Researchers from the Technical University of Denmark have developed a way to get yeast to produce insect pheromones, which farmers can use to keep harmful insects out of their fields. These pheromones are already being produced.
Given a choice, most people prefer to minimize using pesticides on vegetables and fruit.
But what should farmers do when insects swarm over their fields and their larvae devour the crops before they can be harvested and delivered to consumers?
According to a team of researchers involving the Technical University of Denmark, the answer may be to use sex pheromones to disrupt the insects.
Large quantities of insect pheromones can have the amazing effect of confusing male insects so much that they cannot find the females and fertilize them.
Unfertilized females do not lay eggs, and because no larvae emerge, farmers can increase their crop yields and satisfy consumers with pesticide-free foods.
This is a win-win situation – unless you empathize with the males confused by the overpowering scent of female insects without finding any to mate with.
“Pheromones have been an attractive alternative or supplement to pesticides for many years, but production costs have been too high to apply them to row crops. But by getting yeast to produce the pheromones, we can reduce the cost to a level most farmers can afford,” explains Irina Borodina, Professor at the Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark.
Irina Borodina and colleagues have published a review on the existing potential of producing pheromones by using yeasts in Current Opinion in Biotechnology. Irina Borodina is the founder of BioPhero, which is in the process of expanding the concept globally.
Already used for producing apples and grapes
The concept behind using insect pheromones is very simple.
Female insects usually emit pheromones, and the males track the scent to find females to mate with.
The males can intercept and track these pheromones over several hundred metres.
But if a farmer sprays his entire field with pheromones, the males fly around like crazed teenagers, never finding the females and never mating.
This means that the insects do not multiply and slowly but surely disappear from the area and can no longer damage crops.
This strategy is used on 4% of the world’s apple orchards and 4% of the world’s vineyards.
Saving the desirable insects
This strategy has the overriding advantage in relation to using pesticides that the pheromones are quite species-specific.
This means that they can stop one pest from reproducing in the fields, leaving all the other insects alone.
This has several advantages.
The biodiversity of the area is sustained, and the farmers do not have to pollinate the fields, which is a problem in many places globally, because pesticides eradicate all living insects in a field and the surrounding area.
“Pesticides kill everything, but pheromones maintain the ecological system in the fields. Another potential problem for many farmers is that eliminating many potentially beneficial insects in an attempt to destroy a few pests may enable different and perhaps more harmful insects to replace the species that have disappeared,” explains Irina Borodina.
Yeast can produce low-cost insect sex pheromones
Although pheromones have been used in agriculture for up to 20 years, the strategy is not as widespread as it perhaps should be.
The main reason is that making pheromones by chemical synthesis is expensive. Because insects cannot be induced to make enough, using them as production animals makes no sense, so chemists have to get involved, and then the price goes up.
However, Irina Borodina has helped to pioneer another option: using yeast to produce the pheromones in very large quantities, which can be easily and relatively cheaply spread on fields around the world.
“This works by taking the biosynthetic pathways that catalyse the production of pheromones in insects and engineering them into yeast, which we can then get to produce much more at an affordable price,” says Irina Borodina.
Developed large-scale production of pheromones for various moths
Irina Borodina has specifically developed yeasts in her laboratory and company that produce pheromones that attract males of various moth species.
These moths are serious pests of cabbage, cotton and rice.
Pheromones are already being produced and sold in various parts of the world, where farmers have completely or partly replaced pesticides with pheromones, including in rice production in the Ebro Delta in Spain.
In other habitats with various harmful insects, the pheromones have replaced some of the pesticides and thus function as a supplement to reduce their use.
“This is our first product, and we are trying to get it approved for application in several countries,” says Irina Borodina.
Focus on the most relevant crops
Irina Borodina says that seeking the most attractive pheromones requires focusing on the world’s most common crops, including rice, maize and soybeans.
These three crops account for about 40% of all cultivated land on Earth, and replacing the pesticides used on these crops can clearly have a major impact on the overall use of pesticides globally and thus also on the biodiversity of both insects and the plants the insects pollinate.
In addition, the health of farmers and other people is also key.
“Farmers in many parts of the world, such as in Africa and India, are constantly fighting insects that are becoming resistant to the pesticides they spray on their fields. Farmers then use more types of pesticides in greater quantities, which strongly affects their health in both the short and long term,” concludes Irina Borodina.
In both India and Africa, many farmers die every year from acute pesticide poisoning. The pheromones, in contrast, do not harm anyone. Except by driving male insects crazy.