Category Archives: Dutch Elm Disease

Dutch Elm Disease

What is the Cause of Dutch Elm Disease?

Dutch elm disease (DED) is caused by an aggressive fungus (Ophiostoma novo-ulmi) that kills elm trees – regardless of their health. It is considered the most costly shade tree disease ever and will remain active in a community as long as there are susceptible trees. The fungus invades the water transporting vessels and produces toxins. To try and defend against the toxins, the tree produces gums and internal growths designed to block the advance of the fungus. The combination of the toxins and the defense mechanisms of the tree inhibits water flow to the crown, which causes wilting and eventual tree death.

How Does Dutch Elm Disease Spread?

Female elm bark beetles lay their eggs beneath the bark of dead and dying elm trees. If the elm is infected with Dutch elm disease the newly hatched beetles will emerge from the tree carrying the deadly fungus on their bodies. The beetles fly to healthy trees and feed on its 2-4 year old branches, thereby spreading the disease.

Besides beetle transmission, Dutch elm disease may also spread through grafted roots. When elms grow in proximity to each other, their roots can come into contact and graft together. This common root system provides the fungus with a pathway to spread through an entire stand of healthy elms very quickly.

What are the Symptoms of DED?

Dutch elm disease symptoms begin to develop 4 – 6 weeks after infection. The first noticeable symptom that results from the fungal occupation of the water-conducting vessels is wilting or “flagging” of one or more branches, usually starting at the branch tip. Leaves on the infected branches turn dull green to yellow, curl, and become dry and brittle. As the infection spreads the wood beneath the bark displays brown discoloration.

What Can I Do if My Tree is Already Infected?

Most infected elms cannot be saved. In rare cases, if the fungus has not moved into the root system, physically cutting out infected portions of the tree, with a process called tracing, can save the elm.

Sanitation is the most important tool for controlling Dutch elm disease on a community-wide basis. It involves the identification and removal of diseased elms. Such practices eliminate beetle breeding sites and reduce the number of disease-carrying beetles.

Root Grafts

Dutch elm disease can pass from infected trees into healthy trees through grafted roots. Macro-infusion of Arbotect does not prevent root graft infections. The only way to reliably prevent root graft transmission of the fungus is to physically sever the common root system.

How Can I Protect my Elm Tree?

The goal when protecting elms from the fungus is to evenly and completely distribute a fungicide chemical through the entire canopy of the tree.

To protect the tree from beetle-transmitted fungal infection, Arbotect fungicide must be evenly and completely distributed throughout the 2-4 year old branches.
The only way to get an even distribution is by a tree injection method called macro-infusion. Macro-infusion injects a large volume of solution into the root flares of the tree. This solution is then transported throughout the canopy by the tree, providing a protective fungicide barrier.
Arbortect fungicide does not protect elms from root graft infection. You need to physically sever the root system from neighboring trees by trenching at least 36″ down.

Source: Rainbow Treecare Scientific Advancements, 2005.

Want to read more about tree diseases and pests? Click here to read our article on Emerald Ash Borer, an equally destructive scrouge to trees.

All About Trees is caring for Springfield’s urban forest, one tree at a time.

Jumping Oak Gall

Jumping Oak Gall FOREST HEALTH ALERT From the Missouri Department of Conservation

Tree species affected: White oak (Quercus alba) primarily, and some other white oak group species.

Concerns: Leaves on entire crowns of white oak trees turning brown in late spring. In some areas, whole hillsides appear brown.

Description: High populations of a very tiny, native, stingless wasp (Neuroterus sp.) cause pinhead-size galls (abnormal plant growths) to form on the undersides of leaves. Each round, button -like gall contains one wasp larva. Starting at the margins, brown, scorch-like areas appear on leaves where many galls are present. In more severe cases, leaves curl up, turn black, and drop early from trees. Effects of the damage become noticeable in late spring or early summer and remain visible until fall.

Most galls drop from leaves in early summer. Brown pockmarks remain where galls had been attached. Fallen galls are sometimes observed to “jump” due to vigorous movements of larvae within, much like moth larvae of “Mexican jumping beans.” This behavior allows galls to fall deeper into grass and leaf litter where they are sheltered throughout the coming winter.

Many species of gall wasps have two generations per year. It is assumed that the jumping oak gall wasp in Missouri has a similar life history with one generation lasting only a few weeks in early spring and rarely being noticed. The second generation extends from spring through the following winter and causes most of the leaf damage. Outbreaks typically last for one or two years and then fade away as natural controls reduce gall wasp numbers again.

Similar Leaf Issues: In years with cool wet springs, fungal diseases can be abundant on trees and may also cause leaf browning. Anthracnose is common on white oak foliage in those conditions. Botryosphaeria twig canker causes leaves on infected small branches to wilt and turn brown, which results in “flagging” in the canopy during the summer. Typically, twig bark shrivels and turns brown where the canker occurs, near the junction with healthy tissue.

Recommendations: Galls and fungi that affect oak leaves rarely have a significant impact on tree health. Nearly all trees will recover, even if all leaves are brown. Controls are not warranted. By the time the damage is observed, any opportunity to treat has already passed for that year, and populations are likely to decline naturally. However, severe leaf damage stresses trees, particularly if most leaves on a tree are killed which results in a second flush of leaves emerging in summer. The best tactic is using good tree care practices that reduce stress (mulching, watering during drought, avoiding wounds due to lawnmowers and trimmers).

Questions? Contact your local forester with the Missouri Department of Conservation. Find contact information for your county and more at mdc.mo.gov.

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Treating Ash Trees To Prevent Emerald Ash Borer

Emerald ash borer (EAB), Agrilus planipennis Fairmaire, is an exotic beetle from Asia that was discovered (in North America) in the summer of 2002. The adult beetles nibble on ash foliage, causing little damage. However, the larvae feed on the inner bark of ash trees, disrupting the tree’s ability to transport water and nutrients, eventually killing the tree.

The emerald ash borer most likely arrived in the United States on solid wood packing material carried in cargo ships or airplanes arriving from Asia, and has most likely spread by hitchhiking on firewood transported among homes and recreation areas in at least 34 states.

emerald ash borer

In addition to Missouri, the emerald ash borer has been found in Alabama, Arkansas, Colorado, Connecticut, Delaware, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Nebraska, New Hampshire, New Jersey, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Vermont, Virginia, West Virginia, Wisconsin, as well as, the provinces of Manitoba, Ontario and Quebec in Canada.

Since its discovery in the US, the emerald ash borer has:

Killed hundreds of millions of ash trees in at least 34 states.
Caused regulatory agencies to enforce quarantines and fines to prevent potentially infested ash trees, logs or firewood from moving out of areas where EAB occurs.
Cost municipalities, property owners, nursery operators and forest products industries millions of dollars.

Emerald Ash Borer. (n.d.). Retrieved May 22, 2019, from https://agriculture.mo.gov/plants/pests/emeraldash.php

What if you have an ash tree?

Take action before removal is your only option! If you have an ash tree, you have the choice to protect or remove your tree(s). We recommend that residents consider protecting large, well-placed, healthy private ash trees as part of an EAB treatment program.

Considerations for Treatment:

Tree size greater than 10” in diameter.
The Tree is not competing with other trees or infrastructure.
The Ash tree shows no more than 30% of canopy decline if an infestation is suspected.

Managing Ash Trees. (n.d.). Retrieved May 22, 2019, from https://www.rainbowtreecare.com/emerald-ash-borer/managing-ash-trees/

To better address situations such as these, All About Trees has created a Plant Health Care (PHC) & Integrated Pest Management Program.

Objectives of All About Trees Plant Health Care & Integrated Pest Management Program:

All About Trees is focused on appropriate care for trees and shrubs, using safe, effective, and well-timed visits and applications.
We only administer treatments as deemed necessary, and never try to just “make a sale” of pesticide applications.
All About Trees uses the safest methods for application, using as much systemic products as possible, and never doing tree sprays over 25’ high to limit drift possibility.
Our Plant Health Care Arborists will diagnose insect and disease problems, as well as soil, moisture, and fertility issues. We also recommend how and when a plant health issue warrants treatment.

Please give us a call if you’d like to be added to our calendar for a yearly maintenance check of your trees!

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