Trisetacus ehmanni Keifer 1963

Pye, Daniel R. L., 2012, New eriophyoid mites (Acari: Prostigmata: Eriophyoidea) in Britain: one new genus, four new species, 19 new records and two incursions, Zootaxa 3578, pp. 43-68 : 47

Trisetacus ehmanni Keifer 1963

Type host and locality. Pinus ponderosa Douglas ex C. Lawson (Pinaceae) , USA, California, Placerville.

Distribution. Found on many Pinus spp. and widespread in the Nearctic region ( Smith 1984), and also recorded from Cuba ( Torre & Martinez 2004), England (recorded here) and Italy ( Castagnoli 1973). The species has also been recorded on Larix kaempferi (Lamb.) Carr. (Pinaceae) from China ( Xue & Hong 2006).

Relation to the plant host. Inhabits the needles and sheaths, and recorded as causing chlorosis, twisting and shortening of the needles with premature needle drop, and on repeatedly attacked trees the twigs may become twisted ( Furniss et al. 1977). Along with Platyphytoptus sabinianae Keifer 1938 ( Eriophyoidea : Eriophyidae ) and Setoptus jonesi ( Keifer 1938) ( Eriophyoidea : Phytoptidae ), Trisetacus ehmanni has been associated with severe losses in commercial Pinus sylvestris L. (Scot's pine) plantations in the USA ( Saunders & Harrigan 1976).

Collection details. England, North Yorkshire, York, Sand Hutton (54° 1ʹ 2.28ʺ N, 0° 58ʹ 24.6ʺ W), low numbers on P. sylvestris , collected by the author, 11.v.2009; England, North Yorkshire, off Thorpe road between Masham and Grewelthorpe village (54° 11ʹ 57.12ʺ N, 1° 39ʹ 29.52ʺ W), high numbers on P. sylvestris , collected by the author, 25.iv.2010; England, North Yorkshire, Strensall Common (54° 2ʹ 36.61ʺ N, 1° 0ʹ 35.66ʺ W), high numbers on P. sylvestris , collected by the author, 25.iv.2010; England, North Yorkshire, York, Sand Hutton (54° 1ʹ 1.92ʺ N, 0° 57ʹ 1.08ʺ W), low numbers on Pinus nigra J.F. Arnold , collected by the author, 11.iv.2011. No host symptoms were observed in any of these populations.

Discussion. Until Keifer (1963) defined what is now known as T. ehmanni , all previous British records of Trisetacus pini ( Nalepa 1887) and T. ehmanni were made under the name ' pini '. Connold (1909) and Swanton (1912) listed Phytoptus pini Nalepa 1887 on Pinus spp. in their works on British plant galls, but provided no collection details, and Bagnall and Harrison (1928), Burkill (1930) and Turk (1953), listed Eriophyes pini ( Nalepa 1887) on P. sylvestris in England. These records cannot be confirmed as either species because the identifications were made from observed host symptoms alone. The finding of T. ehmanni from Sand Hutton, therefore, is the first confirmed record of this species in Britain.