Sharma and Sharma Egyptian Journal of Biological Pest Control (2021) 31:57 Egyptian Journal of https://doi.org/10.1186/s41938-021-00404-7 Biological Pest Control REVIEW ARTICLE Open Access Fungal entomopathogens: a systematic review Rajat Sharma1* and Priyanka Sharma2 Abstract Background: Apprehensions about the safety and the environment regarding the insecticidal application against insect infestations have directed our attention toward advancement of biological mediators so that they are assimilated into the concept of integrated pest management stratagems to develop a more practical approach for the management of insect pests. Management of insect pests by making use of biological approaches (such as fungal entomopathogens (EPF) or others which are antagonistic to insect population) provides a substitute approach which reduces the continuous use of chemical amalgams against insect pests. Main body: The present review provides a framework of the present status of information on EPF as it identifies with their current use as biological control of pest infestations. To utilize a variety of biological control methodologies against insect hosts, it is essential to improve our comprehension of the ecology of EPF and also their role in nature. This article may assist us with understanding the virulence and the virulence factors related with EPF and present the latest developments and accomplishments in the significant field. We focus on recent instances of studies that show the overall patterns in interactions among insect pests and EPF prompting the advancement of epizootics. Also, we sum up the topical discoveries on current status of mycoinsecticides and propose future research needs. Conclusions: As the current mechanism of fungal pathogenesis on insects is moderately slow and needs improvement, there is likewise the requirement for additional comprehension of the interactions among entomopathogens and insect pests so as to grow soundly planned procedures by identifying potential targets and via the improvement of fungal strains for improving the adequacy of these organisms in field applications. Keywords: Entomopathogenic fungi, Biological control agents, Infection process, Enzymes, Pathogenesis, Host defense, Epizootiology, Mycoinsecticides Background suppressing the insect pest infestations due to their ab- Insect pests are regarded as major deterrents which have stemiously minimal application effort, high usefulness accounted for an estimated 10.80% crop losses on global and expediency (Sharma 2019), but concentrated appli- scale in the era of post green revolution (Dhaliwal et al. cation of chemicals has brought about the advancement 2015). Also, an estimated loss of global annual crop pro- of resistance to either one or even more classes of insec- duction corresponding to 18-26% valued at $470 billion ticides in as much as 500 species of pests (Kumar and has been observed recently (Mantzoukas and Eliopoulos Kalita 2017). 2020). To reduce these losses, insecticides are employed As a result, the microbial agents (entomopathogens) and, as a result, have become an essential method for are viewed as regulatory operators of pest infestations and represent the different species of fungi, viruses, * Correspondence: [email protected] protozoa, and bacteria. Initial studies in reference to 1Department of Plant Pathology, Dr. YS Parmar University of Horticulture and entomopathogens were carried out by Agostino Bassi Forestry, Nauni, Solan, Himachal Pradesh 173230, India who established that the infectious agent, instigating the Full list of author information is available at the end of the article © The Author(s). 2021 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. Sharma and Sharma Egyptian Journal of Biological Pest Control (2021) 31:57 Page 2 of 13 occurrence of muscardine disease in case of silkworms thus, the life cycle of entomopathogenic fungi is contin- was Beauveria bassiana Bals. (Hypocreales: Cordycipita- ued on new hosts. ceae). Entomopathogens which befall naturally are sig- EPF also play an important role as either colonizer in nificant controlling factors against insect populace (Roy rhizosphere (Pava-Ripoll et al. 2011) or plant growth and Cottrell 2008). Tanzini et al. (2001) used the term promoters (Jaber and Enkerli 2017). EPF account for the entomopathogenic for the micro-organisms which regu- principal number of taxa as in the diverse group of late the population of insect pests to the levels wherein fungi, there are more than 100 genera of EPF comprising no economic damage to crop plants is observed. Delgado of 750-1000 (St Leger and Wang 2010). The multi- and Murcia (2011) defined the term in relation to the layered jobs played by EPF could likewise be utilized in a microbial populace which is proficient in attacking in- roundabout way as biofertilizers (Jaber and Enkerli sect pests by incorporating them into their own life cycle 2017), and microbial control specialists in contradiction and by utilizing them as hosts and also classified these of both pests and plant infections (Mantzoukas and micro-organisms as either facultative or obligate para- Grammatikopoulos 2019). sites attacking insect pests, having high potential for survival. Main text Use of microbial population as control agents is not Biological control of insects only effective against insect pests but this approach is Biological control of insect pests with EPF is one of the also environmentally safe and sound for humans (re- most desirable and effectual practice involving uses of duced pesticide residues) as well as the non-target or- natural microorganisms, which hinder their activity and ganisms. The provocation for the impression of using can be used as an alternative to the chemical insecti- microbial insect pathogens against insect pests re- cides. There have been some genera of EPF, which are sulted from close examination of the disease of silk- antagonistic toward field, greenhouse, forest, storage, worm (Audoin 1837). Afterward, the recommendation and household pests. These can be incorporated as EPF, to assign microbial insect pathogens against insects for instance Beauveria, Metarhizium, Isaria, Lecanicil- came from LeConte (1874)andPasteur(1874). The lium, and Hirsutella. The different species belonging to first efficacious mass-produced microbial control ap- these genera are target specific and cause infection in plication on large scale was carried out by Kras- many insects. EPF have several biological attributes, such silstschik (1888)againstBothynoderes punctiventris as target-specificity, high reproductively, short gener- (Germar) (Coleoptera: Curculionidae) (sugar beet wee- ation time, and long survival, which play significant roles vil) by making use of the antagonistic nature of the in biocontrol of insect pest. conidiospores of Metarhizium anisopliae (Metchni- EPF species are mostly isolated from the soil, which koff) (Hypocreales: Clavipitaceae) in Russia. The protects them from the damaging solar radiation (Mey- credit for examining infectious nature of M. aniso- ling and Eilenberg 2007). It has been noted that certain pliae must be attributed to Elie Metchnikoff, who ini- species of Beauveria and Metarhizium can infect and kill tially identified the microbial agent as Entomopthora insects in soil and also EPF interact with roots of plant anisopliae against wheat cockchafer, Anisoplia aus- for their growth and survival which predominately relies triaca (Herbst) (Coleoptera: Scarabaeidae). on insects for carbon and not on soil (Inglis et al. 2001). Out of all the other microbial control agent, EPF are Endophytic EPF evolve inside the above ground plant the most imperative due to accumulation of various fac- tissues and do not produce any perceptible symptoms of tors, such as easy distribution, easy manufacturing tech- infection. Their usage provides numerous advantages niques, availability of large number of already identified consisting of high yield, cost-effectiveness, preservation strains, and over-expression of exogenous toxins and en- of beneficial organisms, safe to humans, no harmful ef- dogenous proteins (St Leger and Wang 2010). EPF legit- fect on environment, and varied biodiversity (Mantzou- imately influence plants more than the most compound kas and Eliopoulos 2020). The most commonly applied pesticides. For instance, endophytic EPF have been ar- and naturally occurring EPF endophyte species are chived in many plants, for example, soybeans, wheat, to- Beauveria bassiana, Isaria fumosorosea Wize (Hypo- matoes, and bananas (Jaber 2015). As per the action creales: Clavicipitaceae), and Metarhizium anisopliae mechanism of EPF is concerned, they release spores (Akutse et al. 2013). The endophytic EPF gives protec-