Severe copper deficiency in orchard grapefruit trees

Abstract

does not appear. First page follows. Introduction In the winter of 1958 several grapefruit orchards near Hemet, California, developed severe copper deficiency symptoms. Because this deficiency is rarely seen in the field in California, its appearance in severe form presented an excellent opportunity for study of the diagnostic symptoms, for laboratory verification through leaf and soil analysis, and for field correction of the deficiency. This paper is a report of copper-deficiency symptoms as they appeared in the grapefruit, and of the use of sprays to achieve full recovery. Materials and Methods Experimental Orchards The three grapefruit orchards studied are located on Hanford sandy loam soil. Orchard A comprised 27 acres of Ruby red grapefruit scion on rough lemon rootstock, while orchard B comprised about 10 acres of Marsh grapefruit scion on rough lemon rootstock. Adjacent to these 10 acres of grapefruit were about 5 acres of Valencia oranges (orchard C) on rough lemon rootstock. Orchard D was a poor-appearing young grapefruit orchard (rootstock unknown) located about a mile south of orchard C. Leaf Sampling and Analysis Spring cycle leaves 4 to 6 months old were taken from fruiting terminals. In each case 10 leaves from each of 10 trees comprised the sample. Leaves were individually washed in tap water and Ivory soap, rinsed in tap water, and dried with clean cloths; this method of leaf washing has been employed in laboratories of the department of Soils and Plant Nutrition at Riverside, California for many years and has been subjected to thorough testing (Wallihan, 1953).3 The samples were then oven dried at 55° C and crumbled by hand previous to weighing a 2-gram sample for spectrographic analysis. Micro-element determinations were made by the spectrochemical method of (Vanselow et al. (1948)). Soil Sampling and Analysis Virgin soil samples of the 6 to 8-inches depth were collected from areas surrounding the orchards showing severe copper deficiency symptoms. Samples were analyzed for total copper by the method of (Pratt and Bradford (1958)).