Kenneth Geisert held up a larva the size of his thumb—five inches of pale, segmented beetle grub that had been destroying blueberry roots across eastern North Carolina for more than a decade without anyone knowing its true identity. Now, thanks to genetic detective work by scientists at North Carolina State University, farmers finally have a name for their mystery pest: Prionus imbricornus, a longhorn beetle species that, until recently, had never been documented attacking blueberry bushes anywhere in America.
The stakes are significant. For over a decade, reports had trickled in from blueberry fields across Pender, Sampson, Bladen, and New Hanover counties of unknown Prionus larvae feeding on and damaging bush roots. But without knowing exactly which species was responsible, farmers couldn't mount an effective defense. "Before now, researchers often just assumed the species of Prionus on their commodities based on adult identification," said Geisert, a graduate student in NC State's College of Agriculture and Life Sciences. "If that guess was incorrect, it could mean using a treatment strategy that did not line up with the problem."
The identification breakthrough came through genetic barcoding—a technique that analyzes small, standardized DNA segments from multiple larvae and compares them against known Prionus species. Researchers had gathered adult beetles using black panel traps scented with sex pheromones at six farms across the region, then matched the mysterious larvae to those adults with 98–99% accuracy. The result confirmed what some farmers had been suspecting: they were dealing with P. imbricornus, a wood-boring beetle with distinctively long antennae.
The problem is as elegant as it is troubling. Female beetles lay their eggs in soil near the roots of hardwood trees and blueberry bushes. The larvae that hatch—which can grow up to five inches long—consume those roots from the inside out, potentially killing the entire plant. The adult beetles themselves don't even feed; their only job is reproduction. That means the real damage happens underground, invisible until the plant begins to wilt or collapse.
What makes this discovery urgent is the vacuum it has exposed. North Carolina is now the first state to officially report P. imbricornus actively feeding on blueberry crops. But there are no insecticides currently labeled to fight this pest on blueberries—a gap that has left growers scrambling. Lorena Lopez, an assistant extension professor in NC State's Department of Entomology and Plant Pathology, acknowledged the bind: "On one hand, it's very important that we know which species we're dealing with. On the other hand, 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 university is already working to close that gap. Lopez has launched insecticide trials designed to identify effective treatments and timing regimens that align with P. imbricornis reproductive cycles. The goal is to limit early larval development before major root damage occurs, giving growers a practical tool they've lacked until now. For farmers who have watched their blueberry bushes weaken for years without understanding why, that scientific work feels long overdue.