Pest categorisation of .

The EFSA Panel on Plant Health performed a pest categorisation of Butler (Lepidoptera: Lasiocampidae), the larch caterpillar, for the EU territory. is a major pest of conifer forests in Japan, northeast China and non-European Russia. However, reports of damage are to conifer species not grown in EU forestry. and are regarded as major hosts. Eggs are laid on host needles and developing larvae feed on host foliage. Larvae overwinter in the soil. In its native range, usually takes one or two years to develop. In principle, host plants for planting and plant products, such as cut branches and wood with bark, could provide pathways into the EU. However, prohibitions on the import of , and from areas where occurs closes such pathways. Nevertheless, a derogation for specific dwarfed plants from Japan exists. Climates similar to those in some of its existing range occur in the EU. Norway spruce () is a known host in Japan although reports of any impact are lacking. Experiments on the related species indicated that larvae were able to develop on forestry conifer species occurring in the EU, but which are found outside the native range of . Were to be introduced into the EU, impacts on are possible and it is conceivable that could expand its host range, as seems possible with . However, this remains uncertain. Other hosts are grown in the EU as ornamentals or amenity trees. satisfies all the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest. Some uncertainty exists over the magnitude of potential environmental and economic impacts.