YANKTON, S.D. (AP) - State officials plan to remove more than 100 sickened Austrian pine trees at the Lewis and Clark Recreation Area in southeastern South Dakota before they infect other trees.

District Park Manager Shane Bertsch tells the Yankton Daily Press & Dakotan newspaper (http://bit.ly/Vxdth3 ) that the trees are afflicted with pine wilt, and their needles are browning. Most of them have been around half a century.

Pine wilt is caused by a microscopic worm. State forestry specialist John Ball says it appeared across the southern part of the state last year.