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Joanne Logan, Dennis E. Deyton, and David W. LockWood

Peach [Prunus persica (L.) Batsch] production in Tennessee has declined since 1985 due to the occurrence of freezing temperatures that kill the buds, usually in the spring. Analyses of long-term (1951-89) daily temperature data from four locations in Tennessee were used to evaluate the freeze risks for `Redhaven' peach tree buds at those sites. A model using daily accumulated chill units and growing degree hours (base 4.4C air temperature) was used to estimate the dates to begin and end chill unit accumulations and the dates of full bloom of `Redhaven' peach trees for each year in the climatological record. The actual dates of freezes with air temperatures at or below –2.2C and the estimated bud developmental stage on the date of each freeze also were determined. The model was tested using peach orchard records and was found to be an improvement over using only freeze data. The model indicated that Spring Hill had the highest risk for peach production and Jackson the lowest. Recent problems with spring freezes at Knoxville and Spring Hill were due to later than normal freeze dates rather than earlier development of the `Redhaven' peach tree buds. At Springfield, the recent freeze problems were due to earlier breaking of rest, earlier full bloom, and later freezes.

Open access

Eric Young and Dennis J. Werner

Abstract

Estimates were determined for chill unit (CU) and growing degree hour (GDH) requirements for vegetative bud break in 6 apple (Malus × domestica Brokh.) rootstocks: Antonovka 313, MM 111, MM 106, M.7a, M.26, and M.9. Rooted layers were lifted in the fall, potted, and kept in a cold room at 4°C for various lengths of time. plants then were moved to a greenhouse, and the percentage of bud break was determined for various GDH intervals. Prediction equations were determined for the percentage of bud break vs. chill unit accumulation and growing degree hour accumulation. M7a had the lowest chill unit and growing degree hour requirements for 50% bud break (590 CU and 4278 GDH). MM 106 required the most chilling (1220 CU), and M.26 the highest number of growing degree hours (6138 GDH) for 50% bud break.

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Clint Wall, William Dozier, Robert C. Ebel, Bryan Wilkins, Floyd Woods, and Wheeler Foshee III

indicator of vegetative chilling requirement. Growing degree hour (GDH) for first budbreak and first flower development were calculated daily using a base temperature of 4.4 °C and a maximum temperature of 25 °C. GDH was regressed against chilling hours

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Brent Black, James Frisby, Kimberly Lewers, Fumiomi Takeda, and Chad Finn

on an hourly basis and sum growing degree hours (GDH), eliminating the need to mathematically approximate diurnal fluctuations. A linear model for accumulated heat units ( Anderson and Seeley, 1992 ) can be defined by a basal, optimum, and critical

Free access

Roberto Hauagge and James N. Cummins

Abbreviations: BB, percent terminal budbreak; BDS, bud development stage; CR, chilling requirement; CU, chill unit; D50, number of days for 50% terminal budbreak; GDH, growing degree hours. 1 Present address: IAPAR-Instituto Agronômico do Paraná

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I. Citadin, M.C.B. Raseira, F.G. Herter, and J. Baptista da Silva

Differences in heat requirements for blooming and leafing were investigated in peach [Prunus persica (L.) Batsch] using artificially chilled excised shoots and potted trees. `Della Nona' and `BR-1' have high heat requirements; `Planalto', `Sunlite', and `Eldorado' are intermediate; and `Precocinho' and `Riograndense' have low heat requirements. Prolonged chilling enhanced leafing more than blooming. Flower and vegetative buds have different heat requirements during ecodormancy.

Free access

Jianlu Zhang and Cathy Taylor

‘Sirora’ pistachio grown in Australia has not been established. After chill fulfillment, temperatures above some base level will result in growth and bud development ( Richardson et al., 1975 ). Growing degree-hours (GDH) are the number of hours of heat

Open access

C.H. Crisosto, P.B. Lombard, and L.H. Fuchigami

Abstract

Ethephon at 120 mg·liter−1 applied to hand-defoliated or nondefoliated trees in late Oct. 1984 delayed ‘Redhaven’ [Prunus persica (L.) Batsch.] full bloom by ≈5 days in 1985. The same treatment applied on 1 Nov. 1985 delayed full bloom by 9 days in 1986. Hand-defoliation alone was ineffective in delaying bloom in either season. Ethephon treatments increased abscisic acid (ABA) and ethylene levels in dormant buds collected throughout the 1985–86 dormant season. Starch and reducing sugar contents and total chilling requirement were not affected by the ethephon and hand-defoliation. Flower primordia were delayed in differentiation and growth during late fall following a 1986 spray of ethephon. A delay in flower development and growth may be caused by increased levels of ethylene and ABA. Chemical names used: (2-chloroethyl) phosphonic acid (ethephon); aminoethoxyvinylglycine (AVG).

Open access

Mary Bauer, C. E. Chaplin, G. W. Schneider, B. J. Barfield, and G. M. White

Abstract

‘Redhaven’ peaches (Prunus persica L. Batsch) were sprinkled from the end of rest, January 22, 1975, until the time check trees reached full bloom, April 18, 1975. Sprinkling delayed bloom by 15 days. Energy models predicted bloom one day before it occurred in the check trees. Wood temperatures were lowered as much as 6.5°C in sprinkled trees, but no significant difference in wood cold hardiness was observed. Sprinkled fruit buds were more cold hardy than non-sprinkled fruit buds until early March. Non-sprinkled buds were more cold hardy than sprinkled fruit buds in late March. Sprinkling reduced the number of viable buds/m by late March. Analyses of total and reducing sugars and protein showed no significant difference.

Open access

D. W. Buchanan, J. F. Bartholic, and R. H. Biggs

Abstract

A delay in flowering of up to 14 days was obtained in the 1974-75 and 1975-76 seasons with ‘Sungold’ and ‘Sunrich’ nectarines and ‘Flordagold’ peach [Prunus persica (L.) Batsch] by intermittent sprinkling when tree temperatures exceeded 18°C. Flowering and foliation was also hastened in 1974-75 on trees shaded with 55% saran cloth. Sprinkling did result in heavy bud abscission on certain cultivars. Shading and sprinkling lowered cambial temperatures by 5 to 10° and delayed harvest from 5 to 7 days.