Virulence, penetration rate and reproductive potential of entomopathogenic nematodes from eastern Australia in Queensland fruit fly, Bactrocera tryoni

Effect of temperature on survival of Australian entomopathogenic nematodes and their virulence against the Queensland fruit fly, Bactrocera tryoni

“…In our study EPNs were still able to kill B. tryoni larvae after three weeks at 25 °C without host availability, and some isolates were able to still kill pupae after two weeks at 25 °C without host availability. In contrast, many previous studies reported no pupal infection with EPNs (Yee and Lacey, 2003;Langford et al 2014), while other studies found lower infection rates in pupae than larvae (Aryal et al 2022b). Several studies have been carried out to find EPN isolates with better persistence in soil after field application.…”

“…The symbiotic bacteria of EPNs provide IJs with the capacity to kill an insect host in which the EPNs can then develop (Waterfield et al 2009). While EPNs are successful biological control agents of a diversity of pest insects with developmental stages in the soil, they have also been proven effective against several fruit fly pests (Sirjani et al 2009;Godjo et al 2018), including B. tryoni (Langford et al 2014;Aryal et al 2022b). However, for effective biological control there is a need for EPN strains that can survive and remain virulent under local conditions.…”

“…Furthermore, earlier studies have shown that larval and adult stages of fruit flies are more susceptible to EPN infection than pupae (Yee and Lacey 2003; Kamali et al 2013;Langford et al 2014), yet larvae and adults are less likely to be exposed to EPNs because they spend most time above ground. In contrast, the pupal stage is the longest developmental stage of fruit flies in the soil (Bateman 1972), but may be less susceptible to EPNs (Langford et al 2014;Aryal et al 2022b). Therefore, in order to have an effect on fruit fly populations, EPNs must be able to survive when no fruit fly individuals are in the soil and maintain high levels of infectivity, or infect alternative hosts in the meantime (Kurtz et al 2007;Susurluk and Ehlers 2008).…”

“…IJs may also need to be able to infect individuals quickly as the available time window of infection of larvae (prior to pupation) and adults (after emergence) in the soil is with a few hours in B. tryoni (Hulthen and Clarke 2006) relatively short. Alternatively, IJs should have the capacity to also infect pupae (Aryal et al 2022b). Furthermore, EPN isolates with longer survival might need to be applied less frequently and may be more economic.…”

“…We investigated the survival and virulence of EPN isolates at different temperatures to identify potential candidates for the biological control of B. tryoni. We assessed these traits in 15 EPN isolates that have recently been isolated from Australian soils and molecularly characterized (Aryal et al 2022a(Aryal et al , 2022b. We also compared these traits between the new EPN isolates and two commercially available EPN strains previously isolated from Australian soils but since then kept in long-term laboratory culture.…”