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

Abstract

Abstract Balaustium medicagoense and Bryobia spp. have recently been identified by the Australian grains industry as emerging pests of winter grain crops and pastures. While reports of damage by these mites appear to have increased in the last decade, limited research has been conducted on their biology and ecology. Here the distribution and seasonal abundance patterns of Bryobia spp. and Ba. medicagoense in southern Australia are investigated. Bryobia spp. had a more widespread distribution than Ba. medicagoense. An Ecological Niche Model for the distribution of Ba. medicagoense constructed using MAXENT predicted the distribution of this species well, and identified associated climatic factors including summer and winter temperature variables and winter precipitation. Monthly sampling suggested that Ba. medicagoense had two generations per year and was active from March until December, with a likely diapause period in summer. The seasonal abundance and life cycle of two species of Bryobia (Bryobia sp. IX and Bryobia sp. I) differed. Bryobia sp. IX had two generations per year, was active from March until December, and was likely to be in diapause over summer. Bryobia sp. I did not appear to have a diapause stage, and had approximately four generations per year. Activity periods of these mites overlapped with those of the pest mite species Halotydeus destructor and Penthaleus major. A survey of pest outbreaks and chemical control failures suggested that while H. destructor and the Penthaleus species remained important pests, outbreaks of Ba. medicagoense and Bryobia spp. had increased. The findings highlight the need to develop effective and sustainable management strategies for these mites.