(WFRV) - The Wisconsin Department of Natural Resources (DNR) warns that hemlock woolly adelgid and balsam woolly adelgid are likely heading toward Wisconsin, threatening to infest the state's hemlock and fir trees. A Facebook post from the Wisconsin DNR says what they're calling "tiny, little critters", hemlock woolly adelgid and balsam woolly adelgid have not yet been found in Wisconsin, they have been detected in Michigan and could soon spread west. DNR: Study reveals unique deer movement patterns that could benefit hunters The hemlock woolly adelgid is an insect that targets hemlock trees. Its white, cottony egg sacs are visible year-round on the undersides of hemlock branches, near the base of the needles. Images from the Wisconsin Department of Natural Resources As the adelgid feeds, it injects toxic saliva into the tree, causing the needles to drop, eventually leading to tree death. The DNR says this poses a threat to both forest and landscape hemlocks. The balsam woolly adelgid is also an insect and attacks true fir trees. Balsam and Fraser firs in Wisconsin are particularly vulnerable, according to the DNR. Paper machine catches fire on Green Bay’s east side, estimated $2,000 in damages Signs of infestation include stunted and swollen terminal branches from toxic substances from the balsam woolly adelgid. The feeding also causes needle discoloration and loss and can kill the tree. The DNR says this is a concern for forest trees, yard trees, and Christmas tree farms. The Wisconsin DNR encourages landowners to watch for potential sightings and report them to local forest health specialists. Reports can also be sent to the Wisconsin Department of Agriculture, Trade and Consumer Protection pest hotline at [email protected].