The pest status and distribution of three cryptic blue oat mite species (Penthaleus spp.) and redlegged earth mite (Halotydeus destructor) in southeastern Australia

Earth mites are pests of crops and pastures in southeastern Australia. Recent studies show differences between earth mite species in their mode of reproduction, preferred hosts and pesticide tolerance. This paper examines the distribution and pest status of each species. The southeastern Australian distribution for each species is mapped, incorporating new data from eastern New South Wales, South Australia and Tasmania. A new population of an undescribed species previously identified from northwestern Victoria was found in northern New South Wales. CLIMEX was used to identify climatic factors limiting the distribution of P. major and P. falcatus, the most broadly distributed species. This analysis suggests tolerance to heat and desiccation limits the inland distribution of these two species. A three-year survey of agricultural outbreaks indicates that all Penthaleus species are major agricultural pests although their pest status on crop types appears to differ. All species contributed to chemical control failures. However P. falcatus, previously identified in laboratory tests as having increased tolerance to pesticides, was the most common species associated with control failures. A laboratory experiment indicated that mites are sometimes pests on crops on which they cannot persist for a generation. Results are discussed with respect to management of these agricultural pests.