North Carolina's blueberry farmers may have a beetle problem.
A new study from North Carolina State University has identified destructive beetles inhabiting North Carolina blueberry fields as Prionus imbricornus, a species of longhorn beetle. Known for their long antennae, the wood-boring beetles are an emerging pest in NC blueberries. Female adults typically lay their eggs in the soil near the roots of hardwood trees; their larvae, which can grow up to five inches long, then consume and destroy those roots, potentially killing the tree, Adults do not feed.
North Carolina is the first state to report P. imbricornus actively feeding on blueberry bushes, though reports of unidentified Prionus larvae feeding on and damaging bush roots stretch back to 2010. Despite these reports, identifying the specific species responsible had proven difficult because the larvae live near the roots of plants. Identification was made harder by the fact that different types of longhorn beetle larvae also look similar.
The lack of species identification complicated efforts to combat the pests, said Kenneth Geisert, graduate student in the NC State College of Agriculture and Life Sciences and lead author of a paper on the new study.
"Before now, researchers often just assumed the species of Prionus on their commodities based on adult identification," Geisert said. "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."
Researchers used a series of black panel traps scented with sex pheromones to attract and gather adults at six farms across Pender, Sampson, Bladen and New Hanover counties. They then used a technique called genetic barcoding, which involves analyzing small, standardized segments of DNA from multiple larvae. The unknown larval sequences are then compared against the same genetic segments from known Prionus adults, allowing scientists to identify the exact species of the larvae.
The results matched P. imbricornus with 98-99% accuracy. Lorena Lopez, assistant extension professor in NC State's Department of Entomology and Plant Pathology and co-author of the paper, said this is both a good and bad thing.
"On one hand, it's very important that we know which species we're dealing with," she said. "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."
To address this shortfall, Lopez has started conducting insecticide trials. By identifying effective insecticides and timing treatment regimens with P. imbricornis reproductive cycles, early larval development can be limited. This could prevent major root damage and provide growers with an effective management tool.
The paper, "Prionus imbricornis (Coleoptera: Cerambycidae), an emerging pest in North Carolina blueberries," is published in the Journal of Integrated Pest Management. Gareth Powell, assistant professor at NC State and director of the NCSU Insect Museum, is a co-author of the paper.
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