Challenges in modelling complexity of fungal entomopathogens in semi-natural populations of insects

Abstract

The use of fungal entomopathogens as microbial control agents has driven studies into their ecology in crop ecosystems. Yet, there is still a lack of understanding of the ecology of these insect pathogens in semi-natural habitats and communities. We review the literature on prevalence of fungal entomopathogens in insect populations and highlight the difficulties in making such measurements. We then describe the theoretical host-pathogen models available to examine the role that fungal entomopathogens could play in regulating insect populations in semi-natural habitats, much of the inspiration for which has been drawn from managed systems, particularly forests. We further emphasise the need to consider the complexity, and particularly the heterogeneity, of semi-natural habitats within the context of theoretical models and as a framework for empirical studies. We acknowledge that fundamental gaps in understanding fungal entomopathogens from an ecological perspective coupled with a lack of empirical data to test theoretical predictions is impeding progress. There is an increasing need, especially under current rapid environmental change, to improve our understanding of the role of fungi in insect population dynamics beyond the context of forestry and agriculture.

Classification and infection mechanism of entomopathogenic fungi

“…Inoculation occurs by direct contact between infectious cadavers and susceptible hosts or indirectly via airborne spores or spores deposited on vegetation or soil particles (HESKETH et al, 2010). Laboratory infection experiments show that some minimum number of spores is generally needed to achieve predictable infections (INGLIS et al, 2012).…”

Exploring sub-lethal effects of exposure to a nucleopolyhedrovirus in the speckled wood (Pararge aegeria) butterfly

“…This has implications for designing effective biological control strategies and 39 for understanding the role of pathogens in regulating natural populations of 40 insects (Hesketh et al, 2010;Roy et al, 2009). Therefore, increasing attention 41 is being focused on the contribution of immune defence to adult fitness in 42 insect systems (Schmid-Hempel, 2005 (mg/cm 2 ) was calculated as; adult wet mass at eclosion (mg)/total forewing 98 area (cm 2 ) and forewing aspect ratio was calculated as; mean forewing 99 length 2 /mean forewing area.…”

Field Level Auto-inoculation of Sorghum chafer, <I>Pachnoda interrupta</I> (Olivier) (Coleoptera: Scarabaedae) with <I>Metarhizium anisopliae</I> based Microbial Bio-control Agents using Locally Affordable Traps

“…Use of AIT to disseminate entomopathogenic fungi for pest control can also be regarded as a low-input approach in conditions where conventional control means raise economic feasibility questions as using chemical sprays can be costly (Dowd and Vega, 2003). Although fungal ecology in crop systems has been studied in attempts to assess their potential as myco-insecticides (Hesketh et al, 2010), knowledge gaps still exist (Roy et al, 2009).This necessitates assessment of the growth and virulence characteristics of candidate isolates under actual environmental conditions as a pre-requisite for successful development to myco-insecticides Kope et al, 2008). Adults of P. interrupta are known to aggregate in plant hosts such as sorghum and acacia trees but also aestivate in the soil in over wintering habitats (Welde-hawariat et al, 2007;Bengtsson et al, 2009).…”