"Fight them on the beaches or let the new order begin"

Lab Note #7
Mar 23, 2015

Have you heard the quote "Those who don't know history are doomed to repeat it"? If not, perhaps you are familiar with the claim "history repeats itself".

One of the best examples of the truth to these quotes is the continual introduction of new tree killing microbes. Chestnut blight, white pine blister rust, dutch elm disease, and sudden oak death are all examples of tree diseases caused by microorganisms that were accidentally introduced to the forests in North America. It is likely that someone you know, or one of your ancestors, has been affected by one of these microorganisms.

American Chestnut Blight

Chestnut blight is a fungal canker disease caused by Cryphonectria parasitica. As a result of the accidental introduction of C. parasitica around 1910, the invasive and exotic microbe had killed most of the mature American chestnut trees throughout its range within 30 years.

Photo Credit: Linda Haugen, USDA Forest Service

Photo Credit: Ministry of Agriculture and Regional Development Archive

Dutch Elm Disease

Dutch elm disease is a vascular wilt caused by two species, Ophiostoma ulmi and O. novo-ulm. Each pathogen is vectored (carried) by wood boring insects that were originally introduced to the United States with log shipments traveling along the railroad lines. Historically, this disease has been driven by two different pathogen outbreaks; the second pandemic, caused by O. novo-ulmi, is estimated to have killed between 30 and 50 million elms in the United Kingdom alone.



Photo Credits: Coalition of Save the Elms

Photo Credit: Minnesota Department of Natural Resources Archive

Photo Credit: Fabio Stergulc, Università di Udine, Italy

White Pine Blister Rust

White pine blister rust is a disease caused by Cronartium ribicola. It infects five needle pine species (western/eastern white pine, sugar pine, whitebark pine, etc) but requires an alternate host to complete its life cycle. The alternate hosts are currant/gooseberry shrubs (Ribes spp.). Since it requires two hosts for reinfection, there was a large push for Ribes spp. eradication programs in areas of the United States where white pine growth was important during the mid 20th century.

Photo Credit: Petr Kapitola,Central Institute for Supervising and Testing in Agriculture, Czechia

Photo Credit: USDA Forest Service - Ogden Archive

Sudden Oak Death

Sudden Oak Death is the most recent introductions of the few that I have featured in this labnote. Sudden Oak Death is a disease in forests of California and SW Oregon. The disease is caused by Phytophthora ramorum. Phytophthora, the Greek term for 'plant-destroyer', is a group of organisms most easily described as water molds. The water mold that causes Sudden Oak Death has killed millions of trees in California alone. One of the reasons it is so difficult to control is because of its enormous host list (species that serve as carriers). Phytophthora ramorum is also causing widespread disease in Japanese Larch plantations of the United Kingdom (see below video).

More information about Sudden Oak Death is available in this other labnote.

Photo Credit: Forest Health and Protection Region 6, USDA Forest Service

Photo Credit: Joey Hulbert

"Fight them on the beaches or let the new order begin" Hal Mooney, Stanford.

I have heard this quote many times during coursework lectures from my MS advisor, Everett Hansen. The idea is: once a new invasive and exotic microorganism has been introduced, the best action is rapid eradication. Otherwise, the microorganism becomes established and becomes extremely difficult (or impossible) to control.

Here is an example: Sudden Oak Death was detected in Oregon in 2001. Shortly after, an eradication program was initiated and slash & burn treatments were conducted at detected outbreaks. The program has had success on local scales (stopping further infection in the area), but regionally, the pathogen continues to spread because of financial deficiencies varying from year to year. The management of Sudden Oak Death in Oregon now focuses on slowing the spread and the effort is justified because the pathogen has spread much slower than it would have naturally, saving landowners outside of the quarantine from being affected. So we lost the fight on the beach, what is the new order? Are we prepared to lose mature tanoak trees throughout their range—similarly to the stories of chestnut blight or dutch elm disease?

Though eradication may be the best management strategy once a species is introduced, preventing the introduction from ever happening in the first place is certainly the best (and cheapest) way to protect our forests. Preventative care and early detection are key to protection—this is true for our bodies and our forests. "Our bodies are ecosystems"

If this is the case, why do new species keep arriving? Why can't we limit their introductions? What are the pathways of introduction? Where is the biosecurity?

"People are part of ecosystems" Globalization of goods and services has unequivically increased the amount of accidental plant pathogen introductions.

This last video is ridiculous (that is a perfect example of how a single person can introduce a plant disease like Sudden Oak Death). Though there are efforts to buy local, globalization is probably not going to slow, especially with continued population growth and a changing climate. So what are our options? Investing more money in biosecurity would help but currently the United States' system only regulates species that we know to be problem causing. How can we regulate the trade of invasive species if we don't know which species that will be invasive? This is why proactive and preventative research is critical.

"The best defense is a good offense" Our research to survey the native forests of South Africa for Phytophthora species is a form of preventative research. By discovering what is out there, we will be able to research and regulate the species that pose threats to major forests around the world. If you see the value in this research, please help us share this lab-note.

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