Early Season Temperatures Impact Peach Yields

By Macy Lacasse (summer student), Kathryn Carter, Fruit Specialist OMAFRA

Introduction

Most peach orchards within the Niagara region have surpassed the FBD – Full Bloom Date (when an orchard has reached an estimated 50% of open blooms) (Table 1) and are now in the critical stage of fruit phenology – first 30 days after full bloom. Fruit phenology is very important for predicting production for the growing season as to when trees will be flowering, fruiting, and possible harvest times. In particular the weather conditions in the first 30 days after bloom can have a significant impact on the yields at the end of the season.

Table 1 Full bloom dates for Niagara orchards (Ontario Tender Fruit Growers Association)

Location	Full Bloom Date
Niagara Parkway	April 15th
Beamsville	April 26th
Lakeshore Region	April 23rd

Why are the first 30 days after bloom critically important in peach production?

Apple trees produce nearly 30% of their leaf surface before bloom as spur leaves. The photosynthetic activity of these spur leaves, and reserve carbohydrates in the woody tissue provide carbohydrates that are important for fruit growth. In contrast, peach trees produce little leaf area until well after bloom, as a result early-season peach growth relies entirely on stored carbohydrates (starch in the woody tissue converted to sucrose and transported to areas of active growth). Researchers have shown that when warm weather occurs 30 days post bloom, peach trees cannot supply resources quickly enough to support the potential fruit growth rates, resulting in carbohydrate stress.  Carbohydrate stress has a negative impact on the growth of fruit and vegetative organs, resulting in a reduction in fruit size.

Researchers have also shown that peach and nectarine harvest dates can be predicted using growing degree hours accumulated during the first 30 days after bloom.  Fruit matures early when temperatures are above average during the 30 days after bloom, resulting in smaller sized fruit.

Rapid fruit growth occurs in all fruit varieties (early and late season) due to cell division from bloom to approximately 30 days after bloom. As a result, water stress must be avoided during this time to minimize negative impact on fruit size.  Researchers have also associated higher rainfall during 30 days after bloom with higher incidence of split pits in early varieties.

Strategies to Help Maximize Production

Market pricing has consistently favored larger-sized fruit, so what are some strategies that growers can use to optimize fruit sizing?

• Begin fruit thinning as early as possible. This will help maximize fruit size by reducing fruit-to-fruit competition and the peach trees are able to allocate their resources effectively and evenly throughout the remainder of the season. Moreover, peach cultivars have different harvest windows, therefore plan to thin the earliest harvested cultivars first to provide more time for fruit to size.
• Consider heavy thinning. While the early season frost has helped with thinning the crop in some orchards. Ensuring enough fruit are thinned from the tree, can help to increase average fruit size. Do not excessively thin varieties that are susceptible to split pits.
• Don’t wait to irrigate. Cell division in fruit is rapidly occurring up to 30 days after bloom.  Receiving adequate water during this time is critical for good fruit sizing and quality. Monitoring soil moisture levels and rainfall can help determine how much water is needed.

 

Conclusion:

Peaches mature early when temperatures are above average during the 30 days after bloom, resulting in smaller sized fruit. Lack of moisture or excess moisture in the 30 days post bloom can have a significant impact on fruit size and split pits.  While there is little that growers can do to control the weather, adapting cultural practices (fruit thinning, irrigation) according to weather, can provide an opportunity to help improve fruit sizing.  

 

Resources

Cassamali et al, 2021. Plant Growth and Physiological Responses to Improved Irrigation and Fertilization Management for Young Peach Trees in the Southeastern United States in: HortScience Volume 56 Issue 3 (2021) (ashs.org) Irrigation. Washington State University Tree Fruit. http://treefruit.wsu.edu/web-article/irrigation/

Jahed, K. & Hirst, P.M.. (2018). Pollen source effects on seed number, fruit quality and return bloom of apple. Journal of the American Pomological Society. 72. 212-221.

Lopez, G. & Dejong, T. (2007). Spring temperatures have a major effect on early stages of peach fruit growth. Journal of Horticultural Science and Biotechnology. 82. 507-512. 10.1080/14620316.2007.11512266

Lopez, G., Johnson, R. S., & Dejong, M. T. (January 2007). High spring temperatures decrease peach fruit size. California Agriculture. https://ucmanagedrought.ucdavis.edu/PDF/2007.CalAg.%20Temp%20&%20Fruit%20Size.pdf