Got Nature? Blog

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

Long Description

Tree with drought stress.

Many homeowners are finding their trees with dry and wilted leaves and no rain in sight. This publication describes how homeowners can deal with these drought-stressed trees, Drought? Don’t Forget the Trees!

Drought 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.

Trees in a weakened state from drought are more susceptible to pests, which can further weaken the tree, and even kill part or all of it. Although there is nothing we can do to prevent drought, it is important to know what can be done to reduce long-term effects of prolonged dry conditions.

Resources:
Water Your Trees, Video, Purdue Extension – Forestry and Natural Resources (FNR) YouTube Channel
Trees in Times of Drought​, Video, Purdue Agriculture
INPREPared, Purdue Extension
Drought Information​, Indiana Department of Natural Resources
Tree Planting Part 1: Choosing a Tree video, Purdue Extension-FNR 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
Thousand Cankers Disease, collaborative website
Walnut Twig Beetle and Thousand Cankers Disease of Black Walnut, Purdue Plant and Pest Diagnostic Laboratory
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

Purdue Extension forester Lenny Farlee tells you where to find and how to identify a species that clings to many of our trees, poison ivy. Protect yourself from the itch by recognizing this species before it is a problem.

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
Poison Ivy, Purdue Landscape Report
Poison Ivy, Purdue Extension
Poison Ivy, The Education Store, Purdue Extension resource center
Investing in Indiana Woodlands, The Education Store
Tree Appraisal and the Value of Trees, The Education Store
Forest Improvement Handbook, The Education Store
ID That Tree, Playlist, Purdue Extension – Forestry and Natural Resources Youtube Channel
A Woodland Management Moment, Playlist, Purdue Extension – Forestry and Natural Resources Youtube Channel

Lenny Farlee, Sustaining Hardwood Extension Specialist
Purdue University Department of Forestry and Natural Resources

Purdue Landscape Report: Hot, dry summers are not that unusual in the Midwest, but 2020’s hot dry spell started considerably earlier than usual, before summer even officially began! To make it a triple whammy, the hard freeze in early May caused some landscape plants to burn up more stored carbohydrate reserves to produce a second round of foliage.

(Figure 2) July Heat Map

(Figure 1) US Drought Monitor

I’m sure I don’t have to point out that most of Indiana is currently experiencing abnormally hot, dry conditions. Although recent rains have brought relief to some areas, any respite is sure to be temporary. Seasonal thunderstorms may deluge some landscapes with water while other areas, even those close by, may stay fairly dry. Much of the area has experienced highs in the upper 80’s to over 90º F over the past month.

Leaf scorch on trees and shrubs, appearing as a browning along the edges of the leaves, is very common in dry summers. While minor cases of leaf scorch are not very harmful, prolonged lack of moisture can spell disaster for landscape plants.

Leaf Scorch on Lilac

Hydrangea wilting

Young and newly established plants are most susceptible to the dry conditions, but even established plants may reach a critical point during prolonged drought. If the heat and drought continue this summer, branch dieback, combined with eventual root death, will make plants more susceptible to winter injury. Plants that were already under stress from other factors may succumb to severely dry soils.

The intense heat makes it difficult for plants to keep up with water and cooling requirements, even in areas where moisture is adequate. One of the ways that plants cool themselves is through transpiration, which allows water to evaporate from the foliage. Plant leaves have pores called stomata that can open and close to allow water vapor and gas exchange with the environment. During extreme heat and/or drought, stomata will nearly close, thus reducing transpiration and exchange of carbon dioxide and oxygen. The end result is seen as wilting foliage and leaf scorch. But not so obvious is that reduced water uptake and gas exchange also leads to reduced production of carbohydrates through photosynthesis and reduced uptake of soil nutrients, having longer term impact on plant health.

There is still plenty of summer yet to get through to see the further challenges ahead. Meanwhile, we can mitigate some of the stress by watering landscape plants as needed where feasible.

Resources
US Drought Monitor
Indiana – Purdue Rural Emergency Preparedness, Purdue Extension website
In Times of Drought, Indiana Yard and Garden, Purdue Consumer Horticulture
Drought? Don’t Forget the Trees, The Education Store, Purdue Extension resource center
Turfgrass Disease Profiles: Summer Patch, The Education Store
Iron Chlorosis of Trees and Shrubs, The Education Store

Rosie Lerner, Extension Consumer Horticulturist
Purdue University Department of Horticulture and Landscape Architecture

Welcome to the Nature of Teaching Professional Development Webinar Series: Ecotoxicology Part 1. This webinar shared by Rod Williams, a professor and extension wildlife specialist with Purdue University Extension, and Jason Hoverman, an associate professor at Purdue University and a co-author on the unit on ecotoxicology, discusses the principles of ecotoxicology, contaminants, and threats to the freshwater ecosystems.

This webinar shares the resources teachers, and K-12 leaders, need to teach students about ecotoxicology. This state standard curriculum includes free downloads of posters, photos, charts, data sheets, and fun activities along with the opportunity to receive a Certificate of Completion. 

Resources
The Nature of Teaching: Ecotoxicology and Environmental Health, The Education Store, Purdue Extension’s resource center
Benefits of Connecting with Nature, The Education Store
The Nature of Teaching: Disease Ecology, The Education Store
Resourceful Animal Relationships, The Education Store
The Nature of Teaching, YouTube Channel
Nature of Teaching, Website

Rod Williams, Professor of Wildlife Science
Purdue University Department of Forestry and Natural Resources

Jason Hoverman, Associate Professor Vertebrate Ecology
Purdue University Department of Forestry and Natural Resources

Figure 1. White oak slime flux

Purdue Landscape Report: Slime flux (also known as wet wood) is a dark, foul-smelling and unsightly seepage of sap from tree trunks (fig. 1). The disease is not usually a serious problem but the appearance can be alarming. Slime flux is caused by common surface-inhabiting bacteria or yeast fungi that enter the trunk through wounds associated with improper pruning, stem breakage, injections, cracks from freeze injury or weak limb crotches. The bacteria and yeast may live on sap nutrients within injured trees for many years without any outward evidence.

Symptoms
The main symptom is the appearance of the dark sap oozing on the trunk exterior which happens when gasses produced by growth of the bacteria and yeast cause the internal pressure of the sap to become high enough to force the sap out through cracks in the bark. The dark streaks usually turn light gray or white upon drying. Oozing sap may be frothy and white at the point of exit. Airborne bacteria, yeasts, and fungi often colonize the wet oozing material, which ferments and releases a foul odor. Slime flux may delay wound healing (callus formation).

Slime flux is extremely common on mature elms (fig 2), oak (fig 3) and mulberry; and is seen less frequently on maples (fig 4), paper birch, sycamore, and walnut.

Figure 4. Silver Maple

Figure 3. White Oak

Figure 2. American Elm

Prevention
There is no control or treatment for slime flux. Inserting a drain tube into the tree to relieve pressure and drain infected sap was once an accepted treatment, but is no longer recommended and may do more harm than good. Boring holes in affected trees causes internal spread of the bacteria within the tree and may allow entry of wood decay fungi.

To reduce the chances of susceptible trees developing wet wood avoid unnecessary wounding of the trunk and branches. Proper pruning techniques, HO-4-W, will allow branches to heal more rapidly. Make sure susceptible trees receive good general care; including irrigation when needed and mulch to conserve moisture and keep mowers away from the trunk. Avoid excess traffic in tree root zone to prevent soil compaction and root injury.

The first and most important step for managing a tree disease is to accurately diagnose the problem. The best approach to diagnosis of tree problems is to start by submitting photos of the tree via the digital upload tool on the Purdue Pest & Diagnostic Lab (PPDL) website. In the case of slime flux it is impractical to collect the type of physical sample needed for confirmation so photos are the best alternative.

References
Sinclair, W. A. and H. H. Lyon. 2005. Diseases of trees and shrubs. Cornell University Press, Ithaca, NY. 660 pp.
Stipes, R. J. and Campana, R. J. (eds.) 1981. Compendium of Elm Diseases. APS Press, St. Paul, MN.

Resources
Diseases in Hardwood Tree Plantings , The Education Store, Purdue Extension’s resource center
Iron Chlorosis of Trees and Shrubs, The Education Store
Surface Root Syndrome, The Education Store

Tom C Creswell, Clinical Engagement Professor – Plant & Pest Diagnostic Laboratory
Purdue University Department of Botany and Plant Pathology

Lindsey Purcell, Chapter Executive Director
Indiana Arborist Association