MINNEAPOLIS -- A recent report shows the scope of a large problem in Minneapolis, caused by something small.

Emerald ash borer (EAB) was first found in Minneapolis in 2010. Since then, it has spread to nearly every corner of the city.

According to the Minnesota Department of Natural Resources, the destructive beetle's larvae feed on ash trees. Once the tree begins to show symptoms of an EAB infestation, trees typically die within one to three years.

"We describe it as sort of a once-in-a-generation pest crisis. The last generation being Dutch elm disease which we're still dealing with," said Ralph Sievert, director of forestry for the Minneapolis Park and Recreation Board.

According to Sievert, they're halfway through an eight year program to help slow the spread of EAB.

When the program first started, there were 40,000 public ash trees on boulevards and in parks in Minneapolis. In 2017, 5,000 public ash trees will be cut down in the city--bringing the total amount of trees removed in four years to 20,000. Those ash trees are being replaced with a diverse mix of trees.

"By having a bigger mix of different tree types, you're sort of building in an immunity for some other pests that might come along," Sievert said.

On one block of Zenith Avenue South in the Linden Hills neighborhood, a green X had been spray-painted on four ash trees.

"We enjoy walking on these streets because they're nice and tree-covered and shaded. But every time you walk by a tree with an X, you know it's going to be gone soon," Neighbor Kaitlin Lytle said. "These neighborhoods are so charming with the tree-covered streets and it's really nice for families to be strolling and in shade versus direct sun."

Sievert acknowledged that during the early years when the new trees are young, there will be a gap in canopy cover. He is encouraging people with these new trees to water them weekly.

The report by the Minneapolis Tree Advisory Commission also mentions more awareness is needed for people who have ash trees on their land.

"A lot of folks don't even know they have an ash tree in their yard and at some point they're going to get surprised when emerald ash borer infests that tree," Sievert said.

Sievert said homeowners have the choice to treat their ash tree or remove it and replace it with some other type of tree.

"It's better to treat it really before the signs of the insect are in the tree. Because once you see the symptoms, the insects have actually been there for 3 or 4 years," Sievert said.

A city ordinance does require homeowners to take care of any infested trees.