FOR THE LOVE OF TREES

BY MITCH HURST THE NORTH SHORE WEEKEND

There’s no definitive answer to the age-old question, “If a tree falls in the forest, and no one is around to hear it, does it make a sound?”

If a tree falls on the North Shore, especially if it’s in our front or back yard, there’s a very good chance we’ll both hear and see it. No one wants that feeling, as a homeowner, of losing a tree, which we may have come to view over time as a kind of natural friend.

The history of oaks on the North Shore and throughout much of Illinois is, pardon the pun, rooted in the type of land that sprouted them. Prairie lands, to be exact. Prairies are unique because they have heavy clay soil, but they also have a lot of organic matter and are very resilient. But over the years, as land was developed, the soil lost many of its benefits.

“Now we're left with soil that’s not as resilient. Really healthy soil is like a kitchen sponge. It's porous and kind of mushy, but it bounces back, and half of that porous space should be occupied by water,” says David Horvath of The Davey Tree Expert Company in Lake Bluff. “The other half of that porous space should be occupied by soil, air, or oxygen.”

Riding lawn mowers, trucks, and landscape equipment squishes the sponge down when running over the soil and unfortunately, North Shore soil doesn't bounce back up. So much of the space has been eliminated and that negatively impacts the trees. The key to maintaining a healthy tree is to make sure the soil underneath is doing its job.

You can think of Horvath and his colleagues at Davey as tree and soil physicians. Trees, like humans, can suffer from a variety of diseases, some unique to their regions. Also, like humans, some tree diseases are not visible to the eye, and can only be diagnosed with a proper checkup. Others can be seen in tree trunks or leaves.

On the North Shore, oak decline—an umbrella term used for diseases and other factors that can harm oak trees—can occur due to improper planting, compaction, construction damage, flooding, and drought. Living causal agents of oak decline include leaf defoliating diseases, leaf defoliating insects, cankers, wood decaying fungi, and wood-boring insects.

Horvath says two particularly invasive causes of tree disease are the two-lined chestnut borer, an insect that is attracted to diseased or weakened oaks, and the hypoxylon (hypo) canker, a fungus with a fondness for red oaks that can ultimately lead to their deaths. Homeowners can be easily fooled because some diseases mimic others, such as wilt, but wilt is prevalent in Wisconsin, and is not yet been found on the North Shore.

“We've been to a lot of properties where people have said, “It’s wilt” and we know it’s hypo, and it's a completely different animal. It is just as quick as oak wilt and very destructive and can be fatal,” says Horvath. “When we talk about what's happening on the North shore, it’s a native pathogen, so it exists here naturally.”

Pretty much all oak trees, when swabbed, will turn up hypo in the culture. Horvath says hypo is opportunistic in its behavior, and it waits for its host to become weakened or stressed. Once that happens, it becomes very aggressive.

“It ties in very well with our native two-line chestnut bore. When its host gets really stressed, it becomes attracted to that host. So really, the bigger picture in this region is this kind of complicated term that we call oak decline,” he says. “That's just looking at a big picture and knowing it's not one thing; it's a combination of different factors coming together that's causing the mortality in our oak trees.”

What’s frustrating for homeowners is a lot of times they want something that is well defined. A tree has a certain disease, and they want to treat it and get it over with. But Horvath says in dealing with decline, there are multiple factors. It was in 2021 that he started noticing more and more oaks dying rather quickly. Fluctuating weather patterns took their toll.

“If we look at the environment, we had gone through several springs of really heavy spring rains. It wasn't a consistent spring where we would get a couple of nice rain showers a week,” he says. “It was where we would go a week or a week-and-a-half without rain, and then we would just get a very significant rainfall.”

In short, not given time to adjust, the soil just can’t keep up. The other part of the equation is in the past couple of years there have been some significantly wet springs, but long periods of draught in summer.

“We come to homeowners in the spring with a retraction of a root system associated with a flooding injury, and then we go into summer where we have drought, which is going to cause even further retraction of that root system because now we're extremely dry,” he says. “So, we have these trees that are experiencing so much root loss and that's a huge stressor for a tree. That sets the stage for these other organisms like hypo.”

Depending on what level homeowners want to care for their trees, there are a number of treatment options. If a tree has the two-line chestnut bore, Horvath says, Davey can come in with very effective treatments to eliminate that pest. If homeowners want to look at the bigger picture, they have to start looking how they can change the oak’s growing environment to make the tree more successful.

“If we can start having the discussion with customers to be open to putting in mulching and getting rid of turf grass, we can come in with air tools and reinvigorate the soil,” he says. “We can work in compost. We can work in materials like biochar so that soil has more resilience to it.”

The reality is North Shore oaks have been under stress for decades, and homeowners might not know or see what’s lurking in them or in the soil.

“We don't see it right away. If we look up at the top of a tree and we just see green leaves, we think everything's great, but lying underneath is a lot of stress,” says Horvath. “It really has to do with what's under our feet, and we just don't see that. We ignore it, and that's why these oaks can suddenly go from looking otherwise healthy to, ‘Wow, there’s something wrong’.”

The Davey Tree Lake Bluff is located at 28913 North Herky Drive, Suite 306, in Lake Bluff. For more information, call 866-530-2719.