Evaluation of spray applications of Metarhizium anisopliae, Metarhizium brunneum and Beauveria bassiana against larval winter ticks, Dermacentor albipictus

A life-and-death struggle: interaction of insects with entomopathogenic fungi across various infection stages

Insects constitute approximately 75% of the world's recognized fauna, with the majority of species considered as pests. Entomopathogenic fungi (EPF) are parasitic microorganisms capable of efficiently infecting insects, rendering them potent biopesticides. In response to infections, insects have evolved diverse defense mechanisms, prompting EPF to develop a variety of strategies to overcome or circumvent host defenses. While the interaction mechanisms between EPF and insects is well established, recent findings underscore that their interplay is more intricate than previously thought, especially evident across different stages of EPF infection. This review primarily focuses on the interplay between EPF and the insect defense strategies, centered around three infection stages: (1) Early infection stage: involving the pre-contact detection and avoidance behavior of EPF in insects, along with the induction of behavioral responses upon contact with the host cuticle; (2) Penetration and intra-hemolymph growth stage: involving the initiation of intricate cellular and humoral immune functions in insects, while symbiotic microbes can further contribute to host resistance; (3) Host insect's death stage: involving the ultimate confrontation between pathogens and insects. Infected insects strive to separate themselves from the healthy population, while pathogens rely on the infected insects to spread to new hosts. Also, we discuss a novel pest management strategy underlying the cooperation between EPF infection and disturbing the insect immune system. By enhancing our understanding of the intricate interplay between EPF and the insect, this review provides novel perspectives for EPF-mediated pest management and developing effective fungal insecticides.

A comparison between the effectiveness of the fungi Beauveria bassiana and Metarhizium anisopliae for the control of Argas persicus with the emphasis of histopathological changes in the integument

Argas persicus is an important ectoparasite of domestic fowl that causes heavy economic losses to the poultry industry. The present study was carried out to compare and assess the effects induced by spraying the fungi Beauveria bassiana and Metarhizium anisopliae separately, on the mobility and viability of semifed adult A. persicus, also to follow the histopathological effect induced by a selected concentration of 10¹⁰ conidia/ml of B. bassiana on the integument. Biological studies revealed a more or less similar pattern of response in adults treated with either of the two fungi (Increasing concentration resulting in more death along with examined period). As the estimated LC50 and LC95 of B. bassiana were recorded 5 × 10⁹ and 4.6 × 10¹² conidia/ml, respectively, and for M. anisopliae were 3 × 10¹¹ and 2.7 × 10¹⁶ conidia/ml respectively, the fungus B. bassiana was more efficient than M. anisopliae when applied at the same concentrations. The study revealed that spraying of Beauveria at 10¹² conidia/ml is sufficient to control A. persicus as it recorded 100% efficacy, so it might be selected to be the effective dose. Histological investigation of the integument treated with B. bassiana revealed the dispersal of the hyphal network on the after 11 days of treatment, accompanied by other changes. Results from our study verify the susceptibility of A. persicus to the pathogenic effect induced by spraying B. bassiana, which is sufficient for its control with the recording better results.

Survival of off-host Dermacentor albipictus (Acari: Ixodidae) adult females and larvae underwater

Dermacentor albipictus (Packard, 1869) [Acari: Ixodidae], the winter tick, significantly affects the health and productivity of North American moose (Alces alces (Linnaeus, 1758) [Artiodactyla: Cervidae]). Survival of off-host stages of Ixodid ticks depends on microclimate driven in part by extrinsic factors resulting from weather, such as temperature, humidity, drought, and floods. The impact of some of these abiotic factors is unclear for D. albipictus. The effect of water submergence on biological parameters of engorged, adult, females and unfed larvae was assessed in the laboratory. Survival of adult females after submergence for three days was 88% with significant effects on their ability to oviposit. After five weeks, 63% of larvae (one-month-old) survived submergence in water whereas survival of larvae (three-months-old) was reduced to 23% after seven days. The off-host stages of D. albipictus have variable tolerance to periods of submergence that may influence the number of larvae available on the landscape for recruitment to moose in autumn.

A Review of Commercial Metarhizium- and Beauveria-Based Biopesticides for the Biological Control of Ticks in the USA

There is a need for the development of sustainable, nonchemical tick management strategies. Mycoacaricide and mycoinsecticide product development worldwide has focused primarily on fungi in the genera Beauveria (Hypocreales: Cordycipitaceae) and Metarhizium (Hypocreales: Clavicipitaceae). Microbial biopesticides containing entomopathogenic fungi have potential in tick management. However, despite considerable progress in the development of fungal biopesticides over the past 20 years, the establishment of commercial products available for use against ticks continues to be slow. We reviewed published scientific literature and compiled a comprehensive list of reports of the effectiveness of commercial biopesticides based on the fungal genera Metarhizium and Beauveria and registered for use in the USA against ixodid ticks under laboratory and field conditions. We also report on results when these biopesticides were used as a part of integrated tick management. Until efficacious fungus-based products become more available, tick management will rely primarily on synthetic chemical acaricides, with natural-product acaricides as the alternative.

Entomopathogenic Fungi and Bacteria in a Veterinary Perspective

Simple Summary

Several fungal species are well suited to control arthropods, being able to cause epizootic infection among them and most of them infect their host by direct penetration through the arthropod’s tegument. Most of organisms are related to the biological control of crop pests, but, more recently, have been applied to combat some livestock ectoparasites. Among the entomopathogenic bacteria, Bacillus thuringiensis, innocuous for humans, animals, and plants and isolated from different environments, showed the most relevant activity against arthropods. Its entomopathogenic property is related to the production of highly biodegradable proteins. Entomopathogenic fungi and bacteria are usually employed against agricultural pests, and some studies have focused on their use to control animal arthropods. However, risks of infections in animals and humans are possible; thus, further studies about their activity are necessary.

Abstract

The present study aimed to review the papers dealing with the biological activity of fungi and bacteria against some mites and ticks of veterinary interest. In particular, the attention was turned to the research regarding acarid species, Dermanyssus gallinae and Psoroptes sp., which are the cause of severe threat in farm animals and, regarding ticks, also pets. Their impact on animal and human health has been stressed, examining the weaknesses and strengths of conventional treatments. Bacillus thuringiensis, Beauveria bassiana and Metarhizium anisopliae are the most widely employed agents. Their activities have been reviewed, considering the feasibility of an in-field application and the effectiveness of the administration alone or combined with conventional and alternative drugs is reported.

Moose Habitat Selection and Fitness Consequences During Two Critical Winter Tick Life Stages in Vermont, United States†

The moose (Alces alces) is a charismatic species in decline across much of their southern distribution in North America. In the northeastern United States, much of the reduction has been attributed to winter tick (Dermacentor albipictus) infestations. Winter ticks are fairly immobile throughout all life stages, and therefore their distribution patterns at any given time are shaped largely by the occurrence of moose across the landscape during the peak of two critical time periods: fall questing (when ticks latch onto moose) and spring drop-off (when engorged female ticks detach from moose). We used recent land cover and lidar data within a dynamic occupancy modeling framework to estimate first-order habitat selection (use vs. non-use) of female moose (n = 74) during the tick questing and drop-off periods. Patch extinction and colonization rates between the fall questing and spring drop-off periods were strongly influenced by habitat and elevation, but these effects were diminished during the fall questing period when moose were more active across the landscape. From the fall questing period to the spring drop-off period, patches where colonization was high and extinction was low had higher proportions of young (shrub/forage) mixed forest at higher elevations. Further, we evaluated the fitness consequences of habitat selection by adult females during the fall questing period, when females and their calves acquire ticks. We compared Resource Selection Functions (RSF) for five females that successfully reared a calf to age 1 with five females whose calves perished due to ticks. Adult female moose whose offspring perished selected habitats in the fall that spatially coincided with areas of high occupancy probability during the spring tick drop-off period. In contrast, adult female moose whose offspring survived selected areas where the probability of occupancy during the spring drop-off was low; at present, natural selection may favor female adults who do not select the same habitats in fall as in spring. Our model coefficients and mapped results define “hotspots” that are likely encouraging the deleterious effects of the tick-moose cycle. These findings fill knowledge gaps about moose habitat selection that may improve the effectiveness of management aimed at reversing declining population trends.