Effect of a Late Spring Application of Hydrogen Cyanamide on High-Chill Peaches

Chunxian Chen,Thomas G Beckman

doi:10.3390/agronomy9110726

Abstract

Due to a record low chilling accumulation in the winter of 2016–2017, many high-chill peach cultivars displayed almost no budbreak by mid-April of 2017 in central Georgia, USA, where budbreak usually occurs around mid-March. In this study, nine of these peach cultivars were used to study the effect of a late spring Dormex spray application (April 13, 2017) on subsequent budbreak, year-end cumulative vegetative growth, and following-season yield. Dormex was found to have strong stimulating effects on lateral budbreak, but little effect on terminal and floral budbreak. It also had apparent phytotoxic effects on lateral, terminal and floral buds, and growth. The effects varied among genotypes, tree ages, and shoot types. The peak of the effects occurred two weeks post-application. Most floral buds abscised before they swelled. Between Dormex-sprayed trees and unsprayed controls, there was no significant difference in the number and average length of the new lateral shoots by the end of 2017, nor in the number and weight of the fruit harvested in 2018. In conclusion, our data showed a late spring Dormex spray application stimulated earlier lateral budbreak and caused some level of phytotoxicity to all types of buds and new growth, but had little impact on flower budbreak, fruit set, year-end vegetative growth, or following-season yield. These findings provide useful information for growers, considering the need for spraying dormancy-breaking compounds when faced with insufficient chilling.

Highlights

Peach (Prunus persica [L.] Batsch) is produced in temperate, subtropical, and Mediterranean climate zones
Hydrogen cyanamide at 0.125 M had the greatest budbreak and lowest phytotoxicity of all treatment dates [12]. These results have demonstrated that hydrogen cyanamide is capable of changing the natural course of budbreak and affecting plant vegetative and reproductive growth routine in the applied year
That received substantially less than their chilling requirement (CR) and which had displayed little floral and lateral budbreak by mid-April were chosen for this late spring Dormex spray study

Summary

Introduction

Peach (Prunus persica [L.] Batsch) is produced in temperate, subtropical, and Mediterranean climate zones. Minimal chilling requirement (CR) must be satisfied for peach cultivars to complete foliar and floral bud differentiation and start budbreak on time [1]. Inadequate chilling, depending on the level of adequacy or percent to cultivar’s CR, can cause budbreak delay or varying degrees of failure up to complete crop loss. Only 466 chill hours (CH) were received by February 15, 1989 at Southeastern Agricultural Weather Service Center, National Weather Service, Auburn, Alabama, USA, and all cultivars that had a CR of 750 CH or over failed to bloom and foliate in mid-April [2]. CH have been commonly used to monitor and estimate CR [1], which are calculated as the sum of accumulated hours below 7.2 ◦ C (~45 ◦ F) between October 1st and the following February 15th in the Northern Hemisphere. Modified approaches or models have been developed with adjustment of the chilling efficacy at different temperature ranges, such as chill units [3], negated chill units [4], or chilling portions [5]

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Results

Discussion

Conclusion