Probability range in damage predictions as related to sampling decisions.

The risk involved in basing a nematode management decision on predicted crop loss is related to the uncertainty in the crop damage function and error in measuring nematode population density. The sampling intensity necessary to measure a nematode population with specified precision varies with population density. Since the density is unknown prior to sampling, optimum sampling intensity for a management decision is calculated for the economic threshold population level associated with the management cost. Population densities below the threshold are measured with greater precision than required; those above the threshold are less precisely measured, but invoke management. The approach described provides resolution to sampling strategies and allows assessment of the risk associated with the management decision.