Incidence and inheritance of resistance to METI-acaricides in European strains of the two-spotted spider mite (Tetranychus urticae) (Acari : Tetranychidae)

A strain of Tetranychus urticae (Koch; Acari: Tetranychidae), collected fro m hops (Humulus humuli L; Cannabaceae) in England with a short history of t ebufenpyrad use, exhibited resistance to four METI (mitochondrial electron transport inhibitor) -acaricides; tebufenpyrad, pyridaben, fenazaquin and f enpyroximate. Resistance factors for these compounds in a micro-immersion a ssay were 46, 346, 168 and 77 respectively, and corresponded to those exhib ited by a Japanese METI-acaricide-resistant reference strain. Levels of res istance remained stable without further selection, and selection with tebuf enpyrad did not increase them. The UK strain was also resistant (c 6-fold) to bifenthrin. Crosses of homozygous, diploid females with hemizygous, hapl oid males showed that, in the UK strain, METI-acaricide resistance was pate rnally and maternally inherited, and was an incompletely dominant trait. An other tebufenpyrad-resistant strain from the UK, originating fi om a chrysa nthemum nursery (Chrysanthemum foeniculaceum Giseke; Asteraceae) was collec ted eight months later at a site c 210 km distant from the first. These are the first published incidences of METI-acaricide resistance in Europe and implications for the future use of these compounds are discussed. (C) 2000 Society of Chemical Industry.