Bioengineered plants help produce moth pheromones for pest control

A bioengineered oilseed plant can produce a moth sex pheromone molecule used to control insect pests.

Pheromones are chemical signals that cause a behavioural response in members of the same or closely related species. For decades, farmers have used pheromones to keep pest insects away from high-value crops like apples and grapes, for instance by baiting traps with the chemicals or saturating fields with them to make it difficult for the insects to find mates. But the chemical process for making pheromones is too expensive to use for lower-value row crops like maize, soybeans and cotton.

Hong-Lei Wang at Lund University in Sweden and his colleagues bioengineered plants to produce a sex pheromone molecule secreted by two damaging pest species: female diamondback moths (Plutella xylostella) and cotton bollworms (Helicoverpa armigera).

The team used the bacterium Agrobacterium tumefaciens to introduce two genes into the oilseed plant Camelina sativa. One gene caused the plant to produce more fatty acids. The other – derived from a moth – shaped the fatty acid chains into the geometry needed for diamondback moths and cotton bollworms to recognise the scent. Once the camelina seeds were harvested, the researchers purified and processed the altered fatty acids in the lab to arrive at the final pheromone.

To compare their plant-derived pheromone to a chemical-derived one, the researchers laced traps for male moths and saturated plots of land with each. In both cases, the effects were similar, with moths trapped and populations declining at the same rate.

A thousand acres of oilseed crop for each pheromone could produce enough for the entire world, says Agenor Mafra-Neto, CEO of ISCA, a US company commercialising the pheromones. The team performed a cost analysis and found pheromones would be cheap enough for crops like soybeans if they could be produced for less than $100 a kilogram. Current methods cost $150 to $400 a kilogram. The researchers estimate their method would cost between $70 and $125 a kilogram.

Unlike regular insecticides, pheromones act only on target species and are not toxic. Insects also don’t develop resistance to them. Anamika Sharma at Florida A&M University says cheaper pheromones could help reduce insecticide use, but they won’t work for every pest and won’t control pest populations on their own. “We want to combine a lot of strategies – not just chemicals – to make sure we can manage the pest population,” she says.