Worms, fungi wreak havoc on pine trees in Oklahoma

"There have been a lot of places in Oklahoma where the mortality rate of trees in one area can be 100 percent," he said.

Pine wilt is caused by two insects, the pinewood nematode, a microscopic worm, that travels on the back of the pine sawyer beetle.

The nematodes feed on the living plant cells around water-conducting passages of pines.

Japanese black pine, Scot pine and Austrian pine are most susceptible to pine wilt, while native pines seem to have developed resistance to the disease.

"In extreme situations, there could be a chance they could be at risk too," said Mark Bays, Oklahoma Department of Agriculture, Food and Forestry urban forestry coordinator.

There is no cure once a pine is infected by pine wilt.

Age is also a factor.

"The pines that are impacted right now were planted in the 1980s and 1990s, and in an urban setting, that is a mature tree," Bays said. "Just like people, trees go through health cycles, and these might be declining in health because these beetles are attracted to trees which are going into a state of decline and these trees are not as vigorous as younger trees."

Bays said if a pine tree turns completely brown within weeks to a month and the edges can snap rather than bend, these are signs the tree is infected with pine wilt.

To prevent pine wilt, Bays said licensed arborists can inject treatment in a pine, but they are $100 to $200 per treatment every couple of years.

Infected trees must be removed, including the stump, to prevent spread of the disease, Ridlen said.

State forester Dan Stidham said pine trees can also be attacked by an airborne fungus, which can be treated if caught early enough.