Experimental insecticides that turn off vital genes in specific pests through a process called RNA interference are more durable and long-lasting than previously suspected, according to new research at Cornell University.
Cornell entomology professor Jeff Scott and his laboratory manager, Keri San Miguel, believe RNAi technology could revolutionize the crop protection industry due to its ability to avoid collateral damage among beneficial insects that offer biological control of pests.
“It has tremendous potential in pest control since you might be able to make it very specific for a pest species,” Scott said, noting growers often encounter new insects of concern after trying a different insecticide that disrupts a natural balance with beneficial insects.
Their findings were recently published in Pest Management Science.
RNA is essentially a copy of a DNA strand created as a messenger, alerting cells which proteins should be manufactured. RNA interference introduces genes to destroy targeted RNA messengers.
Scott and Miguel initially planned to work with an expert in sun screen residues to develop a protectant to enhance their treatment’s durability. In nature, Scott explained the DNA of a decomposing bird, for example, is easy to extract, while the RNA is usually degraded.
But they discovered protecting the RNA was unnecessary. While RNA messengers used by organisms are single-stranded, Scott and Miguel utilized double-stranded RNA, which, like DNA, seems to withstand the elements.
In their greenhouse trials, RNA-based insecticide was effective against Colorado potato beetle for 28 days — and likely would have continued working had the experiment not been disrupted by another pest entering the greenhouse. The RNA-based product worked even after treated foliage was swirled in water, simulating rainfall.
Though ultraviolet light quickly degraded RNA on a glass slide, the treatment was unharmed on foliage — potentially because it was absorbed into cells or shaded by leaf hairs.
Scott is confident the results would stand up in field trials. He said the approach is highly effective against beetles with larvae that feed on plants, but some pest species have enzymes in their guts that destroy the double-stranded RNA before it can enter their cells. More work is also needed to make RNAi effective on aphids, he said.
Major chemical companies have also taken notice of the technology. In 2012, Syngenta and Devgen entered into a six-year agreement to jointly research RNAi technology.
Monsanto researcher Greg Heck said the Cornell results are consistent with findings of his company’s ongoing double-stranded RNA research.
Heck said Monsanto has a transgenic corn product using RNAi to control corn rootworm under regulatory review by agencies around the world. He believes the product offer a new mode of action that would forestall development of chemical resistance. Monsanto is also developing a topical product line utilizing double-stranded RNA called BioDirect.
Heck said Monsanto is currently researching RNAi for use in weed control, combating Colorado potato beetle, curbing diseases and control of Varroa mites and viral diseases affecting bees. Monsanto has purchased the Israeli company Beeologics for its efforts to use RNAi in controlling Varroa mites and the company’s “expertise in the production of double-stranded RNA that would be needed to scale up to field-level applications.”