Studies were conducted to determine methods to restrict inter-orchard spread of Radopholus citrophilus. Experiments focused on the ability of a nematode to migrate in root-free soil and on methods to restrict the growth of citrus roots across root-free buffer zones. In migration trials, the nematode moved 1.4 m in 1 year from infected to noninfected seedlings when host roots were permitted to grow toward one another. However, when citrus root growth was restricted by pruning, the nematode did not infect roots on seedlings growing 1.5 m distant from infected seedlings. In orchards, roots grew at an annual rate of 0.90 m but 1.5 m following pruning with a trenching machine. Sampling following cutting of roots and root system excavation indicated that long pioneer roots did not grow at depths 1.5 m until they grew beyond the undercanopy area of the tree. Therefore, vertical hedging of trees to permit trenching near the trunk will significantly increase the number of major roots
