Production Blog

Here's Hoping We Overestimate Another Invasive Pest

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
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Are the dangers of Old World Bollworm to the U.S. as overstated as the danger of soybean rust was? Let's hope so. (Photo courtesy Gyorgy Csoka/Hungary Forest Research Institute -- Creative Commons).

ROCKVILLE, Md. (DTN) -- Soybean rust was a best case scenario for an invasive pest. When the tropical pathogen swept up into American soybean fields in the fall of 2004, the country's agricultural community was armed and ready.

By the time springtime rolled around, 35 states had prepared more than 300 "Sentinel" soybean plots, to be checked weekly for the insidious yellow rust spores. A website was launched and ready to track the spread of the disease, which had been known to cause up to 90% soybean yield loss in regions like Africa and South America.

Perhaps most importantly, the university Extension system -- an essential but diminishing institution -- was re-charged and energized. Over the years, funding poured in from USDA, the Risk Management Agency and the United Soybean Board.

The details of this reaction can be found in a recent DTN story, Rust Retrospective (http://bit.ly/…). As I penned it, I found myself hoping I write a similar story 15 years from now -- on a completely different beast.

Old World Bollworm, known as Helicoverpa armigera, isn't well known to American farmers just yet. The pest has long been an agricultural pest of immense influence in other regions of the world -- Australia, Europe, China, Africa and Asia -- but only recently did it breach the Western Hemisphere.

In 2013, it was found ravaging the soybean fields of Mato Grasso, Brazil. A pest of impressive migratory abilities, the moth has been moving steadily north ever since. In September 2014, it was found on pea plants in Puerto Rico. By July of 2015, a handful of male moths had fluttered into the continental U.S. and were found in Florida in the western coastal county of Manatee.

For now, that's as far as the Old World Bollworm has ventured (or rather, been found) in the U.S. But given its broad appetite for over 180 species of plants, including cotton, corn, soybeans, small grains, fruits, vegetables and more, entomologists have told DTN again and again that its spread is likely imminent.

Perhaps most concerning is the pest's ability to develop resistance to insecticides rapidly. Old World Bollworm has already overcome pyrethroids in many parts of the world. Now research has shown that it often carries genes that grant resistance to Bt traits the pest has never even encountered.

Take Vip3a, Syngenta's highly effective Viptera trait targeting aboveground pests like the Old World Bollworm.

The trait has not yet been commercialized in Australia. But scientists from Spain and Australia just published a study showing that "resistance alleles" to Vip3a "can readily be detected in Australian field populations despite no obvious selection."

"Natural variation exists in insect populations that could drive resistance once crops expressing Vip3Aa are introduced unless appropriate resistance management measures are implemented," the scientists wrote.

Vip3a is used in the U.S. -- as are a number of other aboveground Bt proteins, which are deployed broadly each season across both corn and cotton fields. This exposure could give the Old World Bollworm a much greater opportunity to become a Bt-resistant threat, the Australian and Spanish scientists concluded.

"With the recent incursion of H. armigera into the New World, there is enormous potential selection for resistance primarily due to the large areas of corn expressing Vip3Aa proteins to control the closely related Helicoverpa zea and other lepidopteran corn pests," they wrote.

Another study, published in March 2015 by a group of international scientists familiar with Old World Bollworm estimated that $843 million worth of U.S. crops would be vulnerable to the pest, given its climactic preferences.

You can find both studies here: http://bit.ly/…and here: http://bit.ly/….

Soybean rust's threat to U.S. soybean growers never quite materialized. Though it remains a disease of prominence in the South, it has never made it to the Midwest early enough to impact yields there.

But in the wake of the disease's invasion, we were left with a blueprint for detecting and monitoring an invasive agricultural pest.

Like soybean rust, Old World Bollworm has roused funding from USDA's Animal Plant Health Inspection Service (APHIS). In 2015, APHIS committed $1.2 million toward research and surveying efforts -- a twelve-fold increase from the previous year. In 2016, APHIS funding for these efforts continued but declined to $865,000.

Just as scientists watched for rust spores each year, the National Cooperative Agricultural Pest Survey is actively conducting searches for Old World Bollworm. Last year, state, government and academic employees surveyed fields in 26 states for the pest. (Track their surveying efforts here: http://bit.ly/….)

This may seem like too much money and time spent on a pest that isn't established yet, just as the preparation for soybean rust might seem like overkill in retrospect.

This isn't and that wasn't.

Soybean rust was a practice run for a dangerous, landscape-changing invasive agricultural pest that could alter American farming habits forever. We did really well on that test. Let's hope we do just as well with Old World Bollworm and anything else that follows.

Emily Unglesbee can be reached at Emily.unglesbee@dtn.com.

Follow Emily Unglesbee on Twitter @Emily_Unglesbee.

(PS/CZ)

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