**6. Future Perspectives**

As a likely heritage of old investigational schemes, there is a cultural propensity in research projects and reports to refer to plant-associated microorganisms within the boundaries of functional categories. However, it is increasingly evident that many endophytic fungi are eclectic and possess a multifaceted connotation enabling them to perform several more or less interconnected beneficial roles in the symbiotic relationship with their host plants. Such a revised concept particularly applies to species of *Lecanicillium* and *Akanthomyces*, which should not be merely regarded as entomopathogenic fungi anymore.

Strains of the species *A. lecanii, A. muscarius, A. attenuatus* and *A. longisporus* are already used as the active ingredients of several mycoinsecticides [72]. Although their inclusion in IPM appears to be an obvious approach, a more efficient employment should be pursued in light of the body of evidence disclosed by recent experimental work that, besides killing pests as a result of inundative treatments, the endophytic establishment of these fungi may have further relevance on plant fitness. That is a clear antagonistic role against plant pathogens, the capacity to stimulate plant defense reactions and various plant growth promoting effects.

These valuable properties, shared with other species of *Lecanicillium* and *Akanthomyces*, make it advisable to carry out extensive investigations in crops to verify the natural endophytic occurrence, and to increase our knowledge on ecology of these fungi. Particularly relevant is gathering additional information on the production in plants of the biochemical factors, which possibly play a role in regulating the tritrophic relationship with the host and its pests/pathogens.

At the same time it is fundamental to assess whether their endophytic establishment is possible following artificial introduction. In this respect, inoculation methods (foliar spraying, soil drenching, seed soaking, and injections) are crucial for an enduring survival within plant tissues, and their compliance should be more accurately evaluated [104]. Particularly in crops where these fungi can exert a positive impact, additional observations are appropriate to verify whether their distribution pattern is localized or systemic. Actually, a great challenge for considering endophytic fungi as a strategy in plant protection is to manage their reproducible introduction into crops, and to predict the outcome. As well, the effectiveness of this attractive phytosanitary tool needs to be proven in the field to stimulate growers to adopt it in view of gaining clear economic benefits.

**Author Contributions:** Conceptualization, R.N.; phylogenetic analysis, A.B.; data curation, A.B.; writing—original draft preparation, R.N.; writing—review and editing, R.N. and A.B. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
