North Carolina’s vital agricultural sector is facing an emerging and previously hidden threat as a destructive species of beetle targets the state’s commercial blueberry crops. While the adult insects remain above ground without feeding, their subterranean larvae wage a silent war beneath the soil, chewing through plant roots and threatening the health and survival of entire blueberry bushes. After more than a decade of uncertainty, scientists have finally identified the specific insect responsible for the widespread subterranean damage, marking a crucial first step toward developing targeted pest management strategies to protect the state’s harvests.
A dedicated research team at North Carolina State University has officially confirmed that the culprit behind the damage is Prionus imbricornus, a distinct species of longhorn beetle readily recognized by its exceptionally long antennae. These wood-boring insects have increasingly alarmed blueberry producers across the region, who have watched helplessly as underground populations steadily expanded their agricultural footprint.
The biological cycle of these beetles begins when female adults deposit their eggs in the soil near the root systems of hardwood trees and, as researchers have discovered, cultivated fruit bushes. Once the eggs hatch, the emerging larvae migrate toward the underground roots, feeding voraciously on plant tissue. In severe cases, the feeding destroys enough root structure to entirely kill the host plant. These subterranean larvae can grow to an impressive and alarming five inches in length, posing a massive biological challenge to the plants they inhabit, while the adult beetles fulfill their reproductive lifecycle without ever consuming plant material.
A Decade-Old Mystery Beneath Blueberry Fields
North Carolina holds the unfortunate distinction of being the first state to document P. imbricornus expanding its feeding preferences to include cultivated blueberry bushes. However, the physical signs of this underground crisis have troubled growers for years. Unidentified reports of Prionus larvae causing severe root damage in blueberry fields date all the way back to 2010. Despite the ongoing agricultural losses, researchers struggled for over a decade to pinpoint the exact species responsible for the destruction.
Much of this investigative difficulty stemmed directly from the insects’ secretive underground habitat. Because the larvae spend their entire developmental cycle hidden deep in the soil near plant roots, they are exceptionally difficult to locate, extract, and study in a controlled setting. Furthermore, the task was complicated by biological similarities among insect families. Larvae from various different longhorn beetle species often look remarkably similar to the naked eye, rendering traditional visual identification methods completely unreliable for agricultural experts.
According to Kenneth Geisert, a graduate student in NC State’s College of Agriculture and Life Sciences and the lead author of the study, this persistent uncertainty has severely hindered the agricultural community’s ability to develop and implement appropriate, effective pest control strategies.
"Before now, researchers often just assumed the species of Prionus on their commodities based on adult identification," Geisert explained, highlighting the historical guesswork involved in regional pest management. "If that guess was incorrect, it could mean using a treatment strategy that did not line up with the problem and incorrectly associating species and their hosts. For instance, while P. imbricornus attacks roots, another type of longhorn beetle might attack the trunk of a tree, or dead branches. Without knowing which species of beetle you’re dealing with and their ecology, incorrect management can cause adverse effects on non-target insects."
DNA Analysis Reveals the Mystery Beetle
To finally solve the mystery and definitively identify the insects plaguing local farms, the NC State research team initiated comprehensive fieldwork across six commercial blueberry farms situated in North Carolina’s key southeastern agricultural regions, specifically targeting Pender, Sampson, Bladen, and New Hanover counties.
To capture and identify the adult populations, the scientists deployed specialized black panel traps equipped with sex pheromones—potent chemical signals specifically designed to attract adult beetles. After successfully collecting the specimens from the field sites, the researchers turned to advanced molecular biology, utilizing a sophisticated DNA identification technique known as genetic barcoding to determine the exact identity of the larvae discovered living beneath the fields.
This modern scientific method examines short, standardized sections of an organism’s DNA and rigorously compares them against established reference sequences from known species cataloged in scientific databases. By matching the genetic material extracted from the unidentified subterranean larvae with the known DNA profiles of adult Prionus beetles collected in the field traps, the researchers were able to definitively determine which species was present in the root zones.
The molecular analysis yielded conclusive results, producing a remarkably high 98 to 99 percent genetic match with P. imbricornus. This definitive match officially confirmed the identity of the longhorn beetle species responsible for the persistent root damage plaguing North Carolina’s blueberry industry.
A Growing Threat With No Approved Insecticides
Although successfully identifying the hidden pest represents a monumental scientific breakthrough for the academic community, it simultaneously brings to light a deeply concerning and immediate challenge for commercial blueberry growers across the state.
Lorena Lopez, an assistant extension professor in NC State’s Department of Entomology and Plant Pathology and a co-author of the research study, explained that the team’s discovery brings a complex mixture of both encouraging and troubling news for regional agriculture.
"On one hand, it’s very important that we know which species we’re dealing with," Lopez noted, emphasizing the value of scientific clarity. "On the other, North Carolina was the first state to ever report Prionus infestation in blueberries, and there are no insecticides currently labeled against this pest in blueberries."
The absence of approved chemical treatments leaves growers in a vulnerable position as they attempt to safeguard their valuable investments against an underground insect that has spent more than a year evading effective management. To help bridge this critical gap, Lopez has already initiated trials to test various insecticides, aiming to determine which commercial treatments might successfully control the resilient beetle populations without harming the surrounding ecosystem.
A major focus of these ongoing trials is determining the precise timing for chemical applications. By carefully coordinating insecticide treatments with the natural reproductive cycles of the beetles, the researchers hope to effectively disrupt larval development before the insects can inflict extensive, irreversible damage on the root systems of the blueberry bushes.
If these current research efforts prove successful, the resulting strategies could finally provide farmers with a much-needed defense mechanism against an emerging pest that has remained elusive, destructive, and notoriously difficult to manage for well over a decade.
The complete findings detailing the discovery and identification of the pest have been published in the Journal of Integrated Pest Management in a formal research paper titled "Prionus imbricornis (Coleoptera: Cerambycidae), an emerging pest in North Carolina blueberries." Additional contributions to the published research were provided by Gareth Powell, an assistant professor at NC State and director of the NCSU Insect Museum.