Articles
EFFECTS OF CHEMICAL THINNING WITH METAMITRON ON FRUIT SET, YIELD AND FRUIT QUALITY OF ‘ELSTAR’
Article number
884_68
Pages
531 – 536
Language
English
Abstract
Here are reported the results of two thinning trials carried out with the herbicide Goltix 700 SC containing Metamitron as the active ingredient.
Metamitron (a Photosystem II inhibitor herbicide) is commercially used in strawberries and is already listed in Annex I. The thinning effects of Metamitron 350 mg L-1 (single and double application at 6-8 mm and at 12-14 mm fruitlet diameter) and Ethephon 216 mg L-1 at balloon stage followed by Metamitron 350 mg L-1 at 10-12 mm on Elstar were evaluated over a three years period (2006 to 2008). Experiments were carried out in the cultivar Elstar apple tree grown at the experimental orchards of Haidegg.
The orchard was planted in 2002 and trees trained to a slender spindle.
Evaluations were made for fruit set (fruits/100 flower clusters), number of fruits/tree and kg/tree.
Yield capacity (number of fruits/cm2 trunk cross sectional area), fruit quality (calibration and internal quality attributes), storability and return bloom were also determined.
The thinning efficacy of Metamitron depended upon time of application and considered years.
Repeated treatments of Metamitron produced a significant reduction in fruit set, expressed as number of fruits/tree as well as yield (kg/tree). The fruit size was usually improved according to the crop load reduction.
Bloom density was evaluated the following year to assess the effect of chemical thinning on return bloom.
Return bloom corresponded strongly with the thinning efficacy (crop load). Metamitron, when sprayed to thin apple fruitlets, did not cause leaf injury, pigmy fruit, fruit malformation and russeting or detectable residue levels in the fruit.
Internal fruit quality increased according to the reduction of crop load.
Adaptation of dosage on the fruitlet diameter and/or light intensity seems to be necessary for optimising the thinning efficacy of Metamitron.
Metamitron (a Photosystem II inhibitor herbicide) is commercially used in strawberries and is already listed in Annex I. The thinning effects of Metamitron 350 mg L-1 (single and double application at 6-8 mm and at 12-14 mm fruitlet diameter) and Ethephon 216 mg L-1 at balloon stage followed by Metamitron 350 mg L-1 at 10-12 mm on Elstar were evaluated over a three years period (2006 to 2008). Experiments were carried out in the cultivar Elstar apple tree grown at the experimental orchards of Haidegg.
The orchard was planted in 2002 and trees trained to a slender spindle.
Evaluations were made for fruit set (fruits/100 flower clusters), number of fruits/tree and kg/tree.
Yield capacity (number of fruits/cm2 trunk cross sectional area), fruit quality (calibration and internal quality attributes), storability and return bloom were also determined.
The thinning efficacy of Metamitron depended upon time of application and considered years.
Repeated treatments of Metamitron produced a significant reduction in fruit set, expressed as number of fruits/tree as well as yield (kg/tree). The fruit size was usually improved according to the crop load reduction.
Bloom density was evaluated the following year to assess the effect of chemical thinning on return bloom.
Return bloom corresponded strongly with the thinning efficacy (crop load). Metamitron, when sprayed to thin apple fruitlets, did not cause leaf injury, pigmy fruit, fruit malformation and russeting or detectable residue levels in the fruit.
Internal fruit quality increased according to the reduction of crop load.
Adaptation of dosage on the fruitlet diameter and/or light intensity seems to be necessary for optimising the thinning efficacy of Metamitron.
Authors
G. Lafer
Keywords
Malus × domestica, apple, ‘Elstar’, fruit thinning, Metamitron, biennial bearing, fruit quality
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