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WSU’s On Solid Ground: Stink Bug Invasion, Unpalatable Poplars, Ag Forum

Posted by | March 13, 2014

Scientist SWAT team combats stink bug invasion

The stink bug is topped with a marbled shield, hence the name “marmorated.” (Photo by Bob Hubner, WSU)
The stink bug is topped with a marbled shield, hence the name “marmorated.” (Photo by Bob Hubner, WSU)

An alien pest that smells like dirty socks and devours crops may become Washington state agriculture’s Public Enemy No. 1 in less than five years, government and university researchers are warning.

To avoid this fate, the scientists are ramping up the fight against the mounting threat to the region’s fruit crop industry.

Washington State University is one of 10 institutions across the nation whose researchers are working to head off an invasion of the brown marmorated stink bug.

Tracy Leskey is an entomologist with the U.S. Department of Agriculture who’s leading this scientist SWAT team. “One of the most disturbing things about this bug is its scope,” she said from her office in Kearneysville, W. Va. “In a relatively short period, they’ve spread to 40 states; and they’ve made it look so easy.”

Bugs gone wild

Since the brown marmorated stink bug, or Halyomorpha halys, was discovered in Pennsylvania in 1998, the shield-shaped insect from Asia has advanced down the east coast and spread west nationwide – gorging on everything from peaches and grapes to soybeans and corn. In a single year, it took a $37 million bite out of the mid-Atlantic’s apple crop.

Now that this voracious bug has landed in Washington and elsewhere in the Northwest, “researchers are trying to learn everything they can about this insect to prevent big crop losses as it establishes itself here,” said WSU entomologist Richard Zack.

“Because they’re nonnative to this country, we have no natural enemies to keep their numbers down,” he said. “They keep expanding their geographical reach and they keep multiplying.”

What’s more, the effectiveness of chemicals for pest control remains iffy: “So far, they’re not as susceptible to insecticides as we would hope,” said Zack.

‘We’ll see more’

Right now, brown marmorated stink bugs are overwintering inside people’s homes, sheds and attics and under wood piles. Some are even being stowed away to new locations in vehicles driven by unsuspecting accomplices.

But come May and June, they’ll emerge to mate, lay eggs and find food, said USDA’s Pete Landolt, research leader of the Yakima Agricultural Research Laboratory in Wapato, Wash.

“I expect that, in 2014, we’ll see more brown marmorated stink bugs and we’ll see them in more places in Washington,” he said. “Based on what we’ve seen happen in the eastern United States, unless we can figure out a viable strategy to control them, we could see severe crop injuries in less than five years.”

Unlike most insects, these bugs are “generalist feeders,” meaning they eat many plant species, said Landolt. They plunge needle-like mouthparts into crops and then suck out the juice or sap. Fruits, in particular, are vulnerable to damage. Given that Washington is the nation’s leading producer of apples, pears and sweet cherries, the implications are far-reaching. Wine grapes are another major crop in Washington, where more premium wines are produced than any state except California.

“The insect’s expanding presence here has got growers nervous,” Landolt said, “not to mention the researchers who are tracking population levels and working on ways to keep those levels from soaring.”

So far, the bugs are most concentrated in Clark and Skamania counties, just across the Columbia River from infestations in Oregon, said Landolt. Sporadic numbers are appearing in areas such as Klickitat County, the Yakima Valley, Walla Walla and Chelan County. All are fertile agricultural areas where orchards and vineyards stretch across landscapes for miles.

Grape growers on alert

A brown marmorated stink bug circles an apple held by WSU entomologist Richard Zack. (Photo by Robert Hubner, WSU)
A brown marmorated stink bug circles an apple held by WSU entomologist Richard Zack. (Photo by Robert Hubner, WSU)

No brown marmorated stink bugs have turned up yet in Washington’s vineyards, said WSU entomologist Jay Brunner, regional leader of the research team. But scientists from Oregon State University, which is also a member of the scientific group, have trapped them at three vineyards.

“It does attack grapes, including wine grapes,” said Brunner. In addition to puncture wounds, another concern is the potential tainting of aroma and flavor if the bugs find their way into lugs, or crates, during harvest, he said.

This could be a problem considering that “dirty socks,” “spoiled cilantro” and “skunky” are terms used to describe the scent emitted by stink bugs when threatened or crushed.

Interstate travel, innocent bystanders

These bugs can fly, but vehicles best explain how, in Oregon and Washington, they’ve settled in areas off the I-5 interstate and highways.

“They are the most amazing hitchhikers,” said entomologist Michael Bush of WSU’s Yakima County Extension. They catch rides in boxes and crates packed in cars, trucks and trailers or even in a groove between seats, he said.

Bush works with other WSU Extension scientists to teach master gardeners, field workers and the public how to tell brown marmorated stink bugs from similar-looking native stink bugs.

“Several of our native stink bug species are beneficial because they feed on other insects that damage crops,” he said. “That’s why it’s important to know the difference and not kill them all.”

He tells people that the easiest way to ID the brown marmorated variety is by the thin white bands on its antennae. Verification questions can be addressed by WSU entomologists, local county extension specialists and related professionals.

Bring in the wasps?

Back home in Asia, the stink bug’s mortal enemy is a parasitic wasp that lays eggs inside stink bug eggs, destroying them. This tiny terrorist – the size of a gnat – could be released on U.S. soil to serve as a natural pest controller, said project leader Leskey of the USDA.

But first, scientists must do “rigorous screening” to make sure it’s safe to introduce in this country, she said.

Chemicals that lure stink bugs into traps and light intensity levels that attract them are also being looked into, she said.

For more information, go to the Stop the Brown Marmorated Stink Bug national research team’s website at

Find the original version of this story at WSU News:

Linda Weiford

Detecting unpalatable poplars

Poplar stems, some damaged by voles. (Photo by Jeff Kallestad, WSU)
Poplar stems, some damaged by voles. (Photo by Jeff Kallestad, WSU)

Imagine you’re a poplar breeder trying to improve poplar varieties for biofuel feedstock. You want them to grow fast and have high levels of defensive compounds in their leaves and bark to keep pests like insects, voles and deer at bay. You’ve carefully planted 100 seedlings in the field and tended them for a full growing season. But now you must select only ten plants with the traits you want for a second round of testing. The rest get sent to the compost heap. How do you choose which offspring hold the best potential to deter pests?

Jeff Kallestad, a member of the Advanced Hardwood Biofuels Northwest research team who is located at the WSU Puyallup Research and Extension Center, is developing screening tools to help poplar breeders answer this question.

“If we can breed for plants that are less tasty and more toxic for pests, then poplar growers can apply fewer pesticides to their tree farms,” said Kallestad. “We call it low impact pest control.”

Cost control

Low impact and cost effectiveness are the name of the game given that you need up to 100,000 acres to supply poplar feedstock for a decent-sized biofuel plant. You can’t put a deer fence around an area that large and insect and vole populations can explode in a monoculture, but you can breed for trees that pests find off-putting. However, to measure the defensive compounds in poplar leaves and bark requires specialized skills, chemistry equipment, time, and a lot of money.

Jeff Kallestad with the NIR spectrometer. (Photo by Jen Vittetoe, WSU)
Jeff Kallestad with the NIR spectrometer. (Photo by Jen Vittetoe, WSU)

A cheaper and faster alternative is to use a near infrared, or NIR, spectrometer, which uses light waves on the spectrum invisible to the human eye, to measure properties of chemical compounds at a molecular level. Kallestad is using NIR spectrometry to measure the abundance of condensed tannins and phenolic glycosides, which are chemical defense compounds. He uses complex statistical methods to calibrate the tool for each specific defense compound found in samples from hybrid poplars.

“The NIR spectrometer can be used to measure hundreds of leaf samples in a relatively short period of time, and for relatively little money. That’s where the payback comes,” Kallestad said. He is also developing criteria to determine whether pest resistance in the trees is associated with the concentration of a particular defensive chemical compound.

In the first two years of the AHB study, Kallestad focused on discovering the abundance and diversity of unpalatable compounds in a wide range of poplars. After collecting hundreds of leaf and bark samples for testing, he successfully created NIR spectroscopic calibrations for most of the phenolic compounds. He also experimented with methods to help poplar breeders determine the optimal leaf age, position on the plant, and season for harvesting the test samples

Feeding preferences 

So far, studies have affirmed that deer and voles prefer to feed on certain groups of poplar and even on particular clones within a group. However, these studies also showed that deer and voles were not particularly averse to poplars with the most abundant phenolic glycosides or condensed tannins. In other words, the animals avoided certain varieties but not necessarily because of these particular compounds.

Even though feeding preference was not associated with a particular set of known compounds, the NIR spectrometer remains a useful tool for poplar breeders concerned about vole damage. Based on what he learned from the NIR spectrometry study results, Kallestad was able to develop a model for predicting the amount of poplar bark that voles will likely consume among different clonal varieties, which would allow breeders to select varieties that would be less likely to be eaten by voles.

This year is the third in the five-year AHB project. Kallestad is focusing on determining whether poplar resistance to insect damage is associated with any of the specific phenolic compounds that can be measured using NIR spectroscopy. Similarly, he plans to see if fungal diseases are associated with the defensive plant compounds. Working with Dr. Posy Busby of the University of Washington, he will also use NIR spectrometry to determine whether inoculating trees with endophytes, microbes that live within plant tissues, increases the defense compounds.

Ultimately, the NIR spectrometry methods Kallestad is developing will result in inexpensive and reliable tools that poplar breeders can use to determine which seedlings show the most promise for low impact pest control to help ensure a high-yielding source of feedstock for biofuel production.

-Sylvia Kantor

The changing face of agriculture

Keiko Tuttle believes the biggest challenge agriculture will face in the next five years centers around a food source that makes up 70 percent of the human diet: cereal grains.

Keiko Tuttle in the small grain plant growth facility at WSU in Pullman. (Photo by Rachel Webber, WSU). View on Facebook.
Keiko Tuttle in the small grain plant growth facility at WSU in Pullman. (Photo by Rachel Webber, WSU). View on Facebook.

“I always ask people, ‘Do you like cookies?’” the WSU doctoral candidate in Plant Molecular Sciences explains lightheartedly, inviting people into a discussion about the influence of cereal grains on the food system and the need to feed a world population some project to near 11 billion by 2050.

Tuttle is researching seed dormancy in wheat – that is, seeds that don’t germinate when planted. Understanding more about the genes and proteins that influence the process of dormancy and how the mechanism is released may provide solutions to other problems growers have in the field.

Because dormancy is related to degradation of the important starch found in cereals, the factors involved can decrease the end-use quality of the grain. Preventing these problems can potentially eliminate economic losses to growers, millers and bakers. This is especially critical in the Pacific Northwest, which provides the nation with about 95 percent of its soft white winter wheat. That is worth a gross $1 billion to the state of Washington, Tuttle said.

Taking answers to D.C.

Tuttle is one of 10 graduate students in the United States whose essay on imminent agricultural challenges earned a trip to the U.S. Department of Agriculture’s 2014 Agricultural Outlook Forum on the Changing Face of Agriculture.

“I was fascinated with the opportunity to travel to D.C. to meet important members of the USDA, better understand their specific missions and speak to these leaders about agriculture today and agriculture for the future,” she said.

In her winning essay, Tuttle points out that “students may be some of the best liaisons to bridge the gap (between the public, scientists and) policy makers. As students we continue to grow in our understanding of basic research and apply our novel findings for agricultural improvement.”

U.S. Secretary of Agriculture Tom Vilsak echoed Tuttle’s confidence in students pursuing higher education in agriculture in a recent USDA announcement. “The future of agriculture and rural America depends on the upcoming generation of leaders in farming, ranching and conservation,” he said. “And the students selected to attend the Agricultural Outlook Forum are among the best young leaders our country has to offer.”

The forum at the end of February provided Tuttle and fellow students with an opportunity to learn, share, and discuss current issues in agriculture, including the Farm Bill, national and international trade, diversifying land-use, and the demographics of farmers in the U.S.—most current farmers are between the ages of 55 and 65, or older. Tuttle also shared a story about meeting a 72-year-old Texas farmer who grows winter wheat for cattle grazing.

“…A farmer at heart, Jerry also confessed that he was a huge Mike Leach fan. Needless to say, our conversation swayed drastically after he realized I attend Washington State University,” Tuttle said. “USDA and external agricultural industry partners understand that baby boomers are retiring now, which creates a substantial outflow of agricultural leaders and employees. Even Jerry from Texas shared with me his concerns about who will be growing, farming, harvesting for our future.”

Tuttle plans to continue her research as part of the biotech industry or USDA, where she will pursue change through policy work.

View this original story online, here.

-Rachel Webber

Calling all women in ag

Making baskets at one of the early Farm Women's camp held at WSU in Pullman. This year's Women in Ag Conference will focus on change. (Photo courtesy of WSU Libraries).
Making baskets at one of the early Farm Women’s camp held at WSU in Pullman. This year’s Women in Ag Conference will focus on change. (Photo courtesy of WSU Libraries).

There are just a few days left to register and attend the 2014 WSU Women in Agriculture Conference. Starting at 8 a.m. Saturday, March 15, women at all levels of agriculture and from all around the Pacific Northwest will gather at 28 locations throughout Washington, Idaho, and Oregon. Regardless of the time you’ve spent farming or the size of your operation, WIA has something for you.

The day-long event features knowledgeable speakers that will share inspiring stories and practical advices on how to improve your farm management skills. Learn more at