Spring Freeze Damage of Pecan Bloom: A Review

Abstract

Pecan is native to the United States. The US is the world’s largest pecan producer with an average yearly production of 250 to 300 million pounds; 80 percent of the world’s supply. Georgia, New Mexico, Texas, Arizona, Oklahoma, California, Louisiana, and Florida are the major US pecan producing states. Pecan trees frequently suffer from spring freeze at bud break and bloom as the buds are quite sensitive to freeze damage. This leads to poor flower and nut production. This review focuses on the impact of spring freeze during bud differentiation and flower development. Spring freeze kills the primary terminal buds, the pecan tree has a second chance for growth and flowering through secondary buds. Unfortunately, secondary buds have less bloom potential than primary buds and nut yield is reduced. Spring freeze damage depends on severity of the freeze, bud growth stage, cultivar type and tree age, tree height and tree vigor. This review discusses the impact of temperature on structure and function of male and female reproductive organs. It also summarizes carbohydrate relations as another factor that may play an important role in spring growth and transition of primary and secondary buds to flowers.

Shade Nets Reduced Growth, Nutrition, and Sugars of Hydroponic Lettuce and Basil

“…Following incubation, samples were centrifuged at 15,000 g n for 5 min. The supernatant was used for measurement after being diluted with UP water (1:4 v/v) (Kaur 2021). A microplate reader (Epoch, Biotek Instruments Inc. Winooski, VT, USA) was used to read sample plates at 620 nm wavelength, which gives sugar and starch content in leaves.…”

Extending the Cultivation Area of Pecan (Carya illinoinensis) Toward the South in Southeastern Subtropical China May Cause Increased Cold Damage

“…In order to examine the risk of damage caused by low temperatures (false spring risk), the occurrence of cold damage events was determined by examining whether the air temperature dropped below a critical threshold, T dam , of the damaging temperature range during a time window of 10 days before the projected leaf-out to May 31. In the absence of explicit data for T dam , the threshold T dam = +5°C was determined on the basis of earlier indicative results ( Kaur et al, 2020 ) and on the basis of recent experiences from a pecan orchard ( Supplementary Figure 3 ). The cold damage was quantified for each year by its incidence (number of damaging days) and severity (the lowest temperature occurring during the day or days).…”

“…Second, warming may advance the spring leaf-out and flowering to the extent that the risk of damage caused by low spring temperatures increases ( Cannell, 1985 ; Hänninen, 1991 ). This phenomenon, more recently called “false spring” ( Marino et al, 2011 ; Chamberlain et al, 2019 ), may cause considerable damage even under the present climate ( Gu et al, 2008 ; Kaur et al, 2020 ). However, if the advancement of spring phenology is not accompanied by the increased incidence of cold damage, then climatic warming may increase the productivity of trees and forests by prolonging the growing season ( Kramer and Hänninen, 2009 ).…”

Overcoming dormancy of pecan trees in mild winter conditions

“…Pecan trees [Carya illinoinensis (Wangenh) Koch] have been grown commercially in all continents nowadays [3][4][5]. Since the species is native to North America and grown mainly in temperate regions in the Northern Hemisphere [6,7], cultivars have high chill requirements [8]. According to [9], when it is grown in regions where chill requirements are not thoroughly met, it may show several abnormalities, such as lengthy and deficient budbreak and flowering.…”