U.S. Pest Invasion

By Emily Unglesbee
DTN Staff Reporter

ST. LOUIS (DTN) — An Old World agricultural pest has officially invaded U.S. territory, and experts say a future invasion of the U.S. mainland is probably unavoidable.

Helicoverpa armigera, known as the Old World bollworm, was detected in the U.S. territory of Puerto Rico in September 2014, an alarming advance that signals a likely U.S. invasion of the pest, government and academic experts have concluded.

"This is a significant event," Louisiana State University entomologist David Kerns told DTN. "Honestly, it’s just a matter of time; if it’s in Puerto Rico, we’re going to have it soon, if we don’t already."

The armigera caterpillar is a far more dangerous pest than its American relative, the corn earworm, also known as the cotton bollworm. It causes enormous agricultural damage each year to cotton, corn, soybean and myriad other crops. Nearly a third of all global pesticide applications are aimed at killing it in China, India, Australia, Africa and Europe. "It’s infamous for developing resistance to a lot of things, including Bt and insecticides," Kerns noted.

Chances of the H. armigera reaching the U.S. became more likely when the pest was discovered in Brazil in 2013. At the time, experts told DTN that a U.S. invasion would require the pest to surpass significant hurdles, such as massive distances over land and air, and a robust U.S. port and border inspection service.

The Old World bollworm has apparently triumphed against these odds. In November of 2014, a group of university entomologists and scientists from the USDA’s Animal and Plant Health Inspection Service (APHIS) met in Portland, Ore., to hammer out the status of the pest’s advance in a technical working group.

Their conclusions were grim. "With the probable establishment of the pest in the Caribbean and possibly other areas of the Western Hemisphere, it is probably just a matter of time before the infestation gets here," the scientists concluded in a published summary of the working group’s meeting.

The pest is likely to move to the U.S. mainland through air currents, they concluded: "The adults are highly mobile and should be able to easily migrate to the U.S. through favorable air currents as the populations are established closer to the U.S. … i.e. if insect populations are high in Puerto Rico, other islands in the Caribbean or eventually Central America."

While H. armigera has only been confirmed in five municipalities in Puerto Rico at the moment, it is likely to have spread to other parts of the Caribbean, the scientists noted. Already, the Netherlands has reported finding H. armigera in a shipment from the Dominican Republic. Efforts are underway to survey the entire Caribbean Basin for the pest, and search efforts in Puerto Rico have expanded to include 327 insect traps, the working group said.

Information about the pest from Cuba is not forthcoming, and the working group recommended that APHIS work with countries currently in contact with Cuba, such as Canada, Australia and Mexico, to ferret out the pest’s possible presence there.

For now, APHIS is planning "increased surveillance in Southern states" in 2015, and the working group did not express much confidence in the government’s ability to keep the pest out.

"Aside from the current regulations of mitigation and inspection of imported commodities from areas where establishment is known, there are not many other regulatory options to prevent the introduction of H. armigera," they noted, adding later that "there is some perception from concerned citizens that inspections and preventative measures to prevent entry of H. armigera are not as effective as we think they are."

Pest populations originating from Puerto Rico are not unusual in the U.S. Most recently, populations of fall armyworms resistant to the Bt-protein Cry1F, appeared in the southern U.S. While their Puerto Rican roots have not been proved definitively yet, that origin is likely, North Carolina State University entomologist Dominic Reisig told DTN. "There is molecular work showing that the migratory pathway comes up from the Caribbean and the [Bt] resistance developed in Puerto Rico," he noted.

Prevailing winds from Puerto Rico typically blow up through Florida and the Carolinas, Kerns noted. Sometimes tropical storms can send winds from the Caribbean even farther west, into Louisiana and even Texas, he added.

ONCE THE PEST IS HERE

Once H. armigera establishes itself on U.S. mainland soil, farmers will have to brace themselves to deal with it indefinitely, the working group concluded.

"There will likely be a recurring influx of H. armigera into the U.S. once it becomes established closer to the border," the scientists concluded. "Eradication is not a likely scenario or a productive solution as it was deemed to have a low chance of success."

The armigera caterpillar would be happy to feast on 180 different plant species in the U.S., including corn, cotton, soybeans, tobacco, sunflowers, sorghum and many other crops.

While cold winters would limit its establishment in the northern U.S., the pest would thrive in Southern states and could produce many generations. One female can lay 3,000 eggs, and the pest can churn out up to 11 generations in warm climates.

Outside of the U.S., H. armigera can cause losses of up to 100% in cotton fields with no protection, the working group noted. In fields with conventional pesticides, 10% to 20% yield loss is typical and Bt cotton fields have seen losses of 5% to 7%. In Brazil, soybean damage from the pest reached 100% in non-Bt soybeans and the scientists pegged Bt-soybean field losses at around 10%. In Australia, where the pest is common, farmers spend about $350 per hectare to control H. armigera each year, the working group scientists added.

Insecticides such as diamides, spinosads, and pyrethroids, as well as Bt crops, would be American farmers’ main defenses against the Old World bollworm, the working group noted.

Figuring out where the Puerto Rican population of H. armigera came from is critical, National Cotton Council Manager of IPM Don Parker noted. "Historically that pest species has had a genetic characteristic of developing resistance to pesticides more rapidly than the bollworm we are currently faced with," he told DTN. "So where that population comes from could really change our pest management strategies."

H. armigera has developed extensive resistance to pyrethroid insecticides globally, and scientists have identified Bt-resistant populations in Pakistan, China, India and Australia. "There is the report of some diamide resistance developing in Brazil, and it would be good to find more information on this in preparation in the event of the arrival of H. armigera to the continental U.S." the working group added.

They recommended initiating efforts to screen the Puerto Rican populations for insecticide resistance.

You can find the working group’s assessment of H. armigera here: http://goo.gl/…. You can find USDA APHIS’ tracking of the pest, as well as its recommendations for scouting and detecting it here: http://goo.gl/….

You can find a map of where in the U.S. federal and state officials have surveyed for the pest over the past decade here: http://goo.gl/….

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

Follow Emily Unglesbee on Twitter @Emily_Unglesbee.

(PS/SK/AG)