Iowa Seminar: Caring for Your Legacy Oaks

Lee Fredericks
Western Great Lakes Territory Manager, Rainbow Ecoscience

Brandon Gallagher-Watson
Creative Director, Rainbow Companies

Cory McCurry
Arborologist, Rainbow Ecoscience

Over the past decade, oak trees across the Midwest have experienced significant decline due to prolonged drought, changing climate, emerging diseases, invasive pests, and general confusion around treatment approaches when multiple problems are occurring simultaneously. As keystone species in both urban forests and residential landscapes, oaks play a vital ecological and aesthetic role, making their protection a valuable service you can offer your customers.

Dr. Kendra Wagner
Research Scientist and R&D Team Lead, Rainbow Ecoscience

Drought is one of the most significant environmental stresses affecting oaks in urban and community landscapes, with implications for tree health, canopy longevity, and the long-term sustainability of the urban forest. This presentation examines the physiological responses of oaks to drought stress, including impacts on water relations, growth, and species-specific tolerance mechanisms across the oak genus. The talk will also explore how drought interacts with other stressors common to Chicago-area oaks to affect long-term tree performance and resilience. Current management strategies for mitigating drought impacts will be reviewed, emphasizing practical, science-based approaches that arborists and urban forestry professionals can implement across public and private oak populations. By connecting current research with real-world applications, attendees will gain a deeper understanding of drought's impact on oaks and learn strategies to promote healthier, more resilient oak canopies in an era of increasing water scarcity.

Dr. David N. Appel
Professor Emeritus, Department of Plant Pathology and Microbiology (PLPM) at Texas A&M University

Oak wilt was one of the more enigmatic diseases to take the stage of forest pathology in the 20th century. Appearing in the wake of the notorious chestnut blight and Dutch elm disease epidemics, oak wilt did not fit the mold created by those devastating tree diseases. The reliance of the pathogen on producing fungal mats for inoculum, nitidulid beetles as vectors, and fresh wounds as infection courts required several years of research to understand the epidemiology of Bretziella fagacearum. Once those and other stages of the pathogen were clarified, then control measures were developed and refined. This first presentation will examine those research efforts and how they translated into the control measures we use today to manage oak wilt.

Dr. Kendra Wagner
Research Scientist and R&D Team Lead, Rainbow Ecoscience

Wood and bark boring insects are contributing factors to the spiral of decline in urban trees. This presentation will provide an overview of the biology, life cycles, and identifying characteristics of these pests, along with the symptoms and damage they cause. Attendees will learn how to distinguish insect-related injury from other stress factors, recognize infestations early, and understand the conditions that influence pest development and population growth. The session will also review monitoring techniques and integrated pest management strategies, including cultural, biological, and chemical control options. By focusing on pest identification and effective management, this presentation will equip arborists, landscape professionals, and urban foresters with practical tools to protect and preserve valuable oak resources throughout the Midwest.

Dr. David N. Appel
Professor Emeritus, Department of Plant Pathology and Microbiology (PLPM) at Texas A&M University

There are several aspects of oak wilt biology and control that are still poorly understood. Unlike many invasive tree pathogens in the United States, the origins of B. fagacearum are unknown. The most widely recognized insect vectors are inefficient in spreading the pathogen, timely and consistent diagnosis has limitations, and control measures are sometimes inconsistent or ineffective. The pathogen is spreading into new regions, and there are resurgences of the disease within the original range where the impact was previously minimal. New technologies are being applied to improve oak wilt management, but the pace of research is slow. This presentation will cover how we might approach the existing gaps in our knowledge about oak wilt to improve on existing tools and develop novel, new tools to help save trees.

Lee Fredericks
Western Great Lakes Territory Manager, Rainbow Ecoscience

Chlorosis is a serious condition where a tree’s ability to manufacture chlorophyll has been compromised. This can become a long-term problem for trees and shrubs because chlorophyll is the molecule that a tree utilizes to make energy for itself. Trees with chlorosis are making less energy than they normally would. This condition results in a weaker, less durable tree that will rarely last until maturity. Chlorotic trees are trapped in a “Catch-22.” A healthy root system requires food made in the leaves to function and grow. Healthy leaves require healthy roots to extract nutrients from the soil. Without one, the other diminishes. Without human intervention, the tree will be stuck in a spiral of decline that will eventually lead to its death.

Lee Fredericks
Western Great Lakes Territory Manager, Rainbow Ecoscience

Soil compaction is a serious consequence of urban development activities and is the basis for many of the problems faced by landscape contractors and managers. In urban soils, compaction can lead to problems with soil drainage, aeration, nutrient cycling, and plant growth. Compaction increases the load-bearing strength of soils by reorienting particles into a stronger, but denser structure. Compacted soils are not ideal for plant growth or water movement through the soil. In fact, it may be a struggle for plants to thrive in soils that are compacted and limited in poor space and organic matter.

In the limited time of this session, we will briefly address the benefits of AirSpading procedures but primarily focus on pricing recommendations and enriched organic materials to incorporate and why. Additionally, we’ll have a discussion of biological enzymes/biostimulants to add to restore soil health and the incorporation of additional nutrients to enrich the soil profile.