In contrast, most of the eggs laid by cyst nematodes are maintained within the body of the female, which tpically breaks through the root surface and is first visible as a white, pin-head size spot or cyst on the root. The sugarbeet cyst nematode (H. schachtii) is economically the most important cyst nematode in California, although it is restricted in host range to beets, cole crops, and spinach. The cabbage cyst nematode (H. cruciferae), a more localized cyst species, parasitizes cole crops. After the death of the cyst female, the body becomes hard or tanned and protects the eggs from adverse environmental conditions. Eggs in cysts can remain viable for several years. Approximately 20 to 60 percent of the eggs hatch annually under suitable temperature and moisture conditons, resulting in new infections on susceptible crops. Newly hatched juveniles soon die, if host plant roots are not available, especially in warm soil in spring and summer. Heterodera schachtii, adaptable to a wide soil temperature, can survive as eggs in cysts in freezing soil and in surface soil that may reach more than 50C in the Imperial Valley. The optimum temperature for development and reproduction is 21 to 27C. The length of the life cycle depends primarily on temperature, and may be completed in 3 to 4 weeks at optimum temperatues for reproduction. Because unhatched juveniles can remain viable for several years, this nematode is very persistent between host crops.
In both root-knot and cyst nematodes, the adult males are vermiform. Adult males are rare in root-knot nematodes and not required for reproduction. In cyst nematodes, males are more common and are required for reproduction. It has been shown that males become more plentiful when food sources are limited.
References:: McKenry, M.V. and P. A. Roberts. 1985. Phytonematology Study Guide. University of California, Division of Agriculture and Natural Resources.