Citrus production is declining worldwide due to several biotic and abiotic factors. The diseases caused by Phytophthora spp. present major economic risks since they are soil-borne and spread quickly if environmental conditions are favorable, or irrigation is poorly managed. Phytophthora species are present in all citrus-producing areas around the world causing significant losses in crop yield and affecting tree health. Bark infection, damping-off, root rot, gummosis, brown rot, and cortical root rot are among the typical symptoms caused by Phytophthora spp. The pathogenicity of Phytophthora spp. depends mainly on the specific interactions between the isolates and citrus cultivars.
Effect of Different Rates of Sulphur Fertilization on Fruit Yield and Leaf Mineral Composition of ‘Valencia’ Oranges in the Subtropical Environment of South Africa
Although sulphur is one of the essential nutrients for plant growth with a crop requirement similar to phosphorus (P), this nutrient element has received little attention because it is supplied in insecticides, fungicides, manure and from the atmosphere. With the relaxation of this requirement, and restrictions on sulphur dioxide emissions by industries it has become apparent that sulphur deficiency is widespread throughout the world. The majority of farmers submitting samples for soil and leaf nutrient analysis do not request a sulphur (S) test. This is due to the fact that farmers are still under the impression that there is enough sulphur in the soil.