Mortality risk from entomopathogenic fungi affects oviposition behavior in the parasitoid wasp Trybliographa rapae

Abstract

Biological control of pests in agroecosystems could be enhanced by combining multiple natural enemies. However, this approach might also compromise the control efficacy through intraguild predation (IGP) among the natural enemies. Parasitoids may be able to avoid the risk of unidirectional IGP posed by entomopathogenic fungi through selective oviposition behavior during host foraging. Trybliographa rapae is a larval parasitoid of the cabbage root fly, Delia radicum. Here we evaluated the susceptibility of D. radicum and T. rapae to two species of generalist entomopathogenic fungi, Metarhizium brunneum isolate KVL 04-57 and Beauveria bassiana isolate KVL 03-90. Furthermore, T. rapae oviposition behavior was assessed in the presence of these entomopathogenic fungi either as infected hosts or as infective propagules in the environment. Both fungi were pathogenic to D. radicum larvae and T. rapae adults, but with variable virulence. When host patches were inoculated with M. brunneum conidia in a no-choice situation, more eggs were laid by T. rapae in hosts of those patches compared to control and B. bassiana treated patches. Females that later succumbed to mycosis from either fungus laid significantly more eggs than non-mycosed females, indicating that resources were allocated to increased oviposition due to perceived decreased life expectancy. When presented with a choice between healthy and fungal infected hosts, T. rapae females laid more eggs in healthy larvae than in M. brunneum infected larvae. This was less pronounced for B. bassiana. Based on our results we propose that T. rapae can perceive and react towards IGP risk posed by M. brunneum but not B. bassiana to the foraging female herself and her offspring. Thus, M. brunneum has the potential to be used for biological control against D. radicum with a limited risk to T. rapae populations.

Passive vectoring of entomopathogenic fungus Beauveria bassiana among the wax moth Galleria mellonella larvae by the ectoparasitoid Habrobracon hebetor females

“…In evolutionary process parasitoids formed defense mechanism against the pathogenic microorganisms. Parasitoids can avoid both insects infected with entomopathogenic fungi and habitats with a high density of fungal pathogens (Rännbäck et al ., ; Cotes et al ., ). However, parasitoids can recognize infected hosts in a latter stages of diseases, but not during the initial stages (Furlong & Pell, ; Baverstock et al ., ).…”

Compatibility between the endoparasitoid Hyposoter didymator and the entomopathogenic fungus Metarhizium brunneum: a laboratory simulation for the simultaneous use to control Spodoptera littoralis

“…reported that the use of commercial isolates of entomopathogenic fungi had no effect on survival rates of the parasitoid, Encarsia formosa Gahan (Hymenoptera: Aphelinidae), and even increased parasitism rates . Other authors have reported that prior inoculation with entomopathogenic fungi could affect fitness of the parasitoid wasp Trybliographa rapae Westwood (Hymenoptera: Figitidae), reducing its life expectancy but increasing its oviposition rates as an adaptation in response to the presence of the fungus …”

“…Although hypocrealean fungi, including some Metarhizium species, have broad host ranges and may infect some non‐target and/or beneficial insects, such as parasitoids, they are generally considered as organisms that have a low environmental risk . Indeed, many recent studies have demonstrated both the safety of these fungi to non‐target insects and the potential for their combined use with arthropod natural enemies . However, interactions between natural enemies in a multitrophic context are complex and should be evaluated case by case if they are to be exploited effectively for pest control.…”

“…25 Indeed, many recent studies have demonstrated both the safety of these fungi to non-target insects and the potential for their combined use with arthropod natural enemies. [26][27][28] However, interactions between natural enemies in a multitrophic context are complex and should be evaluated case by case if they are to be exploited effectively for pest control.…”

Interactions among the Predatory Midge Aphidoletes aphidimyza (Diptera: Cecidomyiidae), the Fungal Pathogen Metarhizium brunneum (Ascomycota: Hypocreales), and Maize-Infesting Aphids in Greenhouse Mesocosms

“…Although there have been studies concerning the non-target effects of Metarhizium on beneficial insects, few have dealt with these effects in more realistic conditions. Most laboratory studies show that beneficial insect populations face low risk from Metarhizium exposure [10,11,12]. However, the consequences of non-target effects on the success of biological control cannot be neglected and should be investigated more thoroughly.…”