Thinning efficacy of metamitron on young 'RoHo 3615' (Evelina®) apple

Penzel, Martin; Kröling, Christian

doi:10.1016/j.scienta.2020.109586

Cited by 9 publications

(8 citation statements)

References 25 publications

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“…This is corroborated by Byers (2002), who found low light conditions and periods of high night temperatures favour the abscission of fruitlets. Penzel and Kröling (2020) observed that a single application of MET at a relatively low rate (165 g ha −1 ) effectively thinned RoHo 3615 apple trees under conditions of high night temperatures and low solar radiation. MET also appears more efficacious in warmer climates such as Israel (Stern 2014(Stern , 2015.…”

Section: Effect Of Met On Leaf Phytotoxicitymentioning

confidence: 97%

“…Gonzalez et al (2020) also found the maximum suppression of chlorophyll fluorescence occurred 2 d following application of MET but recovery took longer. Penzel and Kröling (2020) observed that MET applied at a low concentration (165 g ha −1 ) reduced photosynthesis for at least 2 weeks after application. The duration and extent of photosynthesis suppression and role that cultivar and incident solar radiation conceivably would influence the efficacy of MET on fruit thinning.…”

Section: Introductionmentioning

confidence: 93%

“…Several European, Israeli, Brazilian, and American studies have investigated MET use as an apple thinner on popular cultivars grown in these regions. A majority of these studies have focused on single or double applications of MET, and tank-mix combinations with naphthalene acetamide, NAA, 6-BA, carbaryl, and 1-aminocyclopropane carboxylic acid (Köpcke 2005;Clever 2007; Dorigoni and Lezzer 2007;Deckers et al 2010;Lafer 2010;Basak 2011;Fernandes et al 2013;Maas and Van der Steg 2011;Stern 2014Stern , 2015Maas and Meland 2016;Botton et al 2019;Penzel and Kröling 2020). There is a paucity of research investigating the rate response of MET to determine the optimal thinning concentration of apples, as well as studies on Ambrosia, Gala, and Honeycrisp, all popular commercial cultivars grown in Canada.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Effect Of Met On Leaf Phytotoxicitymentioning

confidence: 97%

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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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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“…Also, when performed less than 30 days after full bloom, CLM avoids a reduction in flower bud development to prevent alternate bearing on susceptible cultivars (Kofler et al, 2019). CLM may include pruning to reduce flower-bud numbers per branch (Breen et al, 2015), mechanical (Penzel et al, 2021) or chemical thinning of flowers (Janoudi and Flore, 2005) or fruitlets (Penzel and Kröling, 2020), and frequently corrective hand thinning after fruit drop.…”

Section: Introductionmentioning

confidence: 99%

Carbon consumption of developing fruit and the fruit bearing capacity of individual RoHo 3615 and Pinova apple trees

et al. 2020

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This paper describes an approach to estimate the photosynthetic capacity and derive the optimum fruit number for each individual tree, in order to achieve a defined fruit size, which is named as the fruit bearing capacity of the tree. The estimation of fruit bearing capacity was carried out considering the total leaf area per tree as measured with a 2-D LiDAR laser scanner, LA LiDAR , and key carbon-related variables of the trees including leaf gas exchange, fruit growth and respiration, in two commercial apple orchards. The range between min LA LiDAR and max LA LiDAR was found to be 2.4 m² on Pinova and 4.3 m² on RoHo 3615 at fully developed canopy. The daily C requirement of the growing fruit and the associated leaf area demand, necessary to meet the average daily fruit C requirements showed seasonal variation, with maximum values in the middle of the growing period. The estimated fruit bearing capacity ranged from 33-95 fruit tree -1 and 45-121 fruit tree -1 on the trees of Pinova and RoHo 3615, respectively. This finding demonstrates sub-optimal crop load at harvest time in both orchards, above or below the fruit bearing capacity for individual trees. In conclusion, the LiDAR measurements of the leaf area combined with a carbon balance model allows for the estimation of fruit bearing capacity for individual trees for precise crop load management. K e y w o r d s: fruit growth rate, fruit respiration, leaf area, LiDAR, precision horticulture

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“…A carbohydrate surplus will lead to a lower fruit drop rate, while a deficit will result in fruit growth decline and stimulation of the abscission zone formation, promoting the efficacy of the thinning compound [22]. Meteorological conditions also play a very important role on the tree's carbon balance [22][23][24], thus with the potential to change the efficacy of metamitron from no thinning at all to an over thinning effect [25]. A study of the interactions between cloudy weather, fruit set, and chemical thinning application methods is therefore relevant to unveil the variability of thinning efficacy.…”

Section: Introductionmentioning

confidence: 99%

Metamitron and Shade Effects on Leaf Physiology and Thinning Efficacy of Malus × domestica Borkh

et al. 2020

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Thinning strategies, namely shade or photosynthetic inhibitors, rely on the reduction of carbon supply to the fruit below the demand, causing fruit abscission. In order to clarify the subject, seven field trials were carried out in Lleida, Girona, and Sint-Truiden (2017 + 2018), using orchards of ‘Golden’ and ‘Gala’ apple trees. At the stage of 9–14-mm fruit diameter, four treatments were implemented: (A) CTR-control, trees under natural environmental conditions; (B) SN-shaded trees, trees above which shading nets reducing 50% of irradiance were installed 24 h after metamitron application date—without application of metamitron—and removed after five days; (C) MET-trees sprayed with 247.5 ppm of metamitron; (D) MET + SN-trees submitted to the combined exposure to metamitron application and shading nets. Low radiation significantly increased metamitron absorption (36–53% in the three locations in 2018) and reduced its degradation. Net photosynthesis and stomatal conductance were strongly reduced in all treatments, with minimum values 2 days after spraying (DAS) and incomplete recovery 10 DAS in MET + SN. All treatments resulted in leaf sucrose and sorbitol decreases, leading to a negative carbon balance. SN and MET + SN promoted the highest thinning efficacy, increasing fruit weight and size, with MET + SN causing over-thinning in some trials. Leaf antioxidant enzymes showed moderate changes in activity increases under MET or MET + SN, accompanied by a rise of glutathione content and a reduction in ascorbate, however without lipid peroxidation. This work shows that environmental conditions, such as cloudy days, must be carefully considered upon metamitron application, since the low irradiance enhances metamitron efficacy and may cause over-thinning.

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Thinning efficacy of metamitron on young 'RoHo 3615' (Evelina®) apple

Cited by 9 publications

References 25 publications

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

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

Carbon consumption of developing fruit and the fruit bearing capacity of individual RoHo 3615 and Pinova apple trees

Metamitron and Shade Effects on Leaf Physiology and Thinning Efficacy of Malus × domestica Borkh

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