Evaluation of GA4+7 plus 6-Benzyladenine as a frost-rescue treatment for apple | WSU Tree Fruit | Washington State University Skip to main content Skip to navigation

Evaluation of GA4+7 plus 6-Benzyladenine as a frost-rescue treatment for apple Published In HortTechnology, 24 (2):171-176, 2014, by S. McArtney, D. Greene, T. Robinson, J. Wargo

Freeze events during bloom can be a relatively frequent occurrence in many apple (Malus × domestica ) production areas in the United States that significantly reduce orchard productivity and profitability. This study investigated the potential for a proprietary mixture of gibberellin A4 + A7 and 6-benzyladenine (GA4+7 plus 6-BA) to increase fruit set and cropping of apple following freeze events at three locations across the United States during bloom in 2012. GA4+7 plus 6-BA increased fruit set in two of five experiments, and increased fruit number and yield per tree in three of five experiments. GA4+7 plus 6-BA increased fruit set and yield of ‘Taylor Spur Rome’ following freezes on two consecutive days during bloom when the minimum temperature reached 23.9 and 28.4 °F. Fruit set was increased due to a stimulation of parthenocarpic fruit growth. Using locally obtained market prices, GA4+7 plus 6-BA treatments increased the crop value of ‘Taylor Spur Rome’, ‘Ginger Gold’, and ‘Jonagold’ by $3842, $977, and $6218 per acre, respectively. Although GA4+7 plus 6-BA application(s) after a freeze increased fruit set and cropping in some instances, tree yields were well below the average yields previously obtained in the test orchards.

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