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Wheat (Triticum aestivum L.) is grown in many arid regions using fallow management whereby no crop is grown in alternate cropping seasons. Although fallowing is important in increasing the availability of water and nitrogen to crops in many environments, experiments in Israel revealed that water carryover from the fallow season for wheat production was rare. This paper examines the possibility that improved water use, and improved root and shoot growth, result from soil sanitation of cereal cyst nematode (CCN, Heterodera avenae Well.) in the fallow season. Pot experiments in controlled environments revealed a dramatic, negative effect of various populations of CCN on wheat root growth. The decrease in root growth was associated with decreased shoot growth and decreased rates of transpiration. Mechanical pruning of roots mimicked the effects of CCN infestation indicating that root pruning is probably the primary damage of CCN. In the field, dry weight yields of wheat were maintained even in continuous wheat management when a soil biocide was used to control CCN. It is proposed that the success of the fallow management is based on the fact that CCN cysts hatch in wet soil during rainy periods of the fallow year but fail to produce a new generation of cysts because no host plants are present.