A PERFECT Trojan horse has been discovered for luring entire colonies of troublesome ants and termites to their doom, without harming other insects, animals or people. The breakthrough could herald a new generation of green pesticides customised to kill the target pest and nothing else.
The covert agent is a fungus at what is known as the 鈥減re-sporulitic鈥� stage of its life cycle. At this stage it forms a mycelium, a structure from which spores eventually emerge. 鈥淚t is a fine, cobwebby mass of filamentous cells,鈥� says Paul Stamets, who has founded a company called Mycopesticide in Kamilche Point, Washington, to commercialise the biopesticide.
Stamets鈥檚 crucial discovery was that the mycelium of this particular fungal species smells irresistible to foraging ants and termites. This was surprising, because spores of the same fungus are lethal to the insects, and the insects find it repellent at all other stages in its life cycle. Stamets thinks a similar aversion to other fungi could explain why attempts to use spores of the common soil fungus Metarhizium anisopliae as a biopesticide have largely failed. Ants and termites guarding nests sniff out colony members infected with spores, for example, and stop them entering.
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The fact that ants and termites cannot resist this particular mycelium gave Stamets the idea of using it to sneak the deadly fungus into a colony. Once forager insects had carried the pre-sporulitic fungus inside, it would transform into a rampant killer, infecting the insects and producing lethal spores that spread throughout a colony, killing the queen and all her minions. And in experiments with fire ants, carpenter ants and termites, Stamets proved that this is just what happens.
鈥淔oraging fire ants took the fungal bait directly to the queen and even laid her on a bed of it鈥�
鈥淚t inoculates the whole nest with the fungus,鈥� Stamets says. In one experiment, foraging fire ants took the fungal bait he鈥檇 planted directly to the queen and even laid her on a bed of it. Once spores emerge from the mycelium, they invade insects through any openings in their bodies and cause death within days, turning the cadavers into furry mummies that generate yet more spores.
Stamets is now screening strains of the fungus to find ones with an especially prolonged mycelial stage. Instead of producing spores within a couple of days, which could deter foragers from taking the material into the colony, using a strain that waits for weeks would allow plenty of time for the nest to become loaded with the fungus.
An added bonus is that when the colony is eradicated, the stench of the spores remains and prevents recolonisation, so infestations do not reappear. He has even used the fungus to stop carpenter ants recolonising his own house.
Stamets says numerous insect species may be vulnerable to the strategy. He is using the yet2.com technology transfer website to commercialise the idea.
