By David Lias
John Ball, a forestry professor at South Dakota State University, warned Vermillion citizens last week that the Emerald Ash Borer may not be in Clay County yet, but there’s not much that anyone can do to stop the tree-killing insects.
“There’s no light at the end of the tunnel; there’s no light at the end of the rainbow. It’s all bad,” he told a small group who gathered in Vermillion’s City Hall to learn the latest trends regarding the emerald ash borer and the steps citizens and communities should take.
South Dakota joined the club in 2018, Ball said, of states where the emerald ash borer’s presence has been confirmed. The insect has been found in Sioux Falls.
And, as if to confirm his warnings that the insect will continue to spread from Minnehaha County to eventually infest ash trees in Clay County, there is news this week that the bugs are on the move.
A new infestation of emerald ash borer has been found in Sioux Falls, according to a report last weekend by KELO. A new infestation, found in the area near 37th Street and Minnesota Avenue in Sioux Falls is separate from a larger infestation that is happening in the northern part of the city.
It won’t be long, Ball said during his Vermillion appearance, before the insects take flight.
“The beetle itself should be flying in another few weeks,” he said. “In South Dakota, flight periods are bookends for summer – between Memorial Day and Labor Day. They begin flying about when black locusts are in bloom and then about the end of June … that’s when we get the emergence. The adults live for about three weeks; the last one emerges sometime in early August so by Labor Day, they’ve already died.
“Summer is when they’re actually out flying; the rest of the year, they’re snug within the tree,” Ball said.
He said he’s received many call from Sioux Falls residents who believe they’ve found emerald ash borers in their trees, when in fact the insects they’ve spotted are cicadas.
During the summer, adult emerald ash borers lay eggs in ash trees. The eggs hatch and insect larvae bore under the bark to feed on the trees. Emerald ash borer larvae stay in that stage for nearly an entire year, Ball said, adding that at about this time of the year, many of the larvae are now in their pupae stage and will soon emerge as adults.
While larvae, however, they burrow into ash trees, chewing the inner bark and phloem, creating winding galleries as they feed. This cuts off the flow of water and nutrients in the tree and eventually causes the trees to die.
“It usually takes four or five years of repeated attacks to kill a tree,” Ball said. “However, it will finish it off.”
His presentation included a graph that showed the 10-year survival of rate of an infected ash tree. The news is not good.
“It’s zero. It’s an important number, because a lot of people are in denial,” Ball said. “When I talk to communities, some people will say ‘it’s not going to hit our community.’ There’s nothing different about any community outside of Sioux Falls that means the emerald ash borer is not going to like it.
“Frankly, you’re going to lose every ash tree in this town once the emerald ash borers arrive,” he said. “In Sioux Falls, that’s 85,000 trees. That’s about a third of the community forest. And the point is, you are going to lose them all.”
He added that every variety of the tree – green ash, white ash, black ash – will succumb to the insects.
“From the day we detect emerald ash borers in Vermillion, you can start a clock and 10 years later, every untreated ash will be dead,” Ball said.
Ash trees won’t completely lose their presence in the community, however. He noted how in Michigan, where the emerald ash borer has been active longer, very small diameter ash trees can be found growing. That’s happening because it’s the mature ash trees that succumb to the insects.
“They (the seedlings) are being attacked, but they get big enough that they produce seed. And so, what you’re going to find in Vermillion for the rest of your lives (after the emerald ash borer arrives) are little ash trees coming in,” he said. “They’ll just get big enough to produce seed and then they’re attacked and they start to decline.
“You’re always going to get seedlings and saplings coming up,” Ball said. “So, you’re always going to have emerald ash borers flying around here so they’re always going to find any (ash) tree that you plant, or any tree that you don’t treat, and kill that as well.”
Woodpeckers like to eat both the adult and larvae emerald ash borers and are effective in finding them under the bark of trees, but they can only reduce the insects’ numbers by a small amount. Non-stinging wasps, which are a natural enemy of the ash borers, have been released in Sioux Falls and other communities, but at best they can only slow, not stop, the insects.
A cold winter, despite what many believe, also does little to slow the emerald ash borer.
“Under scientific tests, you can lose 5 percent at zero degrees, and it has to be zero for a while,” Ball said. “You can kill 99 percent at minus 30 … and yes, we did get to minus 27 … but it wasn’t long enough.”
A survey of affected ash trees in Sioux Falls showed, he said, that the winter cold killed a good number of larvae in upper canopies of trees, but had much less effect on those located in lower trunk portions of trees where the bark is thicker. Ball estimates that winter cold may have killed close to 30 percent of the emerald ash borers in Sioux Falls.
One may get feel optimistic, he said, when adding up the combined total of emerald ash borers affected by woodpeckers, natural enemies and cold.
“But remember, every female emerald ash borer can live for about 80 days, so the population just keeps building and building and building,” Ball said.
He also indicated an important reason for communities to consider removing ash trees as soon as emerald ash borers are found. Using Sioux Falls, with its 85,000 ash trees as an example, Ball noted, with the help of a graph, that tree mortality would remain fairly constant for the first six years or so. But between the seventh and 10 years of infestation, the tree fatality numbers skyrocket to a total of 61,000.
“That’s a lot of trees lost over a very short time,” he said. “Nobody has the resources to cut down that many trees in that short of a time period.” And, he noted, dead or dying ash trees must be cut down because they can easily fall down. “They become very hazardous,” Ball said.
Sioux Falls has begun removing healthy ash trees now, he said, simply to spread the costs of that over a longer period of time.
Ball advises homeowners with ash trees to consider treating those that they like and removing any of that variety that they simply aren’t that fond of.
“If you’re not going to treat the ash, you’re going to lose it,” he said. “It’s an absolute guarantee.”
The emerald ash borer has not been detected Vermillion, so homeowners with “favorite” ash trees don’t have to worry about treating them to save them from the insect – yet.
“But right now is a good time to start making decisions. What ash trees do you have that you don’t like?” Ball asked. “Trees that you have no interest in keeping – it’s cheaper to remove them now rather than later.
“Treatments are very effective, but I tell people there are trees that shouldn’t be treated,” he said. “Trees that are already decayed and rotting, trees that have hollows in them, trees that are pretty much dead – we don’t need to treat those.”
The best treatment of ash trees is to use a system that pumps chemicals directly into them to minimize the damage. He used Sioux Falls, once again, as an example of how much treating a tree will cost.
“If you take the diameter of a tree at about chest level and multiply it by 10 – that’s going to be your price,” Ball said. “That’s today dollars in Sioux Falls and it’s a rough estimate.”
He tells homeowners that once they decide to treat a tree, after the emerald ash borer has been confirmed to be in their community, they must treat it five times every two years over a 10-year period.
“And then after that, you’re going to do it every three or four years,” Ball said.