Citrus growers

Why do citrus growers spray their trees with water to protect them from a freeze See p. 107. 

Pickett et al. (1992) reported that California citrus growers depend on herbicides for weed control. Simazine was rated as the most important herbicide used in citrus production. Abdel-Rehman et al (1994) reported that control of annual broadleaf weeds was most effective with simazine plus fluazifop and least effective with fhiazifop alone. Application of diuron or atrazine once at 1-4kg a.i./ha or twice at 1 + 1, 1 + 2 or 2 + 2kg a.i./ha, significantly reduced grasses and broadleaf weeds. Broadleaf weeds were controlled by 2-4kg a.i./ha of diuron and 2 + 2kg a.i./ ha of simazine at the 60-day sampling period (Singh et al, 1987). Perez (1976) reported that fluometuron, diuron, monuron, and simazine, all at 4.8kg a.i./ha, and bromacil at 4kg a.i./ha controlled weeds without injury to citrus on latosols, while simazine and diuron at 4.8 kg a.i./ha or bromacil at 4kg a.i./ha caused no injury to grapefruit after two applications on sandy soil. 

If the temperature in a citrus orchard drops below -2°C for several hours, the fruit will freeze and be destroyed. Citrus growers spray tiny droplets of heated water to protect the crop if a freeze is predicted. Part of the protection comes from the heat released as the heated water cools. However, much of the heat that protects trees from freezing is released as the water freezes. The phase change from liquid to solid releases 6.01 kilojoules of energy for each mole of water. Creating a layer of ice on the tree actually prevents it from freezing. 

Why Do Citrus Growers Spray Their Trees with Water to Protect Them from a Freeze ... 

Obama K. 1996. Studies on allergic skin disease caused by pesticides in citrus growers Eield survey study and animal experiments. Med J Kagoshima Univ 48 13-22. 

We all know that, said the citrus grower very seriously. 

Citrus growers faced with an impending freeze know they must take preventive measures only if the temperature drops below 0 °C by several degrees. The juice in the fruit has enough dissolved solutes to lower the freezing point by a degree or two. The growers also know they must protect lemons sooner... 

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