| LOCATION | % DECLINE/YEAR | REFERENCE |
| GERMANY | 60-45 | KUHN, 1877 |
| ENGLAND | 33-50 | JONES, 1956 |
| ENGLAND | 48 | MORIARITY, 1961 |
| ENGLAND | 36-61 | MORIARITY, 1963 |
| IMPERIAL VALLEY | 49-80 | ROBERTS ET AL., 1980 |
| SAN JOAQUIN COUNTY | 15-25 | WESTERDAHL & KEGEL |
The length of time that a field must be in nonhost crops or fallow can be predicted by knowing the nematode population at harvest and the rate of population decline or percent yearly decline expected.
Although this can vary from field to field and has been found to be affected, for example, by the presence of nematode parasitic fungi, this table contains average values from the literature.
The length of rotation typically practiced in the Imperial Valley of California is typically much shorter than in San Joaquin County in the central valley which is in keeping with the differences in rates of population decline.
It is interesting to compare these rates of decline for sugarbeet cyst nematode with that of root-knot nematode in the San Joaquin Valley which is around 85% per year.
The tough outer covering or cyst which is the cuticle of the adult female cyst nematode and protects the eggs within is thought to account for the greater survival ability of cyst nematode.