Deciduous Tree Galls

R. Chris Williamson, UW Turf and Ornamental Specialist, UW-Extension Revised:  8/6/2012 Item number:  XHT1024 Galls are abnormal growths on plants that can result from the feeding of living organisms such as bacteria, fungi, nematodes, insects and mites.  There are numerous galls that are caused by insects, the most common of which, in Wisconsin, are ash […]

Chlorosis

Brian Hudelson, UW-Madison Plant Pathology, UW-Extension Revised:  1/8/2012 Item number:  XHT1002 What is chlorosis?  Chlorosis is a common nutritional disorder of many woody ornamentals in Wisconsin, particularly in the southern and eastern parts of the state.  Pin oaks are most commonly affected by chlorosis, although many other trees and shrubs (e.g., white oak, red maple, […]

Gymnosporangium Rusts

Authors: Brian Hudelson, UW-Madison Plant Pathology Last Revised: 01/23/2019 X-number: XHT1009 What are Gymnosporangium rusts? Gymnosporangium rusts are a group of closely related diseases caused by fungi that infect both junipers (in particular red cedar) and woody plants in the rose family (such as, but not limited to, apple, crabapple, hawthorn and quince). These fungi […]

Black Walnut Toxicity

Ann Joy and Brian Hudelson, UW-Madison Plant Pathology Revised:  5/7/2010 Item number:  XHT1017 What is black walnut toxicity? Black walnut trees (Juglans nigra) produce a toxic substance (called juglone) that prevents many plants from growing under or near them. Related trees like butternut (J. cinerea) and shagbark hickory (Carya ovata) also produce juglone, but in […]

Bacterial Blight

Gina Foreman* and Brian Hudelson, UW-Madison Plant Pathology *Completed as partial fulfillment of the requirements for Plant Pathology 875 – Plant Disease Diagnostics Clinic Internship at the University of Wisconsin Madison. Revised:  4/25/2004 Item number:  XHT1093 What is bacterial blight?  Bacterial blight, also known as blossom blight or shoot blight, is a common and often […]

Ash Yellows

Jim Olis* and Brian Hudelson, UW-Madison Plant Pathology *Completed as partial fulfillment of the requirements for a BS in Plant Pathology at the University of Wisconsin Madison. Revised:  8/6/2012 Item number:  XHT1079 What is ash yellows?  Ash yellows is a chronic, systemic disease that affects ash trees of all ages.  White ash is particularly susceptible […]

Armillaria Root Disease

Michael Amman, UW-Madison Forest Ecology and Management and Glen R. Stanosz, Ph. D., UW-Madison Plant Pathology Revised:  8/6/2012 Item number:  XHT1120 What is Armillaria root disease?  Armillaria root disease, also known as shoestring root rot, is an often lethal disease of tree and shrub roots and lower stems.  It can affect almost any conifer or […]

Anthracnose

Brian Hudelson, UW-Madison Plant Pathology Revised:  3/10/2012 Item number:  XHT1001 What is anthracnose?  Anthracnose is the name of several common fungal diseases that affect the foliage of woody ornamentals in Wisconsin.  Trees that are most commonly and severely affected by anthracnose include ash, maple, white oak, sycamore, and walnut.  Anthracnose typically affects young leaf tissue. […]

Black Knot

Brian Hudelson, UW-Madison Plant Pathology, UW-Extension Revised:  5/1/2010 Item number:  XHT1056 What is black knot?  Black knot is a disfiguring and potentially lethal disease of trees and shrubs in the genus Prunus.  This genus includes stone fruits such as wild, fruit-bearing and ornamental plums and cherries. What does black knot look like?  During the first […]

Lichens

Ken Frost* and Brian Hudelson, UW-Madison Plant Pathology Revised:  4/28/2012 Item number:  XHT1027 What are lichens?  Lichens are organisms that arise from mutually beneficial interactions between certain fungi and algae.  The fungi provide the physical structures of the lichens, as well as protection for the algae.  The algae, in turn, produce food for the fungi […]

Sudden Oak Death

Authors: Brian Hudelson, UW-Madison Plant Pathology Last Revised: 08/23/2019 X-number: XHT1024 What is sudden oak death?  Sudden oak death (also called Ramorum leaf blight or Ramorum dieback) is an oftentimes lethal disease that has caused widespread death of tanoak (Lithocarpus densiflorus), coast live oak (Quercus agrifolia), California black oak (Quercus kelloggii), and Shreve oak (Quercus parvula var. shrevei) in California. […]

Maple Gall Mites (Eriophyidae)

Have you found little green or red bumps or other weird growths on maple leaves and wondered what caused that? Inside each bump are tiny eriophyid mites, feeding on the developing gall tissue. If you want to learn more about these mites and what to do about this problem, check out this article on maple gall mites…

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