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

Abstract

BACKGROUND The cotton leafworm, Spodoptera littoralis, is one of the most destructive pests in the Mediterranean basin, being predominantly controlled using synthetic chemical pesticides. Strain EAMa 01/58‐Su of the fungus Metarhizium brunneum and the parasitoid Hyposoter didymator are promising biological control agents for this pest. In this study, we assessed the compatibility between these two agents to control S. littoralis under joint attack scenarios. RESULTS Firstly, the direct and indirect effects of the fungus towards parasitoid adults were studied. The fungus significantly decreased life expectancy of the parasitoid (mortality = 62.5%; mean lethal concentration = 1.85 × 106 conidia ml−1; average survival time = 92.2 h) when applied at high concentrations (108 conidia ml−1), whereas it did not affect the reproductive potential of the parasitoid females during the 3 days after treatment. Secondly, the combinations between the two agents to control S. littoralis under different simultaneous use scenarios (inoculation of S. littoralis larvae with the fungus before being exposed to parasitoid females and vice versa) were investigated, with additive effect in all cases. A significant effect on fitness (preimaginal development time and reproductive potential) of the F1 parasitoid generation were detected. Moreover, parasitization significantly reduced the total hemocytes in S. littoralis hemolymph compared with the control, promoting fungal infection. Finally, parasitoids showed a significant preference for non‐inoculated S. littoralis larvae. CONCLUSIONS We demonstrated compatibility (additive effect) between fungus and parasitoid under different joint attack scenarios to control S. littoralis in laboratory conditions. However, this will be supported by our ongoing greenhouse and field studies. © 2019 Society of Chemical Industry

Delving into the Causes and Effects of Entomopathogenic Endophytic Metarhizium brunneum Foliar Application-Related Mortality in Spodoptera littoralis Larvae

“…Several studies have evaluated the mortality of S. littoralis larvae after the ingestion of EPF-colonized plants [ 3 , 17 , 30 ]. However, this is the first attempt to elucidate the causes of this mortality and the effects of exposure to EPF-colonized plants both using leaf discs from colonized plants and in planta .…”

“…Its control is becoming more difficult due to resistance and cross-resistance to chemical insecticides and to the bioinsecticide Bacillus thuringiensis Berliner [ 10 , 11 ]. However, the use of EPFs and the insecticidal compounds they produce has shown promise against this harmful lepidopteran in both foliar- or soil-dwelling stages and exhibits compatibility with nontarget organisms, including natural enemies [ 3 , 12 , 13 , 14 , 15 , 16 , 17 ]. To date, there are many studies that report the success of using different genera of EPF ( Metarhizium anisopliae (Metsch.…”

Interactions between the Entomopathogenic Fungus Metarhizium anisopliae ICIPE 20 and the Endoparasitoid Dolichogenidea gelechiidivoris, and Implications for Combined Biocontrol of Tuta absoluta

“…The combined application of parasitoids and fungal-based biopesticides may enhance the control of T. absoluta and the overall success of IPM programs against this pest. Several findings have demonstrated that entomopathogenic fungi and parasitoids/predators can coexist and manage different insect pest species [ 31 , 32 , 33 , 34 , 35 ]; however, detrimental effects of entomopathogenic fungi on adult or larval survival and other fitness parameters have been reported on some parasitoids [ 31 , 36 , 37 , 38 , 39 ]. The findings by these authors call for a proper understanding of the nature of the interactions between entomopathogenic fungi and other natural enemies before their potential combined use for effective and sustainable control of insect pests.…”

Compatibility between Entomopathogenic Fungi and Egg Parasitoids (Trichogrammatidae): A Laboratory Study for Their Combined Use to Control Duponchelia fovealis

“…Entomopathogenic fungi (EF) are a potential component of integrated pest management (IPM) programs for strawberry cultivation [14]. While some studies have reported laboratory infections of non-target organisms [15][16][17], EF are less effective under field conditions [18], and generally do not harm ecosystem service providers such as pollinators, earthworms, predatory arthropods, and parasitoids, when at low concentrations. However, given the potential of EF to have negative side effects on biocontrol agents [19], preliminary studies are necessary to evaluate the compatibility of EF with other beneficial organisms.…”

“…The interaction between T. pretiosum and the two strains of B. bassiana used against Ephestia kuniella Zeller (Lepidoptera: Pyralidae) was considered innocuous because the parasitism rate was reduced by less than 30% when these fungal strains were applied either pre-or post-parasitism [22]. Given these results, further studies are needed to determine how to combine different biological control agents without impairing their effectiveness while developing strategies that may improve their efficacy [16,17].…”