Preventing Forest Tree Illness

pine trees
Root diseases usually thin or fade crowns over a period of years. Photo: Chris Schnepf.

Do not wait to act on insect and disease issues until after you see dead branches. Look for visible symptoms or signs of tree illness and learn how to prevent a favorable environment for organisms that harm trees. It is important to understand that successful methods for minimizing forest insect and disease problems are usually preventative, occurring before problems are noticed. Monitoring your forest for …

Invasive Species in Forests

The kudzu vine, pictured here growing on trees in Atlanta, Georgia, is an invasive species brought to the United States from Japan and initially planted in the South to control erosion. Photo: Scott Ehardt, Wikimedia Commons (Public Domain).

A primary goal of a forest owner is to have a healthy forest. To most forest owners, a healthy forest means healthy, living trees. Indeed, inspecting your trees regularly is important. However, to maintain a healthy, thriving forest, you must take other …

A Regional View of Invasive Plants

How does what I do in my yard, on my land and in my garden affect what plants invade our forests and grasslands?  What has happened on the land where you live (its history of use), and what you plant now, can have a long-lasting impact. Land use legacies appear to play a large role in the patterns of invasive plants and the impacts they may have. The progression of time shows how well a plant manages to spread, and …

Oak Decline

Written by D.J. Moorehead and G.K. Douce for Forest Encyclopedia Network

Causal Agents

Oak decline is the name given to a slow-acting disease complex stemming from interactions between biotic and abiotic stressors of oaks (Quercus spp.). Abiotic factors that contribute to oak decline include tree maturity, low site productivity, drought, and spring frost. Biotic factors include root diseases such as Armillaria root disease (Fig. 1) (Armillaria spp.), canker causing fungi such as Hypoxylon canker (Fig. 2) …

Sudden Oak Death in the Eastern United States

  Adapted from: D.J. Moorhead and G.K. Douce for Forest Encyclopedia Network     


Sudden oak death, caused by the pathogen Phytophthora ramorum, is a potentially devastating disease. P. ramorum has been found in nurseries in California, Oregon, Washington, and British Columbia, and more recently in the eastern United States. Sudden oak death causes leaf and shoot blights in most hosts, and is known as Ramorum shoot and leaf blight in the nursery industry. In the forest the fungus can cause bole

Purple Loosestrife-Lythrum salicaria

Written by D.J. Moorhead and G.K. Douce for Forest Encyclopedia Network
Figure 1. Purple loosestrife is easily recognized in the summer and early fall by its showy spike of purple flowers. Photo by Eric Coombs, Oregon Department of Agriculture, courtesy of

Purple Loosestrife is a tall, perennial forb that can grow up to 10 feet in height. It is easily distinguished by the abundant, showy spikes of purple flowers that occur at the tops of the plants (Swearingen et …

Oriental Bittersweet-Celastrus orbiculatus

Written by D.J. Moorhead and G.K. Douce for Forest Encyclopedia Network
Figure 1. Oriental bittersweet’s leaves are elliptical in shade and alternately arranged. The vines can wrap tightly around trees, potentially girdling the tree and killing it. Photo by James H. Miller, USDA Forest Service, courtesy of

Oriental bittersweet is a deciduous, climbing, woody vine that can grow to lengths of 60 ft (Miller 2003). The alternate, elliptical leaves are light green in color (Fig. 1). Small, inconspicuous, auxiliary …

Kudzu-Pueraria montana (Lour.) Merr.

Adapted from: D.J. Moorhead and G.K. Douce for Forest Encyclopedia Network
Figure 1. Distinctive three-parted leaf of kudzu. Photo by James H. Miller, USDA Forestry service, courtesy of

Kudzu is a climbing deciduous vine capable of reach lengths of over 100 feet. The stems can grow to 4 inches in diameter and the large semi-woody roots can reach depths of 3 to 16 feet (Miller 2003). Kudzu is easily identified because it grows in a large dense mat of …

Mimosa – Albizia julibrissin

Written by D.J. Moorhead and G.K. Douce for Forest Encyclopedia Network

A mimosa infestation favors disturbed sites, where they can grow quickly and prevent native plant establishment.

Figure 1.  Mimosa flowers are very showy and fragrant. The leaves are delicate-looking and bipinnately compound.  Photo by Ted Bodner, Southern Weed Science Society. Figure 2.  Mimosa can quickly invade forest edges and old fields. The showy flowers make infestation very conspicuous.  Photo by James H. Miller, USDA Forest Service. Image credits:

Mimosa, also known as silk tree, is a small deciduous tree that is 10 to 50 feet in height, often having multiple trunks. It has delicate looking bi-pinnately compound leaves that resemble ferns (Miller 2003). The bark is smooth and light tan to greenish in color. Mimosa has very showy, …

What Are Invasive Species, and Why Should We Be Concerned About Them?

An invasive species is a nonnative species (in any reproductive stage, including seed, egg, spore, or other propagule) whose introduction causes or is likely to cause economic harm, environmental harm, or harm to human health. These species grow and reproduce rapidly, causing major disturbance to the areas in which they are present.

Yellow Starthistle
Steve Dewey, Utah State University,

The majority of nonnative species, including most of our sources of food and fiber, are not harmful, and many are highly beneficial. …