ASH TREE DECISION GUIDE • BISMARCK, ND
Should You Treat or Remove Your Ash Tree? A Bismarck Guide
Treat your ash tree if it’s healthy, well placed, and worth paying to protect every 2 to 3 years. Remove it if more than about 40% of the top is already dead, if it’s in a bad spot, or if you don’t want the ongoing cost. That’s the core of it.
Emerald ash borer (EAB) was found in Bismarck in late August 2026, so every ash in Bismarck, Mandan and Lincoln now needs a decision. The good news is you don’t have to make it this week. Bismarck’s city forester told residents in September 2026, “You’ve got time.” This guide walks you through the choice one tree at a time. For the bug itself, the quarantine and how to report it, see our emerald ash borer guide for Bismarck.
THE FIRST DECISION
The Quick Answer
Healthy and well placed, or already declining and hard to maintain? Start with these five comparisons.
| Lean toward treating if… | Lean toward removing if… |
|---|---|
| Less than about 40% of the canopy is dead | More than about 40% of the canopy is dead |
| It shades your house, patio or west windows | It’s crowded, leaning or has poor shape |
| It’s big and would be costly to replace | It’s small and cheap to replace |
| It’s well away from wires and the roof | It grows into utility lines or over the roof |
| You’ll pay for treatment every 2 to 3 years | You’d rather pay once and replant |
The 40% line comes from NDSU Extension: trees with more than 40% canopy decline "are not likely to recover from EAB damage and should not be treated."
FIVE QUESTIONS • ONE TREE
Five Questions That Decide It
Answer these in order. Most people know their answer by question three.
1. Is It a True Ash?
True ash has buds directly across from each other and leaves with 5 to 11 leaflets. Mountain ash, with its red-orange berries, is not a true ash and can’t get EAB. Neither can boxelder.
2. How Much of the Top Is Dead?
Stand back far enough to see the whole crown, across the street if you have to. Look at the top third. Is it full, or can you see bare gray twigs against the sky?
- Under about 40% bare: the tree can still be treated.
- Over about 40% bare: removal is the better call.
- Leafy sprouts on the trunk, bark splits or woodpecker flecking: the tree is under attack, even if the top still looks okay.
Here’s a local catch. Green ash turns yellow and drops its leaves early in the fall, so a late September tree can look thinner than it really is. If you’re unsure, judge the crown next summer, in June through August, when a healthy ash is fully leafed out. In winter, watch for woodpecker damage instead, which shows best when the leaves are off.
3. How Big Is the Trunk?
Measure the trunk all the way around at 4.5 feet off the ground, then divide by 3.14 to get the diameter.
Size matters two ways. NDSU says homeowners treating trees larger than 15 inches across "should consider having a professional treat their trees because higher rates and multiple applications may be necessary." Size also drives cost, since treatment is usually priced by trunk diameter, and removal gets pricier as trees get taller.
4. Where Is It Growing?
The same tree can be worth saving in one spot and not in another.
- Worth protecting: an ash on the south or west side that shades the house in July, or the one big tree that makes a new-build yard in north Bismarck feel finished.
- Worth replacing: an ash crowded against a garage, growing into utility lines, hanging over the roof, or planted too close to the foundation.
University of Wisconsin entomologists say a healthy, well-placed ash that gives shade "adds value."
5. Will You Keep Paying Every Few Years?
Treatment isn’t a one-time fix. NDSU says emamectin benzoate trunk injections protect a tree for about 2 to 3 years, then it needs another. If you don’t want a recurring bill, removal and replanting may fit you better.
TREATMENT COSTS • REMOVAL COSTS
Treating vs. Removing: What It Costs Over Time
This is the part most guides skip. Purdue University entomologists ran the numbers for a large, 30-inch ash (published May 2023):
| Cost item | Purdue estimate |
|---|---|
| Trunk injection, every 3 years | About $300 each time |
| Removal with stump | About $1,800 |
| Removal near buildings | About $3,600 |
| Planting a replacement | About $500 more |
Their point: the $1,800 to $3,600 you’d spend on removal pays for about 18 to 36 years of treatment. Add the replacement tree and it covers 23 to 42 years.
There’s a second cost people forget. Purdue notes a new tree grows "a bit less than a half an inch per year" in trunk diameter. A young tree planted in 2027 won’t give you the shade of a mature ash for decades.
Prices vary a lot by market, so treat these as estimates, not quotes. Published Bismarck cost guides put local tree removal around $400 to $1,900 depending on height, with averages near $780 (LawnStarter, September 2026) and about $1,100 (HomeBlue, 2025). Stump grinding usually costs extra.
What a Smaller Yard Ash Might Cost
Most Bismarck yard ash are smaller than Purdue’s 30-inch example. A February 2026 industry cost guide from A.M. Leonard lists professional injections at roughly $7 to $16 per inch of trunk diameter for each two-year treatment. By that range, a 16-inch ash would run about $112 to $256 per treatment. That’s our math from a national range, not a local quote.
For small trees, Wisconsin Extension puts homeowner products at "roughly $20-50/year" for a trunk about 10 inches across. Soil products like these usually have to be applied every year.
THE BISMARCK CALENDAR
The Timing in Bismarck: Decide This Fall, Act by Spring
EAB work in North Dakota follows the calendar.
| When | What to do |
|---|---|
| Fall 2026 | Find your ash, measure, rate the crown, get estimates |
| November to April | Best window to remove ash, per the University of Minnesota, since it "lowers the chances of spreading EAB" when the wood is moved |
| Early to mid-May | NDSU’s best window for homeowner soil drenches |
| Mid-May to mid-June | NDSU’s window for trunk injections, as leaves come out and before eggs hatch |
| Mid-June to mid-July | EAB adults fly in North Dakota |
What this really means is you haven’t missed anything. The next injection window is spring 2027. Use fall and winter to decide, get on a tree service’s spring list, and schedule removals for the dormant season, when frozen ground is easier on your lawn.
WHY TIMING MATTERS
Why Waiting Too Long Costs You
"You’ve got time" doesn’t mean you can wait forever. The North Dakota Department of Agriculture warns that once infested, "an ash tree can die in as little as 2 years."
A dead ash is a different job than a live one. The University of Minnesota Extension says dead ash branches "become brittle, making it much more challenging and dangerous to cut down," and EAB brings decay fungi that can rot branches quickly. It also says, "It is easier and less expensive to remove the tree while it is alive."
So pick your lane while the tree is still healthy. Treat it before decline sets in, or remove it before it dies.
BEFORE YOU HIRE AN ARBORIST
If You Treat It: What to Ask the Tree Service
Any paid tree work inside Bismarck needs a city commercial arborist license. Before anyone injects your tree, ask:
- Are you on the City of Bismarck’s licensed arborist list?
- Who’s the certified pesticide applicator on the job?
- What product are you using? Emamectin benzoate injections are what NDSU reports as giving better than 99% control for at least two years.
- How did you figure the dose? It should be based on your trunk diameter.
- When is the next treatment due? Write it on your calendar.
IF REMOVAL IS THE RIGHT CHOICE
If You Remove It: Plan the Wood and the Replacement
Plan the Wood
The wood stays put. Burleigh County is under a state quarantine. Ash logs, branches, wood chips and hardwood firewood can’t leave the county without a permit, and fines can reach $5,000. Hauling Bismarck ash across the river to Mandan counts, since Mandan is in Morton County. Ask your tree service where the wood and chips are going before the tree comes down.
The Replacement
The replacement. Don’t plant another ash, and pick something different from your block. NDSU’s recommended tree list for North Dakota limits maples on soil above pH 7.2, and a lot of Bismarck clay runs alkaline. Plant soon after removal, since a new tree takes years to catch up. Our tree services page covers removal, stump grinding and replacement planting. For more planting choices, see the best trees and shrubs for Bismarck and learn how to protect the new tree from rabbits and deer.
CITY-OWNED TREES
Boulevard Ash Are the City's Call
The tree between your sidewalk and the curb belongs to the City of Bismarck. Don’t treat, prune or remove it yourself. The city plans to treat about 2,600 of its roughly 5,200 boulevard ash over 3 years and remove the other 2,600 over 4 years. For questions about the tree out front, contact the City of Bismarck Forestry Division.
Questions
Treat or Remove Ash Tree FAQ
Helpful answers about ash treatment, removal, timing, and replacement in Bismarck.
Still deciding about an ash tree?
Compare options using the guide, then speak with a qualified local professional.
Do I have to remove my ash tree now that emerald ash borer is in Bismarck?
No. Finding EAB in Bismarck doesn’t mean every ash has to come down. A healthy ash with less than about 40% of its canopy dead can be protected with treatment. The city forester’s advice to homeowners was, “You’ve got time.”
Is it worth treating an ash tree?
Often, yes, if the tree is healthy, well placed and gives you shade. Purdue University figured the cost of removing a large ash pays for about 18 to 36 years of treatment. It’s usually not worth it if more than 40% of the canopy is dead or the tree is in a bad spot.
How much does it cost to treat an ash tree compared to removing it?
Purdue University estimated about $300 per injection every 3 years for a 30-inch ash, compared with $1,800 to $3,600 to remove it plus about $500 to plant a new tree. Published Bismarck cost guides put local tree removal around $400 to $1,900, depending on height. These are estimates, not quotes.
When is the best time to treat an ash tree in North Dakota?
NDSU says trunk injections work best from mid-May to mid-June, as the leaves come out and before EAB eggs hatch. Homeowner soil drenches are best in early to mid-May.
When is the best time to remove an ash tree?
The University of Minnesota recommends November to April, when EAB adults aren’t active, to lower the chance of spreading it. Remove a declining ash before it dies, because dead ash turns brittle and becomes harder and more dangerous to take down.
Can I treat my own ash tree?
For smaller trees, yes. NDSU lists an imidacloprid soil drench and a dinotefuran bark spray for homeowners. For trees larger than 15 inches across, NDSU says to consider a professional. Always follow the product label.
For more information, explore more ash tree questions.
Bismarck Landscape
Want a Second Opinion on Your Ash?
If you can’t tell whether your tree is at 30% or 50% dieback, we’ll give you a straight answer on treating, removing or waiting.
Contact Bismarck Landscape, or see our other contact options. For more local answers, visit our FAQ.