Articles
ETHEPHON AS A BLOSSOM AND FRUITLET THINNER AFFECTS CROP LOAD, FRUIT WEIGHT AND FRUIT QUALITY OF THE EUROPEAN PLUM CULTIVAR ‘JUBILEUM’
Article number
884_36
Pages
315 – 321
Language
English
Abstract
The European plum cultivar Jubileum (Prunus domestica L.) blossoms abundantly most years and too many flowers can be set if not properly thinned.
For two seasons started in 2007 mature Jubileum/St.
Julien A trees were treated with ethephon at full bloom, using the concentration of 250, 375 and 500 ppm and at 10-12 mm fruitlet diameter using the concentration of 125, 250 and 375 ppm.
The treatments were made to single whole trees in a randomized complete block design with six replications.
Experimental trees were sprayed to run-off with a hand sprayer when temperature was above 15°C. All thinning treatments reduced the fruit set significantly.
The fruit set decreased with increasing ethephon concentration, and the highest rates at bloom and fruitlet overthinned.
Less dosage of ethephon was required at fruitlet time in order to obtain the same fruit set.
The yield did confirm the fruit set response and the yield reductions were significant.
All thinning treatments gave higher percentage of fruits larger than 38 mm fruit diameter compared to the unthinned control.
Fruit quality characterized by blue surface cover and the content of soluble solids was in general high and increased significantly by reduced crop load.
Fruit firmness, however, slightly declined in the ethephon thinned trees.
Other fruit quality parameter like percentage acid content did not show a clear response to the thinning.
Return bloom was little improved on thinned trees the following year.
The crop load per tree was reduced to about the half of the previous year, control trees included.
In conclusion, ethephon application at a rate of 375 ppm applied at full bloom or 250 ppm at 10 mm fruit diameter thinned Jubileum plums to a target of about 10-15% fruit set.
For two seasons started in 2007 mature Jubileum/St.
Julien A trees were treated with ethephon at full bloom, using the concentration of 250, 375 and 500 ppm and at 10-12 mm fruitlet diameter using the concentration of 125, 250 and 375 ppm.
The treatments were made to single whole trees in a randomized complete block design with six replications.
Experimental trees were sprayed to run-off with a hand sprayer when temperature was above 15°C. All thinning treatments reduced the fruit set significantly.
The fruit set decreased with increasing ethephon concentration, and the highest rates at bloom and fruitlet overthinned.
Less dosage of ethephon was required at fruitlet time in order to obtain the same fruit set.
The yield did confirm the fruit set response and the yield reductions were significant.
All thinning treatments gave higher percentage of fruits larger than 38 mm fruit diameter compared to the unthinned control.
Fruit quality characterized by blue surface cover and the content of soluble solids was in general high and increased significantly by reduced crop load.
Fruit firmness, however, slightly declined in the ethephon thinned trees.
Other fruit quality parameter like percentage acid content did not show a clear response to the thinning.
Return bloom was little improved on thinned trees the following year.
The crop load per tree was reduced to about the half of the previous year, control trees included.
In conclusion, ethephon application at a rate of 375 ppm applied at full bloom or 250 ppm at 10 mm fruit diameter thinned Jubileum plums to a target of about 10-15% fruit set.
Authors
M. Meland, E. Birken
Keywords
Prunus domestica L., abscission, fruit set, return bloom, yield
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