JANUARY–MARCH 2011 • VOLUME 65 NUMBER 1 California Agriculture

Growing bigger, better: Artisan olive oil comes of age

University of California | Peer-reviewed Research and News in Agricultural, Natural and Human Resources Editorial Sustainable food systems: The global picture

orldwide, public and private investments in agri- The Merriam-Webster dic- culture and natural resources research benefitting tionary defines sustainable Wour food systems have been enormously success- as “of, relating to, or being a ful. These investments have fostered innovation and new method of harvesting or using technology, improved food security and human nutrition, a resource so that the resource developed new tools to maintain essential natural eco- is not depleted or permanently systems, and generated economic benefits to producers, damaged.” For those of us en- processors and consumers alike. Looking ahead, however, gaged in agricultural research many signs point to the sobering reality that our current and extension, the term sustain- pace of innovation and gains in agricultural productivity ability has often focused on will not be enough. farm-scale practices and solu- By 2050, the world population will top 9 billion people. tions and regional food-system Dan Dooley Most of that growth will come in the world’s develop- issues. The rapidly emerging Vice President, Agriculture ing countries. Improving dietary standards in rapidly international view is that sus- and Natural Resources developing economies like China and India have already tainability must be considered Senior Vice President, increased demand for calories and protein, putting up- in a global context, especially External Relations ward pressure on world cereal and oilseed prices while as it relates to food production, also increasing volatility in world markets. From a natural environmental and social pro- resources perspective, the United Nations estimates that tection, and climate change. in order to meet nutrition goals, world demand for water Moreover, there is increasing awareness that intensive for irrigation will double by 2050, while demand for for- agriculture must and will play new roles in sustainable est products is expected to increase 40% by 2060. Perhaps food systems, and that productivity gains from research, most compelling, global food demands are expected to innovation, new technologies and education are essential. double by the middle of the century. Feeding the world amid a changing climate forces us to At the same time, our understanding of the expected critically review our traditional models and to realign our impact of global climate change points to more stress on thinking with new priorities. the global food system. Populations in the developing We must recognize that enhancing food security and world, already vulnerable to food insecurity, will likely adapting to climate change go hand-in-hand. be the most seriously affected. The International Food We must develop agricultural sustainability programs Policy Research Institute (IFPRI) just published a study on and policies that contribute to food security and climate the impact of climate change on global agriculture, which change adaptation. suggests that climate change will result in additional We must develop technologies to sustainably produce price increases for the world’s most important agricul- more with less. tural crops: rice, wheat, corn and soybeans. Increasing Investment in research, development and delivery is a crop prices will in turn put upward pressure on feed, ani- moral imperative. We already know that meeting local Feeding the world amid a changing climate forces us to and global food demand will require di- verse production systems, and that those critically review our traditional models and to realign our systems must make key adaptations based thinking with new priorities. on understanding the biology of climate change, new pests and diseases, and crop mal products and meat. Higher temperatures, especially adaptations. We also know that the challenges for public in agriculturally important areas of the developing world, policy, resource management and science agencies are will reduce the yields of desirable crops, while changes in growing exponentially and intersect as never before. the amount and timing of precipitation will increase the For all segments of the University of California’s likelihood of short-term crop failures and long-term pro- Division of Agriculture and Natural Resources, these duction declines. challenges offer both exciting opportunities to foster The message is clear. The historic challenges to pro- innovation through research and outreach, and great duce safe and abundant food and fiber, to address poverty responsibility to align our priorities with those is- while safeguarding the environment and guiding sus- sues where we have the greatest potential to make the tainable energy development, and meanwhile to stimulate biggest difference. economic growth and jobs, must all now be assessed in the context of climate change and the need for sustainable Find links to resources for this editorial at: development at the global level. http://ucanr.org/repository/CAO/issue.cfm?issue=current

2 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 TABLE OF CONTENTS JANUARY–MARCH 2011 • VOLUME 65 NUMBER 1 Growing bigger, better: Artisan olive oil comes of age

Research and review articles

8 UC Cooperative Extension sensory analysis panel enhances the quality of California olive oil COVER: The California olive industry Vossen and Kicenik Devarenne has undergone striking changes Sensory panel data continues to be essential to the evolution in recent years. An internationally and growth of the California olive oil industry. certifi ed sensory taste panel has raised the quality of California olive oils, creating new markets (page 8); the 14 Understanding the seasonal and reproductive nonnative, invasive olive fruit fl y has biology of olive fruit fl y is critical to its transformed pest control for oil and table olives (pages 14, 21 and 29); and management super-high-density hedgerow plantings Burrack et al. have contributed to increased oil A statewide monitoring program has provided valuable olive acreage (page 34). Photo: Lisa insights on the olive pest’s occurrence, population dynamics, Romerein. reproduction and other factors.

21 Biological controls investigated to aid management of olive fruit fl y in California Daane et al. News departments Researchers studied the biology of imported natural enemies to determine the best species to release in the state’s climatically 5 Letters varied olive-growing regions. H. White joins Cal Ag, CSIT staff 29 High temperature affects 6 Research news olive fruit fl y populations New methods are transforming in California’s Central table olive and olive oil Valley production in California Johnson et al. 29 Campus trees yield olive oil, Adult fl ies suffer from heat stress in very hot weather, and their body-care products ability to fl y, feed and reproduce is affected.

47 2010 index 34 Mediterranean clonal selections evaluated for modern hedgerow olive oil production in Spain Tous et al. For more information on California Three olive oil cultivars were tested for their horticultural characteristics and sensory qualities in super-high-density olives and olive oil health benefi ts, fi elds. visit California Agriculture: http://californiaagriculture.ucanr.org 39 Olive cultivars fi eld-tested in super-high- density system in southern Italy Godini, Vivaldi, Camposeo

Editor’s note: 41 Methods evaluated to minimize emissions from preplant soil fumigation ➔ Thank you to more than 10,000 Gao et al. subscribers who have renewed their subscriptions! Low permeability plastic mulches are highly effective but costly; water treatment or target-area fumigation are better At the end of January, we will options for crops with low profi t margins. purge our mailing list. You can still renew for a short time or start a new subscription at: The olive engravings used throughout this issue are from The Olive in California by Byron M. Lelong, http://californiaagriculture.ucanr. published in 1888 and reprinted in California’s Olive Pioneers (Robert Mondavi Institute for Wine org/subscribe.cfm and Food Science, 2009).

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 3 About California Agriculture

California Agriculture is a quarterly, peer-reviewed Writing Guidelines before submitting an article; go journal reporting research, reviews and news, pub- to http://californiaagriculture.ucanr.org/submit.cfm. lished by the Division of Agriculture and Natural Letters. The editorial staff welcomes your letters, Resources (ANR) of the University of California. comments and suggestions. Please write to us at the The fi rst issue appeared in December 1946, making address below. Include your full name and address. it one of the oldest, continuously published, land- Letters may be edited for space and clarity. grant university research journals in the country. Subscriptions. Subscriptions are free within the The print circulation is currently about 15,000 do- United States, and $24 per year abroad. Single cop- mestic and 1,800 international, with a strong online ies are $5 each. Go to http://californiaagriculture. presence. ucanr.org/subscribe.cfm or write to us. Interna- Mission and audience. California Agriculture’s tional orders must include check or money order mission is to publish scientifi cally sound research in U.S. funds, payable to the UC Regents. Master- in a form that is accessible to a well-educated audi- Card/Visa accepted; include complete address, ence. In the last readership survey, 33% worked in signature and expiration date. agriculture, 31% were faculty members at universi- Permissions. Articles may be reprinted, provided ties or research scientists, and 19% worked in gov- that no advertisement for a commercial product ernment agencies or were elected offi ce holders. is implied or imprinted. Please credit California Indexing. The journal is indexed by AGRICOLA; Agriculture, University of California, citing volume Current Contents (Thomson ISI’s Agriculture, and number, or complete date of issue, followed Biology and Environmental Sciences, and the by inclusive page numbers. Indicate ©[[year]] SCIE databases); Commonwealth Agricultural The Regents of the University of California. Bureau (CAB) databases; EBSCO (Academic Search Photographs in print or online may not be re- Complete); Gale, including Lexis-Nexis; Google printed without permission. Scholar; Proquest; and others, including open-access databases. It has high visibility on Google and Google Scholar searches. We post all peer-reviewed California Agriculture articles to the California Digital Library’s Peer-reviewed research and news published by the Division of eScholarship Repository. Agriculture and Natural Resources, University of California Authors and reviewers. Authors are primarily VOLUME 65, NUMBER 1 but not exclusively from ANR; in 2008, 15% were 1301 S. 46th St., Bldg. 478, Richmond, CA 94804-4600 based at other UC campuses, or other universities Phone: (510) 665-2163; Fax: (510) 665-3427; [email protected] and research institutions, and 13% in 2009 . In 2008 http://californiaagriculture.ucanr.org and 2009, 14% and 50% (respectively) of reviewers came from universities and research institutions or Executive Editor: Janet White agencies outside ANR. Managing Editor: Janet Byron Senior Editor: Hazel White Art Director: Will Suckow Rejection rate. Our rejection rate ranged be- Administrative Support: Carol Lopez, María Muñoz tween 20% and 25% in the last three years, In ad- dition, associate editors and staff sent back 24% of Associate Editors manuscripts for revision prior to peer review. Animal, Avian, Aquaculture & Veterinary Sciences: Peer-review policies. All manuscripts submit- Bruce Hoar, Kathryn Radke, Carolyn Stull ted for publication in California Agriculture undergo Economics & Public Policy: Peter Berck, Rachael Goodhue, double-blind, anonymous peer review. Each sub- Karen Klonsky, Alvin Sokolow mission is forwarded to the appropriate associate Food & Nutrition: Amy Block Joy, Sheri Zidenberg-Cherr editor for evaluation, who then nominates three Human & Community Development: David Campbell, Richard Ponzio, Ellen Rilla qualifi ed reviewers. If the fi rst two reviews are af- Land, Air & Water Sciences: Mark E. Grismer, Ken Tate, fi rmative, the article is accepted. If one is negative, Shrinivasa K. Upadhyaya, Bryan Weare the manuscript is sent to a third reviewer. The as- Natural Resources: Adina Merenlender, sociate editor makes the fi nal decision, in consulta- Kevin O’Hara, Rachael F. Long tion with the managing and executive editors. Pest Management: Janet C. Broome, Kent Daane, Editing. After peer review and acceptance, all Deborah A. Golino, Joseph Morse manuscripts are extensively edited by the California Plant Sciences: Kent Bradford, Kevin R. Day, Agriculture staff to ensure readability for an edu- Steven A. Fennimore, Joseph Grant, Carol Lovatt cated lay audience and multidisciplinary academics.

Submissions. California Agriculture manages the California Agriculture (ISSN 0008-0845) is published quarterly and mailed at periodi- peer review of manuscripts online. Please read our cals postage paid at Richmond, CA, and additional mailing offi ces. Postmaster: Send change of address “Form 3579” to California Agriculture at the address above. ©2011 The Regents of the University of California

4 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 Letters RSVP

WHAT DO YOU THINK?

The editorial staff of UC plant pathologist on cover We lived on a 30-acre farm in the heart of California Agriculture welcomes your letters, Editor’s note: For the cover of the October-December Pescadero in San Mateo County, and artichokes comments and sugges- 2010 issue (“The Golden State goes gray: What aging were his main crop. My father was born in Jackson, tions. Please write to will mean for California”), we ran a stock image of se- Amador County, on March 24, 1912. My grand- us at: 1301 S. 46th St., nior runners at Lake Tahoe. The image was posted on parents moved the family back to Italy when dad Building 478 - MC 3580, Shutterstock with no information identifying the run- was about 14 months old, Richmond, CA 94804 ners. We were delighted to receive the following letter. and then came back to or [email protected]. America when he was 17 Include your full name and address. Letters may That’s my father on the cover! so that he wouldn’t lose be edited for space and My father is Donald C. Hildebrand, who was a his citizenship. He arrived clarity. plant pathologist at UC Berkeley until about 1992. with 16 cents in his pocket. He earned his Ph.D. there but is now retired. He He made it to Half Moon and several collaborators Bay and worked on farms, named three new bacte- married my mother Mary rial species that affected Neves from Pescadero plants, and published a in 1941. They moved to paper showing for the first Santa Cruz, where he and time that crown gall of a friend trucked produce October 1973 California plants could be cured. up and down the coast for Agriculture article on Several years ago I at- a few years and then went artichoke varieties tended a dinner with him into farming again. at UC Berkeley, where he He had a Brussels sprouts farm in Davenport was honored for donat- for 3 or 4 years and then purchased the 30 acres in ing enough money from Pescadero and planted artichokes. He harvested October-December 2010 the family to establish the California Agriculture them from fall to spring and then cut down the Hildebrand-Laumeister plants and waited for the crop to produce again in Chair in Plant Pathology. the fall, which was the norm for raising artichokes This picture was taken last year by my sister, at that time. After a few years, he began stump- Karin Hildebrand Lau of Sacramento, at a relay race ing the artichokes, removing the dried stalks that in Tahoe. He was 77 in that photo. He now resides had produced the buds and leaving room for new in Sisters, Ore., and will be 79 in a few months. He growth. He increased his annual production from still actively runs every chance he can and is quite about 275 boxes to 500 boxes per acre. He worked an inspiration! The runner with his back to the with Richard (Hank) Sciaroni, keeping charts on camera is Joe McCladdie, another member of the the barn door as to whatever he was doing, and did Lake Merritt Joggers & Striders’ Over 70 team. this with a 3-year school education (in Italy). Thank you so much for choosing such a wonder- Martha Giannini Muzzi ful cover. This is certainly the way I will always Moss Landing remember him. Katie Hildebrand O’Connor Granite Bay H. White joins Cal Ag, CSIT staff California Agriculture is pleased to announce Father doubles artichoke yields that Hazel M. White has been hired as part-time Warner Nancy Editor’s note: We received the following letter regard- senior editor. White will split her time between ing Joseph Giannini, a grower from Pescadero who California Agriculture journal and the publications co-authored an article in the October 1973 issue, unit of Communication Services and Information “Magnifico...a promising new globe artichoke variety,” Technology (CSIT), with responsibility for proofreading, with Vincent E. Rubatzky, Richard H. Sciaroni and copyediting, indexing and writing. White has more Marvin J. Snyder. than 20 years of experience in editorial work, with a focus on gardening and horticulture. She served My father, Joseph Giannini, is now 98 years old, as managing editor for a new edition of the Sunset Hazel M. White and we are putting together a booklet of all he Western Garden Book, and continues to write Sunset quietly accomplished in the farming of Brussels magazine’s monthly “What to do in your garden” feature. She is the author sprouts and artichokes. Thank you for providing of 11 books, and has written numerous newspaper and journal articles on copies of the article that he published in California gardening, landscaping, sustainability and urban farming. White can be reached Agriculture. at [email protected].

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 5 Research news

New methods are transforming table olive and olive oil production in California

live production is evolving rapidly in Cali- 2009, 23,034 tons were harvested valued at $1,200 fornia. The state’s traditional, labor- per ton. Ointensive table olive culture is giving way Just two major canneries process California table to super-high-density, mechanically harvested olives: Bell Carter Olive Company plantings of the fruit for oil. in Corning and Musco Family “The next decade could see California producing Olive Company in Tracy. The a signifi cant amount of the olive oil consumed in harvest runs from September to the United States,” says UC Cooperative Extension November, with crews climbing (UCCE) farm advisor Paul Vossen, whose work has ladders to hand-pick the thou- helped cultivate California olive oil as a unique and sands of olives on a typical tree, growing agricultural market (see page 8). labor that consumes 45% to 60% Meanwhile, scientists are closing in on a me- of table olive producers’ gross returns. chanical harvesting system for table olive trees that UC Davis plant sciences specialist Louise could save the industry from being crushed by op- Ferguson is working with a team of farm advisors pressively expensive hand-labor harvesting costs. to develop mechanical harvest methods for table ol- ives, a particularly challenging task because of the A long and storied history high quality standard. Native to the Mediterranean region, olive culti- “There is zero tolerance for bruised fruit in the vation began some 7,000 years ago for use as food, canned product,” Ferguson says. a beauty aid, in ceremonies and as fuel. The utility The scientists are studying two options — trunk of olives is chronicled in ancient Egyptian hiero- shaking and canopy contact — but both have prob- glyphics, Greek mythology, the Bible and Quran, lems. With age, the trunks of olive trees become Shakespeare’s sonnets and innumerable cookbooks, stout, fl uted and knobby, which hinders mechanical old and new. Today, olives are the most extensively shaking. Canopy contact is complicated by harvest cultivated fruit crop in the world. timing. The fruit must be harvested before it is In 1769, the fi rst olive cuttings were planted fully ripe, so signifi cant force is required to remove in California at the Mission San Diego. During them from the tree. the 1800s, many small olive plantations existed “Both methods now produce acceptable olives around the state, but a statewide industry didn’t with about 65% harvesting effi ciency,” Ferguson emerge until German immigrant Freda Ehmann of says. “However, with some tree pruning and the Oroville, working with Professor Eugene Hilgard development of a suitable conveying and catching Olives are the most extensively of UC Berkeley, perfected the ripe-olive curing pro- platform for the harvesters, I believe that machines cultivated crop in cess at the turn of the century. could be commercially available in 2 years.” the world. Below, Canned black olives (which producers market Olive fruit fl y Lucca, a new as “black-ripe” olives) became a quintessential variety developed at UC Davis, grows California product. Mild, versatile and meaty, Olive fruit fl y is a severe threat to all Califor- in a test plot. California olives fl avor pizza and Mexican dishes nia olives. A pest for at least 2,000 years in Med- and appear on relish iterranean olive production, it fi rst appeared in trays and in tapenade. California in 1998 and quickly spread to all com- Currently, California has mercial olive-growing regions in the state (see about 27,000 acres in table pages 14, 21 and 29). olive production, the bulk The female olive fruit fl y lays her eggs in imma- in Tulare, Tehama, Glenn ture fruit. After they hatch, feeding larvae destroy and Butte counties. the pulp and introduce microbes that rot the fruit. Canning olive tonnage For table olives, the presence of even a few infested has declined in the past fruit can lead to rejection of the entire crop. Oil 5 years, but the price per olives can tolerate some infestation, as long as the ton has been steadily im- fruit are not rotten. proving. In 2006, farmers Super-high-density orchards harvested 123,589 tons of canning olives valued at During the last century, most of the olive oil Alexandra Kicenik Devarenne $700 per ton, but in fall used in California was imported from Spain and

6 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 Karin Higgins Italy. Interest in local products, greater awareness California’s young olive oil industry uses up-to- about the health benefits of olive oil, and a growing date farming and pressing methods to make oils appreciation for fine olive oil’s unique flavor has altogether different from European oils, whose pro- buoyed the California olive oil industry. ducers are following the practices and traditions In traditional olive orchards, about 50 trees per of the Old World. Fine California olive oils taste acre were often planted 30 feet apart, giving them as spicy, peppery and pungent as the olives from plenty of space to reach their full natural size. which they were made. Productive orchards have been maintained in some “California olive oils are not just fats, but are like parts of the world for 100 years or more. But scien- spices or condiments,” says Sonoma County olive tists, interested in boosting yield per acre, reducing oil expert Vossen. “These fine olive oils impart deli- labor costs and bringing olive plantations into full cious, subtle flavors to food.” UC President Mark Yudof (right) production quickly, have developed a new, super- With dozens of olive varieties at their disposal, examines the UC high-density, hedge-row olive production scheme a diversity of climate and soil types, and uncon- Davis Olive Center’s (see page 34). About 10 years ago, Spanish investors strained by tradition, California producers are only “President’s Blend” olive oil, with UC planted California’s first super-high-density olive now beginning to explore the range of flavors that Davis Chancellor plantation near Oroville. The idea took off. can be coaxed from fine olive oil. Linda Katehi. “They’ve introduced super-high-density all “Flavors range from the green end of the spec- over the world — Chile, Australia, Portugal,” says trum, with green apple, grass and green tea, to the Joe Connell, UCCE farm advisor for Butte County. ripe end, with buttery, nutty and tropical flavors. “The method was developed by a nursery near And they can be found everywhere in between,” Barcelona, the largest olive nursery in the world. Flynn says. “Or, you can find all these flavors You can imagine the potential sales for a nursery wrapped up in one very complex olive oil.” when producers need more than 600 trees per acre — Jeannette Warnert to establish an orchard.” In addition, older olive tree trunks and branches become woody and gnarled, characteristics that will interfere with mechanical harvesting. The Campus trees yield olive oil, body-care products super-high-density orchards being established now UC Davis has been producing olive oil from its more than 2,000 ol- may have to be removed and replaced in just 15 to ive trees since 2005, keeping the olives — which used to clutter the 20 years, Connell says. ground — out of the waste stream while generating revenue for According to a 2009 UC Davis Olive Center sur- teaching and research at the UC Davis Olive Center. vey, 12,137 acres of super-high-density olive trees The center recently launched its “President’s Blend” olive oil, were planted in California by the end of 2008, with and teamed up with UC Davis 92% of growers reporting that they planted the alumna Kacie Klein to produce a trees between 2005 and 2008. Many of the planta- collection of olive-oil-based body- tions are coming into production right now. care products including lotion, body Dan Flynn, director of the Olive Center, says butter, hand-cut soap and lip balm. California olive oil production numbers are ex- “These new products are all periencing parallel growth. In 2008, California made with olive oil produced by produced 650,000 gallons of olive oil, and in the campus’s historic olive trees, us- 2009, 800,000 gallons. In 2010, olive oil produc- ing olives and olive oil that would tion will exceed 1 million gallons. “There’s a lot of otherwise have gone to waste,” says high quality California oil this year,” Flynn says. Dan Flynn, executive director of Nicole Sturzenberger “California olive oil will be more readily available the Olive Center. The product sales Olives from the UC Davis around the country.” support research into new olive cul- campus, which once littered the ground, are now used to tivars, mechanical harvesting, olive produce body-care products. Developing markets for olive oil fruit fly control, olive processing Developing a market for the oil will be impor- and the sensory evaluation of olive oil. tant to the industry’s success. Currently, more than “Olives have the potential to be one of the leading crops in the 99% of the olive oil consumed by Americans is state, with UC Davis being a leader in the industry, just like with imported from other countries. Imported oil is gen- wine and almonds,” UC President Mark Yudof said. erally cheaper and blander than the oil pressed by UC Davis olive products are sold in the UC Davis California’s artisan producers, Flynn says. Bookstore and can be ordered online from the its “Campus In addition, an Olive Center study found that Produced” section at: http://ucdavisbookstore.com/MerchList/ 69% of the imported oils sampled from California aspx?ID=16472&CatID=3016. groceries had sensory defects. “This study rocked — Editors the olive oil world,” Flynn says.

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 7 REVIEW ARTICLE ▼

UC Cooperative Extension sensory analysis panel enhances the quality of California olive oil

by Paul M. Vossen and Alexandra Kicenik Devarenne

California’s olive oil industry has evolved from primarily a salvage operation of the table olive industry to a producer of world­class, pre­ mium, extra­virgin olive oil. In 1997, UC Cooperative Extension started the fi rst California olive oil taste panel, which was offi cially recognized by the International Olive Council in 2001. Specifi c protocols were used to screen potential panelists and train California sensory panel members evaluate oils at an offi cial tasting. them to identify defects and positive Interest in planting new orchards is IOC) to develop the fi rst offi cial tasting characteristics, identical to 43 other still high, but the economic crisis has methodology. Their work applied the world taste panels. The UCCE panel reduced the rate of oil-olive acreage principles of sensory science to olive oil. helped the California Olive Oil Council growth. A few large producers make Sensory evaluation evokes, measures, develop a seal certifi cation program about 80% of the state’s olive oil, but analyzes and interprets the responses of more than 90% of the farms are small tasters to the fl avors they perceive. using sensory analysis. Certifi cation scale with less than 20 acres. Production Worldwide, sensory analysis has provides consumers with assurance of premium olive oil in California is become a key part of how olive oils are that labeled oils are free of defects predicted to double in the next 3 years rated for market grade, and it has been and warrant the “extra virgin” grade. from 800,000 to 1.6 million gallons. used to help growers and processors Many of these oils are excellent, taking produce a higher-quality product. Since Sensory evaluation using a unique top awards in global competitions. the late 1980s, many researchers have UCCE profi le sheet provides complete But this was not always the case. The used sensory evaluation to characterize and detailed information about spe­ improvement in California’s olive oil olive oil fl avors attributable to cultivar cifi c positive fl avor characteristics of is due largely to the efforts of a scien- (variety), fruit maturity, terroir, irriga- tifi cally selected and trained sensory tion, tree nutrition, pest damage, fruit olive cultivars grown in California. evaluation panel. Only the most ru- handling and processing methods. The UCCE sensory panel has also dimentary quality testing on olive oil Researchers have also taught sensory contributed to a better understand­ is currently being done by laboratory short courses and workshops for indus- ing of the qualities of California olive chemical analysis; a group of human try professionals and consumers about beings following strict tasting protocols olive oil styles and quality. oil and advancement of the industry is now the standard tool for detecting, Uses of a sensory panel by participating in research on pest identifying and quantifying the many management, cultural practices and positive and negative attributes of A trained sensory panel is an in- processing. olive oil. valuable tool. It provides an objective Although people have been mak- sensory evaluation of olive oil that can ing and using olive oil for thousands be used by regulators to enforce label of years, the methodical sensory standards that protect consumers, pro- uring the California olive oil re- analysis of olive oil is a recent devel- ducers and processors from fraud in Dvival of the past two decades, a opment. Its use in measuring qual- the industry. IOC quality standards are quiescent industry has come dramati- ity was advanced signifi cantly in the used globally to determine whether an cally to life (see box, page 9). Acreage early 1980s, when sensory researchers oil should be graded and marketed as planted in oil olives is increasing rap- in Spain, Italy, Greece, Portugal and “extra virgin” or “virgin,” or refi ned idly. By fall 2010, an estimated 28,500 France began working together with and then sold as “olive oil” (see box, acres were growing in California, a the International Olive Oil Council page 10). In order for an oil to be graded doubling of acreage from 3 years prior. (now the International Olive Council or as “extra virgin,” it must pass several

8 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 laboratory chemical analyses and be analysis showing high polyphenol and fruit maturity, but some studies have evaluated by a sensory panel. The olive antioxidant levels (Alba Mendoza et al. shown that oils from different areas oil must be free of defects and have 1997; Romero and Díaz 2002; Vossen are notably different in fl avor (table 1). some fruitiness. 2005). Sensory characteristics have also been Offi cial IOC tastings that rate oils Terroir. Climate, soil composition used to identify oils by protected grow- for compliance to trade standards note and other environmental factors that ing region (appellation) (Aparicio et al. the intensity of any defects. Only three make up “terroir” may infl uence olive 1997; Ranalli et al. 1999; Tous et al. 1997; positive attributes — fruitiness (either oil qualities, but this is a continuing Vossen 2007c). green or ripe fruit), bitterness and pun- area of research. Most scientists have Irrigation. Irrigation is the most com- gency — are quantifi ed on the profi le indicated that the infl uence of terroir monly manipulated grower practice sheet. The offi cial IOC profi le sheet is minimal compared to variety and that specifi cally infl uences oil sensory includes fi ve standard defects: fusty/ muddy sediment, musty, winey- vinegary, rancid and metallic. Space is left to note negative attributes other than the classic defects (IOC 2006, 2007c). Beyond evaluating by defi ned IOC standards, sensory panels help pro- ducers make better decisions regarding variety selection, pest management, cul- tural practices and harvest timing. With qualitative analysis, processors can also better select processing methods to maximize quality and assess how vari- ous cultivars might contribute desirable characteristics in blends. The sensory aptitude of potential tasters is screened by having them arrange oils along a scale for particular attribute intensities. Sensory evaluation in research Variety. Sensory panels defi ne the Olive oil in California attributes of olive varieties and rate The olive came to California from Mexico with the Franciscan fathers. Al- them according to the intensity of fruiti- though olive oil production likely started within a couple of decades of the ness, bitterness and pungency, but also 1769 founding of the fi rst California mission in San Diego, the earliest written provide an in-depth evaluation of fruit record is from 1803. After a period of decline in the mid-1800s, olive oil pro- fl avor characteristics. The content of duction expanded between 1870 and 1900; the state’s fi rst commercial olive oil volatile aromatics (aroma compounds mill is believed to have been established in Ventura County in 1871. Unable emanating from the oil) and polyphe- to compete with low-priced oil from Europe, around 1900 the California olive nols (complex phytochemicals that act industry turned its attention to table olive production. Table olives dominated as antioxidants) make up much of an the domestic olive scene for more than 75 years. For years, the California olive oil’s fl avor, and are highly variable be- oil industry was largely a salvage operation, using culls from table fruit pro- tween varieties. Qualitative analysis of duction to produce low-quality oil for refi ning. the fruity characteristics of an olive oil In the late 1980s, a small number of growers began to produce high-quality provides valuable information about the olive oil for the gourmet market. Some of these early producers harvested sensory contributions of different culti- existing trees that had been regarded mostly as messy ornamentals for years. vars, helping producers to select variet- But other growers, for the fi rst time in decades, planted olives with the inten- ies and market product to consumers tion of producing oil. Acreage of table olives declined during the same period, (Cimato et al. 1996; Romero et al. 2005; primarily because of competition from inexpensive imports in the California- Tura et al. 2000; Uceda and Aguilera style black olive market. 2005; Vossen 2003, 2007a, 2007d). A 2004 survey of the California olive oil industry found 528 growers in 38 Fruit maturity. Fruit ripeness can counties, producing almost 400,000 gallons of oil on 6,170 acres. From 2005 to have a signifi cant infl uence on the oil’s 2008, another 13,400 acres were planted, and in the last 2 years an estimated fl avor. Immature fruit produces oils 9,000 more have gone in, mostly in super-high-density orchard systems (see with green fruity fl avors such as fresh- page 34). California olive oil currently represents only 2% of domestic con- cut grass, herbs, artichoke or mint. sumption, so there is a vast market to be tapped. Since the domestic industry More mature fruit yields oils with ripe is producing extra-virgin olive oil that is as good as imports, consumer educa- notes such as nutty, buttery, fl oral, ap- tion and the enforcement of quality standards may be key elements in captur- ple, banana, berry or tropical. Sensory ing more of the domestic market. analysis of oils made from greener fruit For more information go to: http://cesonoma.ucdavis.edu. has shown high bitterness and pun- gency, which correlates with laboratory

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 9 qualities (table 2). Large flavor differ- soft fruit rot, even when fruit was 100% sensory rating than if clean and wet ences have been documented in oils damaged. In 2008, however, the sensory (washed) due to the lower moisture from trees given different amounts panel found that off flavors could im- content of the paste. Normally, all leaves of irrigation water (ranging from 15% mediately be detected when fruit rot are removed, but researchers found that to 107% of seasonal need). Drought- ranged from 1% to 5%. Therefore, with some leaves (up to 3%) left in the olives stressed trees tend to produce exces- early harvest and rapid processing, during crushing gave the oil more bit- sively bitter and pungent oils. Trees minor olive fruit fly damage can be tol- terness, green fruitiness and green maintained with a moderate water sta- erated, which can save treatment costs color. This could be desirable if these tus (controlled deficit) tend to produce and reduce environmental contami- characteristics are lacking (Hermoso oils with higher overall fruitiness that is nation (Hermoso et al. 2001; Vossen, Fernández et al. 1991; Di Giovacchino et balanced with bitterness and pungency. unpublished data; Vossen and Kicenik al. 1996). Heavily watered trees generally pro- Devarenne 2006a). Crushing. Differences in paste char- duce bland olive oils with little fruiti- Harvest, transport and storage. Most acteristics have been demonstrated to ness or pungency (Berenguer et al. 2006; olive oil defects come from improper produce various effects on oil sensory Salas et al. 1997). handling of the fruit during and after quality. Finer pastes tend to release Olive fruit fly. Sensory evaluation harvest. If the fruit is compromised in more oil that possesses greener color of oils made in California from fruit any way, it should be milled within 24 and stronger herbaceous, grassy, sweet with different levels of olive fruit fly hours of harvest. This includes broken almond and cypress wood flavors. damage showed that the conventional skins, storage at temperatures above Coarse paste tends to produce less bitter 10% threshold was often too conserva- 40°F (5°C) or fermentation beginning in and pungent oils (Di Giovacchino 1996; tive, and too generic to predict senory piled fruit (García et al. 1996). Koutsaftakis et al. 2000). impacts. In blind sensory evaluations, Washing and leaf removal. In Italy Malaxation. Changing the time, no significant flavor differences could and Spain, researchers found that when temperature and amount of oxygen be detected in fresh oil from early dam- fruit was clean and dry (unwashed), it exposure during malaxation (slow mix- age by fly larva prior to the onset of produced oils with a consistently better ing) of olive paste influences the oil’s

Olive oil definitions and regulations TABLE 1. Sensory attributes of ‘Arbequina’ olive oils grown in three different zones in Spain Extra virgin and virgin. “Extra virgin” is a grade of olive oil narrowly de-

fined by the International Olive Council (IOC). Its standards require oil to be Attribute Siurana Garrigues Andalucía produced entirely by mechanical means, without the use of solvents, under Fruity 2.4 2.2 3.1 temperatures that will not degrade the oil (less than 86oF [30oC]). It must have Green 1.5 1.4 1.8 a maximum free-fatty-acid level of less than 0.8% (an indication of the fruit’s Bitter 1.1 1.8 0.6 condition) and a peroxide value of less than 20 milliequivalent O2 (a measure of oxidation). Most importantly, a trained and IOC-recognized sensory evalua- Pungent 1.6 1.7 0.6 tion panel must find it free from defects and possessing some degree of fruiti- Sweet 1.8 1.8 2.4 ness. The next grade of olive oil is “virgin,” which may have a free-fatty-acid Sensory 7.7 7.4 8.9 level up to 2% and some slight flavor defects. rating* Common and lampante. The * European Union rating scale, 0–9 points. Source: Tous et al. 1997. grades “common” and “lampante” (lamp oil) are lower still, for oil pos- sessing more pronounced defects. TABLE 2. Means of sensory characteristics of oils from trees receiving different amounts Lampante oil must be refined before of irrigation it is usable. While these standards are widely Treatment recognized in the United States, there (% ETc)* Fruity Bitter Pungent is no guarantee that an oil labeled 15 3.60a† 6.00a 4.90a “extra virgin” meets IOC standards. 25 3.20a 4.20b 3.90b In October 2010, new voluntary USDA standards for olive and olive pomace 40 2.70b 1.70c 1.90c oil went into effect, essentially adopt- 57 2.60b 0.93d 1.10d ing the IOC laboratory and sensory 71 2.10c 0.30d 0.30e standards. California, Connecticut 89 1.80c 0.22d 0.22e and Oregon have done the same at 107 1.70c 0.20d 0.20e the state level. Hopefully, these new * Evapotranspiration rate (water use by olive trees) with a standards will be broadly adhered to coefficient corrected for olive trees compared to a general The California Olive Oil Council awards the reference rate. extra-virgin certification seal to member oils in the United States to protect both † Different letters indicate values significantly different at that are defect free. consumers and ethical producers. P = 0.01. Source: Berenguer et al. 2006.

10 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 sensory characteristics. Longer malaxa- weed out poor-quality tion times increase oil yield, lower poly- oils and educate pro- phenol levels and lower the levels of ducers about defects, to aromatic volatiles responsible for some help them avoid making fruity flavor characteristics. Raising the production mistakes. paste temperature causes greater ex- In 1997, the first traction of polyphenols, but every 22°F California screening for (12°C) increase in temperature doubles sensory panel members the loss of volatile aromatics. Paste ma- was conducted at UC laxed at 95°F (35°C) produces oil that Davis, with the aid of is sharply bitter compared with at 77°F Juan Ramon Izquierdo (25°C). Malaxation tanks that exclude from the Spanish oxygen significantly increase bitter- Arbitration Laboratory Olive fruit fly is a major pest of olives. The sensory effects of ness and pungency. Many researchers in Madrid. Using IOC infestation depend on both the quantity and type of damage. are currently investigating the effects procedures, potential of low oxygen exposure on aromatic panelists were screened for olfactory UC Davis Olive Oil Taste Panel, recently compounds that influence fruitiness and gustatory sensitivity and also for certified by the IOC.) (Angerosa 2002; Di Giovacchino et motivation, availability and personal- Tasting protocols al. 2002; Hermoso Fernández et al. 1991). ity (IOC 2007a). Twenty people out of 75 Extraction system. Press systems were selected. Subsequent screenings Samples are presented “blind” and have consistently produced oils with added another 26 panelists. Altogether, in the most appropriate order, so that more defects than continuous-flow 46 tasters were selected out of 217 ap- errors of contrast are minimized (see systems. Sensory evaluation of oil from plicants (21%). About half of those have box, page 12). Oils are identified with continuous-flow processing systems chosen to remain active. a random three-digit number or letter that use different amounts of added Trained panel members’ minds and combination that is not familiar in any water have shown that oils are higher palates must become calibrated over way, to prevent order bias. Special blue in fruitiness, bitterness, pungency time to an absolute scale of intensities glasses are used to obscure the oil color, and green character when less water for all the common flavor attributes of so that color bias does not influence the is added (Alba Mendoza et al. 1996; olive oil. The calibration process takes panelists’ evaluations, and tasters are Hermoso Fernández et al. 1998; Kicenik several years and is not permanent; isolated from one another with divid- Devarenne and Vossen 2007a). panelists must continually receive train- ers. For the most accurate evaluation, ol- Oil styles and excellence recognition. ing if they are to remain sharp. Training ive oils are warmed to 80°F (26.5°C) on a Providing industry professionals with is conducted by a panel leader who pro- warming mat. Because flavors based in accurate evaluations of olive oil flavor vides the group of tasters with samples oil coat the mouth, throat and nasal cav- characteristics is extremely important. of known characteristics and intensities ity, they tend to linger, which influences With flavor profiles of their oils, produc- in order for them to learn and remem- the reaction to subsequent samples and ers can make well-informed decisions ber specific positive and negative at- quickly fatigues the senses. A resting about the styles of olive oils they want tributes. Panelists must also taste oils time of 5 minutes is required between to produce, and consequently, better from all over the world to learn the oils, and green apples and water are olive oils. UC Cooperative Extension characteristics of each variety, so that used as palate cleansers to minimize (UCCE) has produced several informa- varietal differences are not confused sensory fatigue. Panelists usually taste tive handouts on how to define extra- with defects. from three to five oils in 30 minutes virgin olive oil and interpret an olive oil The IOC recognizes sensory panels (IOC 2007c). label, and how untrained tasters can in- that are approved by a government Sensory panelists place a short, verti- advertently promote the use of defective agency such as the U.S. Department of cal mark on a horizontal, unstructured, oils. Many untrained tasters are aver- Agriculture. Panels from around the 10-centimeter line scale where the flavor age consumers who are accustomed to world take compulsory proficiency intensity is perceived to be. Data on defective flavors, identifying them with tests called ring tests, in which they all profile sheets containing individual oil the taste of olive oil (Kicenik Devarenne taste and rate the same five oils. The ratings is compiled by a technician and and Vossen 2007b; Vossen 2007a; Vossen results are compared using a standard analyzed with a statistical computer and Kicenik Devarenne 2006b). procedure that is analyzed statistically program developed by the IOC. The for variability, accuracy and unifor- software places each oil into a specific The California sensory panel mity. In 2001, the UCCE sensory panel category — extra virgin, virgin, com- During a 1996 study leave, farm advi- participated in a series of ring tests and mon or lampante — based on the IOC sor Paul Vossen realized that Europeans became one of 41 officially recognized standards for defect-intensity levels and understood olive oil quality and were IOC taste panels, the first one in the the presence of fruity characteristics. using sensory analysis to describe and United States to have received such The minimum IOC sensory defini- promote positive characteristics. They recognition (IOC 2007b). (Many of the tion of an extra-virgin oil, for example, were also using sensory analysis to original tasters are now members of the is one in which the mean score of the

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 11 eight panelists is zero defects with some fruitiness. This means that five out of eight must agree in their profile-sheet characterizations. If the coefficient of variation (relative robust standard de- viation) of the main defect is greater than 20% in a defective oil, or greater than 10% in an extra-virgin oil for the fruitiness characteristic, the test must be repeated. Tasters must be very close in iden- tifying the primary defect in each oil, if it has one, and the intensities of the defect must be within 2 points on the 10-centimeter scale. For fruitiness, the intensity must be within 1 point on the scale. The statistical program makes a The International Olive Council conducts “ring tests,” sending the same five oils to panels around calculation (median, interquartile inter- the world for testing to ensure that its standards are being upheld. val, robust standard deviation, relative robust and standard deviation) based (COOC), a trade organization. UCCE likely cause. From 1999 through 2004, on each panelist’s evaluation of each oil, farm advisor Vossen was responsible the number of defective oils dramati- and a minimum of eight panelists must for training the sensory panel and cally declined from 50% to less than 3%. be used for an official oil evaluation maintaining scientific protocol. The If an oil was deemed defect-free (and (IOC 1999). COOC seal was awarded to oils that therefore certifiable) but there was room the sensory panel judged “extra virgin” for improvement, the panel’s comments UC and the olive oil industry according to IOC standards. Producers regarding harvest maturity or other fac- In 1999, the California sensory panel also benefited from panelist comments tors were passed along to the producer. began providing feedback to the state’s regarding their oil’s characteristics. If The COOC seal was the first attempt by olive oil industry in the form of a seal an oil failed certification, the farm ad- the domestic industry to give consum- certification program, in partnership visor confidentially informed the pro- ers an assurance of quality when pur- with the California Olive Oil Council ducer of the nature of the defect and its chasing California olive oil. In 2005, a new UCCE profile sheet How to taste olive oil was developed for more detailed analysis of extra-virgin olive oils in Olive oil is best tasted in a blue, California. It records taster impressions tulip-shaped, stemless glass. of additional aspects, including the oil’s The tasting glass is covered harmony and complexity. By select- with either a lid or hand, and ing from a list of descriptors such as the oil gently swirled. The open artichoke, banana, almond or fresh-cut glass is placed close to the nose grass, the tasters note undertones in the and the taster takes a deep olive oil. Previous sensory panel analy- breath, making a mental note of sis emphasized defect identification. the aroma, since much of what Descriptive analysis provides extremely we call flavor is actually smell. valuable data on the more subtle and Next, the taster sips about complex aspects of olive oil. This can 5 milliliters of oil and holds it help producers adjust harvest timing, in their mouth for 10 seconds, Blue glasses are used to taste olive oil, in order to tailor processing methods to particular taking care to coat all parts of prevent color bias. varieties and pinpoint attributes for the mouth and tongue. While blending. the oil is in the mouth, air is sucked in to further volatilize its aromatic com- UC has also been addressing the ponents before swallowing. Then the mouth is closed while the taster breathes needs of the California olive oil indus- out through the nose. The retronasal cavity connecting the mouth to the olfac- try with training programs, such as tory area allows the volatile aromas to be perceived once again. the 2-day Olive Oil Sensory Evaluation The mouth and throat detect flavors such as bitterness, pungency, sweet- Short Course, taught once or twice ness and astringency. Most people taste bitterness primarily toward the back per year since 1999. Likewise, special of the tongue and mouth. Pungency is a physical irritation perceived in the trainings have been conducted for throat, which is why it is essential to swallow some of the oil in order to ap- chefs, food writers, producers, consum- preciate all of its sensory characteristics. ers and educators. In addition, UCCE short courses on olive production

12 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 topics, regional grower meetings This will help growers select varieties harvest maturities, schedule irrigation and field days have also provided that are horticulturally suited to their and generally improve the quality of valuable science-based information. location. Ongoing research on how their oils. California-specific data pro- Two UC Division of Agriculture and olive fruit fly can damage the sensory duced by the sensory panel — using Natural Resources publications, the aspects of olive oil will help producers internationally recognized scientific Olive Production Manual and Organic further adjust their pest control mea- standards and methods — will continue Olive Production Manual, continue this sures to minimize environmental and to be essential to the growth of the tradition. financial impacts, while preserving oil California olive oil industry. quality. A research project comparing Looking to the future different processing systems will pro- Due to UC research and support, and vide valuable information for producers the efforts of the sensory panel volun- seeking the best methods for their par- Paul M. Vossen is Farm Advisor, UC Cooperative teers, it has become a rarity to find de- ticular fruit, depending on variety and Extension, Sonoma and Marin counties; and A. fects in a California olive oil. Research ripeness. Kicenik Devarenne is Freelance Olive Oil Consul- tant, Writer and Educator, Sonoma County. continues to explore the effect of terroir The UCCE sensory panel is provid- Shermain D. Hardesty, Specialist in the UC on olive oil, and a database is being cre- ing feedback on specific flavor char- Davis Department of Agricultural and Resource ated of characteristics in single varietal acteristics of individual oils that helps Economics, served as Guest Associate Editor for oils grown in different parts of the state. producers to choose varieties, adjust this article.

References Hermoso JF, Romero A, Tous J, et al. 2001. Incidencia Salas J, Pastor M, Castro J, Vega V. 1997. Influencia del del sistema de recolección en la calidad del aceite de riego sobre la composición y características organolép- Alba Mendoza J, Hidalgo F, Casado MA, et al. 1996. oliva en el sur de Cataluña. IV Congreso Ibérico de ticas del aceite de oliva. Grasas Aceites 48(2):74–82. Características de los aceites de olive de primera y se- Ciencias Hortícolas. Cáceres, Mayo. p 2012–20. gunda cetrifugación. Grasas Aceites 47(3):163–81. Tous JM, Romero A, Plana J, et al. 1997. Chemical and [IOC] International Olive Council. 1999. Organoleptic sensory characteristics of ‘Arbequina’ olive oil obtained Alba Mendoza J, Izquierdo JR, Gutiérrez Rosales F. assessment of virgin olive oil — computer program Ex- in different growing areas of Spain. Grasas Aceites 1997. Aceite de Olive Virgen Análisis Sensorial. Edito- cel file – statistical analysis. COI/T.20/Doc No 15/Rev. 1. 48(6):415–24. rial Agrícola Española, S.A. Artes Gráficas COIMOFF, S.A. Madrid, Spain. IOC. 2006. Trade standard applying to olive oils and Tura D, Failla O, Bassi D, Serraiocco A. 2000. Sensory olive pomace oils. COI/T.15/NC No 3/Rev 2, Nov 24, and chemical analyses of monovarietal olive oils from Angerosa F. 2002. Influence of volatile compounds 2006. Lake Garda (Northern Italy). In: Vitagliano C, Martelli on virgin olive oil quality evaluated by analytical ap- IOC. 2007a. Guide for selection, training and monitor- GP (eds.). Proc 4th Intl Symp on Olive Growing, Va- proaches and sensory panels. Eur J Lipid Sci Technol lenzano, Italy. Acta Hort 586:595­–8. 104:639–60. ing of skilled olive oil tasters. COI/T.20/Doc No 14/Rev 2, Sept 2007. Uceda M, Aguilera M. 2005. Caracterización sensorial Aparicio R, Morales MT, Alonso V. 1997. Authentica- del aceite. Capitulo 15. (Banco de Germoplasma Mun- tion of European extra-virgin olive oils by their chemi- IOC. 2007b. Guidelines for the accreditation of sen- sory testing laboratories with particular reference dial de Córdoba.) In: Rallo L, et al. (eds.). Variedades cal compounds, sensory descriptors and consumer de Olivo en España (Libro II: Variabilidad y selección). attitudes. J Agr Food Chem 45:1046–83. to virgin olive oil according to standards ISO/IEC 17025:2005. COI/T.28 Doc No 1, Sept 2007. Junta Andalucía, MAPA y Ediciones Mundi-Prensa, Berenguer MJ, Vossen PM, Grattan SR, et al. 2006. Madrid. IOC. 2007c. Sensory analysis of olive oil – method for Tree irrigation levels for optimum chemical and sensory Vossen PM. 2003. California Arbequina and Arbosana properties of olive oil. HortScience 41(2):427–32. the organoleptic assessment of virgin olive oil. COI/T. 20/Doc No 15/ Rev 2, Sept 2007. olive oils get a very high rating from the local tasting Cimato A, Baldini A, Caselli S, et al. 1996. 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http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 13 REVIEW ARTICLE ▼

Understanding the seasonal and reproductive biology of olive fruit fl y is critical to its management

by Hannah J. Burrack, Ray Bingham, Richard Price, Joseph H. Connell, Phil A. Phillips, Lynn Wunderlich, Paul M. Vossen, Neil V. O’Connell, Louise Ferguson and Frank G. Zalom

The olive fruit fl y was fi rst detected in Los Angeles in 1998 and in all the

olive­growing regions of California UC Statewide IPM Program Clark, Kelly Jack soon after. Following its initial detec­ tion, UC researchers and Cooperative Extension farm advisors, county agricultural commissioners and the California Department of Food and Agriculture Pest Detection and Emer­ gency Project established a statewide monitoring program to determine the extent of the olive fruit fl y’s occur­ First detected in 1998, the olive fruit fl y spread quickly throughout the state’s olive-growing regions. The table olive industry has zero tolerance for damaged fruit, but infestation levels of 10% rence, track its seasonal biology and or more may be acceptable for olive oil. Above, the adult fl y’s exit holes; larvae feed just below. evaluate monitoring tools. Fly popu­ particularly important for effective table olive–producing counties. B. oleae lations and infestations can reach management. is managed differently in these two pro- high levels throughout California but The insect’s historic range includes duction systems: there is zero tolerance all of Europe and Africa, and extends for infestation in table olives, while a tend to be lower in the San Joaquin at least as far east as India (Augustinos threshold of roughly 10% infestation is Valley. Trap captures typically exhibit et al. 2002; Nardi et al. 2005). Molecular acceptable for oil olives, although even a bimodal distribution with peaks in studies of B. oleae in California sug- greater levels can produce high-quality the spring and fall. Olive infestation gest that the invasion originated from oil if the fruit is processed quickly Mediterranean populations. Australia (Kicenik Devarenne and Vossen 2007). is related to fl y densities, climate and is the only country where olives are This production difference is par- fruit size. Gravid, mated females vary grown that is not colonized. In the ticularly notable in Butte County, where in density throughout the year but traditional olive-growing regions of high fl y densities and associated dam- are present at some level year­round. Europe and the Middle East, the olive age resulted in crop rejection by table fruit fl y is the primary economic pest. olive processors. Consequently, olives The data is being used to develop B. oleae has become the most important grown in Butte County are crushed for models that will better predict when pest of California olives (Collier and oil. Super-high-density oil plantings the adults are active and olives are Van Steenwyk 2003; Daane et al. 2005), have been established in Butte County and in commercial production control since 1999. These plantings — in which at risk. necessitates regular applications of olive trees are spaced more closely, vari- insecticidal bait sprays from fruit-set eties with smaller fruit are planted and through harvest. defi cit irrigation is used — appear to be he olive fruit fl y was fi rst detected The majority of California’s crop is less conducive to olive fruit fl y infesta- Tin California in 1998 in the Los processed for table olives and is grown tion (Vossen 2007) (see page 34). Angeles Basin and was subsequently in the Sacramento and San Joaquin Statewide monitoring program found in all olive-growing areas within valleys, in Butte, Glenn, Tehama and 4 years (fi g. 1). The olive fruit fl yBac- ( Tulare counties (Connell 2005). Olive oil We and other researchers were in- trocera oleae [Rossi]) is the primary pest is also produced from California olives. terested in understanding the seasonal of olives worldwide and is particularly At the onset of the olive fruit fl y inva- activity patterns of B. oleae in California troublesome due to its multiple, over- sion, oil production occurred primarily as compared to its previously known lapping generations each year. This life in coastal counties, including Napa and range, in order to predict where and history makes understanding olive fruit Sonoma. In recent years, oil production when the fl y was most likely to be- fl y phenology and infestation patterns has been increasing in the traditional come a signifi cant pest. In 2002, UC

14 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 Del researchers and Cooperative Extension a spiroketal phero- Norte Siskiyou Modoc farm advisors, California Department mone lure attractive 1998 Fig. 1. Years of initial of Food and Agriculture Pest Detection to males (Yokoyama 1999 olive fruit fl y detection and Emergency Project personnel, et al. 2006). Plastic Trinity Shasta Lassen 2000 in California counties. county agricultural commissioners and McPhail traps Humboldt 2001 Tehama 2002 pest control advisers assembled a net- (Liquibaitor trap, Plumas 2004 Mendocino Glenn Butte work of monitoring sites throughout the Great Lakes IPM, Sierra

Colusa state, in order to determine olive fruit Vestaburg, Mich.) Yuba Sutter Nevada Placer Lake fl y population dynamics within and baited with an aque- Yolo El Dorado Sonoma Napa Sacra Alpine between California’s diverse climatic ous torula yeast food mento Amador Marin Solano and geographic regions. A network of lure attractive to both San CalaverasTuolumne Contra Mono Costa Joaquin 28 monitoring sites in 16 counties was sexes were shown to San Francisco Alameda Mariposa San Mateo established and data was collected from be more attractive than Santa Stanislaus Clara Merced 2002 through 2006 (table 1). ChamP traps (Burrack et Santa Cruz Madera

San Inyo This large dataset allowed us to track al. 2008), and in 2003 all Benito Fresno B. oleae activity patterns and to relate monitoring locations be- Tulare these patterns to fl y and fruit biology. gan to use two to four of the Monterey Kings

The end-product of this work will be McPhail traps. San Luis Obispo Kern predictive models for fl y activity and Every week the traps were San Bernardino fruit infestation. Because the initial goal checked, fl ies were counted and Santa Barbara of this monitoring effort was to track sexed, and lures were changed. Ventura Los Angeles B. oleae seasonal biology, sites with ac- Trapping was conducted from April Riverside tive, relatively large populations were through December at most locations, Orange selected, and all traps were placed in with a subset of locations (Butte 1, Napa San Diego Imperial olive plantings that received no insecti- 1, Napa 2, Napa 3, Napa 4, San Diego 1, cide applications for the duration of the San Luis Obispo 2, Solano 4, and Yolo 1) study. Therefore, all population fl uctua- continuing year-round. Weekly trap tions observed were due to local biotic and abiotic factors, not anthropogenic TABLE 1. Olive fruit fl y monitoring locations, geographic classifi cations and years active effects. The selection of untreated sites with County Site No. of traps Geographic area Years active large B. oleae populations led to a lack Amador 1 4 North, inland 2005 of locations in the San Joaquin Valley, Butte 1 4 North, inland 2002, 2003, 2004, 2005 because most olive plantings in this Calaveras 1 2 North, inland 2002, 2003, 2004, 2005 area are used for commercial table olive Marin 1 2 North, coastal 2002, 2003, 2004 production and may be treated with Napa 1 2 North, coastal 2002, 2003, 2004, 2005, 2006 pesticides if B. oleae are present. In addi- 2 2 North, coastal 2002, 2003, 2004, 2006 tion, other researchers documented that 3 2 North, coastal 2002, 2003, 2004, 2006 populations in the San Joaquin Valley 4 2 North, coastal 2002, 2003, 2004, 2006 appear naturally lower than coastal Sacramento 1 2 North, inland 2002, 2003, 2004 and Sacramento Valley locations (Rice 2 2 North, inland 2005 et al. 2003; Yokoyama et al. 2006). The 3 2 North, inland 2004 olive fruit fl y had already been detected 4 2 North, inland 2004 in 35 counties prior to 2002. After the San Diego 1 2 South, coastal 2002, 2003, 2004, 2005 monitoring program was initiated, it San Luis Obispo 1 2 South, coastal 2002, 2003, 2004, 2005, 2006 was found in nine more counties (fi g. 2 2 South, coastal 2002, 2003, 2004, 2005, 2006 1), although the detection years do not Santa Barbara 1 2 South, coastal 2004 necessarily indicate initial invasion. 2 2 South, coastal 2004 This is particularly clear in the case of Shasta 1 2 North, inland 2002, 2003, 2004, 2005 Colusa County, which was surrounded Solano 1 2 North, inland 2002, 2003, 2004 by counties in which the fl y had been 2 2 North, inland 2002, 2003, 2004, 2005, 2006 detected, but for which there were no 3 2 North, inland 2002, 2003, 2004 records of olive fruit fl y until 2004. 4 4 North, inland 2002, 2003, 2004, 2005, 2006 Sonoma 1 2 North, coastal 2002, 2003, 2004, 2005 Geography and seasonal activity 2 2 North, coastal 2003, 2004, 2005, 2006 Tulare 1 4 South, inland 2005 Statewide monitoring began using Ventura 1 4 South, coastal 2005 four ChamP yellow sticky traps per site Yolo 1 4 North, inland 2002, 2003, 2004, 2005, 2006 baited with ammonium bicarbonate Yuba 1 2 North, inland 2003, 2004 food lures attractive to both sexes and

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 15 captures were converted to flies per trap per day to allow for comparison between locations. Flies per trap per Jack Kelly Clark Kelly Jack day were summed, divided by the num- ber of locations reporting data for the

Alexandra Kicenik Devarenne week, and graphed to allow observation and comparison of population density trends. Olive fruit fly flight activity has a bimodal distribution, with the highest trap captures observed in spring and fall (fig. 2A). Depending on location, spring peaks occur in March, April or May and fall peaks are in September, Yellow sticky traps, left, are used to monitor the fly’s population densities in different locations October or November. The majority of throughout the year. Right, an adult olive fruit fly caught in a trap. the pooled trapping data points repre- sented at least 15 monitoring sites (fig. 2B), except for the winter dates. Overall 40 A 35 fly activity was low in the winter, 30 and the locations selected for winter 25 monitoring were among those with the 20 highest B. oleae trap captures during the 15 previous summer and fall. Flies were 10 still present during winter at these loca-

Flies/trap/day by site 5 tions, but were trapped in lower num- 0 bers. Trap captures were lower in 2002

25 than in subsequent years, likely due to B the use of a less efficient trap and the 20 shorter time since initial B. oleae estab-

15 lishment in more northern locations. When sites were grouped into broad 10 geographic categories, differences in Sites reporting 5 seasonal activity became apparent. We considered a trapping site to be coastal 0 July Oct Jan Apr July Oct Jan Apr July Oct Jan Apr July Oct Jan Apr July Oct Jan if it was either in a county directly bor- dering the ocean or west of the summit 2002 2003 2004 2005 2006 of the coastal mountain range. Coastal Fig. 2. (A) Average flies per trap per day caught at all monitoring locations over 4 years and (B) locations have milder climates than number of trapping locations reporting each week. those inland, with cooler summers and warmer winters. We considered trap-

100 ping locations to be northern when they were situated at greater than 37° 90 N latitude (roughly Santa Cruz), with Inland 80 Coastal the remainder categorized as southern.

70 Both coastal and inland locations in- cluded sites with very high (10,000 or 60 more flies; San Diego, Butte and Solano 50 2) and very low (under 1,000 flies; Marin and Tulare) trap captures (table 2). Trap 40 data from the same geographic areas

Flies/trap/day by site 30 was pooled and graphed.

20 The sites from Northern and Southern California displayed similar 10 activity patterns and are not presented, 0 but fly trap capture patterns at inland July Oct Jan Apr July Oct Jan Apr July Oct Jan Apr July Oct Jan Apr July Oct Jan versus coastal locations differed mark- 2002 2003 2004 2005 2006 edly (fig. 3). The pooled inland loca- tions exhibited similar bimodal trap Fig. 3. Flies per trap per day caught at combined inland and coastal trapping locations over 4 years. capture patterns to those observed for

16 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 combined data from all sites (fig. 2A), levels and trap captures were low in San Joaquin Valley locations (Rice et but pooled coastal locations lacked a Tulare County for the entire season, al. 2003; Yokoyama et al. 2006). B. oleae spring peak and displayed a gradual in- despite olive size and development populations in the Central Valley may crease of fly captures, with the greatest comparable to the other monitoring lo- be limited by high temperature and numbers captured in the fall (fig. 3). cations (figs. 4A, 4B and 4C). food resources (Wang et al. 2009) (see Previous monitoring efforts have page 29). Solano County Mission olives Tracking olive infestations also reported lower trap captures in were significantly less infested than Olive infestation and olive size were tracked in 2004 and 2005 at seven lo- cations, and fly density was tracked TABLE 2. Total olive fruit flies caught at monitoring locations during olive production season (May through November) in 2003, 2004 and 2005* during 2005. Manzanillo and Mission olives, the most commonly grown varieties in California (Connell 2005), County Site No. of traps 2003 2004 2005 ...... were sampled at most locations, and number of flies Leccino olives were sampled at one lo- Amador 1 4 —† — 10,718 cation because no suitable Manzanillo Butte 1 4 3,880 10,956 8,487 or Mission olives were available (table Calaveras 1 2 406 4,692 — 3). One hundred olives were collected Marin 1 2 331 78 — weekly from four trees at each loca- Napa 1 2 3,499 2,039 1,369 tion, June through December 2004, and 2 2 1,459 2,459 — May through December 2005. Sample 3 2 1,920 3,034 — size was decreased to 52 olives per tree when fruit infestation reached 50%. 4 2 1,001 3,397 — Olives were dissected under a ste- Sacramento 1 2 — 6,988 — reomicroscope, and oviposition scars 2 2 — — 2,942 (stings), live larvae, and pupae or 3 2 — 6,838 — larval/adult exit holes were counted. San Diego 1 2 8,711 5,290 10,008 Olives bearing stings were considered San Luis Obispo 1 2 — 1,227 1,191 infested, as table olive producers have 2 2 3,765 3,756 2,339 a zero tolerance policy for olive fruit Santa Barbara 1 2 — 3,924 — fly infestation. Prior to dissection, each olive was measured to compare fruit 2 2 — 3,979 — size across locations, because olive fruit Shasta 1 2 52 204 1,700 fly adults exhibit a preference for large Sonoma 1 2 1,857 4,895 3,058 fruit under field conditions (Burrack 2 2 602 1,207 1,288 and Zalom 2008; Yokoyama et al. 2006). Solano 1 2 8,216 11,667 — The longest point on the olive (l), the 2 2 10,466 40,422 16,686 widest point (w) and 90° from the wid- 3 2 4,051 9,490 — est dimension (h) were measured and 4 4 1,167 9,914 2,889 used to calculate fruit volume (V = (4/3π)(h/2)(w/2)(l/2)). Fly populations Tulare 1 4 — — 287 were monitored at each location using Ventura 1 4 — — 13,800 four plastic McPhail traps, as described Yolo 1 4 2,454 7,521 5,269 previously. Data from 2004 and 2005 Yuba 1 2 1,163 — — was similar for all locations, therefore * Data from 2002 and 2006 not presented because data collection was not season-long. data from 2005 is presented. † Winter dates and years with incomplete data for a location are omitted. Infestation levels in 2005 reached

100% in Butte and Ventura counties. TABLE 3. Olive infestation data locations Infestations grew slowly at the Amador and Sonoma sites but were high by County Location Trapping location Varieties sampled the end of the season (fig. 4A). Fly trap Amador Abandoned orchard Amador 1 Leccino captures mirrored the delayed infesta- Butte Commercial and fallow orchard Butte 1 Manzanillo, Mission tion pattern at Amador and Sonoma (fig. 4B), and these two locations had the Sonoma Abandoned orchard Sonoma 2 Mission smallest olives throughout the season Solano Wolfskill Experimental Orchard Solano 4 Manzanillo, Mission (fig. 4C). Smaller olives are typically less Tulare Lincove Research Station Tulare 1 Manzanillo infested in the field (Burrack and Zalom Ventura Abandoned orchard Ventura 1 Mission 2008), and both fly population and olive Yolo UC Davis campus farm Yolo 1 Manzanillo, Mission size are affected by weather. Infestation

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 17 Manzanillo olives from the same loca- access to olives (Koveos and Tzanakakis ovaries, was also determined. Mating tion. Field observations from this site 1990, 1993; Koveos et al. 1997; Raspi et status was determined via staining suggest that Manzanillo olives may be al. 2002; Raspi et al. 2005). with 4’, 6-diamidino-2-phenylidole preferable to Mission for oviposition in In order to determine if this phenom- dihydrocholride (DAPI) at 1 micro- the field when female flies have a choice enon occurs in California B. oleae popu- gram per milliliter in phosphate (Burrack and Zalom 2008). lations as well as to determine when buffered solution and observed with flies were capable of infesting olives, UV-flourescent microscopy as adapted Reproductive biology females flies collected from monitoring from Fritz and Turner (2002). Flies were Examination of trap captures com- traps were dissected for five sites (Butte dissected in 70% ethyl alcohol, and pared to ovarian development in the 1, Napa 1, San Diego 1, Solano 4 and spermathecae were removed, placed in female indicated that the olive fruit fly Yolo 1). These locations were selected a drop of DAPI on a microscope slide has at least four generations per year because trapping was conducted year- and crushed with a cover slip. in California, with a partial generation round, and they represented different The morphology of the olive fruit fly spanning the winter (Burrack 2007). An California climates. Ten flies from each spermatheca and ethanol preservation absence of mature eggs in fly ovaries location and sampling date were dis- made quantification of sperm difficult. during the spring and early summer sected, and when fewer than 10 flies per Therefore, flies were classified as mated has often been noted in European week were collected, all flies were dis- or unmated. An overall classification of B. oleae populations (Delrio and Prota sected. Ovarian development, egg load reproductive biology was assigned to 1976; Economopoulos et al. 1982; and mating status were observed for each fly by combining ovarian develop- Fletcher et al. 1978; Raspi et al. 2002; each of the dissected flies. ment rankings and mating status. These Tzanakakis 1986) and is referred to as We determined whether the ova- categories were: (1) unmated (sperm a summer reproductive diapause. A ries of female flies contained mature absent), immature (immature ovaries); similar absence of mature eggs can be eggs and whether their spermathecae (2) unmated, mature (mature ovaries); induced in flies reared in the laboratory contained sperm. Mature eggs are (3) mated (sperm present; mature eggs by exposing larvae to cool, short days easily distinguished from developing in ovaries [gravid]), immature; and (4) and adults to hot, long days with no eggs by a distinctly darker micropile mated, mature. Only flies in category 4 on the anterior would be capable of infesting olives. end. Egg load, or All statistical analyses were con- (A) Fruit infested the total number ducted using SAS version 9.1 (SAS 100 of mature eggs Institute, Cary, N.C.). Analysis of vari- County, variety 90 Amador, Leccino present in both ance was conducted with Proc GLM, 80 Butte, Manzanillo and means were separated via LSD. Solano, Manzanillo 70 Nonparametric rank tests were con- Solano, Mission 60 Sonoma, Mission ducted using the Kruskal-Wallis test via Tulare, Manzanillo 50 Fig. 4. (A) Percentage Proc Npar1way in SAS. Ventura, Mission of fruit infested, 40 Yolo, Manzanillo There were significant differences sampled weekly, (B) between months in the proportion of 30 flies caught per trap

Fruit infested (%) unmated flies with immature ovaries 20 per day and (C) olive development at fruit and mated flies with mature ovaries 10 infestation locations observed (unmated/immature: F8,20 = 0 in 2005. Gaps in lines 5.16, P = 0.0014; mated/mature: F = 5/12 6/12 7/13 8/13 9/13 10/14 11/14 signify dates for 8,20 which olive data was 4.94, P = 0.0018), but there was also a not collected. significant site/month interaction for

(B) Flies per day (C) Olive volume

140 5,000 County County, variety 4,500 120 Amador Amador, Leccino Butte 4,000 Butte, Manzanillo Solano Solano, Manzanillo

100 )

3 3,500 Sonoma Solano, Mission Tulare 3,000 Sonoma, Mission 80 Ventura Tulare, Manzanillo 2,500 Yolo Ventura, Mission 60 2,000 Yolo, Manzanillo

40 1,500 Total ies/trap/day Total Olive volume (mm 1,000 20 500

0 0 5/12 6/12 7/13 8/13 9/13 10/14 11/14 5/12 6/12 7/13 8/13 9/13 10/14 11/14

18 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 both categories (unmated/immature: possible that the proportion of imma- by moderate, coastal-infl uenced tem- F32,20 = 4.01, P = 0.0009; mated/mature: ture fl ies may be even greater than that peratures throughout the year, as op- F32,20 = 5.17, P = 0.0001). The differences observed through trap captures. The posed to hot summer and relatively among years for both rankings were climate at San Diego is characterized cool winter temperatures that fall below nonsignifi cant (unmated/immature: F2,20 = 2.36, P = 0.1205; mated/mature: (A) Yolo 1 (n = 1,133) F2,20 = 1.18, P = 0.3267), and therefore, Mar Apr May June July Aug Sep Oct Nov 100 yearly data was pooled by month. bcd ab d cd bcd bc ab a a Because of the signifi cant interaction 80 effect between site and month, the data 60 for individual sites is presented. The greatest proportion of mated, mature 40 fl ies was observed in March or April 20 abc c a ab abc bc c c c and October through November, for 0 the Yolo, Solano and Butte county sites (B) Solano 4 (n = 972) (fi gs. 5A, 5B and 5C). High proportions 100 of potentially destructive fl ies (mated, ab a bc bc b c b ab a 80 mature) were observed in April, August and September in Napa County (fi g. 60 5D). The greatest proportion of un- 40 mated, reproductively immature fl ies 20 throughout the year was observed at bc c a abc ab a ab bc bc San Diego, where the highest percent- 0 age of mated, gravid fl ies was present in (C) Butte 1 (n = 870) 100 June, July and August (fi g. 5E). a a cd cd d ab bc a ab The proportion of reproductively im- 80 mature fl ies increased in spring or early 60 summer at all locations, a period during 40 which the European literature suggests that a reproductive diapause may occur. 20 bc c a a a bc b bc bc However, reproductively mature fl ies 0 were also present at this time. A de- Dissected females (%) (D) Napa 1 (n = 937) crease in mean egg load was observed 100 bcd abc a d d abcd ab cd cd during the spring and fall (data not 80 shown). At no point during the summer months were reproductively mature fe- 60 males completely absent. 40

Egg load was positively related 20 to mating status (F1, 3049 = 160.20, P < abc bc c a abc bc c ab ab 0 0.0001) at all locations for all months. (E) San Diego 1 (n = 1,095) Mean egg load was larger in mated 100 than unmated fl ies, regardless of bc bc bc ab a ab bc bc c month, and was greatest in March and 80 May and least in September. On aver- 60 age, mated fl ies had 7.30 eggs in their 40 ovaries, while unmated fl ies had 2.44 20 eggs present. Flies with mature eggs ab ab a b b b ab ab a in their ovaries were more likely to be 0 mated (χ2 = 1228.4922, df = 1, P < 0.0001). Mar Apr May June July Aug Sep Oct Nov Population densities as indicated Collection month by trap captures were high at both Unmated, immature Unmated, mature Mated, immature Mated, mature the Butte and San Diego sites (table 2) relative to the other sites. McPhail Fig. 5. Ovarian development and mating status for olive fruit fl y at fi ve locations. Flies were traps are thought to overestimate the categorized as (1) unmated (sperm absent), immature ovaries, (2) unmated, mature ovaries, (3) proportion of gravid female fl ies in mated (sperm present), immature ovaries and (4) mature, mature ovaries. Only fl ies in category a population (Neuenschwander and (4) would be capable of infesting olives. Flies were collected weekly, and data pooled by month. Michelakis 1979), so the abundance of Percentages of a given class (unmated/immature or mated/mature) indicated by the same letter for a single location were not signifi cantly different α( = 0.05) when adjusted means were reproductively immature fl ies is likely compared via LSD; data from December, January and February was eliminated from analysis for not due to greater trap capture and it is all years due to insuffi cient sample sizes.

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 19 the fruit fly development thresholds. Managing olive fruit fly done to develop tools to apply this in- Therefore, more-extensive generational formation in effectively managing this overlap might be expected at the San UC researchers have developed a pest. Models determining when olives Diego site than at the Butte site, result- greater understanding of the behavior become susceptible to olive fruit fly at- ing in more young, reproductively and biology of the olive fruit fly in the tack and how fly populations respond immature females present in the popu- 12 years since its initial detection, but to climatic conditions are being devel- lation year-round. there is still a great deal of work to be oped using the data described here. With a few exceptions, the olive fruit fly has not prevented commercial olive production in California for most grow- ers, but it has significantly changed their insect management requirements.

H.J. Burrack is Assistant Professor of Entomology, North Carolina State University, Raleigh; R. Bingham is Entomologist, Plant Industry, California Department of Food and Agriculture; R. Price is Agricultural Commissioner, Butte County; J.H. Connell is Farm Advisor, UC Co- operative Extension (UCCE) Butte County; P.A. Phillips is Regional IPM Farm Advisor, retired; L. Wunderlich is Farm Advisor, UCCE Amador and El Dorado counties; P.M. Vossen is Farm Advisor, UCCE Sonoma and Marin counties; N.V. O’Connell is Farm Advisor, UCCE Tulare County; L. Ferguson is Professor of Plant Sciences, UC Davis; and F.G. Zalom is Professor of Entomology, UC Davis. The authors would like to thank 19 trappers Statewide surveys have gathered important information about the life cycle of the olive fruit fly, for collecting data from 28 locations in 16 coun- which will be used to improve pest management practices. Above, larvae infest olive fruit. ties over the course of 4 years.

References Economopoulos AP, Haniotakis GE, Michelakis S, et al. Neuenschwander P, Michelakis S. 1979. McPhail trap 1982. Population studies on the olive fruit fly, Dacus captures of Dacus oleae (Gmel.) (Diptera, Tephritidae) Augustinos AA, Stratikopoulos EE, Zacharopoulou A, oleae (Gmel.) (Dipt., Tephritidae) in Western Crete. in comparison to the fly density and population com- Mathiopoulos KD. 2002. Polymorphic microsatellite Z Entomol 93:463–76. position as assessed by sondage in Crete, Greece. Mitt markers in the olive fly, Bactrocera oleae. Mol Ecol Schweiz Entomol Ges 52:343–57. Notes 2:278–80. Fletcher BS, Pappas S, Kapatos E. 1978. Changes in the ovaries of olive flies (Dacus oleae [Gmelin]) during Raspi A, Canale A, Loni A. 2005. Presence of mature Burrack HJ. 2007. The Seasonal Biology of the Olive the summer, and their relationship to temperature, hu- eggs in olive fruit fly, Bactrocera oleae (Diptera Tephri- Fruit Fly in California. Ph.D. dissertation, UC Davis. midity and fruit availability. Ecol Entomol 3:99–107. tidae), at different constant photoperiods and at two 123 p. Fritz AH, Turner FR. 2002. A light and electron micro- temperatures. Bull Insectol 58:125–9. Burrack HJ, Connell JH, Zalom FG. 2008. Comparison scopical study of the spermathecae and ventral recep- Raspi A, Iacono E, Canale A. 2002. Variable photo- of olive fruit fly (Bactrocera oleae [Rossi]) (Diptera: tacle of Anastrepha suspensa (Diptera: Tephritidae) period and presence of mature eggs in olive fruit fly, Tephritidae) captures in several commercial traps in and implications in female influence of sperm storage. Bactrocera oleae (Rossi) (Diptera Tephritidae). Redia California. Int J Pest Manag 54(3):227–34. Arth Struc Dev 30:293–313. 85:111–9. Burrack HJ, Zalom FG. 2008. Oviposition preference Kicenik Devarenne A, Vossen PM. 2007. Monitoring Rice RE, Phillips PA, Stewart-Leslie J, Sibbett GS. 2003. and larval performance of the olive fruit fly (Diptera: and organic control of olive fruit fly. In: Vossen PM Olive fruit fly populations measured in Central and Tephritidae) in several commercially important olive va- (ed.). Organic Olive Production Manual. UC ANR Pub Southern California. Cal Ag 57(4):122–7. rieties in California. J Econ Entomol 101(3):750–8. 3505. Oakland, CA. p 47–51. Tzanakakis ME. 1986. Summer diapause in the olive Collier TR, Van Steenwyk RA. 2003. Prospects for Koveos DS, Broufas GD, Kiliaraki EK, Tzanakakis fruit fly and its significance. Int Symp Fruit Flies of Eco- integrated control of olive fruit fly are promising in ME. 1997. Effect of prevention of flight on ovarian nomic Importance, Crete. p 383–6. California. Cal Ag 57:28–31. maturation and reproductive diapause in the olive Vossen PM. 2007. Olive oil: History, production and Connell JH. 2005. History and scope of the olive indus- fruit fly (Diptera: Tephritidae). Ann Entomol Soc Am characteristics of the world’s classic oils. HortScience try. In: Sibbett GS, Ferguson L (eds.). Olive Production 90:337–40. 42(5):1093–100. Manual (2nd ed.). UC ANR Pub 3353. Oakland, CA. Koveos DS, Tzanakakis ME. 1990. Effect of the pres- p 1–10. Wang X-G, Johnson MW, Daane KM, Nadel H. 2009. ence of olive fruit on ovarian maturation in the olive High summer temperatures affect the survival and Daane KM, Rice RE, Zalom FG, et al. 2005. Arthropod fruit fly, Dacus oleae, under laboratory conditions. reproduction of olive fruit fly (Diptera: Tephritidae). Env pests of olive. In: Sibbett GS, Ferguson L (eds.). Olive Entomol Exp Appl 55:161–8. Entomol 38(5):1496–504. Production Manual (2nd ed.). UC ANR Pub 3353. Oak- Koveos DS, Tzanakakis ME. 1993. Diapause aversion land, CA. p 105–14. Yokoyama VY, Miller GT, Stewart-Leslie J, et al. 2006. in the adult olive fruit fly through effects of the host Olive fruit fly (Diptera: Tephritidae) populations in Delrio G, Prota R. 1976. Osservaziono eco-etologiche fruit, bacteria and adult diet. Ann Entomol Soc Am relation to region, trap type, season and availability of sul Dacus oleae Rossi nella Sardegna nord-occidentale. 86:668–73. fruit. J Econ Entomol 99(6):2072–9. Boll Zool Agrar Bachi 2:49–118. Nardi F, Carapelli A, Dallai R, Roderick GK. 2005. Population structure and colonization history of the olive fly, Bactrocera oleae (Diptera, Tephritidae). Mol Ecol 14:2729–38.

20 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 REVIEW ARTICLE ▼

Biological controls investigated to aid management of olive fruit fl y in California

by Kent M. Daane, Marshall W. Johnson, A B C Charles H. Pickett, Karen R. Sime, Xin-Geng Wang, Hannah Nadel, John W. Andrews Jr. and Kim A. Hoelmer

The widespread and rapid establish­ ment of the olive fruit fl y in Califor­ nia required immediate changes in D E F integrated pest management (IPM) programs for olives. After fi nd­ ing that resident natural enemies did not provide adequate control, researchers began a worldwide search for parasitoids, with explora­ Parasitoids imported into California for quarantine studies include braconid parasitoids reared tion in the Republic of South Africa, from wild olive fruit fl y, (A)Psyttalia lounsburyi, (B) Bracon celer and (C) Utetes africanus, as well as braconid parasitoids reared on other fruit fl y species, including (D)Diachasmimorpha Namibia, India, China and other longicaudata, (E) D. kraussii and (F) Fopius arisanus. countries. Parasitoids were shipped to California, and most were studied which serve as reservoirs and contrib- the immature stages are protected from in quarantine to determine the best ute to the fl y’s reinvasion of treated most generalist predators. species for release. Two parasitoid orchards (Collier and Van Steenwyk Before the larva pupates, it creates species — Psyttalia lounsburyi and 2003). Classical biological control — the a thin window on the fruit surface importation of natural enemies from through which it may be exposed to Psyttalia humilis — are now be­ the pest’s home range — offers the best predators. If the fruit is still fi rm, the ing released throughout the state’s opportunity to economically suppress larva will often pupate inside. However, olive­growing regions, and research­ olive fruit fl y populations in these situ- upon fruit maturation most fl y larvae ers are studying their effectiveness. ations. We review ongoing efforts in leave the older fruit, especially in the California to (1) document the natural late summer and fall, and drop to the enemies of olive fruit fl y already pres- ground to pupate in the soil beneath ent, (2) search for and import novel the tree (Tzanakakis 2006). Orsini et al. he olive fruit fl y was fi rst found in natural enemies from other countries (2007) placed fl y puparia (which enclose TSouthern California in 1998 (Rice et and (3) determine the effectiveness the fl y pupa) on the ground in olive al. 2003). Facilitated by longevity and and limitations of these natural enemy orchards and used different barriers the adults’ ability to fl y long distances, species. To date, California scientists around each to distinguish mortality the fl y dispersed rapidly throughout the have received approval from the U.S. levels due to abiotic (e.g., climate) and state. There was little opportunity to at- Department of Agriculture’s Animal biotic (e.g., predators) factors. In an tempt a statewide eradication program, and Plant Health Inspection Service August trial, olive fruit fl y exposed to so current research efforts emphasize (USDA-APHIS) for the release of sev- predators was reduced by about 60% long-term management practices. Bio- eral parasitoid species, and permits are compared to other treatments (fi g. 1). logical control may be a part of this pro- pending for two others (see page 26). Ants (e.g., Formica species) were the gram (Daane and Johnson 2010). most abundant predators on the ground Natural enemies in California How might natural enemies con- and were observed carrying and kill- tribute to the control of olive fruit fl y Although the olive fruit fl y is native ing olive fruit fl y pupae. Predation rates (Bactrocera oleae [Rossi])? Commercial to Africa and Asia (Nardi et al. 2005), vary among orchards, depending on orchards now rely upon a broad- some North American predators and factors such as the species and densi- spectrum insecticide combined with parasitoids may attack it. Insect preda- ties of predators present and the soil a highly attractive bait (Johnson et al. tors such as lady beetles and lacewings depth at which fl y pupae are located. 2006). The effectiveness of insecticide- are found in olive orchards, but because European studies similarly indicate that based programs is, however, limited the fl y’s eggs are embedded underneath arthropods can infl ict substantial mor- by the abundance of roadside and the fruit’s epidermis and the larvae feed tality on olive fruit fl y pupae (Daane residential olive trees in California, deep inside the fruit (Tzanakakis 2006), and Johnson 2010; Tzanakakis 2006).

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 21 A California-resident parasitoid has A B C also been found attacking olive fruit fl y. The parasitoid is similar to the European Pteromalus myopitae (Graham) (Hymenoptera: Pteromalidae), hence it is currently referred to as Pteromalus species near myopitae (P. sp. nr. myopi- tae). It has been reared from olive fruit fl y collected primarily in coastal coun- ties from San Luis Obispo to San Diego, Pteromalus species near myopitae is resident to California and has been reared from olive fruit although it has also been collected in fl y collected primarily in coastal counties. The adult (A) oviposits onto second- or third-instar fl y larvae, placing an egg (B) on the outside of the larva, where the parasitoid larva (C) develops as a Alameda, Butte, Fresno, Solano and solitary, external parasitoid. Yolo counties. This parasitoid is solitary (one per fl y larva) and feeds externally search started in Africa, where olive of collections). Although P. concolor was on third-instar olive fruit fl y. An olive fruit fl y probably originated and there the only olive fruit fl y parasitoid found fruit fl y survey in San Luis Obispo is a rich diversity of fruit fl y parasi- in Morocco and the Canary Islands, County reported an average parasit- toids. Olive fruit fl y parasitoids were parasitism rates were limited to 14.6% ism level of 2.98% by P. sp. nr. myopitae reported in Africa as early as 1912 by and 2.3%, respectively. Similarly, in the (Kapaun et al. 2010). Parasitism levels the renowned Italian entomologist Republic of South Africa, P. humilis ac- varied considerably, ranging from 0% Filippo Silvestri during surveys for counted for less than 4% of parasitism. to 33% (based on collections of 100 parasitoids of Mediterranean fruit fl y However, in Namibia P. humilis was infested fruit per week) with activ- (Medfl y) Ceratitis( capitata [Wiedemann]) the dominant parasitoid and attained ity highest in August and September. (Wharton 1989). parasitism levels from 18.1% to 35.1%. Because P. sp. nr. myopitae has never Members of the USDA Agricultural In China, few olive fruit fl ies were col- been reported elsewhere, it is likely a Research Service’s European Biological lected, although one (unidentifi ed) North American parasitoid of native Control Laboratory, the California Diachasmimorpha species was obtained, fruit fl ies; it opportunistically parasit- Department of Food and Agriculture, and in India no olive fruit were found izes olive fruit fl y but has never been UC researchers and cooperators ex- on wild olive trees during the 2006 and collected on any native fruit fl y species plored the Republic of South Africa, 2007 explorations (Alan Kirk, personal despite numerous surveys. Namibia, Kenya, La Réunion (an is- communication). land east of Madagascar), the Canary Numerous fruit fl y parasitoids are Foreign exploration Islands, Morocco, Pakistan, India and known to attack other fl ies in the ge- Imported material. Resident natu- China. Collections for “specialists” (i.e., nus Bactrocera. A few of these more ral enemies do not adequately sup- natural enemies that primarily attack “generalist” parasitoids (i.e., natural press olive fruit fl y populations below one species) were made from wild olive enemies that attack numerous spe- damaging levels. For this reason, fruit (Olea europaea ssp. cuspidata) from cies) were also imported to California. California researchers began seeking south to northeast Africa, and from These were Fopius arisanus (Sonan), natural enemies abroad in 2003. The southwest Asia to central China. The Diachasmimorpha kraussii (Fullaway) parasitoids reared from olive fruit fl y and D. longicaudata (Ashmead). All included Psyttalia lounsburyi (Silvestri), were supplied by Russell Messing at a a b 100 Psyttalia concolor (Szépligeti), Psyttalia University of Hawaii, where they had humilis (Szépligeti), Psyttalia ponerophaga been reared on Medfl y. Similarly, colo- 80 (Silvestri), Utetes africanus (Silvestri) and nies of P. humilis maintained on Medfl y 60 Bracon celer Szépligeti. in Guatemala were sent to California, c The greatest yield of parasitoids (% ± SEM) 40 supplied by Pedro Rendon of the USDA came from collections made in South APHIS Plant Protection and Quarantine 20 Africa, Namibia and Kenya (table 1). program (Yokoyama et al. 2008, 2010).

Olive fruit y pupae recovered 0 The most common species were Reported efforts. A parasitoid’s Laboratory Total Predator Exposed U. africanus, P. lounsburyi and P. humilis performance in other regions provides control exclusion exclusion (table 1). The highest levels of parasitism insights for researchers when determin- Fig. 1. Mean percentage (± SEM) of olive fruit were found in Kenya collections where ing which natural enemy species should fl y pupae recovered after 4 days (August 2005) P. lounsburyi and U. africanus together be released. P. lounsburyi was identifi ed when held in laboratory control, and placed in parasitized more than 57% of collected nearly 100 years ago as an olive fruit fl y an olive orchard where treatments were “total exclusion” of all natural enemies; “predator fl ies. The next highest parasitism lev- parasitoid and is often reported as the exclusion,” preventing walking predators from els were in collections from Pakistan most effective natural enemy in wild reaching pupae; and “exposed,” allowing both (27.7% parasitism by P. ponerophaga) and olives of southern Africa (Copeland et fl ying and walking natural enemies access Republic of South Africa (27.8% to 68.0% al. 2004). P. ponerophaga has a similar to pupae. Different letters above each bar indicate signifi cant differences (Tukey’s HSD parasitism by P. humilis, P. lounsburyi, long association with olive fruit fl y test, P < 0.05) (Orsini et al. 2007). B. celer and U. africanus during 3 years and is the only olive fruit fl y specialist

22 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 known from Pakistan (Wharton 1989). was introduced to the Hawaiian Islands Johnson 2010). Diachasmimorpha kraussii However, no systematic effort has been in the 1940s and provided excellent is native to Australia, attacks a range of made to include these parasitoids in control of Oriental fruit fly Bactrocera( Bactrocera species and has been released European biological control (Wharton dorsalis [Hendel]). It now also contrib- in Hawaii to control Medfly (Bokonon- 1989), presumably because they have utes to Medfly control (Wang, Messing, Ganta et al. 2007); we have found no been difficult to import and rear. Bautista, et al. 2003). Following the reports of its use against olive fruit fly, We found no reports of concerted success in Hawaii, F. arisanus was intro- but it has been reported attacking olive efforts to import or manipulate U. af- duced widely to control these and other fruit fly in Israel (C.H. Pickett, personal ricanus for biological control, although tephritid pests in Australia, Central communication). in some South African surveys it is an America, various Pacific and Indian Quarantine nontarget studies abundant olive fruit fly parasitoid in Ocean islands, and the Mediterranean wild olives (Hancock 1989). Similarly, Basin, though not all of these introduc- Before exotic natural enemies are B. celer is often the most commonly re- tions have been as effective. The few released in California, quarantine stud- ported parasitoid attacking olive fruit attempts to establish F. arisanus on olive ies are conducted to determine whether fly in commercial and wild olives in fruit fly in Europe were unsuccessful. or not they will attack insect species South Africa (Neuenschwander 1982), One study reported that F. arisanus other than the intended target (Hoelmer where it achieved parasitism rates as failed to reproduce on olive fruit fly and Kirk 2005). There are more than high as 87%. However, small-scale at- in field cages (Neuenschwander et al. 140 tephritids in California (Foote et al. tempts to rear and/or release B. celer 1983); however, more recent laboratory 1993), including some endemic species in Europe have been unsuccessful work has confirmed that F. arisanus can and others that were brought into the (Wharton 1989). reproduce on olive fruit fly (Calvitti et state for the biological control of weeds. Instead, biological control of olive al. 2002; Sime et al. 2008). Rather than test all of these species, fruit fly has focused on members of the D. longicaudata, a native of Southeast researchers assess parasitoid responses P. concolor species complex, which in- Asia (Wharton 1989), attacks a relatively to fruit fly species found in the three cludes P. concolor from northern Africa wide range of tephritid flies, including common habitats of fruit fly larvae ­— and P. humilis from sub-Saharan Africa, Medfly, Oriental fruit fly, Caribbean fruits, flower heads and stem galls — to especially after an efficient mass- fruit fly Anastrepha( suspensa [Loew]) explore their tendency to specialize on rearing method was developed in the and Mexican fruit fly A.( ludens [Loew]) certain host habitats. Tested species are 1950s using Medfly reared on an arti- (Wang and Messing 2004). It has been selected to maximize both practicality ficial diet (Daane and Johnson 2010). used widely for biological control. One (ease of locating and/or rearing hosts) However, P. concolor has not provided attempt was made to rear and release and potential for host acceptance (re- adequate or consistent olive fruit fly it against olive fruit fly in Greece, but it semblance of infested plant structure to control in Europe and, where it has es- did not become established (Daane and olives in shape or size). Therefore, most tablished, repeated mass re- leases are required to boost TABLE 1. Fruit fly and parasitoids reared from field-collected wild olives for importation parasitism rates (Copeland into California, 2003–2007 et al. 2004). Nonetheless, we consider P. concolor and P. Species reared* humilis to be important to Diachas­ screen for use in California Insects Bactrocera Psyttalia Psyttalia Psyttalia Psyttalia Utetes Bracon mi­morpha Country Year reared spp. humilis concolor lounsburyi ponerophaga africanus celer spp. biological control. Their na- tive range spans much of n ...... % ...... northern and eastern Africa Morocco 2004 318 85.4 0.0 14.6 0.0 0.0 0.0 0.0 0.0 (Wharton and Gilstrap 1983) Canary 2004 965 97.7 0.0 2.3 0.0 0.0 0.0 0.0 0.0 and, given the diversity of Islands habitats and climates en- Pakistan 2005 636 72.3 0.0 0.0 0.0 27.7 0.0 0.0 0.0 compassed, they likely com- La Réunion 2004 700 86.0 0.0 0.0 0.0 0.0 0.0 0.0 14.0 prise several biotypes, or Namibia 2004 597 69.2 18.1 0.0 0.0 0.0 3.7 9.0 0.0 even new species or geneti- 2007 874 58.1 31.3 0.0 9.0 0.0 1.6 0.0 0.0 cally differentiated popula- 2008 3,077 50.0 35.1 0.0 11.0 0.0 3.3 0.6 0.0 tions (Rugman-Jones et al. South Africa 2003 2,218 49.5 3.2 0.0 14.9 0.0 22.8 9.6 0.0 2009), some of which may 2004 794 32.2 2.2 0.0 14.3 0.0 46.1 5.2 0.0 be better suited to control 2005 377 72.2 0.0 0.0 15.1 0.0 12.7 0.0 0.0 olive fruit fly in California Kenya 2005 3,647 42.5 0.0 0.0 35.6 0.0 21.9 0.0 0.0 (Yokoyama et al. 2010). China 2007 438 97.5 0.0 0.0 0.0 0.0 0.0 0.0 2.5 F. arisanus is well known India 2006 0 — — — — — — — — as a generalist parasitoid of 2007 0 — — — — — — — — fruit-infesting tephritids. * Percentages of adult olive fruit fly and parasitoids reared are shown; does not include gall-formers or “unknown” parasitoid species that may Native to Southeast Asia, it have been reared from galls, from other fruit fly species or as hyperparasitoids on primary parasitoids of olive fruit fly.

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 23 of the imported parasitoids were either small cages (about 12 square inches) to were limited to the weed biological- sent directly to the UC Berkeley quar- isolate female parasitoids with either control agents — C. succinea (yellow antine facility, or to the collaborating target (olive fruit fly) or nontarget hosts starthistle fly) and P. regalis (Cape ivy laboratory in France and then to the UC for 48 hours in a no-choice test. Target fly) — and no fruit-infesting fly spe- Berkeley facility. and individual nontarget species were cies were tested. In no-choice tests, P. Olive fruit fly belongs to the tephritid then placed together for a choice test ponerophaga adults probed into galls subfamily Dacinae, which is not native for the next 48 hours. The number of on Cape ivy and produced parasitoid to North America. California’s native searching events (i.e., parasitoids on offspring from this nontarget host, but and introduced fruit fly species fall the host plant) and probing events (i.e., did not probe or reproduce in yellow into two other subfamilies, Trypetinae parasitoids inserting their ovipositor to starthistle (table 2). and Tephritinae (Foote et al. 1993). For place an egg into the fruit, flower head P. concolor and P. humilis. P. concolor a nontarget, fruit-feeding Trypetinae, or gall) were recorded during discrete should be viewed as a “species com- researchers selected the native black observation periods. Afterward, the plex,” as previously mentioned. While cherry fly Rhagoletis( fausta [Osten host material was isolated and held for similar, there may be biological differ- Sacken]), which infests fruit of bitter parasitoid or fly emergence. ences that influence their affectiveness cherry. For a flower-head feeder, they in California. For example, researchers Parasitoids and olive fruit fly selected Chaetorellia succinea (Costa), an found that even P. humilis colonies from imported Tephritinae used to control P. lounsburyi. P. lounsburyi was the different locations had slightly differ- yellow starthistle (Centaurea soltitialis L.). only parasitoid tested that probed only ent levels of host specificity (table 2). For a gall-former, researchers selected into infested olives and reproduced However, P. concolor and P. humilis pop- another Tephritinae biological control solely on olive fruit fly (table 2). That ulations tested were able to reproduce agent, Parafreutreta regalis (Munro), P. lounsburyi is relatively specialized on on nontarget Cape ivy fly. In other labo- which forms stem galls in Cape ivy. The olive fruit fly is supported by the fact ratory studies, P. concolor was similarly testing of C. succinea and P. regalis ad- that it had been reared only from olive reared from numerous fruit fly species dressed the risk posed to beneficial spe- fruit fly in decades of field collections of (Wharton and Gilstrap 1983). However, cies by the candidate parasitoids. Unless African fruit flies (Copeland et al. 2004; small-cage trials are artificial, and olive stated otherwise, these three species Wharton et al. 2000). In addition, its fruit fly and Medfly are the primary were common to all UC Berkeley quar- geographic range is entirely contained hosts of P. concolor and P. humilis in their antine studies; other nontarget fruit within that of olive fruit fly. native African range (Copeland et al. flies were tested when available. P. ponerophaga. It has been sug- 2004; Wharton et al. 2000). There was some variation in the gested that P. ponerophaga specializes B. celer. B. celer also attacked materials and methods used to test on olive fruit fly because the parasitoid and reproduced on Cape ivy fly, but the different species, but procedures has only been reported from this spe- surprisingly did not reproduce on the were generally as described by Daane cies (Sime et al. 2007). Quarantine- black cherry fly, the fruit-infesting et al. (2008). Briefly, researchers used screening studies of nontarget impacts fly tested with this species (table 2). However, B. celer did probe on host ma- terials for all fruit flies presented except TABLE 2. Host-specificity trials — searching, probing and reproduction by imported parasitoids on olive fruit fly and nontarget fruit fly species currant fly. To date, B. celer has been reported only as a parasitoid of olive Yellow fruit fly and Medfly in field surveys Olive Cherry Apple Cape starthistle Currant (Wharton et al. 2000), with an addi- Parasitoids* fruit fly fly maggot ivy fly fly fly Reference tional, unconfirmed record on Ceratitis Psyttalia concolor (Italy) S/P/R† S/P S/P S/P/R S/P NI Unpublished data nigra Graham. Psyttalia humilis (Kenya) S/P/R S/P S/P S/P/R NI S Unpublished data U. africanus. One of the most com- Psyttalia humilis (Namibia) S/P/R — — S/P/R NI — Unpublished data monly recovered species in the South Psyttalia “unknown sp. A” S/P/R S/R NI S/P/R NI NI Unpublished data African collections, U. africanus was Psyttalia ponerophaga S/P/R — — S/P/R NI — Unpublished data difficult to rear in quarantine. It repro- Psyttalia lounsburyi S/P/R NI NI S NI NI Daane et al. 2008 duced on olive fruit fly, as expected, Diachasmimorpha S/P/R S/P/R S/P S/P/R NI NI Unpublished data but this parasitoid was never observed longicaudata to show any interest (by searching or Diachasmimorpha kraussii S/P/R S/P/R S S/P/R S/P/R S/P Unpublished data probing) in either the target or nontar- Bracon celer S/P/R S/P NI S/P/R S/P NI Nadel et al. 2009 get host plants during tests (table 2). Utetes africanus R NI — NI NI — Unpublished data The literature indicates that U. africanus Fopius arisanus S/P/R — — NI NI — Sime et al. 2008 has been reared from olive fruit fly, * Target host was olive fruit fly; nontarget hosts were cherry fly (Rhagoletis fausta [Osten Sacken]), apple maggot (Rhagoletis Medfly, Oriental fruit fly, coffee fruit pomonella [Walsh]), Cape ivy fly (Parafreutreta regalis [Munro]), yellow starthistle fly Chaetorellia( succinea [Costa]) and currant fly (Euphranta canadensis [Loew]). fly Trirhithrum( coffeae Bezzi) and natal † S = host plant searched by parasitoid; P = host plant probed by parasitoid; R = parasitoid successfully reproduced in host; fly Ceratitis( rosa Karsch) (Wharton and NI = parasitoid showed no interest in host plant or host during observation period; — = not tested. Gilstrap 1983).

24 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 Diachasmimorpha species. D. lon- determine the best combination of more time probing olives with larger gicaudata and D. krausii were the most species for release in California’s cli- third-instar maggots (fig. 2A), but more aggressive of the quarantine-screened matically varied olive-growing regions. offspring were produced from olives parasitoids, probing nearly all host Parasitoid host-stage preference, de- containing smaller second- and third- material presented and producing off- velopment time, adult longevity and instar maggots (fig. 2B). Many parasit- spring from nontarget, fruit-infesting fecundity (offspring per female) were oids locate hidden hosts by detecting species as well as the beneficial species determined when colony numbers substrate vibrations. For example, adult (table 2). This result was not surprising permitted these additional quarantine P. concolor are thought to respond more because in total they have been reared studies (table 3). from more than 20 fruit fly species Host-stage preference. Newly in- 8 (Wharton and Gilstrap 1983). fested olives were held for different (A) Parasitoids b F. arisanus. While F. arisanus is con- lengths of time to create fruit with 6 sidered more of a generalist, it is not various olive fruit fly host “age cat- attracted to either C. succinea eggs on egories” (i.e., different immature fly 4 ab yellow starthistle buds, or P. regalis stages). These infested olives were eggs in Cape ivy stems or the associ- placed with mated female parasitoids, 2 a a a ated galls (table 2). These results are and the amount of time the parasitoids Observed on olives consistent with studies in Hawaii that searched and probed on the different 0 show F. arisanus only attacking fruit- age categories was recorded. After the Egg–1st 1st–2nd 2nd–3rd 3rd Late 3rd feeding tephritids (Wang, Bokonon- exposure period, the olives were held Ganta, et al. 2004). The host range in F. to rear either adult parasitoids or flies. 50 arisanus is probably constrained by its These experiments established that P. (B) Adult offspring b 40 host-searching behavior: females are lounsburyi, P. ponerophaga, P. concolor, P. b generally stimulated to search for host humilis, D. longicaudata and D. kraussii 30 eggs by fruit odors; smooth, round fruit were internal parasitoids that preferred b surfaces; and oviposition punctures to oviposit into second- or third-instar 20 ab

left by flies (Wang and Messing 2003). olive fruit fly (table 3). B. celer is an Emergence (%) a Introducing F. arisanus to California external-feeding parasitoid that prefers 10 still requires evidence that native, fruit- late third-instar maggots. F. arisanus is 0 feeding Tephritidae are unlikely to be an egg-larval parasitoid that inserts its Egg–1st 1st–2nd 2nd–3rd 3rd Late 3rd attacked. Sixteen tephritid species na- eggs into olive fruit fly eggs, and the Host stage (instar) tive to California feed in fruit (Foote et parasitoid completes its life cycle in the al. 1993), but at least eight are found at larval olive fruit fly. F. arisanus females Fig. 2. Host-stage preference as mean higher elevations where F. arisanus, a may sometimes lay their eggs in first- percentage (± SEM) of (A) adult female Psyttalia lounsburyi on olives containing tropical species, is unlikely to flourish. instar olive fruit fly. hosts of a given age category during timed Host-stage preference did not always observations and (B) P. lounsburyi offspring Parasitoid biology studies correlate with reproductive success. that emerged from different host-stage categories. Different letters above each bar Researchers studied the biology This was most clearly seen in trials indicate significant differences (one-way of imported natural enemies to help with P. lounsburyi, where adults spent ANOVA, P < 0.05) (Daane et al. 2008).

TABLE 3. Key biological parameters for parasitoids of olive fruit fly studied in UC Berkeley quarantine facility

Development time Offspring per Parasitoid species tested Host-stage preference (egg to adult) Adult longevity female Reference

...... days ...... n P. lounsburyi Second to third instar 22.8 ± 0.8 (75°F) 61.8 ± 8.2 10.2 ± 2.6 Daane et al. 2008 P. ponerophaga Second to third instar 20.5 ± 1.5 (77°F) 36.2 ± 4.9 18.7 ± 2.9 Sime et al. 2007 P. concolor (Italy) Second to third instar — 68.8 ± 16.4 22.5 ± 5.1 Sime, Daane, Messing, et al. 2006 P. humilis (Kenya) Second to third instar — 77.6 ± 15.3 28.7 ± 4.1 Sime, Daane, Messing, et al. 2006 P. humilis (Namibia) Second to third instar 16.4 ± 0.6 (77°F) 36.0 ± 7.3 35.2 ± 4.1 Daane/Sime, unpublished data P. concolor (South Africa) Second to third instar 18.1 ± 0.4 (77°F) 53.2 ± 6.6 48.8 ± 8.5 Daane/Sime, unpublished data B. celer Third instar 35.5 ± 0.8 (72°F) 51.0 ± 11.7 9.7 ± 7.2 Sime, Daane, Andrews et al. 2006 U. africanus Second to third instar* 20.5 ± 1.0 (75°F) — — Daane/Sime, unpublished data D. longicaudata Second to third instar 20.8 ± 0.9 (77°F) 59.2 ± 5.0 23.6 ± 5.3 Sime, Daane, Nadel, et al. 2006 D. kraussii Second to third instar 21.6 ± 1.7 (77°F) 64.1 ± 7.8 22.7 ± 5.5 Sime, Daane, Nadel, et al. 2006 F. arisanus Egg — — 4.4 ± 0.8 Sime et al. 2008 *Few replicates were completed with U. africanus, and only 10 adults were reared from olive fruit fly during the trial.

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 25 relatively cool coastal and hot inland per female F. arisanus when reared on 80 a areas, resulting in different seasonal the Oriental fruit fl y (Ramadan et al. a D. kraussii development of the fl y (Yokoyama et al. 1992). D. longicaudata 2006). Overall patterns of adult longev- 60 Releasing natural enemies ity for all parasitoids tested showed a negative correlation with temperature, California researchers received 40 as shown for the Kenya and Italy colo- USDA-APHIS approval for the release b nies of P. humilis (fi g. 4). of P. lounsburyi and limited release of 20 Lifetime fecundity. Researchers P. humilis; approval is pending for c Mean longevity (days) c studied the parasitoids’ reproductive P. ponerophaga; and permits for the potential by providing newly emerged limited release of F. arisanus are being 0 Honey Olives/ Hosts/ Water Nothing and mated adult females with an over- prepared. To date, P. lounsburyi has been water honey honey water water abundance of infested olives every 2 released and recovered in fi eld-cage days (table 3). All species tested depos- studies, but has not yet been shown to Fig. 3. Adult female Dichasmimorpha kraussii ited most of their eggs during the fi rst overwinter. More work has been done and D. longicaudata longevity given different food provisions. Different letters above each third or half of their life span (fi g. 5). with P. humilis, which is easier to rear, bar indicate signifi cant treatment differences Surprisingly, the two specialists and levels of up to 60% parasitism have (Tukey’s HSD test, P < 0.05) (Sime, Daane, (P. lounsburyi and P. ponerophaga) had been reported from cage studies (Wang, Nadel, et al. 2006). the lowest lifetime fecundity of the Johnson, Daane, Yokoyama 2009; larval endoparasitoids, which develop Yokoyama et al. 2008, 2010). However, strongly to the third than the second in- inside the host (table 3). One hypothesis as with P. lounsburyi, there is no clear star because the larger instar produces to explain these low fecundity rates evidence to date that P. humilis can stronger or more frequent vibrations concerns the relative lengths of their while feeding (Canale and Loni 2006). ovipositors (see below). Another expla- However, the third-instar olive fruit nation concerns the chemical cues used 120 fl y maggots feed deeper in olives and to orient to and identify host larvae and Kenya, female may be beyond the reach of the short the host/plant complex. Domestic ol- 100 Kenya, male P. lounsburyi ovipositor (less than 2 ives differ chemically from wild olives. Italy, female millimeters). These differences could disrupt the 80 Italy, male Development time . The egg-to-adult parasitoid’s host-searching, host- 60 developmental rates of P. lounsburyi, identifi cation or ovipositional behav- P. ponerophaga, P. concolor, D. kraussii and iors, or impede larval development. 40 D. longicaudata were relatively similar, Quarantine studies also reported Adult longevity (days) about 22 days at constant temperatures low lifetime fecundity for B. celer, the 20 near 77°F (25°C), while B. celer required external parasitoid, and F. arisanus, the 0 nearly 40% more time (table 3). Olive egg-larval parasitoid (table 3), although 50 59 68 77 86 95 fruit fl y requires about 23 days at 77°F in each case researchers suggest that Temperature (°F) (25°C), suggesting that (except for B. experimental conditions may have Fig. 4. Adult P. humilis longevity declined with celer) these parasitoids could have gen- negatively infl uenced natural egg de- increasing constant temperature for each eration times similar to olive fruit fl y. position. In the UC Berkeley quarantine gender and culture. Within each culture, no Adult longevity. When provisioned studies, researchers found up to 80% signifi cant differences were found between with water and honey, examined adult mortality of olive fruit fl y eggs exposed female and male longevity at any temperature tested (Sime, Daane, Messing, et al. 2006). parasitoid species lived 36 to 78 days at to F. arisanus (Sime et al. 2008). Similar temperatures around 77°F (25°C) (table fi ndings have previously been reported 3). For all tested species, adults lived on olive fruit fl y (Calvitti et al. 2002) 10 for less than 5 days without food, as and other hosts (Moretti and Calvitti 8 shown for D. longicaudata and D. kraussii 2003). Most likely this direct mortality

(fi g. 3). For most species studied, there results from the egg being repeatedly 6 was also a reduction in longevity when probed (i.e., stabbed) by the F. arisanus adults were provided hosts in infested ovipositor. Olive fruit fl y lays a single 4 olives, suggesting that the parasitoids egg per fruit puncture, whereas the expended energy while handling hosts typical host of F. arisanus, the Oriental 2 Offspring per female Offspring and that the parasitoids were able to fruit fl y, deposits up to 100 eggs per distinguish host-infested olives from puncture (Ramadan et al. 1992). The 0 those lacking hosts. tendency of F. arisanus to probe repeat- 0 10 20 30 40 50 Time (days) Tolerances for high and low tempera- edly within an oviposition puncture tures may be critical for parasitoid es- may be an evolutionary consequence Fig. 5. Mean lifetime production of offspring tablishment in California because olive of its use of this host. By comparison, (± SEM) produced by P. humilis from a Kenyan fruit fl y infestations are found in both more than 100 progeny can be obtained culture (Sime, Daane, Messing, et al. 2006).

26 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 establish and thrive without repeated augmentation. There is a risk with the release of each natural enemy species that some nontarget species will be attacked, but the benefits often outweigh the risks (Hoddle 2004). Also, not all pest species are prime targets for classical biological control — there are potential problems with olive fruit fly and natural enemy biology that may limit the levels of con- trol achieved. Seasonal host availability. The olive Ripe wild olives, left, collected in Africa, where olive fruit fly is considered to be native, are much fruit fly’s survival is limited in regions smaller than the cultivated European varieties used throughout the world. Right, springbok and kudu graze among wild olive trees on a South Africa hillside. The African parasitoids that with high or low temperature extremes specialize on olive fruit fly found in small wild olives tend to have relatively short ovipositors (Wang, Johnson, Daane, Opp 2009). The that may not reach fly maggots deeper in the pulp of cultivated olives. fruit also may not be developed enough for olive fruit fly to survive early in in cultivated olives, B. celer. with its Repeated sprays of GF-120 Naturalyte the summer; young, hard fruit are not much longer ovipositor, predominates, NF Fruit Fly Bait (Dow AgroSciences, preferred for oviposition (Burrack and and the other species tend to be rare Indianapolis, Ind.) are used to control Zalom 2008). Moreover, olive fruit fly (Neuenschwander 1982). In the UC olive fruit fly. Although this spinosad populations are scarce in some inte- Berkeley quarantine studies, both D. bait is classified as a reduced-risk ma- rior valley regions with high summer longicaudata and D. kraussii reproduced terial, its frequent use may disrupt temperatures (Wang, Johnson, Daane, well on cultivated olives, and these biological control. Nadel et al. (2007) Nadel 2009) (see page 29). These facts more generalist parasitoids have very investigated the impact of GF-120 on suggest that parasitoid survival might long ovipositors (Sime, Daane, Messing, a green lacewing (Chrysoperla carnea also be difficult in some regions where et al. 2006). Among the favorable char- [Stephens]), and showed that ingestion their host, the olive fruit fly larvae, is acteristics of F. arisanus as a parasitoid clearly poses some risk to lacewing scarce during some seasonal periods. of B. oleae are its relatively long oviposi- populations due to adult mortality and Wild versus domestic olives. The tor and the fact that it usually oviposits reduced fecundity. Laboratory studies domestic olive is a distinct subspecies into eggs. Both features may help it cir- indicated that several important braco- of wild olive, which has smaller fruit cumvent the difficulties encountered by nid parasitoids of fruit flies — F. arisa- than most cultivated olives. As a result, some larval parasitoids attacking nus, Diachasmimorpha tryoni (Cameron) fly maggots tunnel deeper inside the B. oleae in larger olive cultivars. and Psyttalia fletcheri (Silvestri) — would larger domestic olive. The ovipositors Natural enemy interactions. For best not feed on fresh GF-120 residues, but of specialized parasitoids (P. lounsburyi results natural enemies should coexist, when the insecticide was directly ap- and P. ponerophaga) are too short to but sometimes they interfere with each plied there were high mortality rates reach fly maggots feeding deep within other. For example, the unexpected (Wang et al. 2005). the larger olives (Sime et al. 2007; Wang, appearance of P. sp. nr. myopitae could Expectations in California Johnson, Daane, Yokoyama 2009; Wang, potentially create a conflict with classi- Nadel, Johnson, et al. 2009). The length cal biological control efforts. Parasitoids Biological control can be a practical, of the ovipositor relative to the depth of that immobilize the host, including P. safe and economically effective means the maggot within the fruit apparently sp. nr. myopitae and B. celer, may have a of fruit fly control, and its importance limits the biocontrol agent’s ability to competitive advantage over larval para- continues to grow in regions where pes- successfully parasitize certain hosts, a sitoids that allow the host to continue ticide use is less desirable (e.g., sustain- problem that has been well documented to develop and grow after parasitoid able agriculture) or more restricted (e.g., for other fruit fly parasitoids (Sivinski et oviposition, such as Psyttalia species. urban trees). The research programs al. 2001). Therefore, African parasitoids In quarantine experiments, research- that we describe provide background of olive fruit fly may fail to success- ers found that the egg-larval parasitoid information on natural enemy biology, fully establish on fruit flies in fleshier F. arisanus prevailed in competition and identify specific natural enemies European cultivars, because their short against two species of larval-pupal par- for importation and evaluation, and for ovipositors are adapted for foraging in asitoids, D. kraussii and P. concolor (Sime possible release into California. Over small, wild, African olives. et al. 2008). The intrinsic competitive su- the coming years, researchers will bet- Surveys in wild and cultivated periority of F. arisanus over larval-pupal ter understand the level of controls African olives provide support for parasitoids must be taken into consider- expected from imported natural en- this hypothesis. P. lounsburyi, U. afri- ation for its use in California. emies, and will improve IPM programs canus and B. celer are most commonly Insecticides and biological control. to integrate biological controls with reared from wild olives (Copeland et al. Insecticide use affects biological con- the insecticides currently used in olive 2004; Neuenschwander 1982), whereas trol programs (Mills and Daane 2005). management.

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 27 X.-G. Wang is Associate Specialist, Department of Director, USDA Agricultural Research Service, Eu- K.M. Daane is Cooperative Extension Specialist, Environmental Science, Policy and Management, ropean Biological Control Laboratory, Montpellier, Department of Environmental Science, Policy UC Berkeley; H. Nadel is Supervisory Entomolo- France. and Management, UC Berkeley; M.W. Johnson is gist, U.S. Department of Agriculture (USDA), We thank CDFA for funding this review; and Cooperative Extension Specialist and Entomolo- Animal and Plant Health Inspection Service, Plant the California Olive Committee, CDFA Biological gist, UC Riverside; C.H. Pickett is Research Ento- Protection and Quarantine program, Buzzards Control Program (in collaboration with USDA) and mologist, Biological Control Program, California Bay, MA; J.W. Andrews Jr. was Quarantine Man- USDA Cooperative State Research, Education, and Department of Food and Agriculture (CDFA); K.R. ager, College of Natural Resources, UC Berkeley; Extension Service’s Pest Management Alternatives Sime is Assistant Professor, SUNY Oswego, N.Y.; and K.A. Hoelmer is Research Entomologist and Program for funding olive fruit fly research.

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Comparison of two laboratory cultures of Psyttalia tephritids in Kenyan coffee: A predominantly koinobi- Johnson MW, Zalom FG, Van Steenwyk R, et al. 2006. concolor (Hymenoptera: Braconidae), as a parasitoid of ont assemblage. Bull Entomol Res 90:517–26. Olive fruit fly management guidelines for 2006. UC the olive fruit fly. Biol Control 39:248–55. Yokoyama VY, Cáceres CE, Kuenen LPS, et al. 2010. Plant Prot Quart 16(3):1–7. Sime KR, Daane KM, Nadel H, et al. 2006. Diachasmi- Field performance and fitness of an olive fruit fly Kapaun T, Nadel H, Headrick D, Vredevoe L. 2010. morpha longicaudata and D. kraussii (Hymenoptera: parasitoid, Psyttalia humilis (Hymenoptera: Braconi- Biology and parasitism rates of Pteromalus nr. myopi- Braconidae), potential parasitoids of the olive fruit fly. dae), mass reared on irradiated Medfly. Biol Control tae (Hymenoptera: Pteromalidae), a newly discovered Biocontrol Sci Technol 16:169–79. 54:90–9. parasitoid of olive fruit fly Bactrocera oleae. 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28 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 REVIEW ARTICLE ▼

High temperature affects olive fruit fl y populations in California’s Central Valley

by Marshall W. Johnson, Xin-Geng Wang, Hannah Nadel, Susan B. Opp, Kris Lynn- Patterson, Judy Stewart-Leslie and Kent M. Daane Marshall W. Johnson W. Marshall

Olive fruit fl y commonly infests olives in California’s Central Valley. Field studies indicate that trap counts for olive fruit fl y adults in pesticide­free sites decrease in mid­ and late sum­ mer and then rebound from Septem­ ber to November. Part of this decline is associated with heat stress that the fl ies experience in mid­July and Au­ gust. Studies have shown that adult fl ies will die within a few days if they cannot access adequate amounts of water and carbohydrates. Flight An adult female olive fruit fl y deposits an egg into olive fruit. ability is dramatically reduced when resources are unavailable. Olive fruit by pruning infested trees to facilitate McPhail traps (Johnson et al. 2006). fl y adults may use black scale hon­ greater air movement in the summer, The numbers of adults captured in the which results in signifi cant desiccation Central Valley decline during the eydew as a carbohydrate source to of fi rst-instar crawlers (Daane and Cal- hottest periods of July and August and help them survive hot periods. Heat tagirone 1989). increase in September as temperatures also affects the fl y’s reproduction and However, the establishment of ol- decrease (Rice et al. 2003; Yokoyama immature stages within olive fruit. ive fruit fl y Bactrocera( oleae [Rossi]) et al. 2006) (fi g. 1). For most insect spe- (Diptera: Tephritidae) forced many cies, a decline in trap counts suggests a Geographic information system (GIS) growers onto a weekly treatment re- reduction in adult densities in an area. maps may be useful for predicting gime that runs from mid-June through This is not initially the case with olive the risk of olive fruit fl y infestation. harvest (September to December), fruit fl y, whose behavior changes as using the spinosad product GF-120 daily temperatures rise. NF Naturalyte Fruit Fly Bait (Dow Avidov (1954) reported that below he discovery in 1998 and subsequent AgroSciences) (Johnson et al. 2006). This 62°F the adults are inactive. As tem- Tspread of the olive fruit fl y through- management proto- out the major olive-producing areas of col enables growers California dramatically affected the to deliver fruit with As temperatures surpass 84°F, adult fl ies become pest management activities practiced by near-zero infestation increasingly agitated and egg laying is halted, growers. Prior to its introduction, the levels to the table olive major arthropod pests targeted for con- processors. Olives des- and above 95°F they are motionless. trol in California olives were olive scale tined for oil pressing (Parlatoria oleae Colvée) (Hempitera: Di- may have signifi cant aspididae) and black scale (Saissetia oleae levels of infestation without an appre- peratures increase above the threshold [Olivier]) (Hempitera: Coccidae) (Daane ciable decline in quality, as long as the temperature, adult activity increases. et al. 2005). Olive scale is well managed time between harvest and pressing is Normal activity, fl ight and egg lay- with biological control due to the intro- minimal (Pereira et al. 2004; Torres-Villa ing occur between 73°F and 84°F. As duction and establishment of the para- et al. 2003). temperatures surpass 84°F, adult fl ies sitoids Aphytis paramaculicornis DeBach become increasingly agitated and egg Adult behavior and survival and Rosen, and Coccophagoides utilis laying is halted, and above 95°F they Doutt (Daane et al. 2005). Black scale is Olive fruit fl y adults may be moni- are motionless. Laboratory observa- mainly controlled in the Central Valley tored with fl at-panel sticky traps or tions (M.W. Johnson, unpublished) also

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 29 suggest that adults seek and remain One might assume that acquisition groups of tested flies flew significantly near moisture sources as temperatures of adequate amounts of food and water shorter distances (≥ 42%) than the con- approach and surpass 95°F. would be easy for olive fruit fly adults, trol (F6,252 = 62.7, P < 0.01). Additionally, Reduced adult fly activity can result which are strong flyers. Using a custom- individual flies that were denied food in lower trap counts in the field while designed flight mill, Wang et al. (2009b) and water from the time that they maximum daily temperatures remain reported that adults of both sexes held emerged as adults and were held at around 95°F to 99°F and the flies have for 7 days at 75°F (constant temperature) either 65°F at night and 95°F, or 100°F, access to adequate water and carbo- and provided with ample food (honey during the day for 1 to 2 days, flew sig- hydrate sources (Wang et al. 2009a). and hydrolyzed yeast) and water, were nificantly shorter distances (≥ 92%) than However, as the frequency at which able to fly uninterrupted for an average the flies provided no food and water for daily maximum temperatures equal or of 2,164.8 ± 228.8 yards during a mean 24 hours after having access to food and surpass 100°F increases, greater num- period of 1.54 ± 0.16 hours (fig. 3). water for 7 days (fig. 3). bers of adults will die due to heat stress, Nonetheless, heat stress and lack of In a worst-case scenario, an adult especially when they cannot access water and food can affect flight ability. fly that emerges in mid-August in the adequate quantities of water and food Olive fruit fly adults that were subject Central Valley may commonly experi- (Wang et al. 2009a, b) (fig. 2). Although to the same conditions as described ence maximum daily temperatures over adult females may ingest liquid from for 7 days and then to water only or no 100°F for 3 consecutive days (Lynn- punctures they make in olive fruit, this food and water in diurnal temperature Patterson 2006). Without food or water secretion does not provide the needed regimes (65°F at night; 95°F or 100°F immediately available, an adult will carbohydrates to help them survive during the day) for 24 hours before the only be able to fly an average of 16.4 heat-induced stress (Johnson and Nadel, flight test did not perform as well as ± 4.4 yards to locate these resources unpublished data). the control group (fig. 3). All stressed in a dry and unexplored landscape.

5 (A) 75°F, food and water a Sites 2,500 (B) 95°F, water, 24 hours Treated (C) 100°F, water, 24 hours 4 Untreated (D) 95°F, no resources, 24 hours (E) 100°F, no resources, 24 hours (F) 95°F, no resources 3 2,000 (G) 100°F, no resources

b 2 b 1,500

Mean total ies/trap/week 1

0 10 17 24 1 8 15 22 29 5 13 20 27 4 11 18 25 1 8 15 22 29 6 13 20 27 3 10 17 24 31 7 14 Mean distance (yards) 1,000 April May June July Aug Sept Oct Nov bc

c Fig. 1. Average olive fruit fly populations at nine untreated sites (e.g., urban, landscape and 500 abandoned commercial plantings) and five treated (with GF-120) commercial sites in Fresno and Tulare counties during the 2003 growing season (Johnson, Nadel and Stewart-Leslie, unpublished data). d d

Fig. 2. Mortality of 0 90 Treatment olive fruit fly adults c c subjected to 1 to 3 95°F, water 80 Fig. 3. Mean distances flown by olive fruit fly days exposure to 100°F, water adults exposed to various temperatures and 95°F and 100°F, in the 70 95°F, no resources resources. Flies (A-E) were preconditioned for absence of food and 100°F, no resources b 60 7 days at 75°F with ample food and water with and without b b prior to treatment. Treatments were: (A) access to water (Wang c 50 no treatment (control); (B) preconditioned et al. 2009b). Different at 95°F, then 24 hours of water only; (C) letters above columns 40 preconditioned at 100°F, then 24 hours of representing the same 30 water only; (D) preconditioned at 95°F, then 24

temperature/resource Adult mortality (%) hours with no resources; (E) preconditioned at treatment indicate 20 b a 100°F, then 24 hours with no resources; (F) no significant differences a preconditioning, held from 1 to 2 days at 95°F (P < 0.05; Tukey’s 10 a a with no resources; and (G) no preconditioning, HSD test) within the a held from 1 to 2 days at 100°F with no exposure duration. 0 1 2 3 resources (Wang et al. 2009b). Different letters Days of exposure above columns indicate significant differences (P < 0.05; Tukey’s HSD test).

30 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 A B

(W) (W) (H) (H)

Experimental setup shows (A) the typical distribution of fi ve olive fruit fl y adults (circled) within an observation chamber, with cotton wicks and water (W) and honey (H) at a cool temperature (80°F) and 20% relative humidity, and (B) the congregation of olive fruit fl y adults (circled) around a water wick (W) when the temperature is hot (99.5°F) and 37% relative humidity.

2,000 A B a 95°F, water 1,500 a 100°F, water 95°F, no resources 100°F, no resources 1,200 ab 900 b a b 600 a ab b b 300 ab b C

0 Mean distance
own uninterrupted (yards) 1 2 3 Days of exposure

Fig. 4. Mean distances fl own by olive fruit fl y adults subjected to 1 to 3 days exposure to D 95°F and 100°F, in the absence of food and with and without access to water (Wang et al. 2009b). Different letters above columns representing the same temperature/resource treatment indicate signifi cant differences P( < 0.05; Tukey’s HSD test) within the exposure duration.

Such a fl y would have an 84% chance of dying in the fi rst 24 hours, and of Fly fl ight is measured using (A) a custom-designed fl ight mill setup with computer; (B) an those that did survive only about 25% individual fl ight mill unit; (C) a beam that rotates during insect fl ight; and (D) a tethered fl y would be able to fl y (Wang et al. 2009b). fastened to a rotating beam. Additionally, when olive fruit fl y adults were held at 65°F at night and 95°F or commonly in late July and early August 2009a). Eggs are deposited just beneath 100°F during the day over a 3-day pe- in California (Burrack and Zalom 2008; the fruit epidermis and may be exposed riod with either water alone or no food Wang et al. 2009a). During periods of to high temperatures, depending on or water, those fl ies that survived one high maximum daily temperatures (3 where an individual fruit is located on day could fl y signifi cantly farther than consecutive days at 100°F or above in the tree (Wang et al. 2009a). those that survived 3 days (F2,407 = 18.7, July and August) (Lynn-Patterson 2006), Laboratory studies showed that adult P < 0.01) (fi g. 4). mated adult females may lay their eggs females held under different diurnal in developing olives prior to morning temperature regimes (65°F at night and Egg and larval survival temperatures reaching 95°F. No eggs are 75°F, 95°F or 100°F during the day) laid Reproductive dormancy in olive deposited during the night, even when similar numbers of eggs when the tem- fruit fl y subsides as greater numbers of temperatures are cool enough for nor- perature was 65°F and the experimental mature fruit appear within the orchard, mal activity (Avidov 1954; Wang et al. chamber was illuminated (F2,55 = 0.2,

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 31 P = 0.852). However, under illumination in the same locality in mid- and late examination of temperature trends in and higher temperatures, females laid summer 2007 and 2008 showed that less olive-producing areas in the Central significantly fewer eggs at 95°F (about than 2% of offspring from eggs laid in Valley over 10 years (1992–2001) re- four per female) than at 75°F (about 12 olives completed development to the vealed that it was quite common for per female) (F1,38 = 8.4, P = 0.006), and adult stage (Wang et al. 2009a). temperatures to be greater than 100°F no eggs were laid at 100°F (Wang et al. for 3 consecutive days during mid-July Scale honeydew and heat stress 2009a). and August (fig. 6) (Lynn-Patterson Even after eggs are deposited within This information suggests that it 2006). On the California coast, these olive fruit, they are still susceptible is difficult for olive fruit fly adults to trends were rarely observed. Over to the high temperatures common in survive the high summer temperatures this time period, temperatures greater Central Valley orchards. Eggs within in the Central Valley. Water may com- than 100°F for 3 consecutive days were fruit held at 65°F (night) and 75°F (day) monly be found within or near most more common in the southern (San developed into first-instar larvae after orchards from a variety of sources, such Joaquin Valley) than the northern 6 days (Wang et al. 2009a). In contrast, as morning dew, creeks, ponds, irriga- (Sacramento Valley) Central Valley (see eggs within fruit subjected to 65°F tion water (ditches and canals), sprin- http://arcims.gis.uckac.edu/CIMIS). By (night) and 95°F (day) had a 49% mor- klers, drip tape and fan jets. However, September, most of the Central Valley tality rate, and of the first-instar larvae fly adults also need carbohydrates to rarely had 3 consecutive days greater that did develop, none became second survive heat stress. Honeydew (fresh than 100°F (fig. 6).; in 2003, olive fruit fly instars. When subjected to 65°F (night) or dry) produced by black scale is a surpassed one adult per trap per week and 100°F (day), no eggs hatched after common carbohydrate source in olive at the end of August and continued to 10 days exposure and all died. The over- orchards. Our laboratory tests have increase into November (fig. 1). all finding was that egg (F3,57 = 2472, P shown that fly adults provided with Growers and consultants may wish < 0.001) and first-instar (F3,57 = 2472, P < honey and water, or black scale honey- to use these maps to determine if they 0.001) mortality increased as exposure dew and water, survive temperatures of can temporarily halt insecticide treat- time increased (Wang et al. 2009a). 65°F (night) and 97.5°F (day) with mini- ments for olive fruit fly adults during Later field studies showed that maxi- mal mortality compared to adults only July and August. However, there are mum daily temperatures in olive trees provided honey alone, honeydew alone, many factors other than temperature in the Central Valley (Parlier) varied or no food and water over 5 days (F4, 36 that influence whether olive fruit fly depending on whether measurements = 189.9, P < 0.0001) (fig. 5) (M.W. Johnson will be a problem in a particular olive were taken within the canopy interior and H. Nadel, unpublished data). orchard. Olive fruit fly adults with ac- or the east or west perimeter. Mean The carbohydrate source alone did cess to adequate sources of water and temperatures recorded on the west not reduce the impact of heat on sur- carbohydrates can survive heat stress side of the tree canopy in August 2007 vival. Flies that had food resources in large numbers and will be able to fly were 108°F (and over 104°F for 26 days) (honeydew or pure honey) but no water long distances (more than 1,000 yards) compared to 101°F (and over 104°F for suffered mortality similar to those flies even when stressed. Growers who con- 13 days) on the east side, and 96°F (and without food or water. There was a sider halting their control programs, never over 104°F) within the canopy significant interaction between carbo- especially in the San Joaquin Valley, interior (F2,90 = 52.7, P < 0.001). All of hydrate source and days of exposure should take under consideration the ir- these temperatures are high enough to (F20, 180 = 33.3, P < 0.0001). These results rigation schedules and infestation levels impose some level of mortality on olive are similar to what we have observed in of black scale and other insects that fruit fly eggs and larvae. Field studies our laboratory and field studies on olive might produce honeydew within their fruit fly when 50% honey water was own and neighboring orchards. Also used as a carbohydrate source. These important is the proximity of irrigation findings are significant because they canals, creeks, ponds and rivers, as well 100 suggest that olive fruit fly adults could as abandoned orchards or untreated use black scale honeydew to help them olives trees used for landscaping, which 80 Honeydew only Honeydew and water survive periods of high temperature in can serve as an infestation source of 60 Honey only the Central Valley. The management olive fruit fly. Morning dew in the or- Honey and water No food of black scale populations via cultural chard may provide a moisture source 40 controls such as the pruning of interior for flies, and weedy undergrowth in the canopies may also contribute to the orchard or neighboring crops can afford 20 management of olive fruit fly adults. some relief from the heat. Olive fruit
y survival (%) Perhaps the most useful informa- 0 Temperature maps and fly activity 1 2 3 4 5 tion that one can obtain from the GIS Days of exposure Geographic information systems maps is knowing when temperatures (GIS) enable the examination of temper- historically have dropped to low levels Fig. 5. Survival of olive fruit fly adults when ature trends over specific areas based held at 65°F (night) and 97.5°F (day) with that would be conducive to olive fruit access to various combinations of water, honey on defined criteria, such as temperature fly activity and survival in a particular and black scale honeydew, or no food or water. levels for specific time intervals. The area. As temperatures decline at the end

32 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 July 15 Aug. 15 Sept. 15 Occurrences 0 1–2 3–5 6–8 9–10

Fig. 6. Mean temperature patterns in California over 10 years (1992–2001), showing number of years (occurrences) with maximum temperatures greater than or equal to 100°F for 3 consecutive days ending on July 15, Aug. 15 and Sept. 15 (Lynn-Patterson 2006). of August, olive fruit are increasing in be helpful. Given that olive fruit fl y size and maturing (Martin and Sibbett adults need carbohydrate sources to 2005). Olive fruit fl y adults prefer to lay survive heat stress, it may be best to M.W. Johnson is Cooperative Extension Specialist their eggs in the largest olives avail- continue treating with GF-120 in July and Entomologist, Department of Entomology, able (Neuenschwander et al. 1985). As and August. The adults are attracted UC Riverside; X.-G. Wang is Associate Specialist, fl ies return to normal activity in late to the sweet fruit fl y bait in the GF-120. Department of Environmental Science, Policy and summer, the olives remaining on the If stressed fl ies seek a carbohydrate Management, UC Berkeley; H. Nadel is Supervi- sory Entomologist, U.S. Department of Agricul- trees are at greater risk of infestation source in summer, it may be assumed ture Animal and Plant Health Inspection Service, than at anytime during the summer, that they would then seek out available Plant Protection and Quarantine program, Buz- and protecting the fruit then is of prime bait residues in GF-120. If this is true, zards Bay, MA; S.B. Opp is Associate Vice Presi- consideration. the GF-120 may be having a greater dent, Academic Programs and Graduate Studies, impact than realized. This needs to be California State University, East Bay; K. Lynn- Future directions determined. Also of importance is the Patterson is GIS Academic Coordinator, UC Kear- Research on the ecology and man- impact of summer heat either directly ney Agricultural Center, Parlier; J. Stewart-Leslie is Manager, Consolidated Central Valley Table Grape agement of olive fruit fl y is continuing. or indirectly on parasitoid natural ene- Pest and Disease Control District, Exeter, CA; and A better understanding of the abili- mies that are now being released as part K.M. Daane is Cooperative Extension Specialist, ties of olive fruit fl y adults to disperse of a classical biological control program Department of Environmental Science, Policy and among orchards in the summer would for olive fruit fl y control (see page 21). Management, UC Berkeley.

References Lynn-Patterson K. 2006. Interactive climate maps for Torres-Villa LM, Rodriguez-Molina MC, Martinez JA. olive fl y management decisions. http://arcims.gis. 2003. Olive fruit fl y damage and olive storage effects Avidov Z. 1954. Further investigations on the ecology uckac.edu/CIMIS. on paste microfl ora and virgin olive oil acidity. Grasas of the olive fl y (Dacus oleae, Gmel.) in Israel. Ktavim Aceites 54:285–94. 4:39–50. Martin GC, Sibbett GS. 2005. Botany of the olive. In: Sibbett GS, Ferguson L. Olive Production Manual (2nd Wang X-G, Johnson MW, Daane KM, Nadel H. 2009a. Burrack HJ, Zalom FG. 2008. Olive fruit fl y, Bactrocera ed.). UC ANR Pub 3353. p 15–7. High summer temperatures affect the survival and oleae (Gmel.), ovipositional preference and larval Neuenschwander P, Michelakis S, Holloway P, Berch- reproduction of olive fruit fl y (Diptera: Tephritidae). Env performance in several commercially important olive Entomol 38:1496–504. varieties in California. J Econ Entomol 101:750–8. told W. 1985. Factors affecting the susceptibility of fruits of different olive varieties to attack by Dacus Wang X-G, Johnson MW, Daane KM, Opp S. 2009b. Daane KM, Caltagirone LE. 1989. Biological control of oleae (Gmel.) (Dipt., Tephritidae). J Appl Entomol Combined effects of heat stress and food supply on black scale in olives. Cal Ag 43(1):9–11. 100:174–88. fl ight performance of olive fruit fl y (Diptera: Tephriti- Daane KM, Rice RE, Zalom FG, et al. 2005. Arthropod Pereira JA, Alves MR, Casal S, Oliveira MBPP. 2004. Ef- dae). Ann Entomol Soc Am 102:727–34. pests of olive. In: Sibbett GS, Ferguson L. Olive Produc- fect of olive fruit fl y infestation on the quality of olive Yokoyama VY, Rendon P, Sivinski J. 2006. Psyttalia cf. tion Manual (2nd ed.). UC ANR Pub 3353. p 105–14. oil from cultivars Cobrancosa, Madural and Verdeal concolor (Hymenoptera: Braconidae) for biological Johnson MW, Zalom FG, Van Steenwyk R, et al. 2006. Transmontana. Ital J Food Sci 16:355–65. control of olive fruit fl y (Diptera: Tephritidae) in Califor- Olive fruit fl y management guidelines for 2006. UC Rice R, Phillips P, Stewart-Leslie J, Sibbett S. 2003. nia. Env Entomol 37:764–73. Plant Protect Quart 16:1–7. Olive fruit fl y populations measured in Central and Southern California. Cal Ag 57(4):122–7.

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 33 RESEARCH ARTICLE ▼

Mediterranean clonal selections evaluated for modern hedgerow olive oil production in Spain

by Joan Tous, Agusti Romero, Juan Francisco Hermoso and Antonia Ninot Paul M. Vossen M. Paul Traditional olive oil production is limited by its high cost, mainly due to labor expenses for harvesting and pruning. A new olive planting system based on hedgerows and harvesting machines could decrease production costs while maintaining high quality. To improve the effi ciency of the continuous­straddle mechanical harvesters, vigor must be managed to limit tree size. However, few cultivars are adapted to this system. Selections from three cultivars are typically used in these super­high­ density orchards. We fi eld­tested Olive trees have been cultivated for centuries in Mediterranean climates, including California’s Central Valley (shown). New super-high-density hedgerow systems allow for mechanical ‘Arbequina i­18’, ‘Arbosana i­43’ harvesting, greatly reducing labor costs. and ‘Koroneiki i­38’ in an irrigated, other countries. Clonal selections of varieties — ‘Arbequina’ and ‘Arbosana’ super­high­density planting system local varieties were planted in new olive from Catalonia and ‘Koroneiki’ from in Catalonia (northeast Spain). orchards with tree densities ranging Crete (Greece) — to identify those with We present a review of 6 years of from 600 to 1,000 trees per acre (1,500 to outstanding characteristics such as 2,500 per hectare) to test the suitability compact growth habits, low-medium horticultural data and summarize of the plants to mechanization and the vigor, early maturity and excellent oil sensory characteristics and other production of high-quality, extra-virgin quality (Tous et al. 2003). Agronomical properties of the resulting olive oils. olive oil. Traditional olive orchards have evaluations in Spain and other coun- 80 to 200 trees per acre (200 to 500 per tries have shown that these IRTA clones hectare). are precocious (bearing their fi rst crop he olive tree, olive fruit and olive Just a few olive varieties have at an earlier age than standard culti- Toil have been at the core of Mediter- been compared for their adaptabil- vars), achieve higher yields earlier after ranean agriculture and trade since early ity to high-density plantings and planting and produce extra-virgin oil of cultivation times, providing sustenance continuous mechanical harvest. Our excellent quality. to various cultures and civilizations program at the Institut de Recerca i California olive orchards of the Mediterranean Basin. Over the Tecnologia Agroalimentaria (IRTA) last few decades, olive (Olea europaea) screened three old Mediterranean olive Olives were introduced in California cultivation has undergone important by the Catalan Franciscan fathers, who technological changes, which have planted olive trees in gardens adjacent involved a reduction in the number of to their missions. Their olives and Editor’s note: More than 12,000 acres olive oil varieties used, and an increase oil were appreciated not only as food of olives have been planted in Cali- in the density of new plantations that is but also as an element in liturgical fornia using the super-high-density linked to improvements in harvesting celebrations. system. Research in California is in- machinery and irrigation systems. Today, the predominant table olive conclusive about the long-term viabil- In the early 1990s, a new design industry in California is supported by ity of super-high-density olive culture and management strategy for olive classic cultivars introduced for their under California growing conditions; orchards, the super-high-density hedge- suitability to traditional and inten- further fi eld studies based in the state row system, appeared in Catalonia sive table olive orchard systems (Tous can address these questions. (northeast Spain). Later it was intro- and Ferguson 1997; Vossen 2007). In duced into other Spanish regions and California, the industry generally plants

34 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 fi ve cultivars (Mission, Manzanillo, TABLE 1. Horticultural characteristics of three olive tree clones tested in a super-high-density Sevillano, Ascolano and Barouni) to planting system in Catalonia, Spain produce black-ripe olives (Connell 2005). ‘Mission’ trees were likely intro- Characteristics Arbequina i-18 Arbosana i-43 Koroneiki i-38 duced to California during Franciscan Vigor Low Very low Medium times, via Mexico in 1769 (Sutter 2005). Olive planting for oil production, Growth habit Semi-erect Open Open by contrast, has grown from negligible Canopy density Compact Compact Compact acreage in 1996 to approximately 16,000 Precocity of bearing Early Early Early acres (6,400 hectares) by 2008. Most of Productivity Very high and regular Very high and regular High this acreage, 12,000 acres (4,800 hect- Fructifi cation In clusters In clusters In clusters ares), is planted in super-high-density Harvest season Early, midseason* Late† Midseason orchards with 560 to 870 trees per acre * Maturation occurs in Catalonia from about mid-November to mid-December. (1,400 to 2,175 per hectare) (UC Davis † Matures about 3 weeks later than ‘Arbequina’. Olive Center 2009). Most high-density California olive remarkable quality such as California, hectares]) from traditional orchards plantings are three releases of IRTA’s Chile and Australia. located in the PDOs (protected designa- clonal plant material from the Mas de We describe the performance and tions of origin) of Les Garrigues and Bover research station in Catalonia, limitations of these olive oil clones in Siurana in northeast Spain. ‘Arbosana Spain, the initial selections from their comparative fi eld trials performed in i-43’ was selected in 1987 from sur- olive improvement program started in an irrigated, super-high-density sys- veys of the ‘Arbosana’ cultivar in the the mid-1980s. The IRTA clonal varieties tem in Catalonia, which supports their Alt Penedès region in Catalonia. The currently available are ‘Arbequina i-18’, adoption in modern orchards. We also clone ‘Koroneiki i-38’ was selected in ‘Arbosana i-43’ and ‘Koroneiki i-38’, contribute additional information to 1990 from trees of this Greek variety propagated in California by a few au- help defi ne the suitable orchard design at the Mas de Bover research station. thorized nurseries. The success of these and management of super-high-density Morphological descriptions of the tree, early clonal selections and the super- plantings in California. leaf, fruit and endocarp for these culti- high-density system is also evidenced var clones have been published (Tous et Horticultural characteristics by their early adoption in traditional al. 1999; Tous and Romero 2000, 2002). olive oil–producing countries, such as The clone ‘Arquebina i-18’ was ob- Crop performance Spain, Portugal, Tunisia and Morocco, tained in 1997 in a program to identify as well as diverse, nontraditional olive- and select outstanding individuals of The fi rst comparative fi eld trial with growing regions that are beginning ‘Arbequina’, the most important culti- these clones in super-high-density to produce extra-virgin olive oils of var in Catalonia (160,000 acres [65,000 hedgerow orchards was planted in

A B C

The growth habit of 11-year-old trees is shown for the IRTA clones (A) ‘Arbequina i-18’ (B) ‘Arbosana i-43’ and (C) ‘Koroneiki i-38’, in a hedgerow, super-high-density planting system in 2009, in Spain.

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 35 As the newly planted super-high-density orchards in California enter their optimal olive oil production phase, it will be interesting to compare and follow experiences usually due to shade and observations with other regions. and limited ventila- tion in the tree cano- Tarragona in 1998 (Tous et al. 2003, influence of environment on precocity pies (Tous et al. 2010). The yields of 7- to 2008) (table 1). and average crops achieved was larger 10-year-old orchards are more variable Yields. Differences between vari- in Cordoba due to the higher vegetative and depend on management of the can- etals in cumulative fruit yield became tree growth in this province. opy volume, which should not exceed evident during early years of the trial The mean harvest of super-high- 143,000 to 171,500 cubic feet per acre to (table 2). In Tarragona, the highest density cultivars in Tarragona was facilitate movement of the over-the-row cumulative yields were measured for 4,397 pounds per acre (3rd year), 4,205 harvesters. ‘Arbequina i-18’ (31,875 pounds per pounds per acre (4th year; frost on trees Vigor. We observed the lowest tree acre) followed by ‘Arbosana i-43’ (26,470 affected productivity), 10,344 pounds vigor (trunk cross-section, canopy vol- pounds per acre) and ‘Koroneiki i-38’ per acre (5th year) and 7,291 pounds per ume and sucker emission) in ‘Arbosana (22,361 pounds per acre). In a similar acre (6th year), all similar to harvests i-43’ and ‘Arbequina i-18’ (table 3). trial in Cordoba (Andalusia, southern obtained in other high-density orchards ‘Koroneiki i-38’ is notorious for being Spain), ‘Arbequina i-18’, ‘Arbosana i-43’ in Spain. The high yields observed in more vigorous and producing more and ‘Koroneiki i-38’ showed higher early years of the Spanish trials and suckers than the other cultivars. The mean harvest yields (3 to 6 years after commercial orchards are not sustain- yield efficiency of each varietal clone planting) than other varieties tested able. Under the favorable growing con- was measured to determine the balance (data not shown) (León et al. 2006); ditions that foster vigorous tree growth, between productive and vegetative ac- in this southern location ‘Koroneiki a reduction in potential production tivity during the early bearing phase. i-38’ was the most precocious (table 2). occurs in the 6th to 8th years, with aver- The highest index scores were observed During the first years of both trials, the ages of 7,138 to 8,030 pounds per acre, in ‘Arbequina i-18’ and ‘Arbosana i-43’ (0.12 pound per cubic foot), followed by ‘Koroneiki i-38’ (0.07 pound per cubic TABLE 2. Annual and cumulative yields of IRTA olive clones planted in 1998 (Tarragona, Catalonia) foot). ‘Koroneiki i-38’ showed a higher and 2000 (Cordoba, Andalusia), Spain, in a super-high-density planting system 2 and 6 years after planting, respectively tendency to vegetative growth, and the crop was irregular among trees during Arbequina i-18 Arbosana i-43 Koroneiki i-38 the first years of the trial. Mechanical harvest. Several intrinsic Year Tarragona Cordoba Tarragona Cordoba Tarragona Cordoba varietal characteristics, such as growth ...... lb/acre* ...... Second 1,102 0 803 273 0 3,213 habit and canopy width, influence the efficiency of fruit removal during me- Third 6,002 13,203 4,771 15,305 2,416 18,502 chanical harvest. Our selections display Fourth† 4,428 12,527 2,833 7,990 5,356 5,440 two growth habit categories: semi-erect Fifth 12,038 17,957 12,173 17,279 6,822 11,170 (‘Arbequina i-18’) and open canopy Sixth 8,305 5,519 5,890 6,583 7,678 4,027 (‘Arbosana i-43’ and ‘Koroneiki i-38’). Average (3th–6th) 7,693 12,302 6,537 11,790 5,568 9,786 Straddle machines or grape harvest- Cumulative yield 31,875 49,207 26,470 47,431 22,361 42,354 ers perform better than trunk shakers (lb/acre) for these cultivars. More than 90% of * 1 lb/acre = 1.1209 kg/ha. the fruit was removed in all cultivars, † In the 4th year (2002), crop yield was slightly lower due to frost problems in Tarragona (December 2001). independent of their size, position in Source: Tous et al. 2003, 2008; León et al 2006. the canopy and maturation index. By contrast, the efficiency of trunk-shaking TABLE 3. Vegetative and productive characteristics of three olive cultivars growing in a 5-year-old, harvesters is clearly influenced by super-high-density orchard in Catalonia, Spain, 2000–2003 (2nd–5th year after planting) growth habit (Pastor et al. 1998), and yield is improved with an erect or semi- Cumulative Suckers TCSA* Canopy volume yield erect tree shape, large fruits and low Cultivar (4th year) (5th year) (5th year) (2nd-5th year) Yield efficiency fruit removal force. in2† ft3/acre lb/acre ∑ lb/ft3‡ Disease. ‘Arbequina i-18’ is more Arbequina i-18 0.4c§ 5.54c 192.389ab 23.539a 0.12a sensitive than the other selections to Arbosana i-43 1.4b 5.85bc 168.795b 21.330ab 0.12a olive leaf spot (Spilocaea oleagina) when Koroneiki i-38 5.2a 7.67a 189.674ab 14.594c 0.07bc planted in coastal environments and * Trunk cross-sectional area. humid valleys. ‘Arbequina i-18’ is more † 1 inch2 = 6.4516 cm2; 1 ft3/acre = 0.0700 m3/ha; 1 lb/acre = 1.1209 kg/ha; 1 lb/ft3 = 16.0185 kg/m3. tolerant than the other two cultivars to ‡ Sum of first yields (2nd to 5th year) per cubic foot of canopy volume at 5th year (2003). frost, while ‘Koroneiki i-38’ is the most § Mean separation within columns by Duncan’s multiple range test, P < 0.05. sensitive.

36 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 TABLE 4. Fruit characteristics of three IRTA clones tested in an irrigated, super-high-density planting system in Catalonia, Spain, from trees 3 to 7 years old, 2001–2005 Harvest time. Gradual fruit ripening and maturation is commonly observed Pulp/stone in the three cultivars, although this Cultivar Fruit weight ratio Oil content Moisture Oil content parameter is highly influenced by tree g % fresh weight % % dry weight fruit load and seasonal conditions as Arbequina i-18 1.72 ± 0.18* 4.31 ± 0.59 21.9 ± 1.0 60.1 ± 3.0 54.4 ± 2.5 well as geographical location. Optimal Arbosana i-43 1.59 ± 0.37 4.69 ± 0.54 19.8 ± 0.8 61.1 ± 2.2 50.7 ± 2.8 harvest time is different for each of the Koroneiki i-38 0.90 ± 0.14 3.44 ± 0.84 22.9 ± 0.8 56.0 ± 2.3 52.4 ± 3.4 cultivars: ‘Arbequina i-18’ is optimal in * Mean values ± standard error (SE). Catalonia from mid-November to mid- December, ‘Koroneiki i-38’ matures in late December and ‘Arbosana i-43’ in TABLE 5. Olive oil characteristics* of three IRTA clones tested in an irrigated, super-high-density mid-January. planting system in Catalonia, Spain, from trees 5 to 6 years old, 2003 and 2004 Fruit and oil characteristics. ‘Arbe- Palmitic Oleic acid, Linoleic Linolenic Total quina i-18’ produced larger fruits Cultivar acid, C16:0 C18:1 acid, C18:2 acid, C18:3 polyphenols Bitterness Oil stability than the other two cultivars (table 4). ppm ...... The pulp/stone ratio was higher for % cafeic acid K225 hours † ‘Arbosana i-43’ and ‘Arbequina i-18’, Arbequina i-18 14.5a‡ 69.4c 11.1a 0.72b 234b 0.2a 9.10b followed by ‘Koroneiki i-38’. Fruit wa- Arbosana i-43 13.6a 73.0b 7.9b 0.9a 343a 0.30a 12.8ab ter content ranged between 56.0% in Koroneiki i-38 11.4b 76.6a 6.89c 0.93a 400a 0.45b 15.23a ‘Koroneiki i-38’ and 61.1% in ‘Arbosana * Oil characteristics: main fatty acid composition (%), total polyphenols (ppm cafeic acid), bitterness (K225) and oil stability. i-43’. Oil content expressed as per- † Oil stability against oxidation, applying Rancimat method (hours at 120ºC). centage of dry weight was higher in ‡ Mean separation within columns by Duncan’s multiple range test, P < 0.05. ‘Arbequina i-18’ (54.4%), followed by ‘Koroneiki i-38’ (52.4%) and ‘Arbosana the three, and ‘Arbosana i-43’ oils had The most consistent plant character- i-43’ (50.7%). an intermediate palate profile. Oil com- istics and performance, as observed in The three clonal selections pro- position and flavor change as the olive super-high-density orchards around the duced extra-virgin olive oil of excellent fruit develops. The distinctive and con- world, can be summarized as follows: quality. The fatty acid composition of trasting sensory attributes of the extra- ‘Arbequina i-18’. This highly produc- ‘Arbequina i-18’ and ‘Arbosana i-43’ virgin oils from each varietal allows tive variety is early bearing with little oils was similar (table 5). ‘Koroneiki for unique blends with a wide range of alternating bearing. It is considered i-38’ oil is characterized by a higher interesting sensory characteristics. frost resistant and adaptable to differ- content of oleic acid (more than 76%) ent climatic and soil conditions, and is Field observations at the expense of palmitic and linoleic adaptable to high-density and super- acid, which contribute to longer shelf Initial observations from the Mas de high-density hedgerow orchards. Its life. ‘Arbosana i-43’ and ‘Koroneiki i-38’ Bover cultivar trials and orchard design semi-erect growth habit facilitates its oils were consistently richer in poly- evaluations, initiated in the 1980s, have training on a central leader. It produces phenols than ‘Arbequina i-18’. When been validated by the worldwide adop- medium-fruited extra-virgin oil that compared at the organoleptic sensory tion of IRTA’s clonal selections. The is balanced in the mouth; the sweet level (fig. 1), ‘Arbequina i-18’ oil was three initial selections described here attribute is outstanding and easily ap- the most balanced of the three, with a have been planted in new high-density preciated by new consumers. Its com- medium fruity intensity, balanced in (121 to 242 trees per acre) and super- mercialization can be monovarietal or the palate and an outstanding sweet- high-density (over 600 trees per acre) blended with other oils. ness. ‘Koroneiki i-38’ produced the most olive tree orchards around the world, ‘Arbosana i-43’. This is an early- fruity, green, bitter and pungent oil of and most recently California. bearing cultivar with high productivity.

A B C Fruity Fruity Fruity Green Apple Apple Twiggy Apple Artichoke almond

Ripe Green Ripe Green Ripe Green fruits grass fruits leaves fruits leaves

Sweetness Bitterness Sweetness Bitterness Sweetness Bitterness

Astringency Pungency Astringency Pungency Astringency Pungency Fig. 1. Sensorial profiles of olive oils from three IRTA clones: (A) ‘Arbequina i-18’, (B) ‘Arbosana i-43’ and (C) ‘Koroneiki i-38’. The green polygon represents the intensity of each taste attribute scored on a 10-point scale.

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 37 ‘Arbequina’ i-18 ‘Arbosana’ i-43

Fruit of three clones used in super-high- density planting sources of novel germplasm to produce systems. ‘Arbequina olives of improved agronomic perfor- i-18’ and ‘Arbosana mance and desirable olive oil sensory i-43’ are native to Catalonia, Spain, attributes. and ‘Koroneiki i-38’ As the newly planted super-high- is native to Greece. density orchards in California enter their optimal olive oil production phase, it will be interesting to compare experiences and observations with other regions in terms of economic vi- ability, orchard management and sus- tainability, natural resource utilization ‘Koroneiki’ i-38 and extra-virgin oil qualities.

Due to its low vigor, it adapts well for varietal characteristics that can im- to hedgerow systems for olive grow- prove productivity, a low vigor/compact ing. Sensitive to frost, its fruit is small growth habit, disease resistance and and ripens several weeks later than extra-virgin olive oil with high levels J. Tous is Agricultural Engineer, A. Romero is ‘Arbequina’. It produces intense, green- of antioxidants. IRTA recently initiated Agricultural Engineer, J. Francisco Hermoso is fruited virgin oil with high levels of a project to catalogue a collection of Agricultural Engineer, and A. Ninot is Agricultural Engineer, Institut de Recerca i Tecnologia Agroali- bitterness, spiciness and astringency. ancient trees (estimated 500 to 700 years mentaria (IRTA) Mas de Bover research station, Due to its higher polyphenol content, it old) in local orchards around northeast Constantí, Catalonia, Spain. We are grateful to the is particularly interesting for blending Spain that contain individual trees of owners of the La Boella farm (La Canonja, Spain) and to stabilize and prolong the shelf unclear varietal origin, as potential for their collaboration in this trial. life (time to rancidity) of the milder ‘Arbequina’ oil. ‘Koroneiki i-38’. This is a productive References Tous J, Romero A. 2002. Ficha varietal de olivo ‘Koro- neiki IRTA i-38’. Olint 6:23–5. and early-bearing cultivar. It is consid- Connell JH. 2005. History and scope of the olive in- ered drought resistant but frost sensi- dustry. In: Sibbett GS, Ferguson L (eds.). Olive Produc- Tous J, Romero A, Hermoso JF. 2010. New trends in tion Manual (2nd ed.). UC ANR Pub 3353. Oakland olive orchard design for continuous mechanical har- tive, and well suited to hot growing CA. p 1–10. vesting. Adv Hort Sci 24(1):43–52. areas. It is tolerant to olive leaf spot and León L, de la Rosa R, Guerrero N, et al. 2006. Ensayos Tous J, Romero A, Plana J. 1999. ‘IRTA-i-18’, a clone has very small fruit, which ripen after de variedades de olivo en plantación de alta densi- of the ‘Arbequina’ olive cultivar. Olivae 77(6):50–2. dad. Fruticultura Profesional 160:21–6. ‘Arbequina’ but before ‘Arbosana’. It Tous J, Romero A, Plana J. 2003. Plantaciones super- Pastor M, Humanes J, Vega V, Castro A. 1998. Diseño intensivas en olivar. Comportamiento de 6 variedades. produces quite-stable extra-virgin oils, y manejo de plantaciones de olivar. Monografías, Agricultura 851(4):346–50. rich in oleic acid and polyphenols, with 22/98. Ed. Consejeria de Agricultura y Pesca. Junta de Tous J, Romero A, Plana J, Hermoso JF. 2008. Olive oil intense green color and bitterness, and Andalucía, Sevilla. cultivars suitable for very high density planting condi- Sutter EG. 2005. Olive cultivars and propagation. tions. Acta Hort 791:403–8. a long shelf-life. In: Sibbett GS, Ferguson L (eds.). Olive Production UC Davis Olive Center. 2009. Survey of Super High Manual (2nd ed.). UC ANR Pub 3353. Oakland CA. Density Olive Production in California. http://olivecen- Olive tree breeding program p 19–25. ter.ucdavis.edu/fi les/survey%20111509%20revised. Tous J, Ferguson L. 1997. Olive growing in California. pdf. Scientists at IRTA’s Mas de Bover re- Olivae 67:18–26. Vossen PM. 2007. Olive oil: History, production and search station are evaluating additional Tous J, Romero A. 2000. ‘Arbosana IRTA i-43’. Olint characteristics of the world’s classic oils. HortScience clonal materials and old orchards of ol- 2:13–5. 42(5):1093–100. ive varieties, and prioritizing the search

38 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 Olive cultivars fi eld-tested in super-high-density system in southern Italy

by Angelo Godini, Gaetano Alessandro Vivaldi, California production of extra-virgin ‘Arbosana’ and ‘Koroneiki’, two ad- and Salvatore Camposeo olive oil is reportedly about 2% of total ditional cultivars were introduced: U.S. consumption, with the rest im- ‘Coratina’, the most popular Apulian ported mainly from Italy and Spain. In olive oil cultivar, and ‘Urano’, a new ccording to the International Ol- recent years, California has started in- Italian cultivar considered by our Aive Oil Council, world olive oil creasing its oil olive acreage. California research group to be well-suited for consumption has risen from 2.8 mil- olive growers have planted more than super-high-density olive culture. lion tons (1991-1992) to 3.5 million tons 22,000 acres since 1999, about 12,000 The olive trees were propagated in (2005-2006), due to increases in the acres of which is in the super-high- commercial nurseries by softwood cut- consumption of healthier foods in many density olive system, with tree densities ting, and the experimental orchard was countries, including the United States. of 676 per acre or more. This system al- established according to the super-high- The market outlook for extra-virgin ol- lows for mechanical planting and har- density planting scheme (676 plant per ive oil is very good, and many countries vesting of olives, reducing labor costs. acre, with a tree spacing of 157.5 inches are actively increasing their olive acre- We believe that super-high-density by 59 inches) and a north-south row ages, particularly in North Africa, the olive culture can help to assure profi t- orientation. The trees were trained to Middle East, South America, Australia ability for both European and U.S. olive central leaders. Drip irrigation was sup- and the United States (Godini 2010). growers in the coming decades. This plied to each tree every 3 days between The Mediterranean’s traditional olive model, born in Spain at the end of the late spring and late summer, increasing industry is based on production sys- 20th century, has resulted in noticeable from 423 cubic yards per acre annually tems that are hundreds of years old and increases in yield per acre. Up until in 2006, to 476 in 2007, to 794 in 2008 characterized by low yields and high now, super-high-density olive culture and 2009. Harvesting was performed production costs. The European Union has utilized a limited number of culti- on Nov. 20 in 2008 and 2009, in the third subsidy system, which has helped vars, primarily ‘Arbequina’, ‘Arbosana’ and fourth years after planting, respec- European olive farmers to stay in busi- and ‘Koroneiki’, which possess suitable tively, using the Pellenc Activ’ 4560 har- features such as a semi- vesting machine. dwarf habit, early bearing Cultivar performance (fi rst production at the

Paul M. Vossen M. Paul second-to-third year after Vegetation. In December 2009, the planting), consistent ini- average tree height had reached 107 tial crops (more than 2.2 inches, 5.3 times the initial growth of pounds per plant), crop the previous year, with a maximum of stabilization between 5 7.6 times more growth for ‘Arbequina’ and 6 years, and fruit that and a minimum of 2.2 times more for is impact-resistant and has ‘Urano’ (table 1). Only the crown width good oil quality (Godini of ‘Coratina’ exceeded 79 inches by and Bellomo 2002). The results that we pres- TABLE 1. Tree height at planting (June-July 2006) ent here are preliminary. and December 2009, crown width in December 2009 Considering that Italy’s Mediterranean climate Super-high-density hedgerow planting systems for olives is similar to California’s, Crown employ over-the-row harvesters (shown, in California). Tree height width we believe that soil and December December ness, will end in 2014. Moreover, the climate differences should have little Cultivar Planting 2009 2009 application of a “free exchange” area infl uence on the applicability of these inches in 2010 will legalize the importation of fi ndings to California. Arbequina 14.1b* 107.3b 77.5b lower-cost extra-virgin olive oils from Experimental orchard Arbosana 13.0b 97.0c 77.7b the southern Mediterranean Basin into Europe (Godini 2010). Year after year, In summer 2006, we established Coratina 16.9b 120.9a 96.5a the profi tability of Italy’s traditional a new experimental orchard at Koroneiki 16.0b 117.6a 78.4b olive culture becomes increasingly Valenzano, near Bari, in the experimen- Urano 41.1a 92.7c 74.5b doubtful, notwithstanding the world- tal farm of the Dipartimento di Scienze Mean 20.2 107.1 80.9 wide renown of so-called “Made in delle Produzioni Vegetali at University * Within the same column and for a single parameter, Italy” extra-virgin olive oil (Godini and Aldo Moro of Bari, Italy. In addition different letters mark values signifi cantly different at P = 0.01 (SNK test). Bellomo 2002). to standard clones of ‘Arbequina’,

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 39 December 2009, exceeding the harvester TABLE 2. Fruit production per year, cumulative yield at the third (2008) and fourth (2009) year after tunnel size and requiring pruning planting, and mean oil output and cumulative production intervention to control its transverse canopy growth. Fruit production Annual yields. The average annual Cumulative Mean oil Cumulative oil yield in the third year was 7.7 pounds Cultivar 3rd year 4th year yield* output production per tree, equivalent to 2.3 tons per acre; ...... pounds/tree† ...... tons/acre % tons/acre only ‘Urano’ exhibited a surprisingly Arbequina 5.5b‡ 12.4ab 33.4b 17.7 5.68b high yield of 3.7 tons per acre (table Arbosana 6.2b 12.6ab 35.1ab 17.5 5.83b 2). In the fourth year, the average crop Coratina 7.1b 11.3b 34.1b 17.3 5.86b yield was 11 pounds per tree or 3.3 Koroneiki 8.4b 13.7a 41.3a 15.0 6.89a tons per acre (up 40% from 2008), and Urano 12.1a 4.9c 31.6c 16.8 5.26b it was more variable among cultivars. ‘Koroneiki’, ‘Arbosana’ and ‘Arbequina’ Mean 7.7 11.0 35.1 16.9 5.91 followed by ‘Coratina’ gave satisfactory * Over four years of the trial. † 7.73 pounds per tree = 2.3 tons per acre. yield (between 13.7 and 11.3 pounds per ‡ Within the same column and for a single parameter, different letters mark values significantly different at P = 0.01 tree or 4.1 and 3.4 tons per acre). The (SNK test). yield for ‘Urano’ dropped to 4.9 pounds per tree or 1.5 tons per acre, perhaps efficiency; ‘Arbosana’ and ‘Koroneiki’ We know that higher yields have due to heavy cropping in the previous were less satisfactory. But these differ- been recorded elsewhere with super- year. ences were due to the fruit-ripening high-density olive culture; however, Cumulative yields and oil. We also stages reached by each cultivar at the we consider annual yields of about compared cumulative yields over the harvesting date: mature for ‘Arbequina’, 17.5 tons per acre of fruit to be satisfac- first 4 years of the trial. ‘Koroneiki’ ‘Coratina’ and ‘Urano’, but immature tory. In fact, this value, equivalent to a showed the highest cumulative yield ‘Arbosana’ and ‘Koroneiki’. yield of only about 9.4 pounds per tree, (41.3 tons per acre), and ‘Urano’ was No damaged fruits were reported for would be helpful in avoiding alternate relatively less productive (31.6 tons per ‘Arbequina’, ‘Arbosana’ and ‘Koroneiki’, bearing and subsequent problems that acre) (table 2). The peculiar behavior of whereas ‘Coratina’ and ‘Urano’ exhib- could cause conflicts between vegeta- ‘Urano’ requires further investigation. ited very low percentages of damaged tive growth and cropping consistency. Considering its average overall oil con- fruit. Tree size can be controlled by pruning tent of about 17.0%, ‘Koroneiki’ was the The average percentage of shoots when they grow larger than the size of most productive cultivar with 6.9 tons damaged per tree by the harvesting ma- the harvester head. Our data indicates per acre of oil over 4 years. The other chine beaters was insignificant at less that the noted yield limit was reached cultivars exhibited similar cumulative than 1.0%. Of these damaged shoots, by at least four out of five cultivars in oil production. young and thin current-year shoots just the 4th year after planting. Harvesting efficiency, fruit and shoot incurred the most damage (80.0%), per- damage. Harvesting efficiency was haps because they were more exposed. satisfactory on the whole (93.1%), not- The percentage of damaged shoots up A. Godini is Professor, G. Allesandro Vivaldi is withstanding differences among cul- to 1 inch in diameter was 14.3%, and Ph.D. Student, and S. Camposeo is Ph.D. Re- tivars (table 3). ‘Arbequina’, ‘Coratina’ to shoots thicker than 1 inch was 5.7%. searcher, Dipartimento di Scienze delle Produzioni and ‘Urano’ had the highest harvest Only ‘Coratina’ and ‘Urano’ exhibited Vegetali, University Aldo Moro of Bari, Italy. The a significant percentage of broken authors wish to thank Provincia di Bari, Italy, for shoots or branches thicker than 1 inch: its financial support of this research. ‘Coratina’ because of its spreading habit TABLE 3. Harvesting efficiency, damaged fruits References and damaged shoots per tree, as mean of the between rows, and ‘Urano’ because of third and fourth year after planting Camposeo S, Ferrara G, Palasciano M, Godini A. 2008. its spreading habit and thick, bending Varietal behaviour according to the superintensive olive- branches. culture training system. Acta Hortic 791:271–4. Harvesting Fruit Shoots Camposeo S, Godini A. 2010. Preliminary results about Cultivar efficiency damaged damaged High density, high yields the performance of 13 cultivars according to the su- ...... % ...... n/tree per high density oliveculture training system in Apulia The present data confirms and im- (Southern Italy). Adv Hortic Sci 24(1):16–20. Arbequina 97.2a* 0.0c 0.4b proves upon results obtained in previ- Camposeo S, Vivaldi GA, Gallotta A, et al. 2010. Valu- Arbosana 87.1b 0.0c 0.5ab tazione chimica e sensoriale degli oli di alcune varietà ous experimental trials (Camposeo and di olivo allevate in Puglia con il modello superintensivo. Coratina 97.3a 1.5a 0.2c Godini 2010). In terms of early bearing Frutticoltura 72(6):80-83 (in Italian with summary in Koroneiki 87.6b 0.0c 0.6a and yield consistency, all the tested cul- English). Godini A. 2010. L’olivicoltura italiana tra valorizzazione Urano 96.0a 0.4b 0.2c tivars performed satisfactorily. And in e innovazione. Frutticoltura 72(6):52–69 (in Italian with Mean 93.1 0.4 0.4 sensory evaluations, the resulting extra- summary in English). *Within the same column and for a single parameter, virgin oils had sweet typology and Godini A, Bellomo F. 2002. Olivicoltura superintensiva different letters mark values significantly different at were well-balanced, highly fruity and in Puglia per la raccolta meccanica con vendemmiatrice. P = 0.01 (SNK test). International Congress of Oliveculture. Spoleto (Italy), ready to use (Camposeo et al. 2010). April 22-23:230–4 (in Italian with summary in English).

40 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 ReVIEW Article ▼

Methods evaluated to minimize emissions from preplant soil fumigation

by Suduan Gao, Bradley D. Hanson, Dong Wang, Gregory T. Browne, Ruijun Qin, Husein A. Ajwa and Scott R. Yates

Many commodities depend on preplant soil fumigation for pest control to achieve healthy crops and profitable yields. Under California regulations, minimizing emissions is essential to maintain the practical use of soil fumigants, and more stringent regulations are likely in the future. The phase-out of methyl bromide as a broad-spectrum soil fumigant has created formidable challenges. Most alternatives registered today are reg­ ulated as volatile organic compounds Shank application of 1,3-D is followed by a disking/rolling operation, inset, to break the shank trace and compacted soil surface. because of their toxicity and mobile nature. We review research on meth­ Control Program (CDFA 2008). Without Regulations such as use limits and ods for minimizing emissions from fumigants, the productivity of these buffer zones have been used to mini- cropping systems would suffer from mize emissions and protect public and soil fumigation, including the effec­ yield losses due to diseases, replant environmental health. More-stringent tiveness of their emission reductions, disorders or lack of phytosanitary regulations are being developed for impacts on pest control and cost. certification. fumigants to reduce air emissions, es- Low-permeability plastic mulches Because of its role in depleting pecially in ozone-nonattainment areas stratospheric ozone, methyl bromide such as Ventura County and the San are highly effective but are generally was phased out in the United States and Joaquin Valley (CDPR 2008; Segawa affordable only in high-value cash other developed countries as of January 2008). crops such as strawberry. Crops with 2005, under provisions of the U.S. Clean The UC Statewide Integrated low profit margins such as stone- Air Act and the Montreal Protocol (an Pest Management Program recently international agreement). Some limited prepared a field fumigation guide fruit orchards may require lower-cost uses of methyl bromide are permit- for emission control, which is avail- methods such as water treatment or ted under critical-use exemptions and able on the California Department of target-area fumigation. quarantine/preshipment criteria, which Pesticide Regulation website (UC IPM are subject to application and approval 2009). This paper is not intended to annually. represent or serve as a replacement for oil fumigation with methyl bromide Limited to a few registered com- that guide, but rather to update find- Shas been used for decades in Cali- pounds, growers have turned to ings on emission-reduction technolo- fornia to control a variety of soil-borne alternative fumigants such as 1,3- gies, including projects under the U.S. agricultural pests, such as nematodes, dichloropropene (Telone or 1,3-D), chlo- Department of Agriculture Agricultural diseases and weeds. Major, high-value ropicrin (CP) and methyl isothiocyanate Research Service (USDA-ARS) Pacific cash crops that rely on soil fumigation (MITC) generators (metam sodium or Area-Wide Pest Management Program. include strawberries; some vegetables dazomet) (Trout 2006). In addition to We summarize extensive research on such as carrot, pepper and tomato; direct toxicity, most of these alternative emission reduction from soil fumiga- and nurseries and orchards for stone fumigants are also regulated as vola- tion conducted over the last few years, fruit, ornamentals and grapevines. In tile organic compounds (VOCs). Some and identify agricultural practices for California, tree and grapevine field VOCs released into the atmosphere minimizing fumigant emissions while nurseries must meet requirements of can react with nitrogen oxides under achieving good efficacy. We also iden- the California Department of Food and sunlight to form harmful ground-level tify knowledge gaps and other research Agriculture (CDFA) Nursery Nematode ozone, an important air pollutant. needs for the near future.

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 41 Factors affecting emissions to contain fumigants in the rhizosphere Applying fumigant deeper in the soil Soil fumigants are volatile chemical where plant roots are present and lowers emissions by increasing fumi- compounds. The purpose of fumigation soilborne pests are dominant. Without gant travel time to the surface and its is to achieve maximum control of soil- proper containment, more than half of interaction with soil. Increasing the borne pests, which requires an effective fumigants applied can be lost through shank-injection depth from 12 to 24 concentration or exposure duration and emissions (fi g. 2). the uniform distribution of fumigants Fumigant lost into in soil. A number of processes affect the atmosphere not Fumigant lost to atmospheric emissions not only the fate of fumigants after soil applica- only contributes to contributes to air pollution, but also translates into tion (fi g. 1). Fumigants are subject to air pollution, but wasted resources intended for soil pest control. partitioning into soil air, water and also translates into solid phases (most importantly, organic wasted resources matter); volatilization (emission); degra- intended for soil pest control. inches (30 to 60 centimeters) resulted dation (chemical and microbial), move- Soil conditions (such as texture, in a 20% or greater reduction of methyl ment in soil via diffusion; and potential moisture and organic matter content), bromide emissions in bare soils (Yates leaching. Volatilization and leaching weather and surface barriers, and the et al. 2002). can potentially contaminate the air chemical properties of the fumigant can The general consensus for bare-soil and water. Emission loss is a major air- all affect emissions. Generally speaking, fumigation is that emissions from drip quality concern. To minimize emissions lower emissions are expected from soils application, especially subsurface, are as well as ensure effi cacy, it is necessary with fi ne texture, high water content, lower than broadcast-shank injections high organic-matter content and low (Gao, Trout, Schneider 2008; Wang et temperature compared to dry soils with al. 2009). This is attributable to two fac- coarse texture, low organic-matter con- tors: (1) increasing soil water content Volatilization Air tent and high temperature. Approaches decreases air pore volume (i.e., vapor to reducing fumigant emissions include diffusion) and increases the amount application methods such as equipment of fumigant partitioning in the aque- design (injection depth), physical bar- ous phase and (2) there are no shank Chemical & riers, irrigation, soil amendment with traces (i.e., soil fractures) that can serve Phase (gas/liquid/solid) microbial distribution via diffusion, degradation chemicals or organic materials and as volatilization channels. The fumi- sorption, etc. target-area treatment. gant diffusion rate in the liquid phase Soil Current application techniques is much slower than in the gas phase. include broadcast fumigation and Substantially higher soil water content Leaching chemigation. With standard broadcast would reduce the fumigant’s distribu- fumigation, fumigants are applied tion in soils by reducing vapor diffu- directly to the soil at a certain depth sion, reducing effi cacy. Good effi cacy Fumigant Organic matter Groundwater using conventional equipment or rigs can only be ensured when the fumigant (shanks). Chemigation is injecting moves with applied water for a rela- fumigants into soil with irrigation wa- tively uniform distribution (Ajwa and Fig. 1. Processes affecting the fate of fumigants ter through sprinklers or drip tapes. Trout 2004). However, because fumi- in soil. gants are highly volatile, drip-applied

350 100 fumigants near soil surfaces without A Cis 1,3-D B Total 1,3-D any barriers may still result in high 300 Trans 1,3-D 80 emission losses. Currently, about half of 250 California’s strawberry acreage, espe- /h) 2 cially in the coastal areas, is fumigated 200 60 using drip application. 150 40 Plastic fi lms Flux (mg/m 100 (% of applied) 20 Plastic tarping or “mulching” is the 50 Cumulative loss of 1,3-D most commonly used practice to con-

0 0 tain fumigants in soil and control emis- 0 48 96 144 192 240 288 336 0 48 96 144 192 240 288 336 sions. The effectiveness of tarping on Time (hours) Time (hours) emission reduction depends largely on the chemical’s characteristics and tarp Fig. 2. Emission fl ux from a bare surface soil after shank injection of 1,3-dichloropropene (1,3-D) permeability, and also to some extent on (with 2.5% inert ingredients) at an 18-inch depth into a sandy loam soil. The 1,3-D included cis- and trans-isomers; the sum of the isomers volatilized over time divided by the total applied gives soil conditions. Tarping with polyeth- the cumulative emission loss. ylene fi lm was found to be ineffective

42 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 A company applies fumigant through drip irrigation in a strawberry field. Plastic tarping minimizes emissions following fumigant application. to control 1,3-D emissions, especially in damaged during field installation, with standard polyethylene-based film relatively dry soils (Gao and Trout 2007; potential changes in permeability. (Chow 2008). Information on field emis- Papiernik and Yates 2002). However, Recent field data confirmed that this sion reductions is insufficient because high-density polyethylene (HDPE) tarp type of film can effectively reduce emis- this film has not been made available applied over irrigated soil can sub- sions more than 90% (Ajwa 2008; Gao, commercially. The most recently re- stantially lower 1,3-D emissions, due Qin, et al. 2009). The tarp permeability ported research data indicated that TIF to both higher soil water content and did increase after field installation but can have similar effectiveness in reduc- water condensation under the film (Gao was still substantially lower than that ing emissions as other VIFs; but these and Trout 2007). About 50% emission of polyethylene films (Qin, Gao, Ajwa low-permeability films can cause emis- reduction was measured for an HDPE- 2008; Yates 2008). There are also con- sion surges when the tarp is cut and tarped treatment in relatively cooler fall cerns about damage from field installa- after about 1 week, due to the release weather conditions, compared to bare tion and improper gluing materials in of high amounts of retained fumigant soil (Gao, Hanson, et al. 2009). Tarped the VIF tarp. These potential problems, (Gao et al. 2010). These emission surges treatment in pre-irrigated soil in sum- however, were not observed in a recent would increase exposure risks to work- mer may also improve pest control due field trial (Gao, Hanson, et al. 2009), ers and bystanders. To reduce the risk, to elevated soil temperatures under the when a Bromostop VIF (0.025- the waiting period between fumigation tarp. Shrestha et al. (2006) observed sig- millimeter thickness) from Bruno and tarp cutting or removal should be nificant reductions in weed populations Rimini Corp. (London, U.K.) was ap- long enough for fumigants to degrade due to high temperatures up to 117°F plied to a shank-injected 1,3-D (Telone under the tarp. VIFs can retain fumi- under the tarp, which was partially II) field, achieving greater than 95% gants under the tarp, making lower attributed to the effect of solarization. emission reduction. application rates possible, provided Virtually impermeable film. Low- Totally impermeable film. A new that satisfactory pest control can be permeability films, including virtually type of low-permeability film, so-called achieved. The low-permeability films impermeable film (VIF), showed great totally impermeable film (TIF), was also showed the potential to improve potential in early laboratory or small- reportedly easier to install and main- the uniformity of fumigant distribution plot tests (Wang et al. 1997b). VIF has tain in field applications (Chow 2008; up to a certain depth in the soil profile, much lower permeability to most fumi- Villahoz et al. 2008). This film has even so lower application rates than are cur- gants than HDPE films (Ajwa 2008). lower permeability to fumigants than rently used for bare soil or underneath VIF is generally a multilayered film some other VIFs (Ajwa 2008). For exam- standard polyethylene film would be composed of barrier polymers such as ple, the mass-transfer coefficient (indi- possible. nylon or ethyl vinyl alcohol (EVOH) cating tarp permeability to fumigants) Water seals and pre-irrigation sandwiched between polyethylene for TIF was 0.0004 inch (0.001 centime- polymer layers (Villahoz et al. 2008). ter) per hour for cis 1,3-D compared to With proper management, post- A number of studies have shown that 0.028 inch (0.07 centimeter) per hour for fumigation water seals (with sprinklers) VIF can retain higher fumigant con- Bromostop VIF before field application, and pre-irrigation can reduce emissions centrations than HDPE film, reducing and 0.008 inch (0.02 centimeter) versus to some extent. The latter is used to emissions while improving efficacy, es- 0.106 inch (0.27 centimeter) per hour, re- achieve adequate soil moisture if the pecially for weed control (Hanson et al. spectively, after installation over raised soil is dry, but not to a level that would 2008; Noling 2002). The effectiveness of beds in the field. inhibit fumigant movement/distribu- VIF in large-field applications has been TIF is a five-layer film incorporated tion in the soil profile. Water seals re- difficult to ascertain because it can be with a middle layer of EVOH into a duce fumigant emissions by forming a

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 43 high-water-content layer at the soil sur- water content in surface soil can reduce also reducing emissions in the labora- face, which serves as a barrier prevent- the efficacy of a fumigant to control tory and some field studies. Because ing the fumigant from diffusing into nematodes and weeds at or near the soil fumigants are readily incorporated the air (Wang et al. 1997a). surface (Hanson et al. 2008). Sequential into organic matter (Xu et al. 2003), soil Some earlier studies showed that treatment should be considered when with high organic-matter content was high water content in the surface soil surface pest control is a concern. reported to produce lower emissions provided a more effective barrier to (Ashworth and Yates 2007). However, Chemical treatments 1,3-D movement than HDPE tarp- field data is inconclusive regarding the ing (Gan, Yates, Wang, et al. 1998). Soil amendments with chemicals efficacy of adding organic amendments Intermittent water seals following soil (such as ammonium or potassium thio- such as composted dairy manure right fumigation have been effective in re- sulfate [ATS or KTS], thiourea or poly- before fumigation to reduce fumigant ducing emissions of methyl isothiocya- sulfides) sprayed over surface soil are emissions. nate (Sullivan et al. 2004; Wang et al. extremely effective in reducing emis- Yates et al. (2008b) reported that a 2005) and 1,3-D or chloropicrin in the sions. These chemicals can react with field with organic matter (composted field (Gao and Trout 2007; Yates et al. fumigants such as methyl bromide, municipal green waste) incorporated 2008a). The effect is more pronounced 1,3-D, chloropicrin and iodomethane in the previous year resulted in much in reducing emission peak flux, or vola- (methyl iodide) to form nonvolatile com- lower emissions than a field without the tilization rates from soil, by as much pounds by dehalogenation (Gan, Yates, amendment but with water seals. In a as 80% following fumigant application Becker, et al. 1998; Wang et al. 2000). The field trial with relatively high fumigant (Gao, Qin, et al. 2009). When irrigation practicality of using these chemicals on application rates, manure incorpora- stops, however, the emission flux tends a large field scale to reduce fumigant tion at 5 and 10 tons per acre (12.4 and to increase, depending on fumigant emissions has yet to be determined. 24.7 megagrams per hectare) did not concentrations in the soil. As a result, Considerations include cost factors reduce emissions (Gao, Qin, et al. 2009). cumulative or total emission losses may when large quantities of thiosulfate are Similarly, a recent trial using a higher not be reduced as substantially as the needed, and potentially undesirable amendment rate of 20 tons per acre (49.4 peak flux. Reducing the peak flux is -im soil-fumigant-thiosulfate reactions. megagrams per hectare) also did not portant because it lowers the potential Field trials involving spraying KTS show emission reduction, possibly due exposure risk to workers and bystand- on the soil surface following fumigation to reduced bulk density from too much ers. Buffer zones are determined based revealed that this chemical can signifi- organic material (Gao, Hanson, et al. on the peak emission flux. cantly reduce emissions of 1,3-D (by 2009). The quantity and quality of or- When the proper amount of water about 50%) and chloropicrin (by 85%) ganic matter may also determine its ef- is applied, water seals do not neces- (Gao, Qin, et al. 2008). By destroying fu- fectiveness in reducing emissions. High migant, this chemical treatment would manure application rates accompanied potentially reduce the fumigant dosage by irrigation and/or strong surface com- at or near the soil surface, but studies paction may be needed to achieve emis- showed either no effect or a limited im- sion reduction. However, increasing the pact on its efficacy for controlling nema- incorporation rate may be too costly to todes and/or weeds (Gan et al. 2000; be worthwhile. Gan, Yates, Becker, et al. 1998). However, The fumigation of targeted areas strong reactions between KTS and the such as tree rows or tree sites may be fumigant occurred, which resulted applicable for orchards where replant in a reddish-brown surface soil color disease is a major concern (Browne and an unpleasant smell that lasted for 2008). The shank application of fumi- several weeks. This reaction was not ob- gants in row-strip (shank-strip) or drip served in a strawberry field when KTS application of fumigant in tree sites was applied to the furrows of raised (drip-spot) have been tested in fields for Irrigation with sprinklers forms a water seal, beds, most likely due to the low levels efficacy as well as emissions (Gao, Trout, which minimizes emissions after fumigation. of fumigant emission measured from Schneider 2008; Wang et al. 2009). These the furrows (Qin, Gao, Ajwa 2008; Qin, target-area treatments lower emissions sarily reduce fumigant concentration Gao, McDonald, et al. 2008). Zheng et al. by reducing the treated acreage to less and distribution in the soil profile. This (2007) indicated that the smell may have than 50% (shank-strip) or 10% (drip- would hold true when only a relatively been derived from sulfur byproducts spot), automatically reducing the total wet surface layer (up to 6 inches of soil) of the transformation of thiosulfate and amount of fumigants applied. Applying is maintained, and this layer should fumigants in the soil. surface sealing or water treatment can help retain fumigants in the soil. More achieve further emission reduction. Amendments and target treatments frequent water applications appear Cost estimates to be more efficient in reducing emis- Soil amendment with organic materi- sions than fewer applications with als such as composted manure has been Cost is important when evaluating large amounts of water. But the high effective in degrading fumigants and the feasibility of emission-reduction

44 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 TABLE 1. Emission-reduction potential and cost estimates for surface sealing/treatments to reduce emissions from soil fumigation

Soil-surface treatment Emission-reduction potential Cost (excluding fumigant) Other considerations Bare soil Reference level, often > 60% of Not estimated for field preparations such as disking total applied fumigant emissions and compaction HDPE tarp Up to 50%, depending on soil HDPE: $950–$1,100 per acre (materials, ~ $500; glue, Effective in relatively moist soils moisture and temperature $100; application, $350; cutting and removal, $100) Low-permeability tarps (e.g., VIF) > 90%, if tarp is installed VIF: $1,200–$1,600 per acre, assuming material cost Effective in almost all conditions; successfully is 1.5 to 2 times HDPE, and other costs similar to unclear time needed for safe tarp HDPE removal Water treatment 20%–50%, depending on < $300 per acre, depending on water price and May reduce efficacy at surface soil, water amount and number of whether grower owns or rents sprinkler system requiring double treatments in applications sequence Chemicals (e.g., thiosulfate) > 50% Fumigant-to-thiosulfate active ingredient ratio of Oversupply of nutrients to soil, 1:1 to 1:2, at $150–$300 per acre post-treatment odor and potential soil-property changes Composted manure Inconclusive Depends on application rate and material costs; Improves soil properties; consider commercial composted manure is $15–$30 per ton when free or low-cost materials are available techniques for different commodities ammonium thiosulfate (Thio-Sul, con- environmental benefits, because no (table 1). Field data from a number of taining 12% nitrogen and 26% sulfur). materials must be disposed of. The cost trials showed that low-permeability To meet crop sulfur requirements, am- for a 25-millimeter water application by plastic tarps are the most promising monium thiosulfate is recommended sprinklers ranges from $100 to $300 per technique but also the most costly. The at 6 to 12 gallons per acre for row and acre, depending on whether the grower commonly used standard polyethylene vegetable crops, and 5 to 10 gallons owns or rents the sprinkler system. The tarp costs about $950 to $1,100 per acre per acre for trees and vines using soil overall cost of using water is currently depending on acreage, with higher injection and surface banding, or 15 substantially lower than plastic tarps, costs for small acreage and lower costs to 20 gallons per acre in a broadcast but this may change over time depend- for large acreage (personal communica- spray (www.tkinet.com/thiosul.html). ing on water supplies in California. tion, industry representatives). Costly However, fumigation rates are often Commercially available, clean, com- plastic materials may not be affordable much higher than fertilization rates. For posted manure costs $15 to $30 per ton. for commodities with low profit mar- example, 1,3-D can be applied at a maxi- The costs to apply higher rates than 25 gins, such as stone fruit orchards and mum rate of 33.7 gallons (332 pounds tons per acre may not be feasible for annual vegetables. active ingredient) per acre in California. commodities with low profit margins. Low-permeability films such as VIF Research showed that to significantly In some situations, composted green or TIF generally cost 1.5 to 2 times the reduce emissions, thiosulfate and fumi- waste from municipalities may be avail- cost of polyethylene films. In addition gant are needed at a ratio greater than able at no cost; however, this material to the higher cost for VIF, high levels one-to-one in molecular weight. For may also contain other undesirable of fumigants may be released into the 1,3-D, a one-to-one ratio would require waste products, such as plastic. atmosphere upon removal or when about 75 gallons of ammonium thiosul- Research needs planting holes are cut into the tarp. To fate containing the active ingredient, at reduce potential exposure risks, longer a cost of about $150 per acre. While this Reducing emissions from soil fu- waiting periods between fumigation level of thiosulfate would likely reduce migation is required to comply with and tarp cutting/removal are necessary emissions, it could also introduce exces- environmental regulations. Low emis- to allow fumigant degradation in soils. sive nutrients or salts that cause other sions can be achieved through the This issue requires further detailed serious crop-production concerns. Thus, management of application methods investigation, as the fate of fumigants large-field applications of chemical such as deep injection and subsurface would vary depending on the soil and treatment with thiosulfate are undesir- drip, physical barriers with plastic environmental conditions. If applicable, able. Additional concerns with chemical films, irrigation to form water seals or the injection of thiosulfate through drip treatment are the post-application odor achieve relatively moist soil conditions, irrigation under the tarp may effec- and potential soil-property changes that and the reduction of treatment areas tively reduce this risk (Qin et al. 2007), have not been fully addressed. to planting rows or sites. Soil chemical although no field tests have been done. Water seals, deep injection, drip treatment (e.g., thiosulfate) can be ef- Caution must be taken when consid- application and the incorporation of fective in lowering emissions and may ering a chemical treatment such as thio- high rates of organic materials are also prove to be an effective strategy for sulfate for reducing emissions. The cost low-cost options to control fumigant extreme cases, such as fumigant spills. of this chemical fertilizer is low, at less emissions. Using water costs much Although the incorporation of compos- than $2 per gallon (about 11 pounds) of less than plastic tarps and offers some ted dairy manure to surface soil at or

http://californiaagriculture.ucanr.org • JANUARY–MARCH 2011 45 below 25 tons per acre did not reduce films is needed for large-field ap- emissions in some field tests, the longer plications. Any emission-reduction incorporation times and higher rates ac- technology that enhances degradation companied by certain soil preparations or reduces fumigant concentration S. Gao is Research Soil Scientist, Water Manage- ment Research Unit, U.S. Department of Agricul- or more effective materials may have in soil or surface soil would have an ture Agricultural Research Service (USDA-ARS), the potential to reduce emissions and undesirable impact on pest control Parlier; B.D. Hanson is Cooperative Extension Spe- improve soil physiochemical properties. because of the reduction in exposure cialist, Department of Plant Sciences, UC Davis; Low-permeability plastic tarps such as dosage. This makes it more desirable D. Wang is Research Leader, Water Management VIF have shown the most promise in to use low-permeability tarps, which Research Unit, USDA-ARS, Parlier; G.T. Browne is reducing emissions while improving unfortunately cost the most. Feasible Project Coordinator, USDA-ARS Pacific Area-Wide efficacy. This type of film may also need techniques for different commodities Pest Management Program, UC Davis; R. Qin is Postdoctoral Research Associate, and H.A. Ajwa lower application rates, which can help depend on their availability to the pro- is Cooperative Extension Specialist, Department compensate for its high cost. duction system, effectiveness in emis- of Plant Sciences, UC Davis; and S.R. Yates is Re- Research on the performance of the sion reduction, potential impact on pest search Leader, Contaminant Fate and Transport next generation of low-permeability control and cost. Unit, USDA-ARS, Riverside.

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46 CALIFORNIA AGRICULTURE • VOLUME 65, NUMBER 1 2010 index

The following peer-reviewed research articles, and news and editorial coverage, were published in California Agriculture, Volume 64, Numbers 1 to 4 (January–March, April–June, July–September, October–December), 2010. Back issues are $5 per copy, while supplies last. To subscribe to the journal, order back issues, search the archives and download PDFs of all research articles in full, go to: http://CaliforniaAgriculture.ucanr.org. January–March, 64(1) April–June, 64(2) July–September, 64(3) October–December, 64(4)

Research and Review Articles

Animal, avian, aquaculture and Kaiser LL, Martin AC, Steinberg FM. Re- Pest management Climate change issue, Cal Ag Web site, veterinary sciences search and outreach can lessen the over- Byron win ACE awards. 64(3):117. all burden of diabetes in farmworkers. Varela LG, Walker JTS, Lo PL, Rogers DJ. Corrections. 64(1):5. Favetto PH, Hoar BR, Myers DM, Tindall 64(1):17–21. FW New Zealand lessons may aid efforts to control light brown apple moth in Califor- J. Progesterone inserts may help to im- Suckow hired as Cal Ag’s new art director. Miller LMS. Cognitive and motivational nia. 64(1):6–12. prove breeding readiness in beef heifers. 64(3):117. 64(2):106–11. SF factors support health literacy and acqui- SIDEBAR: Smith RJ. National Research sition of new health information in later Council reviews pest status of light Jinks AD, Oltjen JW, Robinson PH, Calvert life. 64(4):189–94. AG brown apple moth. 64(1):9. Outlook CC. Fecal pats help to predict nutrient in- take by cattle during summer on Califor- Ober BA. Memory, brain and aging: Sokolow AD. Budget cuts threaten the nia’s annual rangelands. 64(2):101–5. SF The good, the bad and the promising. Plant sciences Williamson Act, California’s longstanding 64(4):174–82. AG farmland protection program. 64(3):118– Krasnow MN, Matthews MA, Smith RJ, et Richmond OMW, Chen SK, Risk BB, et al. 20. AL California black rails depend on irrigation- Sokolow AD, Varea Hammond S, Norton al. Distinctive symptoms differentiate four fed wetlands in the Sierra Nevada foot- M, Schmidt EE. California communities common types of berry shrivel disorder in hills. 64(2):85–93. SF deal with confl ict and adjustment at the grape. 64(3):155–9. Research news urban-agricultural edge. 64(3):121–8. AL Van Eenennaam AL, Weber KL, Cooprider SIDEBAR: Sokolow AD, Lobo RE, Lopus SE, Santibañez MP, Beede RH, Meadows R. Aging baby boomers to K, Drake DJ. Integrated data-collection Hukari K. Confi ned facilities create et al. Survey examines the adoption of challenge Golden State. 64(4):165–6. AG system tracks beef cattle from conception confl icts in San Diego County commu- perceived best management practices for SIDEBAR: Meadows R. Minority to carcass. 64(2):94–100. SF nities. 64(3):127. AL almond nutrition. 64(3):149–54. outreach and Alzheimer’s disease. 64(4):165 AG O’Hara KL, Grand LA, Whitcomb AA. Economics and public policy Land, air and water sciences Pruning reduces blister rust in sugar pine Meadows R. Sierra foothills research with minimal effects on tree growth. center celebrates 50 years of rangeland Schmidt EE, Thorne JH, Huber P, et al. A Long RF, Hanson BR, Fulton AE, Weston 64(1):31–6. productivity 64(2):57–62. SF new method is used to evaluate the stra- DP. Mitigation techniques reduce SIDEBAR: Meadows R. Protect- Shaw DV, Gordon TR, Larson KD, et al. tegic value of Fresno County farmland. sediment in runoff from furrow-irrigated ing rangelands from overgrazing. Strawberry breeding improves genetic re- 64(3):129–34. AL cropland. 64(3):135–40. 64(2):59. SF sistance to Verticillium wilt. 64(1):37–41. Volpe RJ III, Green R, Heien D, Howitt Mangiafi co SS, Newman J, Mochizuki Sierra Foothill Research and Extension R. Wine-grape production trends refl ect M, et al. Nurseries surveyed in Southern Center: Research locations. 64(2):51. SF evolving consumer demand over 30 California adopt best practices for water News departments years. 64(1):42–6. quality. 64(1):26–30. Ngo MA, Pinkerton KE, Freeland S, et al. Editorials/editorial overviews Human and community Airborne particles in the San Joaquin Val- development ley may affect human health. 64(1):12–6. Allen-Diaz B. Time for refl ection – time FW for action. 64(4):162. Aldwin CM, Yancura LA. Effects of stress on health and aging: Two paradoxes. O’Geen AT, Dahlgren RA, Swarowsky A, Craigmill AL, Tate KW. SFREC research 64(4):183–8. AG et al. Research connects soil hydrology sustains rangeland and oak woodlands. and stream water chemistry in California 64(2):54–6 (overview). SF Barrett GJ, Blackburn ML. The need for oak woodlands. 64(2):78–84. SF caregiver training is increasing as Califor- Klingborg D, Sams R. What can we do for nia ages. 64(4):201–7. AG Rice EC, Grismer ME. Dry-season soil wa- UC today? 64(1):2. SIDEBAR: Swanson PCW, Varcoe KP. ter repellency affects Tahoe Basin infi ltra- Sams RW. New strategies deliver Long-term care is an important consid- tion rates. 64(3):141–8. solutions-oriented science. 64(3):114. eration in fi nancial planning for later Special issue/section key life. 64(4):206. AG Natural resources Index 2010 Blackburn ML. Limited-income seniors AG = Aging report multiple chronic diseases in quality- McCreary DD. A quarter century of oak 64(1):47. of-life study. 64(4):195–200. AG woodland research in the Sierra foothills AL = Agricultural land supports oak restoration. 64(2):63–8. SF Blackburn ML, Gillogy B, Hauselt P. Re- Letters FW = Farmworker health Pasternack G, Fulton AA, Morford SL. search is needed to assess the unique and safety nutrition and wellness needs of aging Yuba River analysis aims to aid spring-run 64(1):5; 64(2):53; 64(3):117. Californians. 64(4):167–73. AG chinook salmon habitat rehabilitation. SF = Sierra Foothill 64(2):69–77. SF Block Joy A, Hudes M. High risk of de- Other news Research and pression among low-income women Cal Ag art director retires. 64(2):53. Extension Center raises awareness about treatment op- tions. 64(1):22–5.

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Olive production manuals ANR’s Olive Production Manual (2nd ed.) is the defi nitive guide to olive production in California. Notable additions to the 2005 edition include a chapter on defi cit irrigation, a greatly expanded chapter on olive oil production, and coverage of four new pests, including the olive fruit fl y. The manual includes production techniques for commercial growers worldwide — from orchard planning and maintenance to harvesting and postharvest processing, pollination, mechanical pruning and defi cit irrigation. Designed as a companion to the Olive Production Manual, the Organic Olive Production Manual includes detailed information on Clark Kelly Jack plant nutrition, economics, pest and An agritourism operation in the Apple Hill region of El Dorado County. weed control, management of olive wastes, converting existing orchards First survey of California agritourism operators to organic, and organic certifi cation and registration. Other topics include The pressures of urbanization and shrinking profi ts have orchard site selection, irrigation led California farmers to seek alternative approaches. needs, terrain, temperature, soil, Agritourism can provide growers with access to new olive fruit fl y damage, and how customers as well as bolster income. More than 2.4 million these vary for table versus oil olive visitors experienced agritourism at California farms production. and ranches in 2008. They stayed at guest ranches in the foothills, picked peaches in the Sacramento Valley, played Olive Production Manual (2nd ed.), ANR Pub No 3353, 180 pp, $35 in corn mazes up and down the state, shopped at on- Organic Olive Production Manual, ANR Pub No 3505, 112 pp, $18 farm stands, held weddings in fi elds and vineyards, and To order: participated in myriad other agriculture-related tourism activities. In the next issue of California Agriculture journal, Call (800) 994-8849 or (510) 665-2195 UC researchers present results of the fi rst statewide or go to http://anrcatalog.ucdavis.edu or economic survey of agritourism operators, to better visit your local UC Cooperative Extension offi ce understand the goals, needs and economic outlook for the state’s agritourism community.