Prepping for a Pest

By Emily Unglesbee
DTN Staff Reporter

ST. LOUIS (DTN) — Helicoverpa armigera, the Old World bollworm currently munching its way through South America, could be very happy in the United States. That’s the sobering assessment of a new government document aimed at preparing for the pest’s possible immigration to this country.

Taking into consideration climate, cropping habits and wild plant hosts of this country, "H. armigera could potentially become established in every state of the continental U.S.," the USDA’s new Pest Response Guidelines for H. armigera concluded. The new guidelines were developed to help state and federal officials react quickly if the pest were ever to make its way into American agricultural fields.

Until recently, H. armigera has been a very distant threat for American farmers. The caterpillar causes enormous agricultural damage each year across the globe, with nearly a third of all global pesticide applications aimed at killing it in distant places such as China, India, Australia, Africa and Europe.

The pest struck closer to home in January 2013 when H. armigera showed up in cotton and soybean fields in the northeastern Brazilian state of Bahia. Although the pest’s pathway to Brazil is still unknown, U.S. officials would like to make sure the caterpillar doesn’t stray farther. In the case of an invasion, however, the new pest response guidelines document sets forth the regulations and steps involved in identifying and quarantining the pest.

POSSIBLE SOURCES

An invasion by a Bt-resistant population of the caterpillar would represent the greatest threat to American farmers, who rely heavily on Bt-crops to control other agricultural pests.

Globally, the pest has "developed resistance to the widest range of insecticides of any insect targeted, with populations having demonstrated resistance to organochlorines, organophosphates, carbamates, pyrethroids, spinosad and Bt toxins," the guidelines noted.

Specifically, H. armigera populations in China, Australia, India, and Pakistan have shown resistance to some Bt proteins, primarily Cry1Ac.

Knowing where the pest is from and which types of resistance it could sport is part of preparing for an invasion. Like many invasive pests, H. armigera has actually breached U.S. borders on hundreds of occasions in the past. According to the new guidelines, between June 1984 and August 2013, H. armigera has been intercepted at U.S. ports of entry 965 times.

Just over half of those H. armigera interceptions originated from Israel or the Netherlands, and 67% were found on cut flowers.

Fortunately for U.S. farmers, USDA’s Animal and Plant Health Inspection Service (APHIS) is not aware of any documented insecticide or Bt-resistant populations of the caterpillar in the Netherlands or Israel, according to a written response by APHIS officials to DTN’s questions.

Moreover, of the countries seeing H. armigera resistance to Bt proteins, only India surfaced significantly on the pest response guidelines’ list of insect interceptions, where it represented 8% of all H. armigera interceptions in the U.S. since 1984.

PROTOCOL FOR AN INVASION

Should H. armigera ever make it past port inspectors and into an American field, the insects would hit the second line of defense outlined in the pest response guidelines: yearly scouting efforts orchestrated by the Cooperative Agricultural Pest Survey (CAPS). Every year, states work with the USDA to plan out surveys for invasive pests, based on how likely the pest is to enter the state, survive its climate and eat its crops. Since 1995, 39 states have been surveyed negatively for H. armigera, APHIS officials told DTN.

The pest response guidelines lay out the best surveying methods and insect traps for H. armigera, and establish proper identification and regulatory steps in case a potential specimen is found. Official identification of the pest requires dissection of the genitalia for adult moths and DNA analysis for eggs, larvae, or pupae.

Even before experts confirm the pest’s identity, APHIS can issue an Emergency Action Notification that allows the agency "to hold the movement of potentially infested plant products while final confirmatory identification by a recognized authority is completed," APHIS officials told DTN.

If the pest is officially confirmed as H. armigera, then "delimiting surveys" would be launched to establish how widespread the infestation is. "In an emergency response, during the delimitation phase, historically we have set up with state departments of agriculture, on site laboratories with trained personnel to process large numbers of samples from the field," APHIS officials explained.

Ultimately, a lot of things would need to go right for an H. armigera specimen to establish itself successfully after evading port inspectors, APHIS officials concluded.

"It should also be noted that in order for H. armigera to proliferate on U.S. soils large numbers of any life stage would have to escape detections at points of entry, develop to the adult stage on local hosts, find a mate, and successfully reproduce," APHIS officials said.

You can see the new pest response guidelines for Helicoverpa armigera here: http://goo.gl/….

You can find the CAPS survey history and data for H. armigera here: http://goo.gl/….

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

Follow Emily Unglesbee on Twitter @Emily_Unglesbee

(AG)