Screening of Oomycete Fungi for Their Potential Role in Reducing the Biting Midge (Diptera: Ceratopogonidae) Larval Populations in Hervey Bay, Queensland, Australia

Abstract

Biting midges are globally distributed pests causing significant economic losses and transmitting arbovirus diseases to both animals and humans. Current biological and chemical control strategies for biting midge target destruction of adult forms, but strategies directed at immature stages of the insect have yet to be explored in Australia. In the present study, coastal waters of Hervey Bay region in Queensland, Australia were screened to detect the habitats of biting midge at immature stages. These results were then correlated to local environmental conditions and naturally occurring entomopathogenic fungal flora, in particular the Oomycete fungi, to determine their reducing effect on insect immature stages in the search for biological control agents in the region. The dominant species of biting midge found within this study was Culicoides subimmaculatus occuring between mean high water neaps and mean high water spring tide levels. Within this intertidal zone, the presence of C. subimmaculatus larvae was found to be influenced by both sediment size and distance from shore. Halophytophthora isolates colonized both dead and alive pupae. However, the association was found to be surface colonization rather than invasion causing the death of the host. Lack of aggressive oomycete fungal antagonists towards midge larvae might correlate with increased incidences of biting midge infestations in the region.

Diversity of entomopathogens Fungi: Which groups conquered the insect body?

“…Certain genera are well-known plant pathogens, such as Phytophthora that is responsible for the Irish Potato Famine (Haas et al 2009) and sudden Oak death (Brasier & Weber, 2010). Those taxa infecting arthropods (the group containing insects) have been recorded from lobsters (Fisher et al 1975; Khulbe, 1994) and shrimps (Hatai et al 1992) as well as insects (Seymour, 1984; Samson et al 1988; Pelizza et al 2009; Stephen & Kurtböke 2011). As an insect parasite, they are known to infect the mosquito’s genera Aedes, Anopheles and Culex , all vectors of human diseases.…”

9. Case studies of vector-borne diseases in livestock: bluetongue virus

“…Culicoides subimmaculatus larvae was explored by Stephen and Kurtböke (2011) in the mangroves of Queensland, Australia. They tested six isolates including the fungal species Pythium prolatum, Halophytophthora batemanensis, Phytophthora gonapodyides and Halophytophthora spp.…”

1. Livestock pests and vector-borne diseases – a much neglected subject

“…Culicoides subimmaculatus larvae was explored by Stephen and Kurtböke (2011) in the mangroves of Queensland, Australia. They tested six isolates including the fungal species Pythium prolatum, Halophytophthora batemanensis, Phytophthora gonapodyides and Halophytophthora spp.…”