Background
The Colorado potato beetle (CPB), Leptinotarsa decemlineata (EPPO code: LPTNDE), is a European Union (EU) protected zone quarantine pest in certain member states. The Swedish protected zone currently covers five counties in the southern part of the country, i.e. Blekinge, Gotland, Halland, Kalmar and Skåne (Fig. 1A; Annex III of (EU) 2019/20721). However, a recent analysis indicates that the area likely to be suitable for the establishment of the CPB extends much further north than the current protected zone (Björklund et al. 2024).
Commission delegated regulation ((EU) 2022/24042) details the rules for surveys of protected zone quarantine pests. This regulation requires that a stratified survey design should be employed where the member states either create a buffer zone around the protected zone or if that is not possible, an inner band within the protected zone. In Sweden the current protected zone borders the sea and the alternative with an inner band will therefore be used. In contrast to a buffer zone an inner band stretches inwards from the border of a protected zone. In other words, it is as an area in a protected zone surrounding the protected zone on the inner side along its outer border. Surveys in the inner band should be conducted more intensively than in the rest of the protected zone.
SLU Risk assessment of plant pests was requested by the Swedish Board of Agriculture to provide an estimate of a suitable width of an “inner band” for the CPB within an area identified to be suitable for the establishment of the beetle according to the assessment by Björklund et al. (2024). Further, the risk varies along the inner band and therefore the high-risk part of the inner band was also determined since the surveys should be risk-based