Biotic Factors Influencing Tree Development and Condition
This week, we delve into the array of living organisms; insects, mites, viruses, bacteria and fungi that impact tree development and condition.
Pests and diseases can pose the most abrupt, costly and ecologically devastating threats to our urban forests.
Like abiotic factors, biotic factors can affect the physical, chemical and biological functions of trees. The way humans intervene in naturally occurring and planted ecosystems can also influence the frequency and intensity of pest and disease outbreaks.
This chapter's content will introduce biotic factors into the matrix of managing tree physiology and nonliving sources of stress in urban environments. We will gain a deeper understanding of the pressures that biotic agents exert on urban forests, worldwide.
This week's readings will situate the practical issues of tree pest infestations and disease outbreaks within a wider context of global and environmental change. They will explain how human development and actions facilitate the spread of pests and pathogens. These resources will also distinguish between beneficial and damaging organisms for trees on the landscape. Lastly, they will illustrate the interplay between pests, diseases and environmental stress.
A case study is available in this chapter!
You are invited to investigate how Oak Wilt (Bretziella fagacearum formerly Ceratocystis fagacearum) is perceived and managed in the United StatesLinks to an external site. and Canada.Links to an external site. We can draw interesting comparisons between regions anticipating the eventual spread of the disease alongside communities managing the infection and loss of oak (Quercus sp.) trees over several years.
See this chapter's optional readings for more information on this case study.
Learning Objectives
By the end of this topic, you should be able to:
Understand the factors that make urban forests more vulnerable to pest infestations and disease outbreaks
Explain how biotic agents can provoke stress in trees
Recognize some of the most devastating examples of tree pests and pathogens affecting urban forests today
Be familiar with resources that can assist with the identification and management of pests and pathogens
Topic Readings
Required Readings (Considered for the exam!)
Raupp, M.J. & Gonthier, P. (2017). Biotic Factors. Routledge Handbook of Urban Forestry. Routledge, London, (pp. 251–269) (Course textbook).
Hirons, A. & Thomas, P. (2018). Applied Tree Biology. Wiley Blackwell - Chapter 9 Interactions With Other Organisms (Course textbook).
Optional Readings
Looking to get up to speed? Consider this optional reading for more background context and terminology.
Lilly, S.J. (2010).ISA Arborists’ Certification Study Guide. International Society of Arboriculture, Champaign IL (10 Diagnosis and Plant Disorders).
Want to dive a little deeper? Consider a case study to help reinforce the concepts we explored in class.
Oak Wilt (Bretziella fagacearum formerly Ceratocystis fagacearum)