California Fruit and Vegetable

Tag: WSU

  • Grant to Support Affordable Testing to Fight Little Cherry Disease

    Washington State University (WSU) will help cherry growers test more trees for the damaging Little Cherry Disease thanks to a Washington State Department of Agriculture Specialty Crop Block Grant received by the Washington State Tree Fruit Association.

    Named for its most distinct symptom—small, colorless fruit—what growers call ‘Little Cherry’ is a simultaneous outbreak of Little Cherry virus-2 and the X-disease phytoplasma, both of which produce similar symptoms on infected cherry trees and are difficult to tell apart, even by experts. This is more difficult because symptoms are usually noticed only a few weeks before harvest.

    The pathogens are spread in orchards by small insects: the virus by mealybugs, and the phytoplasma by leafhoppers.

    Tests are available for growers to learn if a tree is infected, but they can be expensive. The new three-year, $530,000 grant will help to expand testing capacity at WSU’s Plant Disease Diagnostic Lab in Pullman with more equipment and supplies. This support will reduce testing fees by approximately 50%, to $50 per test.

    “Affordable and available testing is a key element of our industry’s response to Little Cherry Disease” said Jon DeVaney, WSTFA President. “Washington’s cherry growers appreciate the support of the WSDA Specialty Crop Block Grant Program and WSU’s Plant Disease Diagnostic Lab in this effort.”

    “Active, aggressive tree removal is the best way to suppress this outbreak and prevent further spread, and testing is an essential tool to identify trees in the early stages of infection,” said Scott Harper, WSU virologist and director of the Clean Plant Center Northwest. “It will help growers make informed management decisions for their orchards.”

    Harper’s lab supported the initial wave of testing in 2018-2019, and commercial labs took over testing in 2020, but few growers could afford to test every tree that they suspected might be infected.

    “WSU and collaborating laboratories are working hard to provide growers with Little Cherry testing services,” said Tianna DuPont, a WSU Tree Fruit Extension Specialist. “Additional support for the WSU Plant diagnostic lab is essential to provide sustainable robust public diagnostics so growers can identify and quickly manage the multiple problems that attack their trees.”

    Removing infected trees quickly is the best way to fight the disease, as there is no treatment and early removal can limit spread of the virus to nearby trees in an orchard, Harper said. Testing also helps avoid removing a tree exhibiting symptoms that look like the disease, but isn’t infected with little cherry pathogens. — By Scott Weybright, WSU College of Agricultural, Human & Natural Resource Sciences

  • New Lab to Study Evolving Tree Fruit Bacteria

    Joining Washington State University (WSU) as the newly established Endowed Chair in Bacterial Diseases of Tree Fruits, Frank Zhao will study and seek better ways to manage devastating bacterial pathogens in tree fruit.

    In bad years, these microbial disease heavy hitters such as fire blight and X‑disease phytoplasma cost apple, cherry, and pear growers hundreds of millions of dollars nationally in lost fruit as well as treatment and removal of infected trees.

    “We need more tools in our toolbox to deal with bacterial diseases, particularly for organic orchards,” said Zhao, who comes to WSU from the University of Illinois to launch a new, industry-funded research program in tree fruit microbiology.

    Growers’ most effective tool has always been antibiotics—chemical drugs that kill bacteria or make it difficult for them to reproduce.

    But bacteria can develop resistance that renders antibiotics less or even totally ineffective. In organic orchards, chemicals are often prohibited, raising demand for new techniques.

    “Disease outbreaks can be unpredictable in their severity,” Zhao said. “Pathogens change over time—we now know there are at least four different strains of the fire blight pathogen.”

    Becoming interested in plant-pathogenic bacteria as a master’s student in China, he has spent his career studying where pathogens come from and how they adapt and survive, most recently the fire blight bacterium, Erwinia amylovora, which has caused serious damage in Pacific Northwest orchards in the past several years, as well as the pseudomonas family of bacteria, which infect a range of crops.

    Zhao studies both good and bad microorganisms. Devising strategies to control harmful bacteria with beneficial microbes, he has experimented with nanoparticles as a method to deliver biocontrol agents in orchards. He plans to continue studies of biocontrols and ‘good’ microorganisms at WSU.

    Working in the field and the lab, Zhao will screen for and map antibiotic resistance in Washington orchards, identifying the predominant strains of top-priority pathogens such as fire blight and bacterial canker of sweet cherries.

    As he begins his efforts in Washington, Zhao will connect with growers to understand their experiences and challenges.

    “All these will help me tremendously in getting my program started,” he said. “In turn, I can learn from them and better solve the disease challenges that fruit producers are facing.” — By Seth Truscott, Washington State University College of Agricultural, Human & Natural Resource Sciences

  • Study Shows Pest Attack-Order Changes Plant Defenses

    The dining time of different insects impacts a plant’s defenses and nutritional quality—a complexity uncovered in new research with implications for pest management strategies.

    A piercing-sucking, virus-carrying aphid has long worried pea plant farmers, but a more innocuous-seeming weevil that only takes tiny bites from leaves was found to also play a significant role in plant health. Depending if the weevils eat before, or after, the aphids, they can increase or decrease the plant’s ability to fend off the virus.

    While many studies have focused on the impacts of a single pest, this study, published Aug. 4 online in Molecular Ecology, is one of the few to look at the interaction of several antagonists, in this case, two pests and a virus.

    “Plants in the field have a chance of being exposed to many different types of biotic stress elements, what we call antagonists,” said Saumik Basu, a WSU post-doctoral fellow and the study’s lead author. “Based on how these antagonists are coming to the plants, that can change the plant responses and ultimately leads to changes in their overall productivity.”

    Through a set of greenhouse experiments, Basu and colleagues from the Crowder Laboratory at WSU and Cornell University attempted to understand what happens to the pea plant fields of Eastern Washington’s Palouse area. In the field, plants face alternating infestations of pea leaf weevils, Sitona lineatus, and pea aphids, Acrythosiphon pisum, and a pathogen the pea aphids are also known to carry, Pea enation mosaic virus, or PEMV.

    The researchers created experiments where first the weevils feasted on the plants then the aphids, and others that reversed the order. They also included scenarios where the plants were infected with the virus and some where they did not as well as a control group.

    After removing the pests, the researchers let the plants grow for a week. Then, they ran plant samples through different sets of analyses to assess the plants’ defense hormone levels and associated defense genes as well as nutritional qualities.

    Saumik Basu (Photo by Bob Hubner, WSU)

    They found that when the weevil feasts first on the pea plants, it enhances some of the plants’ anti-pathogen defense responses, helping them become more resilient to a virus infection.

    If the weevil dines second, after the aphids, it usually reduces the anti-pathogen defense responses, so the virus spreads more easily.

    In turn, virus-infected plants had stronger anti-herbivore responses, putting out compounds that interfere with the plant-eating pests.

    Further complicating the issue, the study found that when the weevils helped induce the anti-pathogen responses it lowered the nutrition of the plant by reducing the plants’ available amino acids.

    These complex interactions hold important implications for pest management, Basu said.

    “If we know beforehand when these interactions are happening, that information gives farmers a best possible remedy to prevent their fields from the attack,” he said. “This kind of information is really important for designing sustainable pest and pathogen management strategies.”

    Pea aphids (Photo by Bob Hubner, WSU)

    This study is part of a series of investigations into the interactions among many organisms that plants encounter. An earlier study in Functional Ecology looked at the antagonism between a plant virus and nitrogen-fixing bacteria called rhizobia that live in the soil. An upcoming study looks at the interaction between the weevils and rhizobia.

    These complex relationships are critical to understanding plant responses, said Basu.

    “In a natural environment, a plant is exposed to different types of organisms, not just one or two, but many,” he said. “The order and the complexity—how many there are, what different types there are and their interactions—affect how the plant responds to all these attackers.” — By Sara Zaske, Washington State University

  • How Berry Growers Put Dairies’ Plentiful Waste Products to Use

    Dairy farmers generate nutrients in the form of cattle manure. Neighboring raspberry and blueberry farmers import nutrients in the form of fertilizer to maximize production.

    To improve the nutrient loop, Washington State University assembled a team of scientists to study how berry growers can put dairies’ plentiful waste product to a use in their fields. “We want to connect those industries,” said Chris Benedict, a WSU Extension specialist.“If it works, then that will lower the risk of nutrients entering into the environment, encourage farmers in different industries to work together closely, and hopefully help everyone economically.”

    The project required scientists who are familiar with fertilizers, as well as food scientists, economists, and small fruit specialists. WSU has experts in every field, and the team came together to do the work. The results of the project can be found on WSU’s Center for Sustaining Agriculture and Natural Resources (CSANR) web site.

    The main concern about using biofertilizers on food crops is the potential of introducing foodborne pathogens. Dairy manure is a good source of nutrients for crops, but could potentially carry foodborne pathogens. To prevent illness, dairy manure is subjected to different treatments prior to field application to reduce pathogen levels and meet safety standards.

    “There has to be zero risk for berry farmers,” Benedict said. “We were pretty sure the process is safe, but we needed to prove that. So working with food scientists was key. And we had to make sure the cost/benefit worked out, since farmers are running businesses.”

    Meijun Zhu, professor in the WSU School of Food Science, performed food safety testing, while Joe Cook, associate professor in the WSU School of Economic Sciences, examined economic feasibility.

    Benedict works with small fruit producers and has collaborated with dairy farmers on projects focused on anaerobic digestion, as well as nutrient recovery technologies that generate biofertilizers derived from dairy manure. The combined processes have shown a significant reduction in foodborne pathogens in previous research.

    Considering the Economic Impact

    Biofertilizers are a relatively new product, so there isn’t much market research available, Cook said. The economics team designed a survey for local berry farmers to find out who would use them and how much they would be willing to pay.

    “Not surprisingly, cost was a major factor, the less the cost the more likely farmers were to switch,” Cook said. “The survey also instructed growers to assume the product is safe for food crops in the hypothetical, but they still commented on that aspect repeatedly. Clearly people are very concerned about that aspect of the project.”

    Keeping People Safe

    To ensure human safety, researchers had to test the biofertilizers in the field. Benedict collaborated with local small fruit farmers who donated parts of their fields for testing plots. The team applied multiple different biofertilizers to raspberries and blueberries. “We’re lucky, we have really great collaborators who were willing to sacrifice a full season of crops in several fields,” Benedict said.

    Then the berries in each test plot were carefully harvested and sent to Zhu’s lab in Pullman. “This was a big project and teamwork was very important,” Zhu said. “Everything had to be coordinated, so we talked with Chris Benedict’s team about how to properly and randomly collect samples in multiple berry fields.”

    Pathogens can spread unevenly in a single field, so truly random sampling is required to make sure the data is correct, she said.

    Zhu’s team didn’t find any pathogens harmful to humans in their testing. The processed biofertilizers are safe to apply to food crops, hopefully leading to a closing of that nutrient loop in Whatcom County and benefitting farmers and consumers around the country.

    In addition to Benedict, Zhu, and Cook, the WSU team also consisted of Betsy Schacht, Karen Hills, Chad Kruger, Georgine Yorgey, Lina Sheng, and Xiaoye Shen. This project was funded by the USDA Natural Resources Conservation Service, Conservation Innovation Grants program, and the Washington State Department of Agriculture Specialty Crop Block Grant Program. – By Scott Weybright, Washington State University College of Agricultural, Human & Natural Resource Sciences

    Check out a video explaining the research on YouTube

  • Grafting Watermelon Prevents Disease, WSU Study Shows

    A new study from Washington State University’s Department of Horticulture found that splice grafting helps watermelons resist disease.

    For more than 10 years, watermelon growers in Washington’s Columbia Basin have been struggling with a disease called Verticillium wilt, caused by the fungus Verticillium dahliae.

    The findings were recently published in the American Society for Horticulture Science.

    For decades, methyl bromide, a fumigant used to control pests in agriculture, was used to control plant diseases like Verticillium wilt. The colorless, odorless gas was used for protecting crops, and shipments, but methyl bromide was phased out in 2005 due to one of its side effects: depleting the ozone layer.

    Successful watermelon grafts growing at WSU Mount Vernon NWREC.

    “When methyl bromide was disallowed, farmers no longer had access to it, which meant they had less control over disease spread,” said Carol Miles, interim director of the Northwestern Washington Research and Extension Center in Mount Vernon, Wash., who led the study.

    Miles started searching for answers. She looked to other countries who had given up the use of methyl bromide a decade before the United States, wondering how they were dealing with this issue.

    “What many of the growers worldwide were doing was grafting,” she said. This horticulture technique joins parts from two plants together so they grow as a single plant, with the upper part, or scion, of one plant growing on the root system, or rootstock, of a different plant.

    “Grafting watermelon has been used on a commercial scale in Japan for almost 100 years,” Miles said. “This is not a new concept – it’s just new to us.”

    As a professor in the Department of Horticulture, Miles and her team experimented with grafted and non-grafted watermelon plants. The healthy rootstocks, resistant to the pathogen, are squash plants.

    “The study revealed that we can produce grafted watermelon crop yields that are better than non-grafted plants when there is disease pressure,” she said.

    Non-grafted plants died during the study, but the grafted plants survived due to their healthy rootstocks.

    “The fruit from the grafted watermelon is as good, and in some cases better than non-grafted fruit,” she said.
    Miles said the study bodes well not just for watermelon survival, but for agriculture.

    “Having the grafting industry here in western Washington would be a great benefit,” said Miles, who pointed out that purchasing rootstocks from countries abroad isn’t always convenient.

    Splice-grafted watermelon where both cotyledons (embryonic leaves in seed bearing plants) are removed from the rootstock.

    Due to Washington’s relatively low energy costs, the Pacific Northwest is the prime location for grafted transplant production, Miles said.

    “There is the potential for a greenhouse industry we don’t currently have,” said Miles, who is hopeful that transplant production takes off on Washington’s west side where the climate is moderate, year-round.

    “Right now, transplants are expensive, due in part to the grafting methods that are commonly used for this crop,“ said Pinki Devi, a graduate research assistant for the Department of Horticulture. “Our recent research found that grafting watermelon using the splice grafting method could significantly decrease costs of grafting.”

    Watermelons continue to surprise Miles, and she and her team plan to continue studies on melons.
    “I’ve said for a long time that watermelon was my ‘fun crop,’ because it was just delicious,” Miles said.

    She was pleasantly surprised by a recent study by the USDA which found the amount of a compound called lycopene in watermelon is greater than the lycopene in a tomato.

    Lycopene is often heralded as an antioxidant for the prevention of cancer, so that sweet slice of summer fruit packs a healthy punch.

    “Watermelon is actually a very healthy crop,“ Miles said. —By Lauren Paterson

    WSU College of Agricultural, Human & Natural Resource Sciences