WSU Scientists Use Flower Power to Combat Orchard Menace
Apple orchards are intricate webs involving a delicate balance between trees, soils, water, insects and more. To manage the pests that can potentially damage a crop of apples, a grower might apply a pesticide. There are several problems associated with pesticide use, though, including risks to environmental and human health; the costs of the chemicals; and the equipment, labor and expense needed to apply them. That’s why Washington State University researchers have been pioneering alternatives to pesticide use for managing pests.
One of the effects of using a particular pesticide is that, in addition to controlling a target insect, it may also kill populations of insects beneficial to orchard health. WSU researchers have countered that problem by developing and advocating for a broad group of strategies called Integrated Pest Management. IPM tries to minimize the use of harsh chemicals in favor of ones that are highly selective for target pests. WSU scientists have also helped develop methods of biocontrol, in which a good insect is encouraged by various means to prey upon the bad insects that cause damage to trees and fruit.
The sensitive balance of orchard ecology is such that, if one thing is changed (for instance, a pest-control regime), other things may change as well (like the proportion of bad pests to their good natural enemies). For the last decade, one of those changes in Washington apple orcahrds has been an expanding woolly aphid population.
“Growers began noticing an increase in the number of woolly aphids in apple orchards starting in the early 2000s,” said WSU entomologist Betsy Beers. Beers is based at WSU’s Tree Fruit Research and Extension Center in Wenatchee. “There is some evidence that suggests it was a change in pesticide programs that led to an increase in woolly aphids. The question became, what could we do about it?”
Beers said that woolly aphid debilitates trees over the long term by sucking the sugar out of plants. “They are pernicious little beasts. They use the plant’s sap (phloem) as food. They not only suck sap from leaves, but also from the plant’s woody parts. They also infect the roots, reducing the plant’s ability to take in nutrients and water. They cause hypertrophic galls, which are tumor-like protuberances that can kill fruit buds. Dead fruit buds mean lowered productivity, a serious concern for apple growers. “This is one of the meaner aphids.”
Beers said that a survey of woolly aphid’s natural enemies indicated that syrphids are the most commonly seen predator in woolly apple aphid colonies. “We predicted syrphids could control the aphids–the trick is getting more syrphids into the orchard, and making sure they are happy there.”
Syrphids are more commonly known as flower flies or hoverflies. As their name suggests, they like to hang out among flowers, as the adult syrphid’s primary food is nectar. The syrphid larvae, however, grow and thrive on a diet of aphids–and woolly aphids are just dandy for maturing syrphid larvae. “It’s wonderful to watch them chew their way through an aphid colony,” said Beers.
Enter doctoral student Lessando Gontijo, who came to WSU from his native Brazil to study biocontrol. Working with his mentors, Beers and WSU biocontrol expert Bill Snyder, Gontijo set up a series of experiments to test the idea that syrphids could be used to control woolly aphid populations. The team first examined six different flowering plants for attractiveness to syrphids, and sweet alyssum won hands down. This plant is low-growing and flowers from a few weeks after planting until frost, making it an ideal planting for use in orchards. The next step was to plant small plots in orchards, in the lanes between rows of apple trees (normally occupied by grass sod). While all the details aren’t sorted out, the aphids disappeared faster next to the alyssum plots than they did in the grassy control plots. Gontijo used a sophisticated method known as “immunomarking” to prove that the syrphids found in the apple trees had visited the alyssum flowers, further evidence that alyssum could promote biological control.
The results of the small-scale experiments are promising, Beers said. “These experiment are the first steps in a much longer process,” she said. “We needed to pass the initial proof-of-concept tests: do these flowers attract beneficial insects, are they manageable in an orchard, and do we see a decrease in the pest populations. We passed all those tests.”
The next step will be to run experiments in commercial orchards. Beers said she is looking for funding to expand the project, adding “It’ll be a great opportunity for future graduate students to do good science that has a real-world impact on the way apple growers manage pests.”
–Brian Clark
Photos courtesy Betsy Beers/Washington State University
Learn more about WSU’s world-class leadership role in tree fruit research and extension, including in organic apple production, at the tree fruit web portal »
Small Bites: Research News in Brief
Feeding the World
The Nigerian poet and novelist Flora Nwapa calls it “Mother Cassava.” A fundamental staple in the diet of nearly a billion people, the cassava plant produces a root that is processed in a wide variety of ways to produce foods and beverages. After rice and beans, cassava is the most important subsistence crop grown in the tropical regions of South America, Asia, and Africa.
In many parts of Africa, cassava’s hardiness allows it to be grown on land unsuitable to the cultivation of cereals or other staple crops. African farmers like cassava because, on a per acre basis, it produces higher yields than other crops, thus assuring that their families have food and income.
Unfortunately, cassava mosaic disease, or CMD, threatens the crop. The disease has resulted in at least one serious famine in Africa already. CMD causes leaves to become twisted, misshapen, or not to develop at all. Reduced leaf area in turn reduces the size of tubers. Reduced yields mean less food for families. In Africa, seven distinct viruses spread by whiteflies and via vegetative cuttings cause CMD.
“Part of the problem with managing CMD has been in accurately detecting these viruses,” said Naidu Rayapati, a plant virologist based at WSU’s Irrigated Agriculture Research and Extension Center in Prosser. “If these viruses can be detected in vegetative cuttings, it should be possible to quarantine contaminated plant material and supply farmers with clean cuttings for new plantings.”
Cassava is propagated via cuttings from existing plants, so if the parent plant has CMD, so too will the daughter plants. Rayapati has long been involved in the business of insuring that growers use clean, healthy planting stock. “Previous methods of virus detection in plant tissue required commercial kits that were expensive and involved handling toxic or carcinogenic materials,” Rayapati explained. The special training and facilities required to handle the materials, coupled with the expense, made it extremely impractical to use on a wide enough basis to effectively help manage CMD in African countries. “What we did is replace the dangerous materials used in the extraction of plant tissue with safe ones which are also cheaper. When you don’t have facilities or protocols for handling the dangerous stuff, you really need this sort of alternative.” Read more »
Unlocking the Genetic Secrets of Medicinal Plants
Why study medicinal plants? Many of the most valued medicines from plants have very complex chemical structures, and are often only found in tiny amounts in nature, sometimes in remote parts of the world, and sometimes in endangered plant species. Frequently, far too little is known about how the medicinal properties of plants are formed or how this knowledge can be used for humanity’s benefit. Remarkable advances in technology are helping change that. Learn more »
Strawberries Compared
Side-by-side comparisons of organic and conventional strawberry farms and their fruit revealed found that organic farms produced more flavorful and nutritious berries while leaving the soil healthier and more genetically diverse. “Our findings have global implications and advance what we know about the benefits of organic farming systems,” said John Reganold, WSU Regents professor of soil science and lead author of a paper published in the peer-reviewed online journal PLoS ONE. Watch a video in which Reganold explains his research »
People
David James, The Butterfly Man
Life Histories of Cascadia Butterflies, just published by the Oregon State University Press, was coauthored by Washington State University entomologist David James with Seattle-area naturalist David Nunnallee. Life Histories describes and illustrates the immature stages of butterfly species found in Washington state, northern Oregon, southern British Columbia and the Idaho Panhandle. James and Nunnallee collected fertile female butterflies and raised individual species from eggs, usually several times, to document and photograph each step of their development, from hatching through larval evolution to pupation and adulthood.
In the book’s introduction, James and Nunnallee explain that among the reasons for writing Life Histories was the need to raise awareness of how human activity has threatened many of the region’s butterfly species. Several are endangered, with more on lists waiting to be added. “Such listings typically require recovery plans, which in turn may include captive rearing programs,” they wrote. “State agencies, zoos, universities and conservation organizations are currently cooperating to rear some of the listed species for reintroduction to the wild. We cannot protect what we do not understand. We hope this book will increase our understanding of butterfly life histories and that this will lead to more effective preservation programs.”
For James, the book represents his lifelong dream to detail butterfly life histories, which started in England in the 1960s when he was 8, rearing butterflies in the family home. (He dedicated the book in part to his parents, Alan and Doreen, for supporting and encouraging that early fascination.) After receiving his bachelor’s degree in zoology in 1975 from the University of Salford in Manchester, England, James immigrated to Australia to work and pursue his doctorate in entomology, which he earned in 1984 from Macquarie University in Sydney. His doctoral research focused on Danaus plexippus, or the Monarch butterfly.
James stayed in Australia for 23 years, serving as a research entomologist for the New South Wales Department of Agriculture before coming to WSU’s research and extension center in Prosser in 1999. Today, his research centers on biological control to reduce pesticide use in irrigated crops, particularly vineyards. He directs WSU’s Vineyard Beauty with Benefits project, which seeks to use native plants to beautify vineyards and attract beneficial insects like native bees and butterflies as well as predators for pest control.
One of James’s favorite butterfly species, the Monarch, also described in Life Histories, is the world’s best-known butterfly, noted for its long-distance migrations from Canada to Mexico. Regular visitors to the Cascadia region, Monarchs, whether larval or adult, make an unpalatable and toxic meal for birds and other potential predators because their bodies store cardenolides, a type of steroid, from the milkweed they eat. The blue-green pupae are familiar teaching tools in classrooms because they are so easily raised. James admires this species for its tenacity and charisma.
“The Monarch is critical to me being where I am today,” he said. “My fascination with butterflies, specifically their biology and how they adapt to their habitats and live, figured into my future work. I’ll likely finish my career with butterflies, as I started it. They are a symbol of purity, freedom and organicness. A world without butterflies would be a very sad place.”
–Nella Letizia
The 448-page Life Histories of Cascadia Butterflies is available from Oregon State University Press. For details, visit the publisher’s website.
For background on Vineyard Beauty with Benefits, a research project conducted by James involving insects and flowering plants, see WSU’s wine science publication, Voice of the Vine (middle of the page).
Gone Social!
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Events Calendar
Jan. 17: Get your entrepreneurship on! Washington State University Snohomish County Extension is offering a 12-week “Cultivating Success: Agricultural Entrepreneurship and Farm Business Planning” course to help new and existing farmers gain skills in business planning and direct marketing. The course runs on Tuesday evenings starting January 17 through April 17 from 6 p.m. to 9 p.m. at WSU Snohomish County Extension’s Cougar Auditorium in McCollum Park, 600 128th St. SE, Everett, Washington. Learn more »
Feb. 1: The deadline to apply for a Center for Environmental Farming Systems Summer Sustainable Agriculture Internship is Feb. 1. The program, based in Goldsboro, North Carolina, is an eight-week internship program (June 4–July 27, 2012) providing undergraduates with experience in hands-on field production, local community food systems, sustainable agriculture, and research that promotes agricultural sustainability. The goal of the internship program is to provide learning opportunities through collaboration with faculty from North Carolina State University, North Carolina A&T State University, and farm staff from the North Carolina Department of Agriculture and Consumer Services. Learn more »
Feb. 11: The Women in Agriculture Conference will address the unique challenges women face in growing viable farming and ranching businesses because they learn differently than men and like to connect with other women farmers to share experiences, knowledge, and resources. Keynote speakers will be broadcast across the state to 16 locations; and local presenters will reflect the needs of those regions. Save Feb. 11 for this wonderful opportunity to learn and grow. If you are interested in attending one of these workshops, please send your contact information to Debra Hansen Kollock at dkollock@wsu.edu and you will be notified of all upcoming news and details. Please type “Women in Ag” in the subject line. Or call (509) 684-2588. Learn more »
Find more upcoming events on the Green Times blog »