How a Tiny Bit of Rust Blew Across the Sea and Changed the Rules NEED: Photos, 8 minute video, video of life "distinct" cycle, Hurricane Ivan maps

Leaf lesions helped Ray Schneigher (right) discover soybean rust in Louisiana. [Source: Science 306:3, December 2004]

Leaf lesions helped Ray Schneigher (right) discover soybean rust in Louisiana. [Source: Science 306:3, December 2004]

Not too many years ago Ray Schneider was walking a group of Midwestern farmers over LSU's Ben Hur Farm one November Saturday afternoon when they ran into some rust. The harvest up north was finished and these soybean producers were on their way to Brazil to try to figure out how their competition was making more money on beans then they were.

The tour group had stopped in at LSU to ask Ray for some hints about what they should look for in Brazil and to eat a last supper of good Cajun food.

Now as you can imagine, these farmers had seen rust before. It was all over their equipment, buildings, in their joints and seemingly gaining on them for years. But never had they seen rust on soybean, nor did they realize then that what they discovered was to change their world.

Rust has been around since who knows when. Archeologists think they found some over 3000 years old in Israel and its presence is recorded multiple times in the Bible. Theophrastus, one of Aristotle's students and the reputed "father of botany", described rusts on grain crops, some twenty two centuries ago. Some of my colleagues even think that the rust fungi are the most important plant pathogen group known. But how would I know! One thing for sure though, some 4000 different rust species have been described and one or more of these pathogens is capable of parasitizing at least one member of every family of higher plants. I challenge you to prove the same for another plant pathogen group!

Soybean Rust on leavesThe rusty soybean phenomenon, however, is probably not that ancient. Soybean rust was first described some 100 years ago in Japan, which makes a lot of sense since the peoples of eastern Asia have been growing soybeans longer than anyone else. Since then soybean rust has spread worldwide. Luckily for us, North America was the last major soybean production region on Earth to be invaded by this pathogen. Unfortunately, this rust has caused yield reductions everywhere it has been found, and if the disease is not controlled by fungicides these losses have often devastated farmers. Now, just in case you are confused, soybean rust is the name for the plant disease caused by the plant pathogen whose Latin name is Phakopsora pachyrhizi. Most unfortunately however, hardly anyone from the U.S. can say the pathogens name as it was intended to be pronounced.

What is not commonly known about soybean rust is that the U.S. "stock piled" P. pachyrhizi as a biological weapon after the Korean War. Which country the U.S. military was prepared to use it against and how they planned to deploy it, one can only guess. However, it was no accident that this pathogen stayed on the USDA's List of Select Agents for many years and that North American plant pathologists were highly alarmed when they heard the news that it had blown across the Atlantic Ocean from Africa to South America and was riding the winds northward.

So, who do they call in their panic, Scott of course- perhaps the only self-proclaimed Professor of Aerobiology in the U.S. Actually, what really happened is that Ray took pictures of some diseased leaves that afternoon and emailed them to Glen Hartman, a soybean rust expert at the USDA ARS NSRL, and Scott happened to walk into his office while he was inspecting them.

Things happened fast thereafter. Scott called his colleague Joe Russo, who is President of a small Information Technology firm with a weird name (ZedX) that specializes in agricultural applications. ZedX computer programmers work all night running the resolveuid/04221d6eaf9a40f487a958e8bec5758e model (IAMS) that the two of them had built to figure out where and when rust had entered our country. Glen had surmised the critical piece of information that they needed for IAMS from the images - how long the pathogen had been rusting Ray's field.

The next morning, Scott compiled the computer model output that Joe's team had created and presented to Glen a map depicting the IAMS prediction of where soybean rust could be found in the U.S. That afternoon Glen flew to Baton Rouge to join the USDA's Soybean Rust Rapid Response Team that was preparing to scout throughout our country for the dreaded pathogen. The message on the map was clear, "look to the east" - Baton Rouge was on the western edge of the rust incursion zone. No one anticipated just how accurate the IAMS prediction turned out to be - not even Scott and Joe.

The Integrated Aerobiology Modeling System (IAMS) had been under construction for about one year by then. Scott had been indoctrinated into resolveuid/04221d6eaf9a40f487a958e8bec5758e a decade earlier and along with a handful of colleagues had been pushing the idea that with the proper technologies one could accurately forecast the movement of biota in the atmosphere. A few years before the rust invasion, Scott with his crazy ideas and Joe with his computational knowhow had met, clicked, and decided to seek funding to build the Integrated Aerobiology Modeling System (IAMS).

Soon after soybean rust jumped the Atlantic, they teamed up with Glen and using funding from the USDA set out to gather the necessary knowledge and create a computer algorithm to predict where and when soybean rust was going to invade North America.

Research team in ParaguayScott took off for Paraguay with a team of young researchers to figure out what soybean rust was all about, while Joe plied his trade in Happy Valley creating the computer code that they would use.

In summer 2004, the team reported back to the USDA that once soybean rust was present north of the equator in South America, a tropical cyclone traversing the Caribbean basin would likely carry it directly into the U.S. on average, one out of every 2 years.

In addition, they predicted that if soybean rust were to invade the U.S. during the autumn, it would most likely enter through the Gulf Coast states. Late that summer, they found out that soybean rust had spread into the valleys in the northern Andes and with Ray's discovery in the Fall, they were able to use the IAMS to pinpoint Hurricane Ivan as the culprit.

P. pachyrhizi, like the rest of us, goes about life in a distinct cycle. It is an obligate parasite which means that it always needs green tissue to survive. Although it has gained a notorious reputation for rusting soybeans, it can do just as nicely on a bunch of other legumes. Unfortunately, the scourge kudzu, the "mile a minute weed", is one of its favorite alternative hosts and so when the soybean fields in our country are all harvested, the pathogen survives on the green kudzu that is abundant all winter along the shores of the Gulf of Mexico. A soybean or kudzu leaf heavily infected with P. pachyrhizi can produce billions of tiny spores in a day that are easily blown by the wind. With the right weather patterns they can be deposited on and infect young soybean plants 1000s of miles away from their source. To get to the point, information about the abundance of this pathogen in the south and when it is producing spores is critical to Midwestern farmers in the major soybean producing states because: 1) the disease can be transported by winds from its overwintering zone to any North American location in 1- 3 days and 2) farmers must be prepared to treat their soybean fields with a fungicide soon after P. pachyrhizi arrives and infects their crop or face substantial yield loss.

So if you are still not bored and want to know the rest of the story - how researchers, USDA administrators and other stakeholders from around the country cooperated to build a "Coordinated Framework" to anticipate the spread of soybean rust in our country the next year, check out this 8 minute video that was shown on TV around the country a few years back.

USDA Honor Award RecipientsThe key to the coordinated effort was the "state-of-the-art" Soybean Rust Information Technology platform that the PSU/ZedX team built to connect stakeholders on our continent with critical information flows. Suffice it to say that this effort was successful; the USDA Economic Research Service published a report that our team increased soybean growers profits somewhere between $11 - 300 million in 2005 alone over what they would have been without our efforts and that the U.S. Secretary of Agriculture personally conferred his department's highest Honor Award to "Coordinated Framework" team members that year.

Yet with all the accolades, the PSU/ZedX team didn't stop pushing their on-going agenda to provide the American farmer with 'state-of-the-art" information technologies (IT) to fight crop pests. The next year, they converted the Soybean Rust Information System into a general IT platform for pest management that they named the PIPE (Pest Information System for Extension and Education). Fortunately this effort caught the attention of USDA administrators, in particular Kitty Cardwell (who you saw in the video), and was adopted nationwide as the USDA's new paradigm for doing integrated pest management. If you don't believe me, check out the 2009 USDA Specialty Crop Research Initiative that lists as one of its priorities: "Develop new integrated pest management tools such as have been demonstrated with the integrated pest management - Pest Information Platforms for Extension and Education (ipmPIPE) and other wide-area, integrated systems that possess broad impact."

Soybean Production in the United States, Acres Harvested

2002. Map compiled by Annalisa Ariatti, Source: US Department of Agriculture, National Agricultural Statistics Service

Incursion of Soybean Rust in the United States

Soybean Rust Spore Detection by County, January 12th, 2005. Observations overlayed on the predicted soybean rust spore deposition map. Map compiled by Annalisa Ariatti (UIUC) Source: APHIS Soybean Rust Hot Issues Web Page, Dan Borchert, Glenn Fowler and Roger Magarey (USDA-APHIS-PPQ-CPHST-PERAL)


The study of biological and meteorological factors that influence the movement of organisms and biological particles in the atmosphere.