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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #347178

Research Project: Breeding Stone Fruit Adapted to the Production Environment of the Southeastern United States

Location: Fruit and Tree Nut Research

Title: Historical trends in chill hour accumulation and peach bud response to hydrogen cyanamide

Author
item Beckman, Thomas - Tom
item Chen, Chunxian

Submitted to: American Society of Horticulture Science Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/19/2017
Publication Date: 10/18/2017
Citation: Beckman, T.G., Chen, C. 2017. Historical trends in chill hour accumulation and peach bud response to hydrogen cyanamide. American Society of Horticulture Science Meeting. p. 1.

Interpretive Summary: A record low chill accumulation in winter 2016 in some peach production regions in Georgia and other states has led us to look into historical chill data and orchard management adjustments for understanding of and solutions to the issue. Long term historical average chill hour accumulation through February 15th in middle Georgia has dropped significantly over the last 15 years. This new all-time record resulted in an inadequate chill hour accumulation for every commercial peach cultivar typically utilized in this production area. Some high chill cultivars received less than half of their required chilling resulting in widespread late bloom in combination with poor fruit set and vegetative bud break. Trees of nine high-chill cultivars displaying almost no bud break from last year’s shoots were used to study the effect of a late spray application (April 13th) of hydrogen cyanamide on bud break. Cultivars tested differed significantly only in their lateral bud response, in terms of number of buds broken and peak time of bud break. This experiment demonstrates that a late application of hydrogen cyanamide can help promote earlier and more lateral bud break, but had little effect on flower bud break or fruit set.

Technical Abstract: Long held records for (low) chill hour accumulation have recently been broken several times in the southeastern US peach (Prunus persica) production areas. Long term historical average chill hour accumulation through February 15th in middle Georgia has dropped significantly over the last 15 years. Trends in chill hour accumulation will be discussed along with its import for both commercial production and breeding priorities. In the most recent episode of low chill hour accumulation in the middle Georgia peach production area, a new all-time record appears to have been set, resulting in an inadequate chill hour accumulation for every commercial peach cultivar typically utilized in this production area. Some high chill cultivars received less than half of their required chilling resulting in widespread late bloom in combination with poor fruit set and vegetative bud break. Trees of nine high-chill cultivars displaying almost no bud break from last year’s shoots were used to study the effect of a late spray application (April 13th) of hydrogen cyanamide on bud break. Cultivars tested differed significantly only in their lateral bud response, in terms of number of buds broken and peak time of bud break. ‘Ta Qiao’ showed the strongest response to hydrogen cyanamide applications, whereas ‘Julyprince’ the weakest. Peak impact on lateral bud break occurred in two weeks on long shoots (40-60cm) and in three weeks on short shoots (15-30cm). Across all cultivars tested, at the respective peak week the number of lateral buds that emerged on long shoots of treated trees was more than twenty times of that of untreated trees, whereas the number produced on short shoots of treated trees was about eight times of that of untreated trees; and at the seventh week after treatment the differences between treated and untreated trees became approximately two and four times, respectively, as more buds on untreated trees emerged at a slower pace. Almost no flower bud (<1 per shoot) opened prior to dry and drop on both treated and untreated trees. This experiment demonstrates that a late application of hydrogen cyanamide can help promote earlier and more lateral bud break, but had little effect on flower bud break or fruit set.