Flat Mites: A Potential Threat to Turfgrasses Worldwide, or Already Widespread?

Two species of flat mites (Acari: Tenuipalpidae) from the genus Dolichotetranychus have recently been found to cause significant damage to Cynodon (bermudagrass) and Zoysia spp. turfgrasses. Despite records of D. australianus infesting bermudagrass throughout Africa, the Middle East and Australia going back more than 70 years, most turf managers simply assume that any apparent mite damage is due to the more widely publicized eriophyoid bermudagrass mite, Aceria cynodoniensis, rather than checking their diagnosis under the microscope. To an experienced eye, the visual symptoms are distinctly different from those typically associated with A. cynodoniensis and also very similar to the symptoms seen with the zoysiagrass mite, D. zoysiae, in Okinawa (Japan). The possibility that there may be further undescribed or misidentified Dolichotetranychus species affecting turfgrasses is discussed, together with biosecurity implications. One such species that may prove to be more significant than hitherto suspected, if routine microscopic diagnosis were to be implemented, is D. summersi, which has been recorded four times from bermudagrass in the USA but without any indication of the symptoms caused. The importance of making microscopic examinations of suspected mite infestations is emphasized.