An insecticide is used to control harmful pests that could otherwise devastate crops. The problem, of course, is that insecticide use often has serious environmental costs.
By generously spraying harmful insecticides on their crops, farmers can decimate species, including key pollinators like bees, and devastate fragile ecosystems. Worse still, wind and rainwater often carry dangerous chemicals beyond farms, making their effects felt at great distances.
A team of chemists and chemical engineers from the Universities of Bath and Sussex have come up with an ingenious way to limit the use of insecticides. Instead of spraying entire crops, farmers can place insecticide traps in certain areas for more targeted protection.
Scientists have done this by using pheromones from leaf cutter ants to attract these harmful pests to insecticide baits. Ants, which can devastate plants, release chemicals that signal other ants which way to go. Harnessing the power of these pheromones for pest control is a nifty trick.
"Leaf cutter ants are the main pest species of agriculture and forestry in many areas of the tropics causing an estimated $ 8 billion in damage each year to eucalyptus forestry in Brazil alone," the scientists explain. "Traditional pesticides often degrade quickly and are not specific to particular pests, resulting in substantial waste of pest control products, environmental contamination, and harmful effects on other insects."
Pheromones could be the solution
Scientists have created molecular sponges called organometallic structures to absorb the alarm pheromones from leaf-cutter ants before slowly releasing them to lure insects into a trap. They also altered certain chemicals to be able to adjust the rate at which pheromones are released so that they last for several months and not just days.
"Insect pheromones have been used before to attract pests, but the problem is that they are quite volatile, so their effects do not last long," explains Professor Andrew Burrows, Head of the Department of Chemistry at the University of Bath. "Our organometallic structures act like a kind of sponge where pheromones can encapsulate in the pores and then slowly release over time."
The researchers' field trials on a eucalyptus plantation in Brazil worked well, indicating that pheromone-laden MOFs can lure ants into a trap.
"This system could reduce the amount of pesticides sprayed on a crop and could be particularly useful for high-value crops in small areas," Burrows says. "We are currently looking at a variety of other insect messenger chemicals, including those that can be used to control moth pest species in UK fruit orchards."