First record in Malta of Beauveria bassiana – a fungus parasitic on insects

Within all the species on earth, the fungi, commonly known just as mushrooms, are the most successful living organisms in inhabiting different and extreme habitats around the world.

Examples include deep oceans, arid deserts, volcanic areas and even growing on some type plastic or silicone. However, they are most commonly found in soil and forest understories decomposing organic matter.

Studies on local biodiversity by the Ministry for Gozo (the EcoGozo Directorate and the Research Laboratories at the Xewkija Experimental Farm), has recently resulted in a new record of fungus that has a peculiar growth habit.

The fungus, scientifically named Beauveria bassiana, is found dormant in soil and is able to parasitise a variety of insects leading slowly to their death. Biodiversity studies led to the first finding of this species in Malta, where it was found erupting out from a dead ant biting a stalk at the limits of Dahlet Qorrot, Nadur, Gozo, in September this year.The fungus has a way of its own when it infects ants. Once it penetrates the body, in this case a Carpenter ant (Camponotus sp.), it takes control of its mind and the ant becomes as literally described a “zombie ant.”

The fungus drives the ant so it climbs on a stalk, or a plant usually close to the nest and bites the stem firmly and securely, then it dies shortly after. When dead, the ant remains attached to the plant, and the microscopic fungus emerges out from the ant’s natural openings, usually from the joints and the mouth.

It forms small white powdery beads about 0.1 mm wide which release copious white powdery spores about 1/100th of millimetre in size. Since the host ant usually stations itself near its nest, the spores sprinkle down on other ants hence achieving a more successful chance of new infections.

This is considered as an insect disease and known as the White Muscardine Disease. Scientists are clueless about how the fungus is able to take control of the ant’s behaviour and perform very precise actions for the benefit of the life cycle of the fungus.

Gozitan Stephen Mifsud, the mycologist who found the fungus for the first time in Malta, said that he may attempt to propagate the fungus in a closed environment in order to introduce it as a trial for biological control of insect pests.

In other countries, it is frequently used as a biological insecticide to control several pests such as thrips, termites, aphids, whiteflies, cockroaches and phytopathogenic beetles.

The species was first discovered by the Italian scientist Agostino Bassi (1773-1856) and it was named after him.

The distribution is quite peculiar, where the asexually reproducing form of the fungus, Beauveria bassiana – the form found in Gozo – is found in most parts of the world, while the sexually reproducing form (Cordiceps bassiana) is only recorded from eastern Asia.

Stephen Mifsud is a Senior Medical Laboratory Technologist, Botanist, within the EcoGozo Directorate.