Purdue Agriculture News: As autumn settles in, we eagerly await the transformation of leaves into vibrant hues of red, orange and yellow. However, this year might tell a different story due to prolonged periods of hot weather. Ben McCallister, urban forestry specialist in Purdue University’s Department of Forestry and Natural Resources, sheds light on what to expect this fall.
The Impact of Weather on Fall Foliage Timing
“Right now, we’re seeing a mix of fall coming in and shifting temperatures, which is causing trees to respond. This back-and-forth hot weather is creating some color changes related to drought and stress. This can be expressed as brown color where leaves are starting to wilt and look a little crunchy from exposure to heat and drought stress,” McCallister explains.
While the typical color change occurs from mid-September to early November, it’s not unusual for leaves to remain green at this point in the season. McCallister suggests that while the hot weather “most likely won’t affect anything visually, it could influence fall foliage over time as climate change progresses.”
He anticipates a more pronounced display of fall colors extending through October, with some species showing their colors into November. Ultimately, the vibrancy and timing of these changes will depend on daily temperature fluctuations and the amount of sunlight trees receive.
The environment also plays a significant role in how trees respond. For instance, urban areas with more concrete and buildings create a “urban heat island” effect, which can delay color changes compared to more rural settings.
The Science Behind Color Transformation
The science of fall foliage is both fascinating and complex. McCallister explains that different tree species respond to autumn at varying times, with chlorophyll being a key player in this process.
“Changes in chlorophyll production leads to the color changes in leaves. Chlorophyll allows leaves to take up sunlight and convert it into energy, creating carbohydrates in the form of sugars – really anything that gives energy to the tree to help it grow, sustain itself and compartmentalize,” McCallister notes.
As temperatures cool and the sunlight diminishes, chlorophyll production declines, allowing the green hues of leaves to fade. This decline reveals carotenoids and anthocyanins – two chemicals essential to fall foliage. Carotenoids contribute to the yellow and orange shades, while anthocyanins produce reds and purples. As chlorophyll wanes, these vibrant colors emerge.
“It’s a very cool process,” McCallister adds. “Each color absorbs different spectrums of light, altering energy uptake and preparing trees for leaf drop and dormancy. As leaves in deciduous trees transition, trees store energy in their roots and wood so they can brave the winter.”
Viewing Fall Foliage
When it comes to enjoying fall foliage, McCallister emphasizes that Indiana offers many great viewing locations not far from Purdue’s campus.
Locally, Martell Forest, which is open to the public, is a great spot to check out the fall foliage and immerse yourself in the woods,” says McCallister.
What’s Next?
Leaf drop is likely to occur anytime from mid-October into December, although this process may take longer than usual due to the milder winters we’ve been experiencing. Similar to color changing, the timing of leaf drop varies by tree species and their growth patterns, as well as the overall weather conditions.
“For instance, ginkgo trees turn this brilliant yellow and have a cool reaction to leaf drop. Typically, all their leaves fall within a day or so, creating a carpet of yellow. In contrast, trees like maples and oaks, which have a mix of yellow, orange and red leaves, tend to hold onto their foliage a bit longer,” McCallister recalls.
It’s also important to note that while coniferous trees, like pines, spruces and furs, retain their needles year-round, some conifers like bald-cypress trees drop theirs. This sometimes causes confusion for homeowners who mistake these deciduous conifers for dying trees.
To provide the best care for your trees during these changing weather patterns, McCallister advises familiarizing yourself with different tree species. Resources like Google and dichotomous keys in forestry books can help with species identification and lead to tips for care. Regularly checking your trees’ health is essential year-round. Specialists in your local county Extension offices and ISA Certified Arborists can be valuable resources for proper tree management.
Lenny Farlee, sustaining hardwood Extension specialist for Purdue’s Department of Forestry and Natural Resources (FNR), has been named a 2024 Fellow of the Society of American Foresters (SAF). The SAF Fellow Award, one of the highest honors bestowed on an SAF member by their peers, recognizes long-standing service to forestry at the local, state, regional and national levels.
Farlee was honored with the award during the 2024 SAF National Convention, which took place in Loveland, Colorado from Sept. 17-20.
Zhao Ma accepts the 2024 Family Forests Education Award on behalf of Lenny Farlee and the other project team members.
“Being named a Fellow of the Society of American Foresters is particularly meaningful to me since it originates from a nomination by my peers at the state level,” Farlee said. “I am very grateful that my colleagues in forestry here in Indiana considered my service worthy of recognition, and I owe much of the credit to them for their support of me through my career. It has been my privilege to serve the people and the profession as an Extension forester here at Purdue.”
Farlee educates people about forestry in many ways, including through the popular Extension YouTube series “ID That Tree,” which has over 100,000 views.
Farlee, Ronald Rathfon, Don Carlson, Jonathan Ferris,Dave Osborne and Phil Woolery worked together to develop the course. The course introduces forest landowners to the biology and management of forests and what resources and professional assistance are available. According to survey results from 2021 participants, “94.4% stated that the information was useful to help them make future decisions and 92.5% stated that the information was useful to help act to manage their property objectives.”
“We in FNR, along with forestry professionals in Indiana and the landowners who have communicated with Lenny and his colleagues through the ‘Forest Management for the Private Woodland Owner’ course, know how valuable this program has been to sustainable forest management in Indiana,” said Zhao Ma, interim department head and professor of forestry and natural resources. “So it is absolutely wonderful when others outside of our FNR community and beyond Indiana also recognize the excellent work that Lenny and his colleagues have been doing…, I would also like to share one more note about Lenny – not only has Lenny been a highly valued and respected member of FNR and the forestry profession for many years, but he is also one of the nicest people I have met. He is knowledgeable yet humble, effective yet gentle, serious about his work yet able to have fun, very busy yet always willing to help others and try to be present. We are lucky to have Lenny as our colleague in FNR.”
Purdue Landscape Report: August was National Check Your Tree Month, but this is something that every tree owner/manager should be doing year-round. As the last hot days of summer are finishing up and we look forward to cooler fall days, we can look to our trees for different signs of trouble.
Most people tend to look up at the canopy before anything else in trees. Check leaves for dieback, discoloration, stickiness or signs of chewing. Check branches and the main stem for damage like splits and breaks, peeling bark, tunneling patterns under the bark, oozing wet spots, or sawdust around the tree. These could be signs of issues in the root system, pathogens like bacteria or fungal organisms, insect problems, or structural damage.
This is not an exhaustive list and if you notice these or anything else that seems off, it could be time for a deeper dive into what might be wrong. If you know the species of your tree the Purdue Plant Doctor is a great tool to narrow down a diagnosis. You can also contact your local Extension office or an ISA Certified Arborist.
On a more positive side, you don’t have to be on the lookout for damage, decline, or signs of pathogens and pests. It is also a matter of enjoying the trees in your landscape. Take some time out of your day to sit in the shade especially as we transition from hot summer temperatures into the cooling of autumn. Revel in the color changes as chlorophyll production slows revealing the carotenoids (that give us yellows, oranges, and browns) and anthocyanin (that produces reds and purples). In winter, not only can you better see damage in the canopy hidden by leaves in the growing seasons, but also the structure and architecture of the canopies in different tree species and the differences in bark textures. And in Spring, new growth of leaves and flowers shows us Winter is nearing its end, bringing warmer days.
So check your trees throughout the year. But not only for potential issues and risk management but also for enjoyment. Trees offer us no many benefits and sometimes it takes a little reminder. If you do see any signs of decline or damage, again, be sure to contact your local Extension office or an ISA Certified Arborist.
MyDNR,Indiana’s Outdoor Newsletter: Hunters can apply for reserved hunts at on.IN.gov/reservedhunt, the one-stop information spot for the hunts. The online method is the only way to apply. No late entries will be accepted. Applicants must possess a hunting license that’s valid for the hunt for which they apply.
Applications must be submitted by 11:59 p.m. ET on Sunday, Sept. 15. More specific hunt information for individual properties is available on the website.
Hunters will be selected through a random computerized drawing. An email will be sent to all applicants when draws have been completed. Applicants will be able to view draw results online within two weeks after the application period closes.
Please note that only one application per hunt is allowed. No changes can be made once an application is submitted. The application process is now consolidated into the online services website along with licenses, CheckIN Game, and HIP registration. An online account is not required to apply, but a Customer ID number is needed.
In this system, hunts without a registration fee will follow the same process as those with a fee. Applicants must add a hunt to their cart and place an order to submit their application. If the transaction total is $0, the applicant will not be asked to enter credit card information.
Purdue Landscape Report: As summer comes to a close, plants are rapidly releasing seeds and the most noticeable are the flying fluffy type. Thistles, asters and milkweed are just a few of the summer-flowering plants that depend on the wind to disperse their seeds, sometimes carrying them miles away to potentially suitable locations, though seeds typically land within a few meters of the mother plant. This may not be a concern if it’s a desirable plant, but can become extremely problematic when that seed comes from Canada Thistle (Cirsium arvense) (Fig. 1).
Figure 1. Canada thistle (Cirsium arvense), growing amongst common ivy (Hedera helix), produces a fluffy seed that is dispersed by wind.
Canada thistle is found on the list of Indiana Noxious Weeds (IC 15-16-7-2), which mandates that landowners take necessary steps to control and contain the spread of this highly invasive species. Formal enforcement of this Indiana Code falls to Township Trustees, though weed control is a responsibility that is often overlooked. Landowners and homeowners shouldn’t wait for a notice, or knock at the door, from a Township Trustee to begin controlling Canada thistle. It’s listed as a noxious weed for good reason.
Canada thistle is a perennial plant that can reproduce from seed or rhizomes making it difficult to control and contain. Each plant can produce thousands of wind-blown seeds that may remain viable for up to 20 years in the soil. Rhizomes are horizontal underground stems that can grow several feet and put out new shoots (Fig. 2). To add insult to injury, if a rhizome is cut or tilled, a separate plant may grow from each piece of rhizome.
Mechanical and cultural control options for Canada thistle are limited and may reduce plant density, but are not effective at eradicating large, established populations in a landscape. A new population, without an established root system, may be controlled with frequent mowing to deplete food reserves and prevent seed production.Small, isolated populations may be controlled with hand-pulling, but this will need to be repeated every few weeks.
Figure 2. Canada thistle (Cirsium arvense) reproduces by growing horizontal underground stems called rhizomes. Rhizomes can send up new shoots several feet from the mother plant.
Chemical control options include pre- and post-emergent herbicides and, in many cases, applications of both types are needed for complete eradication. A pre-emergent herbicide, with an active ingredient of dichlobenil, is effective at preventing seed from germinating, but will not control established plants. A post-emergent herbicide with the active ingredient of clopyralid is the most effective option for home gardeners. Clopyralid is a selective herbicide for broadleaf weeds, but most vegetable and ornamental plants are susceptible. Precautions should be taken to avoid off-target damage. Read and understand the herbicide label before use. The label is the law.
Regardless of the method used, complete control of an established Canada thistle population will take persistence over multiple seasons. If the fluffy seed is beginning to fly from your thistle patch, it will likely take many more seasons to rid the garden of this pest, but it is possible. To win the battle against Canada thistle, it takes serious grit and an effective herbicide, or a good realtor.
Purdue Landscape Report: Spotted lanternfly (SLF) has been the subject of a lot of media attention in the last few years. In the east, states like Pennsylvania and New York have been dealing with heavy infestations since the insect was first detected in 2014. In Indiana, this invasive planthopper arrived three years ago, infesting two counties on the eastern side of the state. Since then, the Indiana Department of Natural Resources and Purdue University have been working together to mitigate the spread of this insect as well as educate Hoosiers on what they can do to help. Spotted lanternfly is still on the move, and this update will help refresh you on how this bug works, and where they are headed.
Life cycle Spotted lanternfly is an annual insect, having only a single generation in a year under normal conditions. The insect goes through incomplete metamorphosis; immature stages, called nymphs, resemble smaller, wingless versions of the adults. Nymphs will begin to appear in April or May, developing through four instars, until they reach adulthood in late summer. With each instar, the period in between molting, the nymph will grow larger, develop wingpads, and eventually change color. Early instars are black with a white dot pattern, while later instars will be bright red with black and white patterning (Fig. 1). Late instar nymphs are often compared to milkweed bugs or lady beetles. Once they complete development in the late summer or early fall, they will mate and lay egg masses covered in a protective substance that makes them resemble mud. Eggs masses will overwinter until the spring, while adult insects will die as temperatures cool. In Indiana, depending on temperature, adults can be seen as late as early November.
Impact Spotted lanternfly is a sap-feeding insect, using syringe-like mouthparts to drain nutrients directly from plant tissues. Like other sap-feeding insects, the activity of SLF wounds the plant, creating openings for various pathogens to exploit. Feeding by SLF has been shown to reduce overall health of their hosts, reducing their capacity to survive overwintering, and potentially kill the host plant depending on species. They also produce a sugary waste known as honeydew; while honeydew itself is not harmful, it acts as a growing substrate for sooty mold, which can have a serious impact the photosynthesis of understory foliage as well as attract other nuisance insects.
Spotted lanternfly is a generalist herbivore and can feed on over 100 different species of plant and tree in Indiana. However, this insect has shown strong preference towards certain species, often with devastating consequences. The most preferred host is tree-of-heaven, an invasive tree species in North America. Tree-of-heaven is the primary host of SLF in their shared native range, and the insect appears to experience high reproductive success on it even when they share a new environment. Grapes are also highly preferred by SLF, and infestations will typically result in overfeeding and the death of the plant. Black Walnut, American river birch, and various maple species are also at risk of severe damage from this insect. Evidence has also suggested that maple, when used for syrup production, will experience reductions in yield and quality when attack by spotted lanternfly.
Where are they now? Spotted lanternfly has been present in Indiana since 2021, first arriving in Huntington and Switzerland Counties. In Huntington, the infestation occupies a stand of tree-of-heaven next to an industrial parking lot. Tree-of-heaven moved into the neighboring residential area, allowing SLF to also spread with it. The more rural infestation in Switzerland County was traced to a vehicle transported from Pennsylvania, and the insect has taken advantage of patches of tree-of-heaven in nearby wooded areas. While both infestations have strongly associated with the insect’s primary host, there is some evidence that SLF is beginning to take advantage of other nearby plants, such as maple. In the last year, SLF moved a significant distance and has been detected in several more counties, including Elkhart, St. Joseph, Porter, Allen, Dekalb, and Noble Counties. Most of the activity has been found on tree-of-heaven along rail lines, supporting the idea that the insect is dispersed by rail traffic moving westward out of infested areas.
It’s important to remember that trains aren’t the only vehicles that can have SLF passengers. These insects, and their egg masses, can be found on just about any surface, including the car you drive to work, the RV you used for recreation, semi-trucks that cross the country, and more. Purdue Entomology and Indiana DNR are encouraging everyone to inspect their vehicles when traveling through any of the infested areas. Also check all recreational vehicles and trailers for spotted lanternfly egg masses; if found, scrape them off into a bag or bucket filled with soapy water. This fall and winter, we also want to encourage everyone to please burn any firewood where you buy it, and please don’t move it off your property if you chop it yourself- especially if you are burning tree of heaven. Egg masses will stick to firewood and can survive our winters very well.
What can I do? We are still learning about the spotted lanternfly’s distribution through Indiana, and we need the help of citizen scientists to effectively track the insect’s movement. If you believe you’ve seen spotted lanternfly, please report it using any of the resources listed below. You can also feel free to reach out to Bob Bruner, Exotic Forest Pest Educator, by emailing them at rfbruner@purdue.edu, or you can report sightings by calling 1-866-NOEXOTIC. Keep an eye out, and have a great time at state fair!
In this webinar, hosted by Indiana Forestry & Woodland Owners Association, Joe Caudell, state deer biologist with Indiana DNR Division of Fish and Wildlife, shares recent efforts to better understand Indiana deer populations and how they vary across the landscape. The research from the Integrated Deer Management Project, a multi-year research project with Purdue Forestry and Natural Resources team working closely with the DNR biologists, created research management units (RMUs) so that they could be easily incorporated into deer management practices by the DNR.
If you’re interested in learning more about Indiana’s white tailed deer hunting and management, see the IN DNR page. There is a section on deer management with deer reports, survey results, and real time harvest data: White-Tailed Deer Hunting.
Check out the Indiana Forestry & Woodland Association YouTube Channel for videos including: What is IFWOA?; A New Carbon Program for Hardwood Landowners Webinar, Indiana’s Native Orchids, Magnificent Trees of Indiana, Be Tick Aware and much more.
The Indiana Forestry & Woodland Owners Association (IFWOA) was founded in 1977 and is a non-profit organization dedicated to conservation and sustainable management of woodlands in Indiana. IFWOA advocates for scientific best practices for management to achieve objectives of clean water, wildlife habitat, soil protection, native species diversity, timber production, recreation, carbon sequestration and many others.
IFWOA is an affiliate of the National Woodland Owners Association. IFWOA is a partner, collaborator or is represented on leading National and State organizations. These memberships or collaborations are selected to advance Indiana Woodland owner’s interests. IFWOA monitors and influences legislation and economic trends impacting Indiana woodlands and landowners for our members. Membership in IFWOA provides a valuable network linkage to information and resources at the leading edge of science, industry and politics impacting Indiana woodlands.
Purdue Landscape Report: Recently a homeowner in Hamilton County posted on the Indiana Native Plant Society Facebook page with concerns about aphids, mites, and apple scab in her maple and oak trees. She asked for a second opinion and treatment options for these pests. I reached out to the homeowner and requested permission to collect samples from the trees. Let’s look at what I found (or didn’t find) and discuss when and if these issues should be treated.
Apple Scab on Maples?
First, we can eliminate the concern about apple scab because maple and oak trees are not hosts for this pathogen. Apple scab is caused by the fungus Venturia inaequalis, and hosts include apples, crabapples, hawthorn, mountain ash, firethorn, and loquat. There are other fungal diseases which cause leaf spotting in maples, such as Anthracnose, tar spot, and Phyllosticta leaf spot. To diagnosis these diseases, homeowners can submit a sample to the Purdue Plant & Pest Diagnostic Lab, or hire a certified arborist to assess the tree. However, all these diseases are primarily aesthetic issues. A healthy tree will not die from these pathogens and does not require treatment. You can find more information about maple diseases in this publication: Diseases in Hardwood Tree Plantings. You can also find a previous article on Tar Spot in Maple in the Purdue Landscape Report (Issue 18-12).
Fig. 1. Severe spider mite damage on maple leaves. (Photo: S. D. Frank, North Carolina State University)
Spider Mites
The next pest concern on these trees is spider mites. Out of the dozens of leaves I collected, I found only two immature mites on a couple of maple leaves I examined. This is a very small mite presence, and it is not recommended to treat for spider mites unless the populations threaten the health or appearance of the tree. Limiting pesticide usage will conserve the natural enemies, which are vital to keeping mite populations in check. In fact, improper pesticide applications can kill these important natural enemies and worsen mite infestations.
When do you know if the mite population is large enough to merit intervention? Check your trees for signs of heavy feeding damage, such as leaf stippling (Fig. 1), or dense webbing on the leaves. Mites can also be monitored by placing a sheet of paper (8.5×11”) beneath a branch and striking the limb. Chemical treatments should be considered when you count ≥24 mites per strike. You can find detailed management recommendations and a full list of pesticide options in this Purdue Extension publication: Spider Mites on Ornamentals.
Fig. 2: Adult painted maple aphids found on maple in Hamilton Co, Indiana. (Photo: Andrew Johnston, Purdue University).
Aphids
The aphids I found on the homeowner’s maple trees are Drepanaphis acerifoliae, or the painted maple aphid (Fig. 2). This species only feeds on maple trees, and is not a threat to the oak tree on this homeowner’s property. Painted maple aphid is a very common aphid in our region. I found only a few aphids on one of the maple trees I sampled, which is not enough to require treatment. In addition, one of the aphids was a “mummy”, or a carcass left behind from a parasitoid wasp. This indicates that natural enemies are already at work managing the aphid population. Aphids may rarely require chemical control if their numbers grow large enough to produce significant amounts of honeydew, which can result in sooty mold outbreaks.
Tussock Moth
The only insect I found on the oak tree was a white-marked tussock moth caterpillar, Orgyia leucostigma (Fig. 3). This is the likely culprit for the minor feeding damage I noticed. These are not significant pests and do not require treatment. Don’t touch them, though! The setae of this caterpillar are irritating and may cause allergic reactions.
Overall, the pests I found were minimal and non-threatening to the trees. It’s normal to find some insect pressure in the landscape. Knowing when and if to treat requires accurate diagnosis and monitoring of pest levels. Check out PurduePlantDoctor.com for an easy-to-use diagnostic aid and treatment recommendations.
In this episode of A Woodland Management Moment, Purdue Extension forester Lenny Farlee talks about the importance of oak regeneration. Oak is a ‘keystone’ species, integral to supporting many different facets of wildlife. This includes insects to large mammals all across the environment in Indiana and the central hardwood region. This video also shares details regarding Purdue’s initiatives to ensure the diverse ecosystems maintained by oak and to provide the resources needed to keep regenerating this integral tree
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.
The long lifespan of many trees, which could be centuries or even millennia in the case of a few species, is a source of awe and inspiration for many. The bark of trees can often tell some stories about their life and history, if we know how to interpret what we see. Here are a few examples you may run across in Indiana.
Is this tree sick? That may be a natural question to ask when looking at the striking difference in the bark pattern on this white oak. In fact, it is an infection, but not a harmful one to the survival of the tree. This is called smooth patch and is caused by a fungus that infects the outer bark of oak and some other tree species. There are several species of fungus that may cause this appearance, but the most common is Aleurodiscus oaksii. The fungus gradually decomposes the outer layers of bark, producing the flattened and smooth surfaces which contrast with the rough bark that is uninfected. If you look closely during moist periods, you may see the small cup-shaped fruiting bodies of the fungus on the bark. It is not a threat to the health or integrity of the tree as only the outer bark is impacted.
Figure 1 – Smooth patch on white oak. The normal bark pattern can be seen on the lower trunk.
Figure 2 – Smooth patch fungus, Aleurodiscus oaksii, fruiting body on white oak bark.
This isn’t the same species of tree, is it? Yes, it is! Bark pattern differences in some species may reflect the growth rate or relative vigor of the tree. These photos show black walnut bark from two very different growing sites. The blocky, alligator-hide bark pattern is often an indication of slow growth and may result from a tree growing on a very difficult site, like the dry hilltop where this tree is located, or severe competition from surrounding trees. The strongly interlacing ridges of the bark in the second photo are from a black walnut growing in a plantation on a creek bench with deep, moist and fertile soils, resulting in more vigorous growth.
Figure 3 – Black walnut with slow-growth bark pattern.
Figure 4 – Black walnut with vigorous growth bark pattern.
What happened here? The pattern in a horizontal line across these trees looks too perfect to be natural, but it was not produced by a human. This is the feeding activity of the yellow-bellied sapsucker, a species of woodpecker that migrates through Indiana. The sapsucker, true to its name, uses its sharp bill to create holes through the bark that ooze sap. The sapsucker feeds on the sap and may also feed on insects drawn to the sap. They tend to create straight lines of holes that leave this diagnostic pattern behind, even long after the birds have ceased their activity. This activity is usually not fatal to the tree, but does cause some damage to the wood beneath the bark, so trees that have been used by sapsuckers may have discolored spots or other blemishes in the wood revealed when processed for wood products. To see images and learn more about sapsuckers visit American Bird Conservatory Website.
Figure 5 and 6 – Yellow-bellied sapsucker feeding activity on sugar maple trees. These are older holes being covered by wood growth.
Humans also may leave a history of our presence on trees. This American beech tree in a recreation area has recorded the comings and goings of visitors, with some apparent editing as well! I do not endorse this activity as it can be harmful to the tree by introducing avenues for decay and disease, and is generally prohibited on public property. Instead, enjoy reading the nature stories found in bark.
Figure 7 – American beech bark defaced by carving.
