Why is Dutch elm disease considered to be an invasive species?

 

An “invasive species” is defined as a species that is:

  1. Non-native or alien to the ecosystem under consideration and
2. Whose introduction causes or is likely to cause economic or environmental harm or harm to human health (Executive Order 13112).
The harm these species can cause comes in a variety of forms including alteration of evolutionary pathways of native species through competitive exclusion, niche displacement, hybridization, introgression, predation, and extinction. Other problems commonly accompanying invasive species that make them dangerous to native ecosystems are:

- Ability to form a monoculture
- Ability to prevent native canopy tree regeneration
- Cloning
- Extreme competitiveness
- Hybridization
- No disturbance requirement
- No natural enemies
- Prolific reproduction
- Shade tolerance
- Shade generating
- Smothering
- Overgrazing
- Environment modifier

(U.S. Department of the Interior)
The success of invaders is ultimately depending on its behavior and interactions with the new environment it inhabits (Mooney 2001) . Invasive species can be plants, animals, and other organisms such as microbes. Dutch elm disease is an invasive species because it is non-native to the United States. Secretary of Agriculture Wallace quarantined all Elm products from Europe after he stated the Dutch elm disease was introduced by elm burl logs that had been shipped from over to the United States from Europe. There had been eight shipments that had been found to be infected. A quarantine was placed on elm trees entering the United States in the form of lumber, timber, crates, boxes, or containers. These products had to be free from all bark and had to undergo a hot water or other approved treatments to kill the fungus (Science, 1933).

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