Overgrazed grasslands tied to locust outbreaks

January 24, 2012

While residents of the United States and much of Europe think of locust plagues as biblical references, locust swarms still have devastating effects on agriculture today, especially in developing countries in Asia and Africa. In a study to be released in the journal Science on Jan. 27, scientists from Arizona State University and the Chinese Academy of Sciences show that insect nutrition and agricultural land management practices may partially explain modern day locust outbreaks.

During an outbreak year, locusts can populate over 20 percent of the Earth’s land surface, negatively affecting more than 60 countries and the livelihood of one out of every 10 people. In this study undertaken at the Inner Mongolia Grassland Ecosystem Research Station in China, researchers examined Oedaleus asiaticus, one of the two swarming locusts of Asia. A closely related species, Oedaleus senegalensis, is a major pest in Africa. ASU doctoral student Arianne Cease checks her locust experiments. Download Full Image

Led by Arianne Cease, a doctoral student, in concert with scientists Jon Harrison and James Elser, and undergraduate student Colleen Ford from the School of Life Sciences in ASU’s College of Liberal Arts and Sciences, the collaborative team also included Chinese researchers Shuguang Hao and Le Kang. Funding for their work was provided by the National Science Foundation.

The team’s initial experiments were designed to test the hypothesis that locusts form swarms partly to escape deteriorating conditions or to seek out better food sources. Most herbivores, including insects, are thought to be limited by obtaining sufficient protein. The researchers began, therefore, by fertilizing grassland plots with nitrogen. Their expectation was that the added nitrogen would raise the plants’ protein levels, enhance locusts’ survival and growth and stop locusts from swarming.

They couldn’t have been more wrong. Locusts fed on nitrogen-fertilized plots either died or grew more slowly. Puzzled, the scientists took a step back, examining which host plants these locusts preferred. The results showed that these locusts ate plants lower in nitrogen; not higher.

It had been known for some time that overgrazing in Inner Mongolia caused soil erosion, leading to nitrogen depletion from the soil, and reductions in the protein levels in plants. The team’s surveys had showed that heavily grazed plots were populated by much higher numbers of locusts, so the scientists compared the preferences and performances of locusts for plants from grazed versus ungrazed plots. Remarkably, the locusts preferred to consume the low-nitrogen plants from the heavily grazed plots.

Moving the study into the laboratory and using chemically-defined diets, the scientists next tested the effect of different protein and carbohydrate levels on the locusts’ growth rates. These experiments confirmed their field studies: Oedaleus locusts strongly preferred low protein, high carbohydrate diets. This ratio was about one part protein to two parts carbohydrate – lower than any grasshopper previously studied. “These experiments confirmed that consuming foods with too much protein is deleterious for this locust, explaining why heavy grazing promotes populations of Oedaleus,” said Harrison.

“Our results fit with an emerging paradigm that animal species can vary dramatically in their nutritional responses,” said Cease. “The particularly low protein: carbohydrate preference of Oedaleus may explain their success in a heavily-grazed world.”

Besides revealing new understanding about an age-old plaguing question, the authors’ findings offer new possibilities for improving land management strategies. “Our study also showed that nitrogen fertilizer may be an inexpensive, environmentally less-damaging alternative pest control solution for this species,” noted Cease, with a sidenote from Elser, who added, "Who knows? With the large global increases in atmospheric nitrogen from air pollution, we might find, at least in this limited way, some ‘good news.’ That is, that the airborne nitrogen deposited on grasslands may interfere with future locust outbreaks."

The scientist's work on the grasslands was also groundbreaking in one other way. Ford, Cease's undergraduate co-author, who is now a Phoenix Teaching Fellow at Yuma High School, said of her experience: "Being in the field surrounded by nothing but hoppers, grass, and fellow scientists made me realize the amount of patience, dedication, and passion research pulled out of me. At the end of the experiment, when questions became answers that led to further research, the days in the sun and rain were worth it. Not only did I enjoy the field research, but the collaboration between Chinese and U.S. citizens made me more deeply understand the ability of individuals to work together towards one goal that may have the potential to bring about 'real world' impacts throughout the globe."

Margaret Coulombe

Director, Executive Communications, Office of the University Provost


Baseball ranked No. 17 in Baseball America preseason poll

January 24, 2012

The Arizona State baseball team has been ranked No. 17 by Baseball America in their annual preseason poll, the publication announced.

The Sun Devils are set to play a total of 16 games against five ranked opponents this season, including four Pac-12 series'. They travel to Los Angeles March 16-18 to face No. 14 UCLA before hosting No. 23 Oregon State at Packard Stadium April 5-7, and play No. 2 Stanford in Palo Alto, Calif., April 20-22. ASU hosts No. 5 Arizona for two separate single-game sets on April 17 and May 16, respectively, and finishes the season with a three-game series against the Wildcats in Tucson May 25-27. No. 25 Cal State Fullerton visits Packard Stadium for a two-game tilt March 27-28. Download Full Image

Florida is ranked first, followed by Stanford, South Carolina, Arkansas and Arizona. Including the Sun Devils, the newly expanded Pac-12 Conference (with the addition of Utah) features five ranked opponents, including No. 2 Stanford, No. 5 Arizona, No. 14 UCLA and No. 23 Oregon State. The conference is tied for second with the ACC for number of teams in the poll.

The preseason poll can be found online at baseballamerica.com

For a first look at the 2012 Sun Devil baseball team, ASU is hosting the annual Alumni Game at Winkles Field-Packard Stadium at Brock Ballpark on Feb. 11. First Pitch will be at 1 p.m. (MST) and admission is free.

The Sun Devils open the season by hosting a three-game series against Western Michigan from Feb. 17-19 at Packard Stadium in Tempe, Ariz. For the full 2012 schedule, click here.

Baseball America Top-25 Preseason Poll (2011 Final Record, '11 Final Ranking)
1. Florida 53-19 2
2. Stanford 35-22 13
3. South Carolina 55-14 1
4. Arkansas 40-22 24
5. Arizona 39-21 NR
6. Rice 42-21 15
7. Texas A&M 47-22 7
8. Louisiana State 36-20 NR
9. North Carolina 51-16 5
10. Vanderbilt 54-12 4
11. Georgia 33-32 NR
12. Georgia Tech 42-21 20
13. Texas 49-19 6
14. UCLA 35-24 22
15. Texas Christian 43-19 19
16. Clemson 43-20 21
17. Arizona State 43-18 9
18. Miami 38-23 23
19. Oklahoma 41-19 NR
20. Florida State 46-19 8
21. Central Florida 39-23 NR
22. Mississippi 30-25 NR
23. Oregon State 41-19 10
24. Louisville 32-29 NR
25. Cal State Fullerton 41-17 14