The resistance of the citrus rootstock Forner-Alcaide 5 to Tylenchulus semipenetrans was assessed in comparison to the susceptible Carrizo citrange (S) in two replant situations. Changes in soil and root population densities were monitored after planting the new trees to detect tree infection and nematode population growth over time. The efficacy of pre-plant control methods such as fumigation with 1,3 Dichloropropene (1,3D) or 2-year fallowing was also assessed. Fumigation and fallowing reduced juveniles + males/250 cm3 soil to undetectable levels for 3 and 2 years, respectively, and postponed root parasitism on Forner-Alcaide 5 for 3 and 2.5 years, respectively. Forner-Alcaide 5 supported lower densities of juveniles + males/250 cm3 soil and females/g root than Carrizo citrange in both replant situations The efficacy of the resistant rootstock was enhanced when combined with 1,3D fumigation or 2-year fallowing because the pre-planting control reduced densities of juveniles + males in soil before establishing the orchard, and the resistant rootstock, the female densities in the roots

his work was supported by Instituto Nacional de Investigación Agraria y Alimentaria (INIA) of Spain (grants SC98-103-C2; RTA02-068 and RTA05-00086-00-00) and European Funds for Regional Develop- ment (FEDER). We acknowledge Dr. J. B. Forner, who passed away while we were preparing the manuscript, for providing the rootstocks used in the study. The assistance of A. Alcaide in the field experiments and Dr. A. Catena in the statistical analyses is greatly appreciated. Thanks are also given to Miguel Fabregat (in memoriam) and Maria Carmen Fabregat for allowing conducting experiment 1 at their prop- erty.