit set, number of fruits per tree and crop load depending on the application rate. A dose effect was observed in all yield parameters. Moreover, when metamitron showed high efficacy, there was an improvement in fruit weight, coloration and diameter. The estimated parameters A, α and B using a biexponential equation were related with final fruit set, however the period of inhibition has to be finished before prediction can be made of metamitron efficacy in the year. The fluorescence analysis showed a dose effect, with metamitron dose increasing inhibition. Additionally, the same result was also observed in the area under curve analysis, with metamitron dose reducing the area and inhibition increasing. In all yield parameters, the fluorescence and area under curve analyses showed differences between cultivars, with the inhibition caused by metamitron higher in Gala than in Fuji. Moreover, differences between years were observed. 2015 was warmer than 2016, and the higher temperatures increased the thinning efficacy of metamitron.

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confidence: 99%

Effect of different application rates of metamitron as fruitlet chemical thinner on thinning efficacy and fluorescence inhibition in Gala and Fuji apple

González¹,

Torres²,

Carbó

et al. 2019

Plant Growth Regul

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“…Application of a PSII inhibitor such as MET to apple trees can result in a transient carbohydrate stress that may persist for several days Brunner 2014;Stern 2015;Rosa 2016;Gonzalez et al 2019) and increase the sensitivity of the fruit to a chemical thinner. In addition to this direct effect, if MET is applied in combination with a chemical thinner that has been formulated with a wetting agent, then the resulting carbohydrate stress may result in aggressive thinning compared with a chemical thinner not formulated with a wetting agent.…”

Section: Introductionmentioning

confidence: 99%

Multi-year investigation on the rate, timing, and use of surfactant for thinning apples with post-bloom applications of metamitron

2022

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Several experiments were conducted in Simcoe, Ontario to evaluate the efficacy of metamitron (MET) as a post-bloom thinner for Ambrosia, Gala, and Honeycrisp apple trees. Trees were treated with rates of MET ranging from 165-480 mg.L-1, as well as different timings ranging from 5-22 mm fruit diameter. The effect of including a non-ionic surfactant on thinning efficacy with MET was also evaluated. Treatments were compared with untreated trees and industry standard sprays of carbaryl, NAA, 6-BA, or combinations thereof. Response to MET varied by cultivar and season. In six of the seven experiments, MET reduced fruit set, but in only four did MET reduce the number of fruit per tree or crop load compared with the untreated control trees. Petal fall (5-7 mm) applications of MET were less effective than later timings. Thinning response increased with higher rates of MET in four of the seven studies. For Honeycrisp and Ambrosia, 175 mg.L-1 MET was effective in reducing fruit set and crop load, while rates at or above 263.mg L-1 MET were required to thin Gala. MET improved fruit size distribution into larger categories and caused minimal leaf phytotoxicity with or without a non-ionic surfactant. Environmental factors such as nighttime temperature and solar radiation largely could not account for the seasonal or application timings in thinning response to MET. Greater understanding of the carbon balance and interplay of solar radiation, nighttime temperature, cultivar and fruitlet size on thinning response is required to improve the predictive thinning response of apple to MET.

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“…Cultivar traits can lead to different responses to thinning applications [13,15]; therefore, adjustments are often made depending on the cultivar thinning susceptibility, which can be classified as easy ('Braeburn'), average, or difficult ('Golden Reinders') to thin [16]. Associated with specific plant responses, the variability of a chemical compound's uptake is highly dependent on the meteorological conditions before, during, and after application, namely the air relative humidity [17,18].…”

Section: Introductionmentioning

confidence: 99%

Effects of Metamitron under Different Relative Humidity Conditions on the Fruit Abscission of Malus domestica Borkh. Cultivars

Rosa

Verjans²,

Àvila³

et al. 2020

Horticulturae

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Metamitron is an apple (Malus domestica Borkh.) fruit thinner that acts by reducing the photosynthetic capacity of trees. Relative humidity may influence thinning efficacy; however, the broadness of this effect is not yet fully understood. Trials were set in Sint-Truiden (Belgium) in 2018 and Lleida and Girona (Spain) in 2019, using 4-year-old cvs. Braeburn and Elstar trees in Belgium, and 16-year-old cv. Golden Reinders trees in Spain. Four treatments were implemented at the stage of 12–14 mm fruit diameter: (a) CTR—control, trees under natural environmental conditions; (b) HH—high humidity, trees submitted to artificially increased air relative humidity applied for 3 h prior to the beginning of the experiment; (c) MET—trees sprayed with 247.5 mg/L metamitron; (d) MET + HH—trees submitted to the combination of increased humidity (HH) and metamitron (MET) application. In Belgium, metamitron absorption by leaves was greater than in Spain. This might be related to morphological characteristics of the leaves which developed under greater natural relative humidity levels in Belgium than in Spain. Compared to MET alone, ‘Braeburn’ and ‘Elstar’ demonstrated significantly greater metamitron absorption, 59% and 84%, respectively, under MET + HH, accompanied by declines in leaf net photosynthesis (10% and 32%, respectively) and sucrose (31% and 26%, respectively). At harvest, MET + HH treatment reduced yield by 24% and 32% in ‘Braeburn’ and ‘Elstar’, respectively, when compared with MET alone. A large reduction (considered over thinning) in the yield of ‘Elstar’ occurred. In contrast, metamitron absorption by ‘Golden Reinders’ using MET alone was similar to MET + HH; however, there was a slight foliar sugar reduction in the latter treatment. In addition, both treatments enhanced shoot growth and increased fruit abscission with similar improvements in fruit weight and size. In this study, high relative humidity enhanced fruit thinning efficacy under certain circumstances, such as age or genetic predisposal, which left the tree more susceptible to a negative carbohydrate balance. For instance, ‘Braeburn’ and ‘Elstar’ were easier to thin when compared to ‘Golden Reinders’. In addition, this study raises a question that requires further research regarding the impact of HH before and after spraying as well as its effect in combination with higher temperatures.

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Comparison between 6-benzyladenine and metamitron as thinning agents in ‘Royal Gala’, ‘Cripps Pink’ and ‘Red Delicious’ apple cultivars

Cited by 13 publications

References 20 publications

Effect of different application rates of metamitron as fruitlet chemical thinner on thinning efficacy and fluorescence inhibition in Gala and Fuji apple

Effect of different application rates of metamitron as fruitlet chemical thinner on thinning efficacy and fluorescence inhibition in Gala and Fuji apple

Multi-year investigation on the rate, timing, and use of surfactant for thinning apples with post-bloom applications of metamitron

Effects of Metamitron under Different Relative Humidity Conditions on the Fruit Abscission of Malus domestica Borkh. Cultivars

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