11 Nematode Parasites of Citrus *

Citrus is grown in more than 125 countries in a belt within 35° latitude north or south of the equator. The major limiting factor to citrus production is a requirement that the occurrence of freezing temperatures be of very short duration. Within the family Rutaceae, the genera Citrus (oranges, mandarins, pomelos, grapefruit, lemons, limes and citrons), Fortunella (kumquats) and Poncirus (trifoliate oranges) contain the principal commercial species (Swingle and Reese, 1967). Citrus production worldwide exceeded 96 Mt in 2002. Approximately 68% of the world’s citrus production is consumed as fresh fruits, and about 11% of total production is used in international trade (Anonymous, 2002). Citrus spp. are naturally deep-rooted plants (Ford, 1954a,b), and optimum growth requires deep, well-drained soils because roots will not grow into or remain in saturated zones. Nevertheless, trees can be well managed in areas with high water tables if grown on beds. Citrus grows well under any rainfall regime provided that adequate soil moisture can be maintained. Irrigation of citrus is commonly practised by a variety of methods that range from orchard flooding to low-volume drip or microsprinkler systems. In areas with sporadic rainfall, the ability to manage soil moisture is critical for good production, particularly during the period when fruit are set after the first seasonal flower bloom (Sites et al., 1951). There is a tendency at present in the USA and elsewhere to increase early returns by planting higher density orchards with shorter life expectancies due to such diseases as citrus blight, tristeza and greening (Hearn, 1986).