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  • Author or Editor: E. L. Proebsting Jr. x
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Abstract

An accurate frost alert system is the first step in planning for frost protection. Forecasting methods are being updated by statistical studies from historical records at the fruit frost forecast stations. It is planned to put information in a computer at Yakima, Washington, which will permit retrieval of data for all past days with meteorological characteristics similar to the day of the forecast (7). Florida uses a regression-based model to relate forecast temp of 300 stations to actual forecasts for 15 key stations. Forecasts are updated at 10 pm based on new weather data and reports from growers on current conditions including extrapolations made with inexpensive net radiometer measurements (14, 23).

Open Access

Abstract

As pomologists, our primary responsibility is to fruit trees growing in the frequently hostile environments which we insist on calling “fruit sites.” For most of the country the most consistently and effectively hostile element in a fruit tree’s environment is low temperature.

Open Access

Abstract

There is need for rapid determination of cold resistance of plants in the field. Exotherm analysis was adapted to such needs for dormant fruit buds of peach (Prunus persica (L.) Batsch). Buds were excised with 1-2 mm of vascular tissue attached and then held near the thermocouple junction with an A1 foil wrap. Exotherms could be recorded from most of 25-30 buds per junction. Resolution was improved by slow rates of temperature decrease in the critical range (near l°/hour). At high rates of temperature decrease (8 to 15°/hour) buds were killed at higher temperatures. The distribution of bud mortality with temperature was very close to the standard skewed curve for buds evaluated by the tissue browning method.

Open Access

Abstract

Trees of peach (Prunus persica (L.) Batsch) and pear (Pyrus communis L.) were grown without irrigation and received only 86-mm rainfall during the growing season. Many peach trees died after experiencing leaf water potentials below −30 bars in July and August. Defoliation began in July, fruit growth was arrested, flavor was astringent, and flower buds failed to differentiate. Pear trees survived under similar conditions although tops died back or grew poorly and flowering was reduced. Regrowth came from trunks and lower scaffolds. Heavy pruning (“dehorning”) delayed the appearance of drought symptoms until very late in the season and resulted in 100% survival of both peach and pear trees. Heavy thinning of peaches in early June did not affect current season's symptoms but apparently reduced dieback and death of trees.

Open Access

Abstract

Severe frost injury was incurred about full swell on one group and about 4th leaf on another group of ‘Concord’ (Vitis labrusca L.) vines where sprinkling was interrupted during the night. The wet tissues were less cold resistant than dry tissues. Yield was reduced 22% by the early frost, 52% by the later frost. Bloom was delayed 10 days by the early frost, 18 days by the later frost. At harvest the berries were larger than non-frosted on the early-frosted vines and equal in size on the late-frosted vines. Color and soluble solids were lower on the frosted vines.

Open Access

Abstract

Chemical regulation of cold hardiness is a fascinating objective for pomological research. In the past 5 years gibberellic acid (GA) and N-dimethylamino succinamic acid (Alar) have been reported to increase fruit bud hardiness of peaches (3, 4, 7). Trees treated with these two chemicals and 2-chloroethane phosphonic acid (Ethrel) were exposed to -11°F on December 30, 1968, permitting us to observe their effects on resistance of fruit buds to cold injury.

Open Access

Abstract

The variability of color, soluble solids, weight, and firmness of individual sweet cherries ( Prunus avium L.) on trees from 15 locations throughout the central Washington production district was measured at weekly intervals. Between the first and third harvest, the cv for color decreased from 24% to 9%, for soluble solids from 16% to 13%, was a constant 14% for weight, and increased from 19% to 24% for firmness. Within groups of cherries of similar color, the cv was 13% for soluble solids, 14% for weight, and 19% to 24% for firmness. Firmness measured by durometer or shear press was not correlated with bruising induced by a standardized bruising test. It was concluded that color picking could solve only partially the problem of variability in sweet cherry quality.

Open Access

Abstract

Flower buds from 10 ‘Bing’ cherry (Prunus avium L.) and 5 ‘Elberta’ peach (Prunus persica [L.] Batsch) orchards were tested for cold resistance each week for 3 years during the dormant and pre-bloom periods. The cold resistance of dormant buds was most affected by temperature prior to sampling. Additionally, buds from certain sites were consistently more resistant than buds from others. Elevation, soil type, and cultural practices are the site characteristics likely to influence cold resistance of buds. During the pre-bloom period differences among sites were closely related to bud development which, in turn, was associated with elevation and temperature.

Open Access

Abstract

(2-Chloroethyl)phosphonic acid (ethephon) applied Sept. 8, 1971 at 250 and 500 ppm delayed sweet cherry (Primus avium L.) bloom 3 to 5 days, thereby reducing spring freeze injury and increasing yield. Preliminary data from a nonfrost year indicate no deleterious effect of treatment on maturity or quality.

Open Access

Abstract

Late summer sprays of (2-chloroethyl)phosphonic acid (ethephon) increased hardiness of dormant sweet cherry (Prunus avium L.) fruit buds, delayed bloom, and improved survival of spring frosts thus increasing yields. Wood hardiness was increased slightly. Autumn defoliation was sometimes hastened. Fruit size was reduced but color, soluble solids and firmness were not affected. Ethephon applied in late summer induced gumming of branches the following May in 1 year out of 6. Ethephon probably does not influence normal acclimation. Its effect is superimposed on the natural cycle.

Open Access