The biology of Penthaleus species in southeastern Australia

Abstract

Earth mites are major pests of pastures and crops within southern Australia. While the biology and ecology of the redlegged earth mite (Halotydeus destructor) have been studied extensively, the blue oat mite (Penthaleus major) and its recently discovered relative, Penthaleus falcatus, have received little attention. The distribution of H. destructor, P. major and P. falcatus is described in Victoria, Australia, and the inland borders in central New South Wales are re-described. A new undescribed Penthaleus species identified from mallee samples is recognized, and its restricted distribution in Victoria is mapped. Electrophoretic data and the complete absence of males indicate that all Penthaleus species are obligate thelytokous parthenogens. The three Penthaleus species differ in clonal diversity. All species are pests of pastures and/or crops, however the preferred plant hosts of P. major and P. falcatus differ. Tolerance of a commonly used pesticide (omethoate) differs between the species. P. falcatus shows the highest LC 50 , and may be responsible for pesticide control failures. Rearing methods for P. major and P. falcatus are described. The large differences between these blue oat mite species point to difficulties in interpreting early published data that failed to distinguish them.

Competitive Interactions Between Two Pest Species of Earth Mites, <I>Halotydeus destructor</I> and <I>Penthaleus major</I> (Acarina: Penthaleidae)

“…The signiÞcant increase of H. destructor at all sites at the end of the season is likely to offset the high mortality that occurs during diapause (Ridsdill-Smith 1991, Ridsdill-Smith andAnnells 1997). However, the inability of P. major to increase in abundance when they also have a high reproductive potential (Weeks and Hoffmann 1999) suggests that H. destructor may have had a negative effect on P. major in the Þeld because of limited resources. Experiments conducted herein conÞrm competitive interactions between these species and also indicate that P. major can have a negative impact on H. destructor.…”

“…However, this is not the case because both P. sp. x and P. falcatus use different hosts to P. major (Weeks and Hoffmann 1999). It is not known if these host differences have arisen from past competition within this complex of earth mite species.…”

“…There are two main types of earth mites: Halotydeus destructor (Tucker) (Acari: Penthaleidae), and the blue oat mite complex Penthaleus spp. The latter consists of at least three species, P. major (Dugé s) (Acari: Penthaleidae), P. falcatus (Qin & Halliday), and an undescribed species (Weeks and Hoffmann 1999). Earth mites are usually controlled by chemicals although programs have been established to develop plants resistant to H. destructor (Jiang and Ridsdill-Smith 1996) and there is continued research for the development of integrated control programs.…”

“…H. destructor is highly polyphagous, feeding on agriculturally important plants, including most pasture plants and crops (Ridsdill-Smith 1997). P. major is also polyphagous although it tends to feed primarily on pasture grasses as well as wheat, barley, oats, and peas (Weeks and Hoffmann 1999). Both species have a similar distribution throughout southern Australia, although P. major extends into drier inland regions (Wallace and Mahon 1971) and higher rainfall areas.…”

The distribution, abundance and life cycle of the pest mites Balaustium medicagoense (Prostigmata: Erythraeidae) and Bryobia spp. (Prostigmata: Tetranychidae) in Australia

“…Previous studies have also found differences in the levels of tolerance of mites to pesticides that could be related to control failures. In particular, P. falcatus has a high level of tolerance to a range of registered pesticides compared to other earth mites, and has been responsible for many chemical control failures (Umina & Hoffmann 1999;Weeks & Hoffmann 1999;Robinson & Hoffmann 2000, 2001. Given the high tolerance levels present in Ba.…”