Opiine parasitoids (Hymenoptera: Braconidae) and biological control of fruit flies (Diptera: Tephritidae) in Australia: Past, present and future

Abstract

Opiine braconids are parasitoids of the immature stages of frugivorous tephritids. The female wasp lays her eggs into the eggs or larvae of the fruit fly host, where the immature wasp develops before emerging as a next-generation adult from the now dead host pupal case. In support of a new generation of Australian fruit fly parasitoid research, this paper comprehensively reviews what is known about the Australian fruit fly infesting opiines. Based on the most recent taxonomic revision 11 fruit fly infesting opiine species are documented to occur in Australia, but we consider as doubtful the record for Diachasmimorpha longicaudata and consider the record for Fopius illusorius to be tentative without further collections. We identify that the systematics and taxonomy of the Australian native fruit fly infesting opiines are in urgent need of further work. The history of fruit fly biological control in Australia is comprehensively reviewed, including the export of native Australian opiines for fruit fly control elsewhere in the world. Australia was actively involved in three major classical biological control programmes against fruit flies from the turn of the 1900s until the mid-1960s. Despite the introduction of 11 opiine species, plus numerous other natural enemies, only Fopius arisanus established in eastern Australia, where in South-east Queensland it can now cause between 30 and 40% mean parasitism. In addition to the exotic F. arisanus, the native species Diachasmimorpha kraussii and Diachasmimorpha tryoni also cause fruit fly parasitism in agriculturally important crops: both species have also been liberated widely outside of Australia for fruit fly control. Other Australian opiines have not been reared from fliesinfesting commercial crops and appear biologically restricted to the fruits and environs of Australian east-coast rainforests. The biology literature for D. tryoni and D. kraussii is comprehensively reviewed, while for F. arisanus, already reviewed elsewhere, key literature only is covered. Forward looking, we consider the potential for inoculative or inundative releases of opiines in areas where they do not currently occur to be good, while conservation biological control may help to increase the impacts of parasitoids in areas where they are already established.

Conservation biological control of the fruit fly parasitoid Fopiusa arisanus (Hymenoptera: Braconidae)

“…This is also occurring in Australia (Zamek et al 2012;Zamek et al 2013) as pest management of Queensland fruit fly pivots away from on-farm pesticide applications to area-wide management (Dominiak & Ekman 2013;Schwarzmueller et al 2019). A recent increase in reported field parasitism rates of Australian fruit flies (Clarke et al 2022) is suggestive (but does not prove) that the decline in broad-spectrum cover-spray usage for fruit fly control (Dominiak 2019) is having a beneficial flow-on effect for natural enemies, which may help the implementation of conservation biological control. For area-wide management, parasitoids can potentially play a key role in reducing total fly pressure, both on-farm and off-farm in feral hosts and urban areas (Clarke et al 2022).…”

“…It occurs in coastal and subcoastal eastern Australia from Cairns to Melbourne (Symon 1981). The plant has small berry-like fruit that hosts larvae of the wild tobacco fly, B. cacuminata, a non-pest native fruit fly (Drew 1989), which is itself a host of F. arisanus (Clarke et al 2022). This experiment sought to examine if the wild tobacco/wild tobacco fly system could act as a non-crop reservoir for F. arisanus, particularly during autumn and winter months when B. tryoni reproduction and populations are low (Clarke et al 2019).…”

“…For presentation, the number of F. arisanus (and a second collected parasitoid, Diachasmimorpha kraussii) reared from a sample is converted to a parasitism rate of the total B. cacuminata potentially present in that sample. As F. arisanus and D. kraussii are both solitary endoparasites (Clarke et al 2022), the parasitism rate of the B. cacuminata larval population in a sample = ([F. arisanus] or [D. kraussii]/[(F. arisanus + D. kraussii + B. cacuminata)] * 100) (Merkel et al 2019).…”

“…In South East Queensland, the species is the dominant member of the fruit fly parasitoid guild and causes 30-40% parasitism of Queensland fruit fly, Bactrocera tryoni (Froggatt) (Merkel et al 2019;Mahat & Clarke 2021). The parasitism levels currently being recorded for F. arisanus are approximately 20% higher than the levels reported prior to the regulatory withdrawal of the organophosphate pesticides dimethoate and fenthion a decade ago (Clarke et al 2022).…”

“…The biology of F. arisanus and its use as a biological control agent are reviewed in Rousse et al (2005), with more recent information provided in Geib et al (2017), Monsia et al (2019), Nanga Nanga et al (2019) and Cai et al (2020). Fopius arisanus was introduced to Australia from Hawaii in the late 1950s (Snowball et al 1962a;Snowball et al 1962b) and now occurs along the east coast from Cairns to Sydney, but it rarely extends far from the coastal strip (Clarke et al 2022). In South East Queensland, the species is the dominant member of the fruit fly parasitoid guild and causes 30-40% parasitism of Queensland fruit fly, Bactrocera tryoni (Froggatt) (Merkel et al 2019;Mahat & Clarke 2021).…”