The Minnesota Department of Natural Resources has news rules for using firewood in state parks and forests in its continued effort to stop the spread of invasive species such as emerald ash borers and gypsy moths. The DNR continues to say the best bet always is to buy bundles of firewood upon arrival at campgrounds. The agency also now says the wood must be bought from a DNR-approved vendor and harvested in the county where it will be used. For example, your approved firewood at Sibley State Park can't be hauled for use at parks up the North Shore. Certified wood will labeled with a seal from either the federal or state departments of agriculture. Keep a receipt for proof of purchase. Wood-sellers approved by the state are listed online at Be mindful that federal lands and private campgrounds also have rules about firewood use.