Bioinsecticides offer eco-friendly alternatives to chemical insecticides and thereby meet the need for sustainable pest control. Entomopathogenic fungi (EPF) represent one of the core classes of microbial insecticides, distinguished by their advantageous contact-based mode of action. Several products have been successfully commercialized, and with continuing improvements to the technology, the market size for EPF continues to grow. The translation of EPF into reliable field performers relies upon formulation technologies that ensure product quality, stability, virulence, and cost-effectiveness. Current formulations comprise diverse solid and liquid states (e.g., wettable powders, oil dispersions) that deliver a range of propagules (conidia, blastospores, microsclerotia). While advanced approaches like nanoparticle encapsulation show promise, some limitations hinder their widespread use. Major constraints include maintaining fungal viability during storage/transport and protecting propagules from harsh environmental factors post-application. Regulatory requirements also present significant barriers to widespread uptake. Addressing these formulation challenges through continued research is essential for advancing mycoinsecticide technology and increasing their contribution to integrated pest management. This review aims to present the latest scientific advances in EPF formulation technologies and application strategies, alongside an overview of current regulatory frameworks and an up-to-date analysis of registered microbial biopesticide products in some of the world’s largest markets.

Metarhizium brunneum is a highly effective entomopathogenic fungus that also functions as a plant biostimulant. It can act as both an endophyte and rhizosphere colonizer; however, the mechanisms driving biostimulation are multifactorial. In this work, oilseed rape (Brassica napus) seeds were grown in composts treated with different concentrations of M. brunneum strains ARSEF 4556 or V275, or the M. brunneum-derived volatile organic compounds 1-octen-3-ol and 3-octanone. Biostimulation efficacy was found to be strongly dose dependent. Concentrations of 1 × 10⁶ conidia g⁻¹ compost were found to be most effective for the M. brunneum, whereas dosages of 1 µL 100 g⁻¹ compost were found to be efficacious for the volatiles. These optimized doses were assessed individually and in combined formulations with a hydrogel against oilseed rape (Brassica napus), sitka spruce (Picea sitchensis), maize (Zea mays) and strawberry (Fragaria annanassa). Both volatile compounds were highly effective biostimulants and were found to increase in biostimulatory efficiency when combined with M. brunneum conidia. Hydrogels were not found to interact with the growth process and may offer avenues for novel formulation technologies. This study demonstrates that Metarhizium-derived volatile organic compounds are actively involved in plant growth promotion and have potential for use in novel formulations to increase the growth of a wide range of commercially relevant crops.

Wireworm, the larval stages of click beetles, are a serious pest of tubers, brassicas and other important commercial crops throughout the northern hemisphere. No effective control agent has been developed specifically for them, and many of the pesticides marketed as having secondary application against them have been withdrawn from EU and Asian markets. Metarhizium brunneum, an effective entomopathogenic fungus, and its derived volatile metabolites are known to be effective plant biostimulants and plant protectants, although field efficacy has yet to be validated. Field validation of a combined M. brunneum and derived VOC treatments was conducted in Wales, UK, to assess the effects of each as a wireworm control agent and biostimulant. Plots were treated with Tri-Soil (Trichoderma atroviridae), M. brunneum, 1-octen-3-ol or 3-octanone, or combinations thereof. Treatments were applied subsurface during potato seeding (n = 52), and potatoes were harvested at the end of the growing season. Each potato was weighed individually and scored for levels of wireworm damage. Applications of both the VOCs and the M. brunneum individually were found to significantly decrease wireworm burden (p < 0.001). Combinations of M. brunneum and 3-octanone were also found to significantly decrease wireworm damage (p < 0.001), while no effect on yield was reported, resulting in an increased saleable mass over controls (p < 0.001). Herein, we present a novel ‘stimulate and deter’ wireworm control strategy that can be used to significantly enhance saleable potato yields and control wireworm populations, even under high pest pressure densities.

Mosquitoes of the genera Aedes, Anopheles and Culex vector a wide range of pathogens seriously affecting humans and livestock on a global scale. Over-reliance on insecticides and repellents has driven research into alternative, naturally-derived compounds to fulfil the same objectives. Steam distilled extracts of four plants with strong, yet attractive, volatile profiles were initially assessed for repellency in a dual-port olfactometer using Aedes aegypti as the model species. Picea sitchensis was found to be the most repellent, proving comparable to leading products when applied at 100% (p = 1.000). Key components of conifer-derived volatile profiles were then screened via electroantennography before those components eliciting an electrophysiological response were assayed individually in the olfactometer; according to WHO protocol. The most promising 5 were selected for reductive analyses to produce an optimised semiochemical blend. This combination, and a further two variations of the blend, were then progressed to a multi-species analysis using the BG-test whereby bite-attempt frequency on hands was assessed under different repellent treatments; assays were compared between Aedes aegypti, Anopheles gambiae and Culex quinquefasciatus. Efficacy was found against all three species, although it was found that Ae. aegypti was the most susceptible to the repellent, with An. gambiae being the least. Here, a novel, naturally-derived blend is presented with weak spatial repellency, as confirmed in laboratory assays. Further work will be required to assess the full extent of the potential of the products, both in terms of field application and species screening; however, the success of the products developed demonstrate that plant metabolites have great capacity for use in the repellent sector; both to improve upon known compounds and to reduce the usage of toxic products currently on the market.

Aedes aegypti (Diptera: Culicidae) is the principal vector of dengue and other viruses that cause disease among 100 to 400 million people each year. The recent development of widespread insecticidal resistance has led to the rapid development of biological control solutions aimed at larval control. While the efficacy of Metarhizium brunneum has been shown against Aedes larvae, the impact of larval population dynamics will need to be determined to formulate effective control strategies. In this study, larvae were subjected to four concentrations of M. brunneum (10⁵, 10⁶, 10⁷, 10⁸ conidia ml⁻¹). Larvae were found to be susceptible to M. brunneum with dose-dependent efficacy. When constant larval immigration was added as a parameter, peak mortality was consistently found to occur on the fourth day, before a significant reduction in control efficacy linked to a decline in conidial availability within the water column. This suggests that M. brunneum treatments should be applied at a concentration 1 × 10⁷ conidia ml⁻¹ every four days to effectively control mosquito larvae in the field, regardless of the fungal formulation, water volume, or larval density. Understanding fungal-mosquito dynamics is critical in developing appropriate control programs as it helps optimize the fungal control agent’s dose and frequency of application.

Aedes aegypti mosquitoes are capable of vectoring a wide range of diseases including dengue, yellow fever, and Zika viruses, with approximately half of the worlds’ population at risk from such diseases. Development of combined predator–parasite treatments for the control of larvae consistently demonstrates increased efficacy over single-agent treatments, however, the mechanism behind the interaction remains unknown. Treatments using the natural predator Toxorhynchites brevipalpis and the entomopathogenic fungus Metarhizium brunneum were applied in the laboratory against Ae. aegypti larvae as both individual and combined treatments to determine the levels of interaction between control strategies. Parallel experiments involved the removal of larvae from test arenas at set intervals during the course of the trial to record whole body caspase and phenoloxidase activities. This was measured via luminometric assay to measure larval stress factors underlying the interactions. Combined Metarhizium and Toxorhynchites treatments were seen to drastically reduce lethal times as compared to individual treatments. This was accompanied by increased phenoloxidase and caspase activities in combination treatments after 18 h (p < 0.001). The sharp increases in caspase and phenoloxidase activities suggest that combined treatments act to increase stress factor responses in the larvae that result in rapid mortality above that of either control agent individually. This work concludes that the underlying mechanism for increased lethality in combined parasite–predator treatments may be related to additive stress factors induced within the target host larvae.