A naturalist at the Cylburn Arboretum wondered why a cluster of pine trees was dying. Entymologist Stanton Gill and pathologist David Clement went to the arboretum to investigate.

When they sawed off samples and tested them back at their lab, they found culprits they hadn’t seen since the early 1980s – a microscopic mass of nematodes, worm-like creatures that were killing the trees.

Gill and Clement are issuing a statewide alert, saying that landscapers, arborists and homeowners should be on the lookout for a disease called pine wilt.

Gill said the disease, which is prevalent in the Midwest, is carried by a non-native, longhorned “sawyer” beetle, which probably came here via a shipment of cargo.

Preventive measures include treating tree trunks with insecticides, Gill said.

Although the arboretum is the only site where pine wilt was found, he said he sent a statewide notice to landscapers and arborists, to alert them to the find and tell them how to collect samples for testing.

Insecticides can kill adult beetles before they lay eggs or feed, he said.

But he and Clement said the best way to stop pine wilt disease is chop down the infected trees. They should be destroyed soon, before sawyer beetles emerge again in June, he said.