First record of the subterranean termite Reticulitermes grassei in Switzerland

Switzerland has no native termite species. Historically, drywood termites have been introduced on six occasions, and subterranean termites were introduced on two occasions (Reticulitermes lucifugus and an undetermined Reticulitermes species). Only one of these introductions resulted in establishment; however it was subsequently eradicated. A new subterranean termite infestation was found in 2018, in the winter garden of a house on the lake of Zurich (northeastern Switzerland). Mitochondrial DNA analysis (cytochrome oxidase subunit II and 16S ribosomal RNA genes) showed that these termites belong to the Franco-Iberian species Reticulitermes grassei, and are genetically similar to populations from southern Spain. Termites were probably introduced with olive and palm trees that were planted in the affected property and in a neighbouring one. Damage was limited to the wooden floor and walls of the winter garden. The infestation was initially treated with diatomaceous earth followed by the insect growth regulator diflubenzuron. The infestation is nearing eradication.