DENVER – The bark beetle epidemic now has infested 4 million acres in Colorado and southern Wyoming and it’s spreading fast in the Black Hills of South Dakota, U.S. Forest Service officials said Friday.

The figures released from an annual aerial survey of the U.S. Forest Service and the Colorado State Forest Service showed the bark beetle epidemic that started in 1996 spread to 400,000 new acres last year. The hardest hit forests are the Arapaho, White River, Roosevelt, Medicine Bow and Routt. Forest Service officials said the new acreage includes lodgepoles, ponderosa pine and five-needle trees.

Aerial survey results also showed that the size of the infestation doubled last year 2010 in the Black Hills of South Dakota and Wyoming. The epidemic has spread to 44,000 acres, up from 22,000 in 2009, according to the aerial survey.

The Forest Service in Colorado said it’s working with 8,500 landowners to “address forestry concerns on their property” and that efforts are under way to protect the public from the danger of falling trees that have been devastated by the bark beetle and mitigate fire dangers.

Tony Dixon, acting regional forester for the U.S. Forest Service for the Rocky Mountain Region, said officials “were extremely aggressive in 2010 with our efforts to remove trees killed by the bark beetle to reduce the risk falling trees to forest visitors and employees.”

In South Dakota, where the infestation has reached 384,000 acres in the Black Hills since 1998, officials said they were working to thin the forest and remove “newly infested trees.”