Fungal Parasites of Insects & Nematodes Notes

Fungal Parasites of Insects & Nematodes

Insect-Pathogenic Fungi

• Fungi commonly attack insects, nematodes, and other invertebrates in natural environments.
• They act as natural population regulators, helping to keep insect and nematode pests in check.
• Some insect-pathogenic and nematode-destroying fungi can be exploited as biocontrol agents; some are available commercially as alternatives to chemical pesticides.
• Entomopathogenic fungi are specifically adapted to parasitize insects and depend on them for survival.
• Beauveria and Metarhizium species are commonly found in natural environments and have strong potential for practical control of insect pests, especially in glasshouses and other protected cropping systems.
• Beauveria bassiana produces beauvericin toxin, which extensively invades insect tissues before death.
• Beauveria spp. also produce an antibiotic, oosporein, after insect death; it has no antifungal effect but is active against Gram-positive bacteria, potentially suppressing bacterial invasion of the cadaver and enabling the fungus to exploit the dead host tissues.
• Metarhizium anisopliae produces destruxins toxin in laboratory culture; these are active upon injection into insects, causing rapid death before extensive tissue invasion.
• Lecanicillium lecanii (formerly Verticillium lecanii) commonly occurs as a parasite of scale insects in subtropical and tropical environments.
• Lecanicillium lecanii is used as a biological control agent in glasshouse environments in cooler regions.

Developments in Practical Biocontrol-Commercial Formulations

• Approximately 10,000 tons/annum of spore powder containing Beauveria bassiana are produced for treating 0.8–1.3 million hectares of forest and agricultural land in China.
• In France, commercial biocontrol agents for locusts and grasshoppers, such as LUBILOSA (Lutte Biologique contre les Locustes et Sauteriaux), have been developed on a large scale.
• International development agencies have collaborated to develop a biocontrol agent for grasshoppers and locusts in Central African countries.
• Metarhizium anisopliae var. acridum has been used for LUBILOSA.
• Lecanicillium lecanii (Verticillium) is a successful commercial biocontrol agent of insects.
• Developed in the late 1970s, it is primarily used in glasshouses to control aphids on potted chrysanthemums and whiteflies on cucumbers and other indoor crops.
• L. lecanii is currently marketed as Mycotal® and Vertalec® by Koppert BV.
• Mycotal is primarily used to control whitefly and thrips in protected crops like cucumbers, tomatoes, sweet peppers, beans, aubergine, lettuce, ornamentals, and cut flowers.

Commercial Formulations- Mycotal & Vertalec

• Beauveria bassiana is reported to colonize some maize/corn cultivars in the USA via larvae of the European corn borer, Ostrinia nubilaris, which is the most important insect pest of maize.

Commercial Formulations-Lubilosa

• LUBILOSA
• GREEN MUSCLE
• MEERA

The Endoparasitic Fungi

• Nematodes can attack fungi, but fungi can also kill nematodes.
• Nematode-trapping fungi and endoparasitic fungi initiate infections from spores that adhere to the nematode surface and germinate to infect the host, feeding inside the nematode's body as their main food source in nature.
• A classic example of biological control is the spontaneous decline of cyst nematode (Heterodera avenae) infections in oat crops when the crop is infected by the fungus Nematophthora gynophila (Oomycota).