Prionus imbricornis threatens blueberries in North Carolina

Researchers at North Carolina State University have identifiedPrionus imbricornisas an emerging pest in commercial blueberry crops in North Carolina, United States. The species belongs to the Cerambycidae family and attacks the roots of Vaccinium corymbosum. The study confirmed, through genetic comparison, the presence of the beetle in infested plants in the state's main production center.

The identification resolves a question that has existed since 2010, when producers in Sampson, Pender, and Bladen counties reported severe damage to the roots and crowns of Duke cultivar plants. Subsequent reports indicated larvae of Prionus in blueberry growing areas, but the species involved remained unconfirmed. The difficulty stemmed from the subterranean habits of the larvae and the morphological similarity between species of the genus.

First case

Researchers report that North Carolina has recorded the first case in the United States of Prionus imbricornis in active feeding on commercial blueberry plants. The research also confirms Vaccinium corymbosum as a new host of the species through comparative larval barcoding. Prior to this, hosts confirmed by emerged adults included oak, chestnut, and apple trees.

Main damage

The larvae cause the main damage. They bore into and consume roots, create galleries, and compromise the root system. In blueberries, symptoms include shoot dieback in early spring, leaf wilting, and weakened plants. Many infested plants can be pulled from the soil by hand or during mechanized harvesting. Once these signs appear, recovery is usually not possible.

The infestation has already reached a significant scale in the producing region. Scientists report hundreds of dead plants with active larvae, thousands of suspected plants, and more than 202 hectares with confirmed presence of the parasite. Prionus Over the past two years, the Duke, O'Neal, Star, and Legacy cultivars have been among those infested. Most of the affected plants are ten to fourteen years old, but the study also cites five-year-old plants.

Researchers installed black-panel traps with sex pheromones on six commercial farms between April and September 2025. The areas were located in Pender, Sampson, Bladen, and New Hanover counties. The traps captured adult males. Prionus imbricornis e Prionus pocularisAmong 5.150 adults surveyed, 89,6 percent belonged to Prionus imbricornis.

The team collected two larvae actively feeding on roots of Vaccinium corymbosum, on two farms belonging to Pender and Sampson. Then, he sequenced the CO1 gene of these larvae and compared the results with identified adults of Prionus imbricornis e Prionus pocularisThe larvae showed a 98 to 99 percent correspondence with adults of Prionus imbricornis.

Species involved

The result indicates Prionus imbricornis as a species involved in blueberry infestations. The article highlights, however, a possibility that remains open: Prionus pocularis It can also occur on plants, as adults of this species have appeared in the traps. Confirmation depends on further barcoding or the rearing of larvae to the adult stage.

The biological cycle makes management difficult. Adults do not feed. Females lay eggs in the soil, near the base of the plants. The larvae burrow into underground tissues and can take three to five years to pupate. In North Carolina blueberries, the larvae can reach up to 62 millimeters in length and 15 millimeters in width.

chemical control

Research points to limitations in chemical control. There are no registered insecticides effective against beetles. Prionus in blueberries in the United States. The larvae remain protected in the soil, inside roots and stems, which reduces the reach of contact and systemic products. The most susceptible stage tends to occur soon after hatching, a few weeks after mating.

Insecticide trials

Lorena Lopez, an assistant extension professor in the Department of Entomology and Phytopathology at North Carolina State University, has begun insecticide trials. The goal involves identifying effective molecules and tailoring applications to the reproductive cycle of insects. Prionus imbricornisThe goal is to limit the initial development of the larvae and reduce root damage.

The work also addresses the use of pheromones. Previous studies with other species of Prionus Studies have indicated potential for mating disruption in hops, cherry, and pecan. However, the effectiveness of this tactic for Prionus imbricornis The use of pheromones in blueberries has not yet been evaluated. The pheromone traps used in North Carolina were employed to monitor adult emergence and estimate populations.

Scientists warn of a limitation in monitoring. The number of males captured in pheromone traps does not, by itself, indicate the level of infestation in the plants. Adults can come from areas hundreds of meters away, including from neighboring woody hosts. The presence of larvae actively feeding on the roots remains the main evidence of infestation in the crop.

Further information can be found at doi.org/10.1093/jipm/pmag018