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Arbotect 20-S is a systemic fungicide formulated with Thiabendazole and is applied through a process called macro-infusion. Arbotect 20-S is the only scientifically proven fungicide that provides multi-year protection from Dutch Elm Disease.

In Canada, Arbotect 20-S is registered by Health Canada’s Pest Management Regulatory Agency (PMRA) as a preventative treatment against Dutch Elm Disease (PCP 16694).

Macro-infusion rapidly introduces a large volume of solution directly into a tree’s vascular system. Macro-infusion delivers complete and even distribution of solution throughout the tree’s canopy, which provides for predictable results.

Prevention of DED

One application of Arbotect 20-S protects the entire tree for up to three years yielding significant cost savings. The most common method of transmission of DED is on the bodies of elm bark beetles that feed on two- to four-year-old branches. There are multiple generations of elm bark beetles per year. Thousands of beetles may hatch from a single tree.

To ensure even distribution, Arbotect 20-S is injected using the Macro-Infusion injection method. Macro-Infusion injects a large volume of solution into the root flares of the tree. This solution is then transported throughout the canopy providing a protective fungicide barrier.

Only Arbotect 20-S has the ability to move into the newly formed sapwood, while resisting degradation resulting from cold, heat, and other adverse conditions.

Arbotect 20-S was first registered over 30 years ago and has a proven 99% success rate when applied as per manufacturer’s directions.

Related Pest & Pathogens

Arbotect® 20-S Labels
Arbotect® 20-S

The product label contains directions and application rates


This Safety Data Sheet contains occupational safety and health data for this product.


Dutch elm disease is caused by two strains of an aggressive fungus (Ophiostoma-ulmi Ophiostoma-novo-ulmi) that provoke elm trees to die regardless of their health. It is considered the most costly shade tree disease 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 which the tree reacts. In defense to the toxins, the tree produces tyloses designed to block the spread of the fungus. The combination of the toxins and the defense mechanisms of the tree inhibit water flow to the crown, which causes wilting and tree death.

Dutch elm disease symptoms begin to develop 4–6 week 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 infected branches turn dull green to yellow, curl, and become dry and brittle. As the infection spreads, the wood beneath the bark displays a brown discolouration.

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 to feed on 2–4-year-old branches, and thereby spreading the disease.

Dutch elm disease can also be spread by root contact/root grafting from one diseased elm to a healthy elm.

Most infected elms cannot be saved. In rare cases, if the fungus has not moved into the root system, physically cutting out the 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 identification and rapid removal of diseased elms. Such practices eliminate beetle breeding sites and reduce the number of disease carrying beetles.

The goal when protecting elms from Dutch elm disease is to evenly and completely distribute a fungicide throughout the entire canopy of the tree.

  • To protect a tree from beetle-transmitted fungal infection, Arbotect 20-S, must be evenly and completely distributed throughout the 2–4-year-old branches.
  • The only way to get even distribution is by macro-infusion of a large volume of solution into the root flares of the tree.
  • Arbotect is a fungicide that protects elms from beetle-transmitted infection, and is the only fungicide that provides three growing seasons of protection.
  • Arbotect does not protect elms from root graft infection.

Applications can be made after leaves have fully flushed in the spring. Treatments can continue throughout the growing season, or until leaf senescence in the fall.

Treatment should be used in conjunction with an insect control and sanitation program (early detection and rapid removal of infected trees) in order to obtain best results. Use of Arbotect 20-S does not prevent the transmission of Dutch elm disease via root grafts.

Arbotect Macro-Infusion Manual
Arbotect Macro-Infusion Manual

Learn more technical information and application rates in this injection system manual.

Tips and Tricks
Tips and Tricks

A micro-infusion guide and dosing table

Dutch Elm Disease: Basic Fact Sheet
Dutch Elm Disease: Basic Fact Sheet

A technical sheet to better understand Dutch Elm Disease.

Protecting Elm Trees Using Arbotect 20-S

Arbotect 20-S is a preventative treatment for Dutch Elm Disease (DED). It is the only scientifically proven systemic fungicide that provides multi-year protection (up to 3 years) from DED, with a proven success rate of 99% when included in an DED IPM program.