of wireworm (Agriotes obscurus) resulting in an increase in stand density and yield
of corn. M. anisopliae contributed to the control of the rice leafroller
(Cnaphalocrocis medinalis) after foliar spray application under field conditions
(Hong et al. 2017). Suppressive effects of endophytic Metarhizium spp. have also
been observed for larval Plutella xylostella (Batta 2013), aphids (Castrillo et al.
2011; de Faria and Wraight 2007; Dutta et al. 2015), wireworms (Reddy et al. 2014),
cabbage maggot (Delia radicum) (Razinger et al. 2014), and the western corn
rootworm (Diabrotica v. virgifera) (Rudeen et al. 2013). Under laboratory
conditions, Mayerhofer et al. (2017) observed that M. brunneum colonization of
tomato effectively controlled the growth of Agriotes obscurus. Endophytic colonization by M. brunneum helped strawberry plants tolerate an infestation by
two-spotted spider mite (Dara and Dara 2015). In a detached leaf assay, colonization
of maize after seed inoculation resulted in suppressed growth of black cutworm
(Agrotis ipsilon) larvae compared to uninoculated plants (Ahmad et al. 2020b). Pest
suppressive effects have been attributed to the systemic response of plants against
herbivory (Lopez and Sword 2015; Lopez et al. 2014). Such herbivore growth
suppressive effects could also be due to accumulation of anti-herbivory fungal
metabolites and mycotoxins in plant tissues (Gurulingappa et al. 2010).
Although most reports on the interaction of EIPF and insects indicate negative
effects on insect pest performance, in some cases, EIPF may increase the susceptibility of plants to insect pests and phytopathogens or have neutral effects. For
example, Clifton et al. (2018) reported that seed inoculation of soybean with
M. brunneum increased aphids but the effects of B. bassiana were neutral. Increased
plant susceptibility to insects could possibly be due to decreased plant defenses to
allow EIPF colonization, thus resulting in increased plant susceptibility.
The capability of Metarhizium spp. as an antagonist of various phytopathogens
could contribute to crop protection from plant diseases (Lacey et al. 2015).
M. robertsii protected haricot bean from root rot caused by Fusarium solani f. sp.
phaseoli (Sasan and Bidochka 2013). In vitro, M. brunneum produced secondary
metabolites with antagonistic activity against Verticillium dahliae and Phytophthora
megasperma pathogens of olive, Olea europaea (Lozano-Tovar et al. 2017).
M. anisopliae inoculation protected banana plants against F. oxysporum and the
authors attributed these effects to the production of hydrolytic antifungal compounds
(Picardal et al. 2019). In a laboratory bioassay, conidia and the cultural filtrate of
M. anisopliae caused mortality of green peach aphids and showed antifungal
properties against the phytopathogen, Botrytis cinerea (Yun et al. 2017).
Endophytic Beauveria has also been shown to suppress phytopathogens (Ownley
et al. 2008). Endophytic colonization of cotton and tomato by B. bassiana exerted
antagonistic effects against disease caused by Pythium myriotylum and Rhizoctonia
solani (Ownley et al. 2008). Raad et al. (2019) reported that B. bassiana protected
A. thaliana from Sclerotinia sclerotiorum. Other less-studied EIPF have been
reported to suppress herbivores and phytopathogens. For example, endophytic
colonization of pepper plants by Isaria javanica protected the pepper, Capsicum
sp., plants from green peach aphids and from the fungal phytopathogens,
Colletotrichum gloeosporioides and Phytophthora capsici (Kang et al. 2018).
13 The Role of Endophytic Insect-Pathogenic Fungi in Biotic Stress Management
389
of corn. M. anisopliae contributed to the control of the rice leafroller
(Cnaphalocrocis medinalis) after foliar spray application under field conditions
(Hong et al. 2017). Suppressive effects of endophytic Metarhizium spp. have also
been observed for larval Plutella xylostella (Batta 2013), aphids (Castrillo et al.
2011; de Faria and Wraight 2007; Dutta et al. 2015), wireworms (Reddy et al. 2014),
cabbage maggot (Delia radicum) (Razinger et al. 2014), and the western corn
rootworm (Diabrotica v. virgifera) (Rudeen et al. 2013). Under laboratory
conditions, Mayerhofer et al. (2017) observed that M. brunneum colonization of
tomato effectively controlled the growth of Agriotes obscurus. Endophytic colonization by M. brunneum helped strawberry plants tolerate an infestation by
two-spotted spider mite (Dara and Dara 2015). In a detached leaf assay, colonization
of maize after seed inoculation resulted in suppressed growth of black cutworm
(Agrotis ipsilon) larvae compared to uninoculated plants (Ahmad et al. 2020b). Pest
suppressive effects have been attributed to the systemic response of plants against
herbivory (Lopez and Sword 2015; Lopez et al. 2014). Such herbivore growth
suppressive effects could also be due to accumulation of anti-herbivory fungal
metabolites and mycotoxins in plant tissues (Gurulingappa et al. 2010).
Although most reports on the interaction of EIPF and insects indicate negative
effects on insect pest performance, in some cases, EIPF may increase the susceptibility of plants to insect pests and phytopathogens or have neutral effects. For
example, Clifton et al. (2018) reported that seed inoculation of soybean with
M. brunneum increased aphids but the effects of B. bassiana were neutral. Increased
plant susceptibility to insects could possibly be due to decreased plant defenses to
allow EIPF colonization, thus resulting in increased plant susceptibility.
The capability of Metarhizium spp. as an antagonist of various phytopathogens
could contribute to crop protection from plant diseases (Lacey et al. 2015).
M. robertsii protected haricot bean from root rot caused by Fusarium solani f. sp.
phaseoli (Sasan and Bidochka 2013). In vitro, M. brunneum produced secondary
metabolites with antagonistic activity against Verticillium dahliae and Phytophthora
megasperma pathogens of olive, Olea europaea (Lozano-Tovar et al. 2017).
M. anisopliae inoculation protected banana plants against F. oxysporum and the
authors attributed these effects to the production of hydrolytic antifungal compounds
(Picardal et al. 2019). In a laboratory bioassay, conidia and the cultural filtrate of
M. anisopliae caused mortality of green peach aphids and showed antifungal
properties against the phytopathogen, Botrytis cinerea (Yun et al. 2017).
Endophytic Beauveria has also been shown to suppress phytopathogens (Ownley
et al. 2008). Endophytic colonization of cotton and tomato by B. bassiana exerted
antagonistic effects against disease caused by Pythium myriotylum and Rhizoctonia
solani (Ownley et al. 2008). Raad et al. (2019) reported that B. bassiana protected
A. thaliana from Sclerotinia sclerotiorum. Other less-studied EIPF have been
reported to suppress herbivores and phytopathogens. For example, endophytic
colonization of pepper plants by Isaria javanica protected the pepper, Capsicum
sp., plants from green peach aphids and from the fungal phytopathogens,
Colletotrichum gloeosporioides and Phytophthora capsici (Kang et al. 2018).
13 The Role of Endophytic Insect-Pathogenic Fungi in Biotic Stress Management
389