Tetranycopsis horridus was first reported on hazelnut in Victoria in 2016. Further surveys during February 2016 have shown a widespread distribution in Victoria. Tetranycopsis horridus was then detected in New South Wales as a result of targeted surveillance following its detection in Victoria. Tetranycopsis horridus has a broad host range but infestations in Australia are restricted to hazelnut plantations. The mite feeds on hazelnut leaves, causing discolouration that includes visible white or yellowish spots. The mites are found mainly on the underside of the leaves and have been reported as being destructive to commercial hazelnut crops.