Fungi used as a Insecticide

From BIOL 2P96 Jan 2013 Group 07

Introduction

Certain species of fungi can act as parasites of insect. When a fungus is used as insecticides, it is called mycoinsecticide. In recent years, crop protection has been trending towards integrated pest management (IPM) using bacteria and fungi as insecticides. Approximately 750 species of fungi are pathogenic to insects. Only 12 have been utilized as insecticides. Two prominent species of fungi used as insecticides are Beauveria bassiana and Metarhizium anisopliae. Mycoinsecticides function by first being applied to the insects in spray form. The fungi then use their hyphae to burrow into the insects. The hyphae spread the insectotoxins throughout the insect to activate them, eventually leading to the the insect’s death.

General Process

Insecticides act differently from bacterial and viral pathogens of insects in terms of infection by contact and not consumption. Adsorption serves as the major rate limiting step for pest control in terms of insecticidal usage ^[1]. Entomopathogenic fungi require a multi-step process that includes various different physical interactions, germination, and penetration which varies by species^[1]. Each of these different processes also goes on to serve different physiological, chemical and physical specificities^[1]. Changes in normal physiology as well as the development of alterations including but not limited to an eventual reduction in both feeding and mobility as well as behavioural fever responses and alterations in typical migration patterns are all results of infection by Entomopathogenic fungi ^[1].

Specific Examples

Beauveria bassiana causes what is most commonly known as white muscadine disease. There are over 200 species, in 9 different orders that serve as hosts. The mode of action includes the invasion of the haemocel by spores and proliferation of the fungus^[2]. Germ tubes develop and mycelia from the elongated germ tubes are septate and release blastospores. Cell death occurs due nutrient depletion of the haemolymph or toxaemia by fungal toxic metabolites^[2]. Successful infection is dictated predominantly by different enzymatic activities for degrading proteins, lipids and chitin^[2].

Notes and References

1. ↑ ^{1.0 1.1 1.2 1.3} Khachatourians, G. G., Valencia, E., & Miranpuri, G. S. (2002). Beauveria bassiana and other Entomopathogenic Fungi in the Management of Insect Pests. Microbial biopesticides, 2, 239-275.
2. ↑ ^{2.0 2.1 2.2} Feng, M.G., Poprawski, T.J. and Khachatourians, G.G. (1994) Production, formulation and application of the entomopathogenic fungus Beaveria bassiana for inset control: current status. Biocontrol Science and Technology. 4:1,3-24