A University of Kentucky Martin-Gatton College of Agriculture, Food and Environment (CAFE) forest entomologist is closing in on a pest management strategy that could give landowners, cities and forest managers a highly targeted alternative to conventional insecticides - one that kills invasive beetles by silencing their own genes and leaves surrounding wildlife untouched.
Lynne Rieske-Kinney, Ph.D., a professor in the Department of Entomology, has spent roughly a decade developing RNA interference (RNAi) as a tool against two of the most damaging forest pests in the eastern United States, the emerald ash borer and the southern pine beetle. Her current work is supported by a cooperative agreement awarded in 2024 and running through 2027.
"We can definitely kill insects in the lab, in a petri dish," Rieske-Kinney said. "The challenge is scaling it up to a usable technology, and that's what we're focusing on now."
RNAi exploits a natural cellular defense. Researchers custom-design a double-stranded RNA molecule that matches a short sequence - 16 to 21 base pairs long - in a specific gene of a target insect. When the insect ingests it, its cells mistake the molecule for a virus and shut down production of the corresponding protein. If that protein is essential, the insect dies.
Because the match must be nearly exact across billions of possible base-pair combinations, the treatment is remarkably species-specific.
"If you design a double-stranded RNA for a specific insect, the chances of it affecting anything else is very, very low," Rieske-Kinney said.
Her lab has completed non-target organism studies for RNAi molecules designed against both emerald ash borer and southern pine beetle and has shown that the treatments are compatible with the classical biological control agents already being released to suppress emerald ash borer populations.
Two pests, two strategies
Emerald ash borer, an invasive Asian beetle that has been detected in 110 Kentucky counties and killed millions of ash trees throughout 38 states, is being addressed at the individual-tree scale. Rieske's team has demonstrated that double-stranded RNA delivered to an ash tree through foliar spray, bark application or root application circulates throughout the tree and remains bioactive for at least 30 days. Current work is testing whether that protective window can be pushed to a full growing season or even multiple years.
"Ideally, what we would like is a single application to provide season-long protection against emerald ash borer," Rieske-Kinney said. "But what if we could provide three years of protection? That would be comparable to what current chemical insecticides are providing for ash protection."
Ash is also a signature species of the Bluegrass State's urban and community tree canopies, making single-tree protection a practical fit for homeowners and municipalities.
By contrast, the southern pine beetle is a landscape-scale problem. Rieske's team is pursuing an indirect delivery route: engineering fungal symbionts that live in association with the beetle to produce the bioactive RNA. Beetles carry those fungi with them as they move through a forest, potentially propagating gene silencing in beetle populations across a much wider area than any single application could reach.
The current focus gene is a heat-shock protein, one of several essential genes the lab is screening. Others govern membrane permeability and additional core cellular functions.
Conventional insecticide inputs have grown increasingly expensive for landowners and farmers, and broad-spectrum treatments carry well-documented risks to pollinators and other beneficial insects. A species-specific, biodegradable approach that spares non-target organisms could offer a meaningfully different tool.
"With emerald ash borer, we're looking at how we can protect an individual tree, while with southern pine beetle, we're thinking on the scale of an entire forest," Rieske-Kinney said. "They're very different challenges, but the goal is the same: using this gene-silencing technology in a very targeted way to protect trees from destructive insects."
This material is based upon work that is supported by the Forest Service of the U.S. Department of Agriculture, under cooperative agreement 24JV11330101060. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the US. Department of Agriculture.
