Got Nature? Blog

Purdue Landscape Report: While fungi are responsible for many of our foliar disease problems, different fungal pathogens present as problems throughout the country, depending upon the host plant grown and the environmental conditions. This is a brief overview of several common types of fungal leaf diseases that occur in Indiana and throughout North America (and Europe). Recognizing the symptoms and signs is an important first step to diagnose a disease problem, followed by how to manage these diseases by combining cultural and chemical controls.

Common fungal leaf diseases of deciduous trees and shrubs

Figure 1. Anthracnose is a yearly problem on sycamore in the Midwest. Photo by Janna Beckerman.

Anthracnose. Anthracnose diseases probably are the best-known foliar fungal diseases of deciduous trees. They affect many ornamental trees including major shade-tree genera such as sycamore (Platanus spp.), oak (Quercus spp.), maple (Acer spp.), elm (Ulmus spp.) and ash (Fraxinus spp.) (Fig. 1). Anthracnose actually is a general term describing symptoms such as dead irregular areas that form along and between the main vein of the leaf. The leaves may also become curled and distorted and twigs may die back. The fungus overwinters in infected twigs and the petioles of fallen leaves, and the spores disseminate in the spring by wind and splashing rain. The disease, while unsightly, rarely results in the tree’s death. Sycamores and other trees often withstand many years of partial defoliation. However, one anthracnose disease is more serious. Dogwood anthracnose (Discula destructiva) is a devastating problem on the Eastern seaboard, but has not been a significant issue here in Indiana.

Figure 2. Leaf blister on oak. Photo by Janna Beckerman

Leaf blisters result in the blistering, curling and puckering of leaf tissue. Oak leaf blister (Taphrina caerulescens) is a common blister disease of oaks (Fig. 2)., particularly the red oak subgenus, which includes Northern red oak (Q. rubra) and pin oak (Q. palustris) among others. The symptoms begin as a slight yellowing of the infected leaf followed by round, raised blisters. These turn brown, and the infected leaves fall prematurely. This fungus overwinters as spores on the buds.

Leaf spot is a general symptom caused by a multitude of pathogens and infect all deciduous trees and shrubs, and include dead spots with a defined boundary between living and dead tissue. The dead tissue often separates from the surrounding living tissue creating a “shot-hole” appearance on the infected leaves. Common hosts include dogwood, maples, hydrangea, rose, holly, and Indian-hawthorn.

Figure 3. Tar spot is increasing in incidence and severity in Indiana. Photo by Janna Beckerman.

Tar spot (Rhytisma spp.) is a leaf disease with initial symptoms similar to leaf spot. The disease is most common on red (Acer rubrum) and silver maple (A. saccharinum) (Fig.3), but it can occur on a wide range of maple species from sugar (A. saccharum) and Norway (A. platanoides) to bigleaf maple (A. macrophyllum). The symptoms begin in the spring as small greenish-yellow spots on the upper leaf surface that, by mid-summer, progress to black tar-like spots about 0.5 inch in size. The disease is not fatal to the tree, but the appearance of the tar spots alarms some tree owners. A major outbreak in New York about 10 years ago left many maples completely defoliated by mid-August.

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Resources:
Diplodia Tip Blight of Two-Needle Pines, The Education Store, Purdue Extension resource center
Boxwood Blight, The Education Store
Disease of Landscape Plants: Cedar Apple and Related Rusts on Landscape Plants, The Education Store
Planting Your Tree Part 1: Choosing Your Tree, Purdue Extension – Forestry & Natural Resources (FNR) YouTube Channel
Tree Planting Part 2: Planting a Tree, Purdue Extension – FNR YouTube Channel
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
Why Is My Tree Dying? – The Education Store
Tree Risk Management – The Education Store
Tree Pruning Essentials, Publication & Video, The Education Store
Tree Wound and Healing, Got Nature? Blog, Purdue Extension – FNR
What are Invasives Species and Why Should I Care?, Got Nature? Blog, Purdue Extension – FNR
Subscribe – Purdue Extension-FNR YouTube Channel

Janna Beckerman, Professor of Plant Pathology
Purdue Department of Botany and Plant Pathology

Figure 2: A young spruce tree under the effects of transplant and root stress.

Figure 1: A spruce tree suffering from root damage and water stress.

Figure 4: Phomopsis dieback with excessive needle loss on branch tips.

Figure 3: Dieback symptoms in a mature tree associated with Phomopsis infection.

The disease begins in the lower canopy and moves upward, but in some cases it progresses quickly, causing dieback through a large portion of the tree. Besides needle death and drop, there are virtually no other external symptoms to indicate where the original infection took place. Occasionally you may find resin building on the outside of a canker. Cutting into the thin bark will show the brown discolored tissue where the canker is developing. Cankers are often located in between two areas of healthy tissue. This can lead to older needle loss similar to needlecast diseases, but leaving terminal buds alive. However, once the pathogen spreads and girdles the branch, the rest of the branch will begin to die out to the tip.

For full article >>>

Resources
Borers of Pines and Other Needle Bearing Evergreens in Landscapes, The Education Store, Purdue Extension resource center
Ask an Expert Question: Blue Spruce dying, what can I do?, Got Nature? Blog, Purdue Extension – Forestry and Natural Resources
Why Spruce Trees Lose Their Needles, Purdue Extension
Diseases Common in Blue Spruce, Purdue Extension

John Bonkowski, Plant Disease Diagnostician
Purdue Department of Botany and Plant Pathology

Purdue Landscape Report: When the irises begin to bloom, expect up to 1.5 million cicadas per acre to begin boiling out of the ground. This spring Indiana will see the emergence of the 17-year cicadas (Brood X). These insects feed underground for most of their lives drinking sap from tree roots. Once every 17 years they emerge en masse, climb up trees, sing (though it sounds more like screaming), mate, and lay their eggs on the tips of tree branches. This cycle is completely natural and has a long history in written and oral records. Cicadas are not harmful to humans, provide a feast for wildlife, and mostly only cause cosmetic injury to trees. However, there are some trees that will need protection to survive.

17-year cicadas have much brighter colors than their annual cousins. They can be recognized by their bright red eyes, black bodies, and orange wing veins. Image by John Obermeyer, Purdue Entomology, Purdue University.

Cicada Emergence Timing and Locations
Where can you find cicadas?
17-year cicadas can be found throughout Indiana but the biggest populations will be in southern Indiana. According to Cicada Mania, these cicadas were reported to be more abundant in the following areas during their last emergence in 2004: “Bloomington, Brookville, Clinton Falls, Dillsboro, Fishers, French Lick, Indianapolis, Lawrenceburg, Lexington, Martinsville, McCormick’s Creek State Park, Nashville, North Vernon, Skiles Test Park, Spencer”

An example of a heavily damaged full grown tree. The brown, dead leaves are twigs that were killed by cicada egg laying. The damage may look severe, but this tree should recover from the cicada damage by the following year. Image by John Obermeyer, Purdue Entomology, Purdue University.

What do cicadas look like?
Cicadas tend to have sturdy, thick bodies with mostly clear wings that are longer than their bodies. 17-year cicadas are distinctive from the annual cicadas in that their bodies are a dark, nearly black brown with amber highlights on their wing veins, and red eyes (figure 1). Check out this video to see the full life cycle and hear what a chorus of cicadas sounds like!

How many species of cicadas are there in Indiana?
There are more than you’d think! There are three main species of 17-year cicada in Indiana and about 16 species of annual and 13-year cicadas. You can find a full list here.

Cicada Damage and Control
What do cicadas prefer to eat?
17-year cicadas aren’t picky! They’ll feed on more than 270 species of woody plants. They show a slight preference for deciduous trees like maple, fruit trees, oak, and dogwood, but will generally feed on any deciduous tree or bush available to them.

How do cicadas injure plants?
Cicadas lay eggs by stabbing their ovipositor into tree bark. This can create scars in the bark. If enough cicadas lay eggs on a small branch, it can kill the twig. As a result, large trees sometimes have minor dieback at the ends of branches but overall tree health isn’t affected (figure 2). Small or young trees and shrubs, however, may be more seriously harmed.

What kind of plants should be protected from cicadas?
Cicada females prefer to lay their eggs in branches that are about 3/16 to 1/2 inch in diameter. Therefore, young deciduous trees or bushes that have major branches less than ½ inches in diameter should be protected in areas with high numbers of cicadas emerging. Mature trees do not require protection.

All vulnerable parts of trees should be completely covered. Note how the branches are fully covered by the fine netting and the fabric is tied tightly at the trunk of the tree. Photo by James B Hanson USDA Forest Service.

How should I protect my trees from cicadas?
Homeowners:
Homeowners only need to worry if they have newly planted trees (3-4 years old). The best way to protect these young trees is to cover them in a mesh fabric for the ~1 month period when the cicadas are active in the area. The mesh bags can be made from a variety of materials as long as the holes are smaller than 1 cm (~3/8 inch). Drape the fabric over all the twigs and branches that are smaller than 3/8 inches and secure it at the bottom so that cicadas cannot climb up from underneath (figure 3). The goal is to prevent the cicadas from having access to the branches so that they will lay their eggs elsewhere.

Well-maintained trees provide many benefits including increased property values, improved air quality and curb appeal. Trees are living organisms making them vulnerable to pests and environmental extremes resulting in health issues which result in defects. This publication will help guide you on where and how to identify tree defects and a better understanding of when to contact an arborist for assistance.

Resources
Tree wounds and healing, Got Nature? Blog, Purdue Extension – Forestry and Natural Resources
How to Identify Tree Defects and What to Do About It?, Got Nature? Blog
Iron Chlorosis of Trees and Shrubs, The Education Store, Purdue Extension resource center
Surface Root Syndrome, The Education store
Tree Appraisal and the Value of Trees, The Education Store

Lindsey Purcell, Urban Forestry Specialist
Purdue University, Department of Forestry and Natural Resources

Purdue Landscape Report: Tubakia leaf spot, caused by the fungus Tubakia, is the disease we find more commonly on oak than any other. Throughout the world, there are 11 species of Tubakia known to infect oak, with Tubakia dryina (previously known as Actinopelte dryina) being the most commonly encountered species in our landscapes. Apple, ash, black gum, chestnut, elm, maple, and redbud are all reported as hosts of Tubakia species, but oaks are the most frequently and severely affected. Among the oaks, the red oak group, specifically red, pin, and black oaks, are reported to be more susceptible to infection compared to those in the white oak group.

Figure 2: Oak leaf with circular shaped Tubakia leaf spots along with extensive veinal necrosis.

Figure 1: Oak leaf with irregularly shaped Tubakia leaf spots and veinal necrosis.

Figure 3: Marginal blighting due to coalescing spots and veinal necrosis.

Figure 5: Blighting of large leaf area caused by veinal infection by Tubakia.

Figure 4: Typical Tubakia leaf spot symptoms illustrating how the fungus spreads along leaf veins.

John Bonkowski, Plant Disease Diagnostician
Purdue Department of Botany and Plant Pathology

Tom C Creswell, Clinical Engagement Professor – PPDL
Purdue Department of Botany and Plant Pathology

The Nature of Teaching, a Purdue Extension signature program, was honored as the third place finisher in the central region for the Environmental Education Award presented by the National Extension Association of Family and Consumer Science (NEAFCS).

Join Purdue Extension urban forester Lindsey Purcell, exotic forest pest educator Elizabeth Barnes and entomology extension specialist Cliff Sadof as they share about how to inspect trees, what to look for, who to contact, etc., as well what invasive pests and diseases you should keep your eye out for.

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
Ask an Expert, Playlist, Purdue Extension – Forestry and Natural Resources Youtube Channel
Tree Risk Management, The Education Store, Purdue Extension resource center
Tree Appraisal and the Value of Trees, The Educational Store
Surface Root Syndrome, The Education Store
Iron Chlorosis of Trees and Shrubs, The Education Store
Facebook Live – Ask The Expert: Pests in Your Woods, Got Nature? Blog, Purdue Extension – Forestry and Natural Resources
Fall webworms: Should you manage them, Got Nature? Blog
How to Identify Tree Defects and What to Do about It?, Got Nature? Blog

Lindsey Purcell, Urban Forestry Specialist
Purdue University, Department of Forestry and Natural Resources

Elizabeth Barnes, Exotic Forest Pest Educator
Purdue University, Department of Entomology

Cliff Sadof, Professor / Ornamental / Pest Management / Coordinator of Extension
Purdue University, Department of Entomology

Purdue Landscape Report: Trees are incredible survivors in spite of the challenges from pests of all kinds, including us! They are vulnerable to injuries such as mechanical wounds from lawn equipment, vehicles and ice. Pruning results in an intentional wound which is of importance to consider. Tree owners and managers need to prune trees to maintain aesthetic characteristics, remove infected limbs, reduce risk, or improve structural stability. Proper pruning practice and understanding tree wounds can minimize the impact of creating wounds on trees.

Wounds attract pests due to the phytochemicals dispersed from exposed tissue. When tree tissue is damaged or wounded, the newly uncovered tissue is exposed and that is when to expect an attack. Insect pests are drawn to trees in distress, feeding on the tissue and weakening the tree. Diseases affecting trees will introduce enzymes into the cells, digesting living tissue responsible for food and water translocation (phloem and xylem) or structural support resulting in unhealthy, unsightly, or unsafe trees.

Wound wood Formation
Trees attempt to close wounds by sealing or compartmentalizing the affected area, naturally.

Tree trunk damaged by construction equipment developing wound wood around the edges to eventually seal the wound.

Pruning cuts will develop callus tissue on the exposed tissue giving rise to wound wood.

Wound recovery rates vary widely for different tree species. The speed of recuperation is greatly affected by developmental environmental conditions, vigor and health of the tree. Some trees may never completely close their wounds due to their genetic capacity or perhaps inadequate resources to keep the tree vigorous. However, numerous studies reveal that faster wound closure results in fewer health issues for the tree. Quick healing is always better!

A healthy tree will seal wounds faster and the same for younger trees as well. Trees that are planted in well-drained, quality soils, with good texture, structure, and containing adequate nutrition levels, grow in a way that favors the healing process. Thus, when planting trees, homeowners should be aware of the effects of site selection, soil quality, and other site factors that may impact tree growth.

Wound dressings slow closure and can prevent healing.

Complete wound closure improves tree health and slows decay.

Basically, the best way to help insure proper wound closure and quick and effective sealing of the tissue is a proper pruning cut and preventing damage whenever possible.

Find a professional
Be sure to always hire an insured, tree care professional, preferably and ISA Certified Arborist with the experience, expertise, and equipment to provide proper tree care. Require proof of liability insurance to protect yourself as well.

Another easy way to find a tree care service provider in your area is to use the “Locate Your Local Tree Care Industry Association Member Companies” program. For more information refer to the publication Trees and Utilities at the Purdue Education Store.

Find an ISA Certified Arborist in your area by visiting the Trees Are Good website.

Resources
Tree Pruning Essentials, Publication & Video, The Education Store, Purdue Extension resource center
Tree Pruning: What Do Trees Think?, The Education Store
Mechanical Damage to Trees: Mowing and Maintenance Equipment, The Education Store
Tree Installation Process and Practices, The Education Store
Tree Pruning for the Landscape, Webinar, Purdue Extension – Forestry and Natural Resources Youtube channel

Lindsey Purcell, Chapter Executive Director
Indiana Arborist Association

Brown or black spots with yellowing are signs of anthracnose.

This time of year, many black walnut trees’ leaves may have black spots, turn yellow and begin to drop. This is commonly known as anthracnose, a fungal disease that causes trees to drop their leaves prematurely.

Anthracnose is worsened by wet weather, and some trees are more genetically susceptible to anthracnose than others. It is not fatal but can look like a serious problem. The absence of leaves can slow a tree’s growth and can reduce the nut crop, although by this time of year growth may have slowed or stopped for the season.

Anthracnose generally begins as small circular brown to black areas on the leaflets. Over the season those spots expand and cause leaf drop. There are a few other leaf spot diseases of black walnut, see the references below for descriptions of those diseases.

Although unsightly, there is no need for further action if you are growing timber and have anthracnose in a plantation or woods. It can be an issue if you are growing walnuts for a nut crop, and there are resources and spray products to help manage the fungus in those situations.

If you have individual landscaping trees and want to limit anthracnose spread there are few things you can do:

• Gather fallen leaves and compost or remove them from the site.
• Control weeds which could carry the fungus.
• Plant walnut trees where there is good air circulation.
• Keep the trees healthy and vigorous by managing soil fertility and thinning competition as needed.

Resources
Walnut Anthracnose, Walnut Notes, U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station
Indiana Walnut Council, Industry Representatives include 45 states and 3 foreign countries
Diseases in Hardwood Tree Plantings, The Education Store, Purdue Extension resource center
Study: Fungus Behind Deadly Disease in Walnut Trees Mutates Easily, Complicating Control, Purdue Agriculture News
Indiana Walnut Council
Diseases in Hardwood Tree Plantings, The Education Store, Purdue Extension resource center
Why are my walnut trees dropping their leaves?, Purdue Extension – Forestry & Natural Resources (FNR) Got Nature? Blog
Invasive Species Walnut Twig Beetle Detected in Indiana, Purdue Extension – FNR Got Nature? Blog
Intro to Trees of Indiana: Black Walnut, Purdue Extension – FNR Got Nature? Blog
Planting Hardwood Seedlings in the Central Hardwood Region, The Education Store
Regenerating Hardwoods in the Central Hardwood Region:  Soils, The Education Store
Fertilizing, Pruning, and Thinning Hardwood Plantations, The Education Store
Resources and Assistance Available for Planting Hardwood Seedlings, The Education Store

Liz Jackson, Manager Walnut Council / IN Forestry Woodland Owners Association (IFWOA) & Engagement Specialist
Purdue University Department of Forestry and Natural Resources