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Fungal pathogens

Fungal diseases of insects (also known as entomopathogenic fungi) occur naturally in the environment. Epizootics (naturally occurring outbreaks) can rapidly decimate pest populations, particularly where pests are in close contact (such as aphid colonies).

Scientific name

Many species exist. Among the most commonly found in crop pests are:
  • Beauveria bassiana
  • Entomopthora sp.
  • Metarhizium anisopliae
  • Nomuraea rileyi.

Description

A fuzzy or velvety layer covers the insect. Fungal spore colour varies between species, but the most commonly found species range from white to dark green:

  • Beauveria—white
  • Entomopthora—white (spores are forcibly discharged, forming a halo around the dead insect)
  • Metarhizium—dark green
  • Nomuraea—light green.

Distribution and habitat

Generally more successful in moist or humid environments.

Hosts

Caterpillar hosts include Helicoverpa, loopers, Spodoptera and other armyworm species.

Metarhizium sp. also infects grasshoppers, locusts, cockroaches and true bugs.

Fungal pathogens also affect a wide range of other arthropods including aphids, beetles, ants, flies, and even mites, ticks and fleas.

Life cycle and ecology

Fungal spores are usually spread by wind and infect insects through the skin unlike Bt and NPV, which must be ingested.

Spores germinate and grow through the exoskeleton. As the fungus develops, the insect is filled with threadlike structures (hyphae). Millions of spores are then produced on the dead insect's surface.

Factors that influence effectiveness

Successful establishment of the fungus in an insect population is highly dependent on environmental conditions.

Many entomopathogenic fungi have been investigated as potential biocontrol agents. In Australia, a biopesticide containing spores of the fungus Metarhizium anisopliae is available for locusts and grasshoppers in pastures.

Further information

Registered chemicals database—Australian Pesticides and Veterinary Medicines Authority (APVMA)