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  • Author or Editor: Roger Young x
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Abstract

Although citrus is grown in the southern regions of the United States, it is exposed to periodic freezes. Freezes are a serious production problem, as evidenced by the enormous loss of fruit and trees in recent years in the major citrus-growing areas (8). In 1962 in Florida, approximately 50 million boxes of fruit were lost, and substantial wood damage and loss of bearing surface occurred in approximately two-thirds of the citrus-producing areas (12). The monetary loss was estimated to exceed 500 million dollars. In Texas in 1951, 85,000 acres of trees were killed, and in 1962, 40,000 acres. Surviving trees lost their entire bearing surface. Many trees were killed back to 2-inch wood (27). Severe freezes also occur periodically in California and Arizona. In 1963, for instance, temperatures as low as 20°F occurred in some areas in California for eight consecutive nights. Injury was primarily to the fruit and very young trees (12). Studies of long-term weather records have indicated that freezes of 22°F minimums and lower occur in all major citrus-growing areas in the United States every 8 to 13 years on the average (5). Thus, it is expected that citrus-growing areas will be exposed to damaging freezes periodically.

Open Access
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Abstract

Tree and fruit losses from cold injury are important problems in growing citrus. Severe losses from the freezes of 1894-95, 1957-58, 1962, and 1970-71 in Florida; 1949, 1950, and 1962 in Texas; and 1913, 1937, 1949, and 1950 in California, have stimulated research on cold hardiness of citrus. One method of reducing losses from freezes is the production of cold hardy cultivars by breeding and selection. Citrus physiologists and breeders with the USDA at Orlando, Florida; Indio, California; and Weslaco, Texas, have coordinated their research to develop more cold hardy citrus cultivars (2, 3). This paper summarizes some recent efforts to develop methods for screening citrus hybrids for cold hardiness. The glossary (Table 1) of the citrus types and names used here include cold hardiness ratings. Common names or a designated number will be used for simplicity of discussion.

Open Access

Abstract

The flesh of ‘Redblush’ grapefruit exposed to 41.8°C day/36.1°C night temperatures in environmental growth chambers for 60 days did not increase in lycopene content, while fruit exposed to natural conditions in sunlight and under shade did. Lowering the temperature from 41.8°C/36.1°C to 32.2°C/21.1°C produce a high level of lycopene. Carotene concns. of fruit exposed to 41.8°C/36.1°C and natural conditions remained the same. Exposure to 32.2°C/21.1°C caused a small increase in carotene, while exposure to natural conditions, at lower temperatures, caused a larger increase in carotene.

Open Access

Abstract

In an assessment of natural hazards on world crop production, an average of more than $ 100 million per year is lost in the continental United States due to freeze damage to 22 major crops. The greatest loss is in citrus production and amounts to about one-third of the national average. A severe freeze occurred in 1962 which cost Florida more than one-third of its total production, in excess of 10 million boxes (41 kg.) of fruit and onefourth of its 52 million trees. Similar losses occurred again in 1977 and, most recently, in 1981 and 1982. These losses impact negatively not only on the present and future economic stability of an industry, but also in meeting the dietary needs (supply and nutrition) of an expanding world population, which is facing ever-increasing uncertainties in adequate nutrition and subsistence levels.

Open Access

Abstract

2-Chloroethylphosphonic acid (Ethrel) applied at 50 to 200 ppm as a preharvest spray, showed considerable promise in degreening ‘Robinson’ and ‘Lee’ tangerine fruit. The preharvest degreening resulted in less postharvest degreening time required for acceptable color and less fruit decay during storage. Ethrel concn between 100 and 200 ppm caused abscission of some old leaves, but had no apparent effect on external appearance other than color.

Open Access