Australasian Science Magazine

By Stephen Luntz

A component of tarantula venom can kill common insect pests that eat it, opening up the possibility of an insecticide with fewer environmental problems than those on the market.

“There is an urgent need for new insecticides due to insects becoming resistant to existing products and others being deregistered due to perceived ecological and human health risks,” says Prof Glenn King of the University of Queensland’s Institute of Molecular Bioscience.

Spider venoms contain hundreds of toxins, and each species is different. However, only orally fatal insecticides are of much use. Topical toxins are usually equally damaging to non-target species, including important pollinators like bees.

Dr Maggie Hardy, who had been completing a PhD under King, identified the toxin OAIP-1 and demonstrated that it is orally effective against termites and cotton bollworms. “Cotton bollworms cause major economic damage to crops, and the toxin we have isolated is more potent against these insects than existing chemical insecticides,” says King, who published the research in PLoS One.

“From an evolutionary perspective it is a little surprising a spider toxin is orally active, but from a biochemistry point of view it is not surprising at all,” Hardy says. “These sorts of peptides are very thermally and chemically stable.” Consequently, they survive in the insect’s digestive system.

Hardy is planning to test OAIP-1 against non-target species, and has high hopes. “These chemicals are like table salt to vertebrates – they’re bad for you only in large quantities so it can be used around people and pets,” she says. Beneficial insects pose more of a challenge, but Hardy hopes that spraying will be avoided at times when pollinators are active.

Any new insecticide will eventually spur resistance, but Hardy says: “The resistance gene against chemicals that hit the nerve channels makes insects less susceptible to conventional chemical pesticides but more susceptible to venoms like these.” Consequently, by alternating existing pesticides with one that operates in a manner similar to OAIP-1 it may be possible to keep both effective.

Hardy adds that improved understanding of how resistance develops should also mean that insecticides reaching the market today will be used more responsibly than previous generations.

Although commercial quantities of OAIP-1 will be produced from bacteria, Hardy has high praise for her research subjects. “They’re like little cows, lining up at feeding and milking time: the perfect animal to work with.”