Chlorosis Produced by Fluorine on Citrus in Florida

Abstract

A unique chlorotic leaf pattern on citrus trees in Florida that is attributed to fluorine is reported. The chlorosis was first noted in Polk County in April 1950 and was associated with a triple superphosphate manufacturing plant that recently opened. The polluting condition was corrected, but as new triple superphosphate plants opened, chlorosis increased. Florida pebble rock phosphate contains 2-4% fluorine which is released during the production in triple superphosphate. Chlorotic leaves from affected groves ranged in fluorine content from 370 ppM to as low as 478 ppM. Chlorotic citrus leaves were observed up to 6 miles away from the nearest plant, but the leaves were not abnormally high in fluorine content. It appears that fluorine causes leaf chlorosis and is then dissipated by translocation. Normal appearing leaves away from the affected area contained from 12 to 30 ppM fluorine. In 1955 sprays of aqueous acids were applied at concentrations 0.1 n to 4 year old ruby red grapefruit trees located 20 miles from the nearest triple superphosphate plant. Seven sprays of 1 l of solution each were applied during a 2-month period, and an identical chlorotic leaf pattern emerged in the trees sprayed with hydrofluoric and fluosilicic acid. Citrusmore » trees in California that contained up to 211 ppM fluorine did not develop chlorosis and may be the results of differences in climatic conditions, primarily the higher humidity in Florida. 6 references, 1 figure, 1 table.« less