Search

• Comprehensive study of 36 Australian EPN strains. • All EPN strains infected and killed larvae of Bactrocera tryoni. • Most EPN strains (84%) also caused pupal mortality. • EPN strain baited with B. tryoni was virulent against both developmental stages. • Seven EPN strains are promising candidates to control B. tryoni. Queensland fruit fly (Bactrocera tryoni) is Australia's most significant horticultural pest, yet limited options are available for its biological control. Here, we assessed the virulence and reproductive potential of 32 newly isolated Australian entomopathogenic nematode (EPN) strains of Heterorhabditis bacteriophora , Heterorhabditis indica, Heterorhabditis marelatus , Heterorhabditis zealandica and Steinernema feltiae against the late third larval instar and pupal stages of B. tryoni under laboratory conditions, and compared their performance with four commercially available strains of H. bacteriophora , H. zealandica , S. feltiae and S. carpocapsae. All EPN strains caused significant larval mortality, and, remarkably, 29 also pupal mortality. Among the EPN strains the mean LD 50 value, presented as the number of infective juveniles (IJs) per B. tryoni individual, ranged from 25 to 114 IJs per larva, and from 114 to 360 per pupa; therefore, 3.2 to 4.6× more IJs were required to kill pupae. The penetration rates of IJs in B. tryoni larvae varied from 2 to 6.8%, and the number of IJs recovered per larva varied between 2,100 to 5,683. Our findings highlight the potential of Australian EPN strains for controlling larval and pupal stages of B. tryoni. Overall, based on the three tested traits, one H. zealandica strain (Hz.NAR1), three H. indica strains (Hi.ECCH, Hi.HRN and Hi.HIE2), one H. bacteriophora strain (Hb.HIE), one H. marelatus strain (Hm.ENCBF2) and one S. feltiae strain (Sf.Y13) were found the most promising candidates as potential biological control agents against the soil inhabiting stages of B. tryoni. Further laboratory testing is required to assess their persistence under a broader range of environmental conditions before their biological control efficacy can be trialled under field conditions. [ABSTRACT FROM AUTHOR]

Highlights: [•] EPNs widely deployed against root feeders have potential against fruit flies. [•] EPNs caused mortality in Bactrocera tryoni larvae while pupae were not susceptible. [•] Steinernema feltiae caused high mortality under various conditions. [•] Steinernema carpocapsae and Heterorhabditis bacteriophora caused high mortality under more restricted conditions. [ABSTRACT FROM AUTHOR]