This table is adapated from the UCIPM Project Integrated Pest Management on Tomato manual.
If fields are sampled at harvest in late summer or fall, population levels in infested fields are usually easily detectable.
If fields are then left fallow or planted with a nonhost crop during the winter, the rate of population decline has been found to be approximately 85 percent.
Populations in the Spring are consequently much lower and in many cases may be below the detection level of normal methods of extraction.
A susceptible tomato crop is then planted, and populations increase until the fall, at the rates indicated. The table indicates the yields that can be expected based on the initial populations present in the field.
Note that these numbers are per gram of soil which is approximately one-tenth of a teaspoon.
If meaningful damage threshold levels for nematodes on annual crops are to be developed, they will likely need to be based on samples taken at harvest for a following crop rather than shortly before planting which is the typical practice.