Harnessing Nature's Arsenal: Identification and Characterization of Wild Strains of Entomopathogenic Fungi for Wireworm Control

Project Outline

The control of wireworm (the larval form of the click beetle) is currently problematic for growers across a range of crops with the deregistration of accepted conventional controls² and a lack of commercially ready biological alternatives³. The biological control of wireworm currently shows most promise with the application of biopesticides created with entomopathogenic fungi (EPF), with several products available for other invertebrate pests. The primary groups identified for pathogenicity towards wireworm occur within Hypocreales; Metarhizium brunneum (Petch), Beauveria bassiana (Balsamo) and Isaria fumosorosea (Wize)⁵.

Wireworm exhibit particularly robust defences against the physical penetration of EPF hyphae and the action of enzymes for initial infection⁷. Previous research has demonstrated the efficacy of EPF Metarhizium in controlling wireworm under laboratory conditions⁸, but application in the field is restricted by the ability to accurately target the larvae and the time taken to kill and spread infection^9,10. Additionally, the impact of abiotic factors (e.g., moisture, temperature, pH) can affect both the stability and efficacy of the EPF once applied to the soil⁶.

As a result, commercial products containing EPF for insect control must ensure that not only do they have a pest specificity but also are stable through multiple infections (for both mass production and in-field persistence) and robust against abiotic variability. As such, it is crucial that species specific strains of EPF are identified, sequenced and screened for pathogenicity, stability and suitability for commercial viability. The UK is currently far behind Europe and other wireworm hotspots in identifying control solutions for the pest in line with a modern IPM perspective. The use of EPF has been shown to be an effective measure utilised with proper consideration for the ecology of pest and pathogen¹¹ but current knowledge of appropriate species and strains for control is either outdated or potentially regionally specific⁸.

This project aims to utilise a network of field collected wireworm samples to isolate and identify wild strains of entomopathogenic fungi which may fulfil the requirements for an effective control measure. It will combine molecular techniques with more classical methods for identification of pathogens as well as the host pests (often morphologically indistinct). Experiments post sample collection will focus on insect bioassays to quantify the survivability of the key pest species against found strains and compare this against more generalist commercial strains. Glasshouse or semi field studies may be scaled up from this to diagnose stability and variability in success in a more natural setting. The volatile organic compound profiles of the EPFs will be evaluated with the use of gas chromatography mass spectrometry, with the bioactivity of the EPF constituents towards wireworm quantified to help build a profile of the strains and their natural products.

References

² Poggi S, Le Cointe R, Lehmhus J, et al (2021) Alternative strategies for controlling wireworms in field crops: A review. Agriculture (Switzerland) 11:1–30

³ la Forgia D, Verheggen F (2019) Biological alternatives to pesticides to control wireworms (Coleoptera: Elateridae). Agri Gene 11:100080

⁵ Kabaluk T (2014) Targeting the click beetle Agriotes obscurus with entomopathogens as a concept for wireworm biocontrol. BioControl 59:607–616

⁶ Sharma A, Jaronski S, Reddy GVP (2020) Impact of granular carriers to improve the efficacy of entomopathogenic fungi against wireworms in spring wheat. Journal of Pest Science 93:275–290

⁷ Eckard S, Bacher S, Enkerli J, Grabenweger G (2017) A simple in vitro method to study interactions between soil insects, entomopathogenic fungi, and plant extracts. Entomologia Experimentalis et Applicata 163:315–327

⁸ Ansari MA, Evans M, Butt TM (2009) Identification of pathogenic strains of entomopathogenic nematodes and fungi for wireworm control. Crop Protection 28:269–272

⁹ van Herk WG, Vernon RS, McGinnis S (2013) Response of the dusky wireworm, Agriotes obscurus (Coleoptera: Elateridae), to residual levels of bifenthrin in field soil. Journal of Pest Science 86:125–136

¹⁰ Traugott M, Benefer CM, Blackshaw RP, van Herk WG, Vernon RS (2015) Biology, ecology, and control of elaterid beetles in agricultural land. Annual review of entomology 60:313–34

Techniques

• Molecular sequencing for the identification of fungal strains
• Field sampling for subterranean invertebrate pest species
• Gas chromatography – mass spectrometry for comparisons of volatile organic compound profiles
• Insect bioassays to determine survivability and behavioural reactions to entomopathogens
• Morphological identification techniques for both insects and entomopathogens
• Fungal culturing and production