Got Nature? Blog

Join Purdue Extension forester Lenny Farlee in this episode of “A Woodland Management Moment” as he highlights the breeding programs with the native Indiana tree Butternut. This episode introduces viewers to the once frequently found species and why there’s been a notable decline in its population. Watch the video to learn the reason behind butternut’s decline, how we have been trying to combat that with conservation efforts and details about how butternut grows.

 

If you have any questions regarding trees, forests, wildlife, wood products, or other natural resource topics, feel free to contact us by using our Ask an Expert web page.

Resources:

ID That Tree: Butternut
Hardwoods of the Central Midwest: Butternut
Hardwood Lumber and Veneer Series: Butternut, The Education Store
Morton Arboretum: Butternut
Identification of Butternuts and Butternut Hybrids, The Education Store
Conservation and Management of Butternut Trees, The Education Store
The Plight of the Butternut
HTIRC Seed Propagation Protocol for Purdue and Hybrid Butternut
Purdue Arboretum Explorer
Butternut, Native Tree of Indiana River Walk, Purdue Fort Wayne
The Woody Plant Seed Manual, U.S. Forest Service
A Woodland Management Moment, Playlist, Purdue Extension – Forestry and Natural Resources (FNR) YouTube Channel
Conservation Tree Planting: Steps to Success, Purdue Extension – FNR YouTube Channel
Shrubs and Woody Vines of Indiana and the Midwest, Purdue University Press
Native Trees of the Midwest, Purdue University Press
ID That Tree, Playlist, Purdue Extension – FNR YouTube Channel
Investing in Indiana Woodlands, The Education Store
Woodland Stewardship for Landowners Video Series, Playlist, Indiana Department of Natural Resources YouTube Channel
Ask an Expert: Tree Selection and Planting, Purdue Extension – FNR YouTube Channel
Forest Improvement Handbook, The Education Store
Find an Indiana Professional Forester, Indiana Forestry & Woodland Owners Association (IFWOA)
Purdue Arboretum Explorer

Lenny Farlee, Extension Forester
Hardwood Tree Improvement and Regeneration Center
Purdue Department of Forestry & Natural Resources

---

Several things come into play when it comes to determining the colors that we find on leaves of our trees. As our days get shorter and our nights get longer there is a chemical change that happens in the tree. In this video Lenny Farlee talks about the several pigments that are found in trees and what changes from summer to fall that brings us the bright colors on leaves.

Explore IndyStar Story Behind Our Fall Colors
For more on what determines the specific colors our leaves turn and how weather and other factors influence the fall display check out this recent IndyStar article: What determines what color leaves turn in the fall? The story features insights from Lenny Farlee, Purdue Extension forester, who shares his expertise on the science and beauty behind Indiana’s fall foliage.

Fall Foliage by Tree Species (click on the image to expand)

Resources:
Indiana Fall Foliage Map, Explore Fall
Why Fall Color is Sometimes a Dud, Purdue Landscape Report
U.S. Forest Service Website and Hotline, Highlight Fall Colors on National Forests
ID That Tree Fall Color: Sugar Maple, Purdue Extension – Forestry and Natural Resources YouTube Channel, ID That Tree Playlist
ID That Tree Fall Color Edition: Black Gum, Purdue Extension – FNR YouTube Channel, ID That Tree Playlist
ID That Tree Fall Color Edition: Shagbark Hickory, Purdue Extension – FNR YouTube Channel, ID That Tree Playlist
ID That Tree Fall Color Edition: Virginia Creeper, Purdue Extension – FNR YouTube Channel, ID That Tree Playlist
ID That Tree Fall Color Edition: Winged Sumac, Purdue Extension – FNR YouTube Channel, ID That Tree Playlist
Autumn Highlights Tour – South Campus, Purdue Arboretum Explorer
Why Leaves Change Color – the Physiological Basis, The Education Store, Purdue Extension resource center
ID That Tree, Playlist, Subscribe to Purdue Extension – Forestry and Natural Resources YouTube Channel

Lenny Farlee, Extension Forester
Purdue University Department of Forestry and Natural Resources
Hardwood Tree Improvement & Regeneration Center (HTIRC)

---

As the crisp autumn air settles in and campfires become a seasonal staple, October brings an important reminder: your firewood choices matter. That’s why October is officially Firewood Month, a nationwide campaign to raise awareness about the risks of moving firewood and the spread of invasive forest pests.

Why “Don’t Move Firewood” Matters
Transporting firewood, even just a few miles, can unintentionally spread destructive pests like emerald ash borer, Asian longhorned beetle and spongy moth. These invaders often hide inside or on firewood, threatening Indiana’s forests, parks and urban trees.

The Don’t Move Firewood website offers excellent resources to help you make informed choices. Whether you’re heating a cabin, heading out to hunt, or planning a backyard bonfire, they recommend:

• Buying firewood where you’ll burn it
• Choosing certified heat-treated wood
• Gathering wood on-site when permitted

You can also explore their Firewood Month Toolkit, maps of regulations and a webinar series designed for professionals and outdoor enthusiasts alike.

While October is Firewood Month, the risk of spreading invasive pests lasts well beyond the fall. Many forest pests remain a threat throughout the year. Adults may still be visible until the first hard freeze, and egg masses can be observed from now through June. The spotted lanternfly females lay egg masses in late summer through early winter, often peaking in October. These masses can survive through winter and hatch in the spring. Learn more about the Spotted Lanternfly from the Indiana Department of Natural Resources. This is why it’s important to practice safe firewood habits year-round.

Spotlight on ReportINvasive
Check out the latest post on the ReportINvasive Facebook which reinforces the importance of Firewood Month. ReportINvasive is a trusted source for updates on invasive species in Indiana, and their social media outreach is a great way to stay informed and engaged. Give the Facebook page a LIKE and FOLLOW for future webinars and workshops.

Concerned About Insects? Purdue Extension Entomology Can Help
If you suspect insect damage or want to learn more about forest pests, the Purdue Extension Entomology team is an outstanding resource. Their experts provide science-based guidance on insect identification, management strategies, and outreach materials to help protect Indiana’s ecosystems.

Let’s work together to keep Indiana’s forests healthy and resilient. This October, make the smart choice—don’t move firewood!

More Resources
Spotted Lanternfly – including map sharing locations, Indiana Department of Natural Resources
October is Firewood Awareness Month!, Purdue Landscape Report
Indiana Department of Natural Resources: Invasive Species
Indiana Invasive Species Council
Cooperative Invasive Species Management Area (CISMA)
Aquatic Invasive Species, Illinois-Indiana Sea Grant (IISG)
Emerald Ash Borer Information Network, Purdue University and Partners
Invasive plants: impact on environment and people, The Education Store, Purdue Extension’s resource center
Entomology Weekly Review, Indiana Department of Natural Resources, Division of Entomology & Plant Pathology
Division of Entomology & Plant Pathology, Indiana Department of Natural Resources

Diana Evans, Extension and Web Communication Specialist
Purdue University Department of Forestry and Natural Resources

---

Purdue Landscape Report: It’s finally October, and we should be enjoying lovely fall temps and colors. While some of the trees are changing, it’s not necessarily due to the change in seasons. As I write this, the temperature is 84 F (29 C). I look out my window and see mostly green leaves with some colors from the short cold snap we had and some from heat and drought stress. Whether you are worried about the trees in your yard and community or not, there are some simple tasks that we can do to assist them as we await the cooler temperatures of Autumn.

Mulching: One simple task to better prepare your trees for winter is to add a new layer of mulch, which benefits your trees in multiple ways. Adding a 2-3 inch thick layer of mulch will better maintain moisture levels and buffer extreme temperature changes in the soil and will add some organic matter too. Mulching to the drip line will benefit the tree the most, but in the case of larger trees it’s not always feasible. Try for at least a 3-foot radius from the trunk and make sure to leave a 2 inch or so gap between the trunk and the mulch. Remember, no volcano mulching.

Fertilizing: That mulch you just added will add some organic material to your soil as it slowly breaks down, but an autumn fertilization can benefit your trees too. Unlike trees in the forest that have a natural supply of nutrients from fallen leaves and twigs, trees around our homes are usually deprived as we rake and clean up our yards. Adding a slow-release fertilizer in the fall helps provide a nutrient boost over the winter, can promote root growth, and better prepare your tree for Spring.

Watering: Water is still an essential part of your tree care plan, but as temperatures drop and trees begin to head into dormancy they don’t need as much water as is required in the hit summer months. If you have irrigation systems in your yard start to drop the frequency of watering. You can water up until the first freeze, but make sure soils are just a little damp and not soaked. Evergreens in particular will benefit from slow deep watering 1-2 times a week until the soil freezes. Winter winds and temperatures can desiccate the needles without an adequate supply of water.

Pruning: Now is a good time to prune out any dead, damaged, or diseased limbs in your trees. If you have access to hand saws and pole saws or pruners, you can remove smaller branches or those closer to the ground. Make sure you are making proper pruning cuts though, and if there are large limbs, those at heights, or you are just unsure of how to make a good cut enlist the help of a professional arborist.

Trunk Damage: Sunscald or southwest damage occurs on young and/or thin barked trees in the winter. Wounds can occur between the south to southwest facing part of the trunk on sunny days in the winter as temperatures rise and suddenly drop. Over time these wounds can become quite large. Trees can also incur damage from deer during the rut. Bucks will scrape trees with their antlers, scraping off the bark and damaging the cambium. Both of these injuries can be reduced one younger trees by installing tree guards in the fall. Tree guards are plastic barriers you place around the main stem of the tree. I recommend using white corrugated drainage pipe that can be found at most home centers. You can make a cut lengthwise along the pipe for easy installation and make sure it has a large enough diameter to leave a space between it and the tree. Just remember to remove it come Spring.

Inspections: Visual inspections can be done year-round, but this time of the year it might be easier to see changes in your tree as leaves are falling and the canopy becomes more visible. From the ground up to the canopy, some of the things you’re looking for include fungal growth around the base of the tree, any sort of damage on the main stem or branches, premature leaf drop or color change, and branches that are dead, cracked, diseased, or seem weak. Any concerns you find are also great information to share with an ISA Certified arborist which can be found using the Trees Are Good website.

View the original article on the Purdue Landscape Report website: Help Your Trees Transition into Autumn.

Subscribe and receive the newsletter: Purdue Landscape Report Newsletter.

Resources:
Re-mulch Your Trees, Purdue Landscape Report
Find an Arborist video, Trees are Good-International Society of Arboriculture (ISA)
Trees and Storms – The Education Store, Purdue Education’s resource center
Moist soil and rotten roots makes it easy for trees to come crashing down – Fox 59 News
Expert: Some storm damage can be easily prevented – Fox 59
Why Is My Tree Dying? – The Education Store
Tree Risk Management – The Education Store
Tree Pruning Essentials, Publication & Video, The Education Store
Mechanical Damage to Trees: Mowing and Maintenance Equipment – The Education Store
Trees and Electric Lines – The Education Store
Tree Defect Identification, The Education Store
Planting Your Tree, video, Purdue Extension
Tree Installation, The Education Store
Tree Wound and Healing, Got Nature? Blog, Purdue Extension – Forestry and Natural Resources
Subscribe – Purdue Extension-FNR YouTube Channel

Ben McCallister, Urban Forestry Specialist
Purdue Forestry & Natural Resources

---

Purdue Landscape Report: Aspen, cottonwood, and poplar are all names for the fast-growing Populus tree species. Used widely for building materials, these trees are often located around ponds, riverbanks, and sloping areas toward water bodies (especially cottonwood). Cottonwood flowers produce little white tufted seeds that float through the air which a lot of people love (my kids included), unless it lands in their mouth. These beautiful trees are susceptible to a fungus that can cause significant damage under the right conditions: Marssonina (newer name is Drepanopeziza).

There are three species of Marssonina that can infect Populus – different tree species may only be susceptible to one of the Marssonina species. The fungi cause the same kind of disease and develop similarly on the host. Marssonina can infect the leaves, stems and seeds of Populus, which can lead to large amounts of leaf loss during wet weather, girdled stems and dieback, and aborted seeds. Since seeds can carry the fungus, the seed will take it with it to where it lands and can become infected immediately after germinating. It is common to see high disease severity in the canopy, but unless there is significant leaf loss (up to 70% defoliation) it may not reduce plant vigor. Leaf lesions typically develop as small black to brown dots or flecks which expand in size as time goes one. As the disease progresses, large areas of the leaf will become necrotic, creating odd dead blotches, potentially killing the majority of the leaf blade.

The fungus produces asexual spores in a small black pustule on the upper surface of the leaf which will eventually burst and release the spores during humid weather early in the spring. Marssonina will continue to produce spores and cause disease the whole season, creating repeat infections on the same tree. Symptoms tend to start lower in the canopy and ascend up the tree as the season progresses. The spores are spread by water splash, so rainfall will help spread this fungus in the landscape.

For trees planted in native landscapes, this disease will likely be inevitable and may make the foliage look less than stellar. That being said, removing leaves that drop or at the end of fall will reduce total inoculum for future seasons and can reduce total disease long-term. Similarly, trees that are stressed will typically develop increased disease severity, so if you are seeing large amounts of leaf spots or leaf loss, I would recommend employing stress mitigation strategies to keep the tree happy and healthy (fertilizer, mulch, irrigation as needed, etc.). If a tree appears to develop significant disease every year and has reduced limb growth, you may consider removing the tree if you are concerned it may die early and replace with a resistant clone, as disease susceptibility can vary greatly between clones of the same species.

View the original article on the Purdue Landscape Report website: Marssonina leaf spot and blotch of Poplar.

Subscribe and receive the newsletter: Purdue Landscape Report Newsletter.

Resources:
ID That Tree, Playlist, Purdue Extension – FNR YouTube Channel (Invasive White Mulberry, Siberian Elm, Tree of Heaven)
Eastern Cottonwood, Article, Purdue Fort Wayne
Find a Certified Arborist, Trees are Good-International Society of Arboriculture (ISA)
Video: Step by Step to Find an Arborist, Trees are Good-International Society of Arboriculture (ISA)
Professional Forester, Indiana Forestry Woodland Owners Association
District Forester, Indiana Department of Natural Resources, 10+ acres
Trees and Storms – The Education Store, Purdue Education’s resource center
Why Is My Tree Dying? – The Education Store
Tree Risk Management – The Education Store
Tree Pruning Essentials, Publication & Video, The Education Store
Tree Defect Identification, The Education Store
Planting Your Tree, video, Purdue Extension
Tree Installation, The Education Store
A Woodland Management Moment, Playlist, Purdue Extension – FNR YouTube Channel (Against Invasives, Garlic Mustard, Autumn Olive)
Woodland Stewardship for Landowners, Playlist, Purdue Extension – FNR YouTube Channel (Common Buckthorn, Japanese Barberry)
Indiana Invasive Species Council
Indiana Department of Natural Resources: Invasive Species
Subscribe – Purdue Extension-FNR YouTube Channel

John Bonkowski, Lead Extension Administrator
Purdue Department of Botany and Plant Pathology

 

---

We are thrilled to announce the launch of the Explore Oak Resources webpage — a dynamic new hub created by Purdue Forestry and Natural Resources Extension to celebrate and support one of Indiana’s most iconic tree groups: the oaks.

Whether you’re a landowner, educator, natural resource professional or simply an oak enthusiast, this comprehensive collection of science-based resources is designed to deepen your understanding and enhance your stewardship of oak ecosystems.

What You’ll Find
The new oak resource page is packed with tools and insights, including:

• Expert-reviewed publications on forest stewardship, oak regeneration, and habitat management
• Engaging videos like the ID That Tree series, featuring 17 oak species native to Indiana
• Webinars and podcasts exploring topics from oak woodland restoration to wildlife-friendly forestry
• Practical guides on threats like oak wilt and invasive beetles
• Seedling purchasing info for select white and red oak varieties developed at Purdue

Why Oaks Matter
Oaks are more than just majestic trees — they’re keystone species that support biodiversity, provide critical wildlife habitat and contribute to Indiana’s ecological and cultural heritage. With challenges like invasive pests and regeneration difficulties, informed management is more important than ever.

Start Exploring
Ready to dive in? Visit the new Explore Oak Resources page and discover how you can help steward Indiana’s oak landscapes for generations to come.

Other Resources of Interest:
Purdue Extension – Forestry and Natural Resources (FNR) YouTube Channel:
A Woodland Management Moment, Playlist
Conservation Tree Planting: Steps to Success
ID That Tree, Playlist
Ask an Expert: Tree Selection and Planting
Woodland Stewardship for Landowners Video Series, Playlist

The Education Store – Purdue Agriculture’s resource center:
Investing in Indiana Woodlands
Forest Improvement Handbook

Purdue University Press:
Shrubs and Woody Vines of Indiana and the Midwest
Native Trees of the Midwest

Purdue Extension – FNR Got Nature? Blog:
Learn How to Support Oak-Hickory Ecosystems
Inonotus Dryadeus, Butt and Root Rot of Oaks

Hardwood Tree Improvement & Regeneration Center (HTIRC):
Predicting the Height Growth of Oak Species Reproduction Over a 23-year Period Following Clearcutting,

Indiana Forestry & Woodland Owners Association (IFWOA):
Find an Indiana Professional Forester

Purdue Arboretum Explorer

District Foresters, Indiana Department of Natural Resources

Diana Evans, Extension & Web Communications Specialist
Purdue University Department of Forestry and Natural Resources

---

Dr. Rado Gazo, professor of wood processing and industrial engineering who has been a part of the Purdue Forestry and Natural Resources faculty since 1997, has been named as the 2025 recipient of the Wood Engineering Achievement Award – Lifetime Achievement by the Forest Products Society.

“I joined the Forest Products Society as a graduate student in 1990 and have actively participated in various roles ever since,” Gazo said. “While I did not seek this award, now that I have received it, I am very humbled by the recognition of my colleagues and peers.”

The Forest Products Society is a premier international not-for-profit technical association founded in 1947. The award recognizes accomplishments and innovations in the discipline of wood engineering including structures, structural elements, building codes, consensus standards, design procedures and education.

According to the FPS announcement,

“Gazo has educated students, industry professionals and the public about the applications of industrial engineering and operation research techniques to problems in primary and secondary wood products manufacturing industries. His research and development activities have focused on evaluating tree, log, and lumber quality using CT, laser, and image scanning techniques. His efforts led to the first commercially available industrial-grade CT scanner and related optimization software, as well as the first successful automated hardwood lumber grading system. Dr. Gazo also created Hardwood University for the continued education of hardwood industry professionals and landowners in the Central Hardwood Region.”

In 2020, Gazo created Hardwood University, a self-sustaining collaborative program with the Indiana Hardwood Lumbermen’s Association, which aims to provide hardwood industry professionals and landowners in the Central Hardwood region with cutting-edge information and training. Gazo is one of the primary instructors for the program, which trains around 200 professionals annually.

Hardwood University, which consists of 10 sessions annually, is intended for new employees in the hardwood industry as well as those preparing for advancement or cross-training. The program, which takes place monthly at various Indiana hardwood plants and Purdue agricultural centers, offers informational and technical sessions on topics ranging from forest taxation to tree and log scaling and grading; log bucking; marketing hardwood veneer, stave and sawlogs; grade-sawing lumber; air drying and kiln drying lumber; hardwood lumber grading; lean manufacturing and logistics; and sawmill efficiency and quality control.

In addition, Gazo has worked with more than 130 companies, providing technical assistance, troubleshooting and consulting services as well as implementation of manufacturing best practices.

Most recently, Gazo was named among Purdue researchers working on the Indiana Wood Utilization Team, which will aim to create and implement a strategic plan to increase awareness of the benefits of using forest resources in the state, after gathering input from an industry advisory board and a series of roundtable discussions across the state.

Gazo has authored or co-authored more than 320 publications and has given more than 450 presentations in his field.

In 2017, he received the Southern Regional Extension Forestry Award for Excellence for the online book chapter “Critical Factors Affecting Supply Chain Management: A Case Study in the US Pallet Industry,” coauthored with Dr. Henry Quesada and Scarlett Sanchez.

To view this article along with other news and stories posted on the Purdue Forestry and Natural Resources website view: Rado Gazo Receives Lifetime Achievement Award from Forest Products Society.

Resources:
Wood Products Manufacturing Technology Minor, FNR Minor
Hardwoods of the Central Midwest, The Purdue Arboretum
Wood Products, Purdue Extension – Forestry & Natural Resources (FNR)
Wood is Best Video, Forestry and Natural Resources YouTube Channel, Woodisbest.org
An Introduction to Trees of Indiana, The Education Store, Purdue Extension resource center
Native Trees of the Midwest, Purdue University Press
Shrubs and Woody Vines of Indiana and the Midwest, Purdue University Press
ID That Tree, Playlist, Subscribe to Purdue Extension – Forestry and Natural Resources YouTube Channel
A Woodland Management Moment, Playlist, Purdue Extension – FNR YouTube Channel
Investing in Indiana Woodlands, The Education Store
Forest Improvement Handbook, The Education Store
Finding help from a professional forester, Indiana Forestry & Woodland Owners Association
District Foresters for 10 plus acres, Indiana Department of Natural Resources
Hardwood Tree Improvement & Regeneration Center (HTIRC)

Wendy Mayer, FNR Communications Coordinator
Purdue University Department of Forestry and Natural Resources

---

With rainfall well below average, watering your trees is more important than ever. Indiana typically receives around 3.14 inches of rain in September, but as of 2025, only 1.31 inches have fallen—making this month even drier than last year. These conditions can lead to dry, wilted leaves and stress for trees across the state, especially during prolonged heat. To see how drought is affecting your area, visit the U.S. Drought Monitor for Indiana-specific maps.

In this video, Lindsey Purcell, Executive Director of the Indiana Arborist Association, explains why consistent watering is critical and shares practical tips to help your trees stay healthy through dry spells.

Extreme heat can have a major impact on tree health and survival. Water is the most limiting ecological resource for a tree, and without adequate moisture, decline and death are imminent. It reduces carbohydrate production, significantly lowering energy reserves and production of defense chemicals in the tree. Check out this publication titled Drought? Don’t Forget the Trees! to learn what to look for for any weakening issues including pests that like the dry conditions.

If you have any questions regarding wildlife, trees, forest management, wood products, natural resource planning or other natural resource topics, feel free to contact us by using our Ask an Expert web page.

More Extreme Heat Resources:
Climate and Drought Maps, Purdue Indiana State Climate Office
Summer Tree Care, Purdue Landscape Report
Drought? Don’t Forget the Trees!, The Education Store, Purdue Extension resource center
Extreme Heat Including Fact Sheets, Purdue Extension – IN-PREPared
Extreme Heat – Resources, Extension Disaster Education Network (EDEN)
Drought Information​, Indiana Department of Natural Resources
Planting Your Tree Part 1: Choosing Your Tree, Purdue Extension YouTube Channel
Tree Selection for the “Un-natural” Environment, The Education Store
Tree Pruning Essentials Video, Purdue Extension YouTube Channel
Tree Defect Identification, The Education Store
Tree Wound and Healing, Got Nature? Blog, Purdue Extension – Forestry and Natural Resources
Surface Root Syndrome, The Education Store
Submit Sample, Purdue Plant & Pest Diagnostic Lab
Find an Arborist, Indiana Arborist Association

Ben McCallister, Urban Forestry Specialist
Purdue Forestry & Natural Resources

---

 

Purdue Landscape Report: Tree care, in many cases, can be expensive if you require the assistance of an arborist for pruning or removals.  Extreme weather events, characterized by extensive rain and wind, can cause damage to the canopy or, in worst-case scenarios, lead to tree failure.  In cases of failures, weather is often the final push to already existing issues.  One cause that can lead to decay, decline, and failure if applied incorrectly can also extend the life of your tree with proper application.

Mulch is the double-edged sword that can promote healthy growth by maintaining soil moisture and temperature through extreme heat, cold, and drought, enrich the soil in the critical root zone, maintain a safety area from mechanical damage from lawn care tools, and add a nice aesthetic.

But it can also cause decay through excess moisture to the root flare, damage from pests like mice and insects that can live in mulch, expose the tree to pathogens, and promote unnecessary root growth and/or stem girdling roots that cut off nutrient supply between the root system and the rest of the tree.

The application is the same if it’s the first time mulching a tree or a re-application.  Add enough mulch so there is a 2–3-inch layer sloping away from the tree with at least a 3–5-foot radius around the stem (older, larger trees can benefit from larger mulch rings).  No volcano mulching, make sure you also have around a 1-2-inch gap between the stem and the start of the mulch ring.

If you are reapplying mulch, first rake the old mulch to even the layer and mix some into the soil if possible.  If your tree has already been mulched and has been volcano mulched, simply dig out the excess, exposing the root flare and creating that 1-2-inch gap between the stem and the mulch.

This simple act is relatively inexpensive, does not require a lot of time, and will help keep your tree healthy, extending its life.  If you notice any other issues with your trees, hiring an ISA Certified arborist is the next step in managing your trees’ health.  To find an arborist near you and verify credentials, use the link at Find an Arborist, Trees are Good, International Society of Arboriculture (ISA).

View the original article on the Purdue Landscape Report website: Simple Steps to Care for Your Tree: Mulching.

Subscribe and receive the newsletter: Purdue Landscape Report Newsletter.

Resources:
Re-mulch Your Trees, Purdue Landscape Report
Find an Arborist video, Trees are Good-International Society of Arboriculture (ISA)
Trees and Storms – The Education Store, Purdue Education’s resource center
Moist soil and rotten roots makes it easy for trees to come crashing down – Fox 59 News
Expert: Some storm damage can be easily prevented – Fox 59
Why Is My Tree Dying? – The Education Store
Tree Risk Management – The Education Store
Tree Pruning Essentials, Publication & Video, The Education Store
Mechanical Damage to Trees: Mowing and Maintenance Equipment – The Education Store
Trees and Electric Lines – The Education Store
Tree Defect Identification, The Education Store
Planting Your Tree, video, Purdue Extension
Tree Installation, The Education Store
Tree Wound and Healing, Got Nature? Blog, Purdue Extension – Forestry and Natural Resources
Subscribe – Purdue Extension-FNR YouTube Channel

Ben McCallister, Urban Forestry Specialist
Purdue Forestry & Natural Resources

---

Purdue Landscape Report: Recently, there has been an uptick in questions related to one of Indiana’s most notorious invasive pests: the emerald ash borer.  Homeowners, businesses, even professionals have asked if ash trees are still present in Indiana, and if the insect is still a threat to our ecosystem.  Emerald ash borer wreaked significant havoc among Indiana’s hardwoods, and a person could be forgiven for believing that there are no ash trees at all in our state, but this is simply not true.  Ash still survives in Indiana and can be found both as ornamental plantings and in untended woodlots; unfortunately, emerald ash borer is also still present and just as deadly to them as ever.  The question of protecting ash versus removal them is complex, but entomologists and tree specialists have learned from this insect’s invasion.

The emerald ash borer (Agrilus planipennis), a wood-boring insect native to Asia, is responsible for decimating ash (Fraxinus spp.) throughout the United States and elsewhere.  In Indiana, this insect’s presence was confirmed in 2004, though it had probably been in the state for some time before then.  Since its arrival, Hoosiers have been forced to watch as ash trees have rapidly declined and died due to the insect’s feeding and life cycle.  The insect lays its eggs in crevices in the bark of an ash that is 8 to 10 years old, and after hatching, the new larvae begin to bore through the tree’s cambium tissue. The tree relies on its cambium tissue to transport water and nutrients and supply cells for new growth.  Often, the only signs of the insect’s presence are a reduction in canopy coverage and D-shaped exit holes in the bark, indicating adult emergence.  As time goes on, however, the tree will continue to lose canopy, experience limb death, and often have large chunks of bark detach. Unprotected trees will typically die within 2 to 5 years of infestation.  Dead and dying ash trees represent a serious hazard to health and property as infestation will leave them extremely brittle. Brittle ash will often fall during weather events or even collapse over time as limbs fall off.

While emerald ash borer did significant damage to ash tree populations in Indiana, they did not destroy the population entirely.  While virtually all untreated trees will eventually become infested, saplings with a trunk diameter of ½ to 1 inch will remain untouched, allowing annual replacement of trees to continue.  Since the initial invasion killed so many trees, the borer’s populations have been proportionally reduced as well due to a lack of a food source.  This combination of factors has created a cycle of growth and infestation that allows both populations to survive, but at significantly lower levels as compared to the period of the initial infestation.  Unfortunately, this also means that emerald ash borer is now a permanent fixture in the hardwood ecosystem in Indiana.

While many may believe ash trees are a total loss, there are still options to protect ash tree and even rescue ash that have already been infested.  The first step in this process is to determine the extent of damage in a given tree.  As the cambium tissue is consume by ash borer larvae, the tree will experience a steady loss of canopy and limb death.  The proportion of lost canopy makes a great indicator for treatment viability.  For example, a tree that has only lost 10% of its canopy will normally respond well to treatment.  As more canopy is lost, recovery is more challenging, until the tree has lost %30 of canopy coverage.  After that point, there is very little chance that a rescue treatment will be successful, and removal will most likely be necessary.  It is also important to remember that limb death may occur; these limbs will not recover and will need to be removed to avoid any potential hazards.

There are several insecticides with varying ranges of efficacy that can be used to manage emerald ash borer.  These include imidacloprid, dinotefuran, azadirachtin, and emamectin benzoate. Several studies have been conducted to find the best combination of chemical and application type, such as the difference between using a soil drench compared to a trunk injection. While all of the above chemicals can be effective against the insect, the combination of emamectin benzoate applied through a trunk injection offers the best, longest lasting protection from infestation.  This combination has a durable effect lasting for two years under dense infestations.  However, the reduction in emerald ash borer populations have spread the distribution of the insect thinner, and longer intervals between treatments are possible.  A ten-year study conducted by Purdue University demonstrated that treating trees once every three years provided sufficient protection from the beetles, while also showing that 4 to 5 years after last treatment coincided with an increase in damage to the trees.  This same study also found that by six years post-treatment, the trees would decline to the point of making removal a necessity.  This research concluded that increasing time between intervals after three years increased the risk of catastrophic damage due to emerald ash borer activity, thus the recommendation for three-year intervals.

Ultimately, many will see this as a financial issue: the cost of treatment over time against the cost of removal to avoid potential damages.  The above study estimated the cost of treating a single tree with an emamectin benzoate injection at $300 per treatment. Since treatment only needs to happen once every three years, the cost per year per tree would be $100, approximately.  Tree removal was estimated between $1800 and $3600, depending on tree location and other factors.  Also consider replacement costs if you wanted to continue to grow ash in that area, and how long the tree would need to grow to match the size of the tree you just replaced.  Additionally, add in any treatment costs to make sure it survives infestation.  When looked at from this angle, maintaining regular treatment on rescuable trees would appear to be the most cost-effective route for managing ash.  Any treatment plan should be discussed with a professional, such as a certified arborist.

Read the original article posted in the Purdue Landscape Report April 2025 Newsletter: Revisiting Ash Tree Protection.

Subscribe and receive the newsletter: Purdue Landscape Report Newsletter.

Resources:
New Hope for Fighting Ash Borer, Got Nature? Purdue Extension-FNR
Invasive Pest Species: Tools for Staging and Managing EAB in the Urban Forest, Got Nature?
Emerald Ash Borer, Purdue Extension-Entomology
Emerald Ash Borer Tools & Resources – Purdue Extension Entomology
Planting Your Tree Part 1: Choosing Your Tree, Purdue Extension YouTube Channel
Tree Planting Part 2: Planting a Tree, Purdue Extension – Forestry and Natural Resources YouTube Channel
Indiana Invasive Plant List, Indiana Invasive Species Council, Purdue Entomology
Landscape Report Shares Importance of Soil Testing, Purdue FNR Extension
Find an Arborist website, Trees are Good, International Society of Arboriculture (ISA)
Tree Risk Management – The Education Store, Purdue Extension’s resource center
ID That Tree – Video Playlist, Purdue Extension – Forestry and Natural Resources (FNR) YouTube Channel
Purdue Arboretum Explorer
Conservation Tree Planting: Steps to Success, Purdue Extension – FNR YouTube Channel
A Woodland Management Moment, Playlist, Purdue Extension – FNR YouTube Channel
Woodland Stewardship for Landowners, Playlist, Purdue Extension – FNR YouTube Channel
Indiana Department of Natural Resources: Invasive Species
Indiana Invasive Species Council
Cooperative Invasive Species Management Area (CISMA)
Report Invasive, Purdue Extension
Native Trees of the Midwest, Purdue University Press
Professional Forester, Indiana Forestry Woodland Owners Association
Forest Improvement Handbook, The Education Store

Bob Bruner, Exotic Forest Pest Educator
Purdue Entomology

---