A new sampling method for the detection of low population densities of potato cyst nematodes (Globodera pallida and G-rostochiensis)

To reduce the use of nematicides in The Netherlands, a new sampling method for the detection of potato cyst nematodes has been developed. The method detects small infestations with a predefined probability so eliminating the need for precautionary soil fumigation by farmers. Moreover, when a focus is detected, the area where a control measure has to be applied can be minimized. As many infestations are still quite small at the time of detection, other control measures than soil fumigation, which has a poor cost to benefit ratio, can successfully be applied. Analysis of intensive sampling data from 40 patchy infestations representing all growing areas in The Netherlands produced a simple exponential model describing expected cyst numbers within infestations. Differences in parameter values of the model between different growing areas were sufficiently low to enable one detection method for small infestation foci to apply to all potato growing areas. A pilot version of the method was introduced in 1989 in the Flevopolders and applied in all the seed and ware potato growing areas in the following years. In 1992, soil fumigation was decreased by 90% in the Flevopolders, where the sampling system was introduced first. Since 1992, the sampling system has been used as a basis for an advisory system. In 1994, an 80% reduction was realised in all seed and ware potato growing areas and a 90% reduction is estimated for 1995. As a result the total reduction of soil fumigants in The Netherlands (including the starch potato growing areas) was 75% in 1994. Current research is directed to improvements in the estimation of the size of potato cyst nematode infestation foci using sampling data originating from these new detection methods to generate improved advisory systems for farmers. Copyright (C) 1996 Elsevier Science Ltd.