The world is crying out for an eco-friendly pesticide, and now researchers may have found one within a common plant called sorghum.
Last month, the EU banned the pesticide chlorothalonil due to concerns about both the risk posed to surrounding wildlife and the potential harm it could cause to humans. This was but one in a number of calls by campaigners to end the use of artificial pesticides, given that a number of species – such as bees – are seriously under threat of extinction.
Now, in a bid to come up with an eco-friendly alternative, researchers from Penn Sate have discovered that a compound produced by sorghum plants – a common crop used for food and agriculture across the world – could hold the key.
In a paper published to the Journal of Chemical Ecology, researchers said this compound could be isolated, synthesised, and used as a targeted, nontoxic insect deterrent. This was discovered after the analysis of sorghum chemicals called flavonoids – specifically 3-deoxyflavonoids and 3-deoxyanthocyanidins – and their ability to deter corn leaf aphids.
To defend against these tiny blue-green insects that suck the sap from the plants, sorghum has evolved defences that harness biosynthesis of secondary metabolites, including flavonoids to poison the pests.
Previously, these flavonoids were found to be regulated by a gene called yellow seed1 (y1) that responds to stresses.
It’s ‘very, very potent’
For this study, the researchers grew two strains of sorghum: one with a functional y1 gene and another with a mutant gene called null y1, which could not produce flavonoids.
When comparing the two, the researchers found that a significantly higher number of adult corn leaf aphids colonised the null y1 plant, unlike the regular y1 strain, which showed no sign of stress and minimal bugs.
In a companion experiment, they fed aphids a diet of sorghum leaves, including one laced with an extract containing flavonoids. After a few days, the bugs that had eaten the laced leaf died and reproduction dropped significantly. These findings suggest flavonoids could be used as a potent insect deterrent to protect crops.
“Sorghum plants have evolved to precisely emit compounds offering defences against harmful predatory insects that threaten them, and yet these chemicals in their defences don’t hurt beneficial insects,” said Surinder Chopra, who led the study. “If we could develop nontoxic insecticides, it would be a game-changer – given that the toxicity of synthetic pesticides is of great concern, and they are considered to be dangerous to human health.”
He added that there is still much more research to be done but, at least when it comes to dealing with corn leaf aphids, flavonoids are “very, very potent”.