If you want to keep insects off your crops, you have a couple of options: Spray the plants with pesticides or confuse the bugs with pheromones. The latter—chemicals used by insects to communicate—are more environmentally friendly, but manufacturing them involves harmful chemicals. Now, scientists have devised a method that enables them to produce pheromones from plants themselves, a safer and potentially more economical approach.
The work is a "breakthrough" and "a wave of the future," says chemical ecologist Steve Seybold of the U.S. Department of Agriculture Forest Service’s Pacific Southwest Research Station in Davis, California, who was not involved in the study. "It will change the way that commercial pheromone outfits do business and will significantly enhance the quality and potentially lower the cost of the products that they provide."
Farmers have been using pheromones to keep insects off their crops for nearly 4 decades. Some pheromones help bugs attract mates; others are danger alerts. So farmers either employ them to trap insects or to confuse them so they can’t breed. Synthetic pheromones are nontoxic and biodegradable, but their production often involves use of harmful chemicals, such as the neurotoxins hexane and dichloromethane.
Seeking a greener method, a team led by Christer Löfstedt, a chemical ecologist at Lund University in Sweden, turned to the tobacco plant. The researchers genetically modified the plants to make components of pheromones produced by the bird cherry ermine moth (Yponomeuta evonymella) and the orchard ermine moth (Y. padella). In the wild, female moths emit these sex pheromones to attract male suitors.
The researchers extracted the pheromone components from the plant and prepared pheromone concoctions for the two species. They then pitted their plant-derived mixtures against synthetic pheromones on moth populations in the field.
The plant-produced pheromones were effective at trapping insects, the team reports online today in Nature Communications. Traps baited with plant-derived pheromones attracted on average 130 male bugs per trap, approximately half the catches obtained with synthetic pheromones. “This is a high number for a proof of concept experiment,” Löfstedt says.
Farmers have dramatically ramped up their use of pheromones to control pests, Löfstedt notes. "Total land area treated by pheromones has approximately doubled since the turn of the century." He believes his method could be an easier and cheaper way to produce these chemicals. Pheromones are effective in very small amounts. “You need just tens of grams per hectare for trapping insects,” he says. "Right now, we derive pheromone components from plants and prepare baits for trapping from these products, but our next goal is to develop GM plants that can release these pheromones into the environment."
The work is an important advance, says Coby Schal, an entomologist at North Carolina State University in Raleigh. "The new technology promises to engineer plants for both synthesis and sustainable release of insect pheromones, bypassing the need to produce the compounds in the laboratory and formulate them." It might reduce the labor costs associated in the deployment of mating disruption strategies, he adds.