Evaluation of the causes of citrus decline in southern Iran and the required soil and water management strategies

Citrus fruits are of special economic importance; hence, the factors affecting their production need special attention. The citrus decline disorder is the cause of serious losses to the citrus industry due to the economic failure or total degradation of citrus orchards in the south of Iran. Even though the causal agents of the disorder in these regions are not yet fully known, a combination of environmental stresses and biological agents, depending on the affected region, seem to play roles in the spread of the disorder. Whatever the major causal agents, it is well established that the affected trees lose their hairy roots that are responsible for water and nutrient uptake. Drawing upon literature reports, field investigations, observational experiments, and the past experience of the present authors, the present paper proposes a number of remedial and preventive practices to mitigate, or even eradicate, the citrus decline disorder. Some of the most important strategies proposed include well managed irrigation regimes, timely application of proper fertilizers, reducing environmental stresses, orchard sanitation, and proper horticultural practices. Although such recommended practices as reducing environmental stresses may not be easily applicable under certain conditions, most seem readily practical.