By Alec Rosenberg
Some of California's biggest challenges come in the smallest packages: tiny insects, weeds and other pests that can destroy crops, clog waterways and threaten ecosystems.
These invasive pests cause an estimated $3 billion a year in losses to California agriculture alone — and larger damages loom, as seen by the latest quarantine in Napa Valley for European grapevine moth, a pest that threatens grapes and other fruit.
"Could you imagine California without grapes, citrus and avocados?" said Mark Hoddle, director of UC Riverside's Center for Invasive Species Research. "All three of those crops are under threat by invasive species."
Exotic pests are attacking all corners of the state, from farms to forests to lakes. The University of California is a key player in educating the public about invasive species, identifying pests and finding better ways to manage them. Often partnering with industry and government agencies, UC has developed solutions that save Californians millions of dollars a year. While state budget cuts have led to a 20 percent cut in UC's Integrated Pest Management Program, the university remains committed to helping control invasive pests, making it one of its agricultural division's five strategic initiatives.
From Cooperative Extension to the Berkeley, Davis and Riverside campuses and beyond, UC scientists are addressing invasive species on multiple levels: detecting pests, assessing their risk, rapidly developing initial controls, improving management practices, understanding how pests spread and investigating longer-term solutions.
"UC's research and extension efforts with invasive species have helped to sustain California's agriculture industry and protect its environment," said Dan Dooley, UC vice president for agriculture and natural resources. "We're advancing science to create practical applications that benefit the people — and economy — of California."
Invasive species are non-native animals, microbes, diseases or plants that cause economic or environmental problems. They range from diseases that kill trees to fungi that kill frogs to aquatic weeds and agricultural pests. Invasive pests spread easily — by ships, packages and people. California attracts a high share of pests with its inviting climate and levels of trade, travel and tourism. As U.S. Department of Agriculture commercials say, "They're here and they're hungry."
UC works to educate the public, government and industry about invasive species, from pest management guidelines and newsletters to workshops and Web sites such as UC IPM and UC Riverside's Center for Invasive Species Research. There even are mobile phone applications such as UCLA's What's Invasive app for locating invasive plants at national parks and UC Berkeley's OakMapper for mapping sudden oak death.
Invasive species can spread quickly, so tracking them is important. A top concern is Asian citrus psyllid, which can transmit the bacterium that causes huanglongbing, a devastating disease of citrus trees.
"It is the worst imaginable disease," said UC citrus entomologist Beth Grafton-Cardwell. "There is no cure. The leaves turn yellow. The fruit gets small. It renders the fruit unmarketable and it kills the tree."
The psyllid has been found in backyard citrus trees in Southern California, but huanglongbing has not been found yet. Both the pest and disease are found in Florida, causing devastating losses of citrus there.
To prevent that from happening in California, Grafton-Cardwell is helping develop insecticide treatment protocols for growers. Also, she has compiled educational materials for UC and assisted with the CaliforniaCitrusThreat.org Web site, designed to inform people about Asian citrus psyllid so they will identify it and report it. The goal is to limit its spread before it reaches the heart of California's $1.6 billion citrus industry.
"If we can keep it out of the San Joaquin Valley, we can buy time for the researchers to come up with solutions to the problem," Grafton-Cardwell said. "We have the potential to lose our citrus industry."
Citrus's competitive edge
Ted Batkin heads the California Citrus Research Board, an industry organization that sponsors the CaliforniaCitrusThreat.org site. California's citrus industry has relied on UC for everything from developing new varieties to controlling pests such as scale, thrips and now psyllid, he said.
"Without that scientific input, everybody would be scrambling," Batkin said. "The citrus industry has had a very strong and close relationship with the University of California for over 100 years. It's what we consider our competitive edge. It's the constant research work that keeps us ahead of the curve."
It's a constant challenge. Six types of invasive pests enter California a year, the state estimates. Hoddle thinks the problem is accelerating. He worries about redbay ambrosia beetle arriving with laurel wilt, a fungus found in the southeastern United States that could wipe out avocados in California and South America, as well as bay laurels. "We should do everything we can to keep that out of California," said Hoddle, including educating people about the dangers of moving plants, animals and firewood between regions.
Heard it through the grapevine
Once pests arrive, UC works to alert the public. Right after European grapevine moth was spotted last fall in Napa, UC North Coast IPM adviser Lucia Varela issued a fact sheet and wrote an article about the pest. UC is setting traps to help determine when to apply insecticides, while Varela and Napa County viticulture adviser Monica Cooper are working with UC Berkeley colleagues to evaluate the impact of native parasites on this pest.
Olive fruit fly invaded California in 1998, causing some regions to lose their entire crop. Zalom looked at the fly's limits in California, evaluated monitoring traps, studied how to best use a less-toxic insecticide and found that harvesting earlier or planting smaller varieties of olives could limit damages. Now, he's looking at the fly's genetics, which could provide clues to its origins and ways to control it.
Meanwhile, he's concerned about spotted wing drosophila. Detected in fall 2008 in Santa Cruz County, the fruit fly damaged 30 percent of the state's cherry crop last spring and affected berry crops, Zalom said. Found in coastal California, Oregon and Washington, drosophila could cause $500 million in damages to the three states. Japan sprays to treat drosophila, but Zalom hopes to develop a better strategy here. "We have newer tools all the time," Zalom said.
Trouble at Tahoe
Controlling invasive pests can be particularly challenging in waterways such as Lake Tahoe. UC Davis has done research at Tahoe for a half century, detailing declines in lake clarity and rises in lake temperature. In 2008, researchers noticed growing populations of Asian clams. The clams, which live in the sandy bottom of the lake and are concentrated in its southeast part, have led to algal blooms that make the water look lime green.
"It's shocking," said John Reuter, associate director of the UC Davis Tahoe Environmental Research Center. "It's an important indication of what's going on in the lake."
UC Davis and University of Nevada, Reno, researchers are testing non-chemical control efforts. The most promising is placing rubber sheets in the water — bottom barriers — to cut off the clams' oxygen. The goal is to wipe out the clams before they spread.
"The problem is relevant and we're taking unique approaches," said UC Davis postdoctoral researcher Marion Wittmann. "We have the great opportunity to learn about how species invade in higher elevations and cold water environments."
By increasing localized calcium concentrations and increasing available substrate through shell deposits, the clams could make Lake Tahoe more hospitable to quagga and zebra mussels. Those mussels are "a nightmare" that could worsen California's water crisis, Hoddle said. "It will cost tens, maybe hundreds of millions of dollars a year to manage them if they spread."
Under the radar
Sometimes, an invasion may seem harmless. Vine mealybug was a hidden problem in California for about five years, said Kent Daane, UC Berkeley extension specialist. Initially misidentified here, the grape pest reached nurseries and spread through nursery stock. Daane recalled going to a San Joaquin Valley site where a farm adviser suggested removing 30 infected vines, but the grower applied pesticides, which failed. Since then, some insecticides have worked, including less-toxic ones. Meanwhile, Daane and colleagues developed a pheromone trap to prevent mating, researchers are seeking a natural enemy, and nurseries have done a good job cleaning up plant material. "We don't know what insect will be the next big great pest in California, so it's difficult to monitor all of them," Daane said.
Still, UC Riverside entomology professor Timothy Paine points to UC's many successes in controlling pests from glassy-winged sharpshooter to red imported fire ants, a concern for nurseries. "UC campuses and the Cooperative Extension have essentially enabled the (California nursery) industry to survive," Paine said.
Glassy-winged sharpshooter can transmit Pierce's disease, a fatal bacterial disease of grapes. UC helped develop protocols the state and industry have adopted to allow plants to be shipped within California, Paine said.
Meanwhile, UC Riverside extension specialist emeritus Nick Toscano led development of an areawide program to control the sharpshooter. Toscano has worked with invasive species his whole career, including pink bollworm and silverleaf whitefly — two examples where UC helped educate the public and evaluate the best controls. Getting citrus growers to cooperate was key because citrus is an important sharpshooter host, he said. "They wanted to be good neighbors (to grape growers)."
UC researchers have contributed additional tools. Hoddle worked with UC's Gump research station to find a natural enemy that controlled the sharpshooter in Tahiti and is being used in California. UC Davis researchers are trying to breed grapes resistant to Pierce's disease.
"It's still a major worry," said Toscano, who produces a weekly newsletter to update growers on the sharpshooter. "The growers have to get together and work in unison. You can't do it piecemeal."