University of California Cooperative Extension First Press Newsletter of Olive Oil production and Evaluation

Volume 1, Number 2 Winter 2005–06 Foliar Diseases on Olive Trees So Many Weeds, So Little Time... By Paul Vossen on the label, a legal requirement, is important for control longevity. The Weed control around young olive When the weather is wet, wet, wet, ideal time for the first application would trees is absolutely critical. Orchards That means leaf spot, leaf drop, be before any major fall rains. This is with inadequate weed control can take And poor fruit set. a problem for oil producers because 2-3 times longer to reach full production the fruit is usually still on the tree, so compared to orchards with no weed That’s the chorus to my new competition. In an example comparing Country-Western song; now I just need the compromise has been to apply it immediately after harvest. the influence of various types of orchard a tune and the rest of the lyrics. Kidding floor management treatments under aside, this is a warning, because I saw trees, there was a 25-61% decrease in a lot of defoliated and half-defoliated tree shoot growth and 25-45% decrease trees in 2005. in trunk diameter when weeds were Last year was a wet year, allowed to grow within 3’ (1 m) of the especially in the spring with trunks. Translating the growth rates numerous rainy periods right up of this experiment over to real olive to bloom. That was reflected in the orchards, means that it may take 16 to 32 number of orchards with significant years to get full sized trees instead of the Peacock Spot or Cercospora Leaf normal 8 to 10 years. Spot causing defoliation and fruit set Weeds not only remove water and problems. Those diseases also carry nutrients from the same area as the over on fallen leaves and existing High rainfall can cause severe peacock spot foraging tree roots, but the physical infections in the trees, starting off competition between weed roots and tree the new rainy season with lots The question arises, however, as roots also slows tree growth. Even when of inoculum. It is critical to put on a to the need for additional late winter extra water and fertilizers are applied protective spray as soon as possible or early spring sprays to supplement to the ground under the trees to offset after harvest and to strongly consider disease suppression into April and May. what the weeds use, the trees don’t grow applying a second spray if we continue There is no simple answer; no research as well. Good weed control is also one to have wet weather. that I have found anywhere indicates of the key factors in reducing alternate Fixed copper fungicide is still the that a second spray either is or is not bearing in olives by eliminating as much only thing proven to work. The copper necessary. We do know, however, that competition for shoot growth as possible mineral prevents infection of the leaf fixed copper fungicides wear off over in the “on” years. by the germinating fungus spores time, and that the more it rains, the less For non-organic growers, when there is a protective coating on effective they are. conventional herbicides have very the whole leaf. The different brands These are the points I use to specific known abilities to control certain and types (copper hydroxide, copper determine if a second spray in late weeds on certain soil types when used at oxychloride, tribasic copper sulfate, winter or early spring is warranted: labeled rates. Both pre-emergence and and copper oxide) have been shown in contact herbicides are more effective • Your trees had a high incidence various trials to work about the same. against certain weeds than others. See of disease last year with The most important factors are getting the University of California (cont. on p.2) it on at the right time, mixing the significant defoliation correct concentration, and getting good • Your orchard gets a lot of winter In this issue coverage. rainfall (> 30 inches/year) UC Davis Olive Oil 3 Covering all the leaves on both sides • Your trees received significant Calendar of Events 4 requires a high pressure sprayer in good rainfall before being sprayed Olive Fly Update 4 working order. Following the directions in the fall or winter First Press Newsletter of Olive Oil Production and Evaluation Winter 2005-06

(Weeds, cont. from p.1) Integrated Pest Management (IPM) Guidelines section Organically Acceptable Herbicides: on weed control for more detailed In recent years, several organic, information: http://www.ipm.ucdavis.edu/ contact-type herbicide products PMG/selectnewpest.olives.html . See side have appeared on the market. bar for specifics on some of the organic herbicides. These include the clove oil Mowing is not weed control products (Matran II produced by If the ground cover is green, it is still EcoSmart), and acetic acid/citric alive, stealing moisture and competing acid products, AllDown (produced with olive tree roots. Just because it is Weeds growing through a wood chip mulch by Summerset). These products shorter after being cut by a mower or will damage any green vegetation chewed off by a grazing animal does not European Olive Oil equate with removal of competition. New contacted including the leaves and growth in olive trees can begin as early as young stems of olive trees, though Prices on the Rise January, and certainly by February and they are safe if they are applied Rain at flowering time and a summer March, so for young trees, it is best to directly to woody stems and trunks. drought resulted in a substantial drop never have any weeds within 3’ of the Because these herbicides only kill in production for European olive oil. tree trunks - ever. Calling it a cover crop In Spain, the harvest was down 40%; does not make it any less of a weed, if it is contacted tissue, good coverage in Italy, it was down about 50-60%. competing with the olive trees. is essential. Thus, adding an Drought in parts of Greece has also drastically reduced production there. Mulch comparison trial organically acceptable surfactant According to Darrell Corti of Corti Organic and fabric mulches were is recommended. Because these Brothers market in Sacramento, the compared in a trial at the Santa Rosa materials lack residual activity, scarcity of fruit will force price increases Junior College super-high-density olive repeat applications will be needed orchard over the last two years. The all along the production system, to control new flushes of weeds. affecting refined as well as virgin olive fabric mulch we used was Lumite weed oil products. The price of rectified and cloth. It is a synthetic black fabric that The efficacy of all these materials is pomace oil have gone up in price to allows water to pass through, but not much less than synthetic herbicides. over 2 euros/kilo. The Italian National light, and weeds will not grow through Food grade acetic acid (vinegar) is Federation of Oil Traders (Federolio) it. It is guaranteed for 5 years and some organically acceptable and when experimental orchards have gotten 10 predicts a 40% increase in all oil used as a soil supplement, controls products from Italy. years of useful life out of it. We applied (Source: Corti Bros. newsletter, fall 2005) it in a 3’ wide strip on each side of the small annual weeds. The higher tree row and pinned it down with 6” the concentration of acetic acid, wire hoop stakes. The cost of weed cloth First Press is produced by the better it works, although food University of California for this orchard (rows spaced 12’ apart) grade typically is 8% acetic acid or was $1,480/acre, including wire staples Cooperative Extension less (pickling acetic acid is closer to 133 Aviation Blvd, Suite 109 and installation labor. This material Santa Rosa, CA 95403 controlled the weeds very well, but 15%). Repeat treatments are often 707-565-2621 required some attention to weed removal necessary as there is no residual www.cesonoma.ucdavis.edu immediately adjacent to the tree trunks. Paul Vossen, Farm Advisor activity. Generally, vegetation is The organic mulch was recycled sprayed to wet, which may require Alexandra Kicenik Devarenne, Staff yard waste. We applied it twice (once Research Assoc. (Editing & Layout) each year) with a side discharge mulch high volumes if weed density is Articles published herein may be spreader 3-4” deep in a 4’ wide band on high. Another organic herbicide reprinted, provided no advertisement for a top of the mowed weeds. The cost was that has appeared on the market commercial product is implied or imprinted. $4,235/acre based on a material cost of in the last few years is corn gluten Please credit First Press, University of $12/yd, plus delivery, and application California Cooperative Extension Sonoma meal, which is sold under many with a rented spreader for $150/day. The County, citing volume and number, or trade names. It is expensive and complete date of issue, followed by inclusive cost alone is prohibitive for using organic page numbers. Indicate © [date] The Regents mulch for weed control especially if it has failed to provide even minimal of the University of California. Photographs needs to be applied every year. It also weed control in the vast majority may not be reprinted without permission. didn’t work that well; existing annual © 2006 The Regents of the of California trials. Organic University of California weeds grew through the mulch in several herbicides are expensive at this places. —Paul Vossen 2 First Press Newsletter of Olive Oil Production and Evaluation Winter 2005-06 When Life Gives You Olives, Make Olive Oil By Alexandra Devarenne Like many other California a healthy smattering of other varieties. institutions, UC Davis has landscape The oldest trees, a couple of Missions olive trees. Lots of olive trees. Like that once stood next to the Jerome Davis two thousand olive trees. And these ranch house, date back to 1855. Dan trees produce olives. Lots of olives. The Flynn, the Olive Program Manager at yearly cost of maintaining these trees, UCD, estimates that the majority of the primarily spraying them to prevent fruit trees are at least 70 years old. set and then cleaning up and disposing The Pomology Department’s of the fruit that sets anyway, is about Wolfskill Experimental Orchard is home ripe Mission and the Heinz 57 mix of $60,000. And that cost does not include to another collection of olive trees, some other varieties from the experimental the costs, both tangible and intangible, dating back to 1860. The Wolfskill trees orchard. The result is a wonderful mild that result from people slipping on are about 75% Mission and 25% a mix of oil, ripe but with much more complexity fallen olives on the bike path. Late Blanquette, Rubra, Meski, Zarazi, and depth in the fruit than one usually Sal Genito, Director of Buildings Barouni, Meslale, Gigante di Cerignola, finds in later harvest oils. and Grounds for the UC Davis campus, Leccino, Lucca, Criolla, Sevillano and This year, the plan is to market a has been responsible for the care of the Manzanillo. second blend, called Gunrock after olive trees for the past twelve years. A The UC Grounds crew harvests the UC Davis mustang mascot (in case second generation Italian-American, Sal using a tractor mounted Verdegiglio you’re not up on your UC Davis history, was the right man in the right place to shaker that they purchased used from an Gun Rock was a real horse, related to come up with an innovative solution olive grower. On the occasions when the Man O’ War, who was brought to the to this ongoing olive issue. Got olives? shaker was in the shop, the crew used Davis farm in the 1920’s, as breeding Make olive oil! stock for the cavalry). Paul Vossen The eureka moment came in will create a blend chosen from the late November of 2004 while Sal various single oils the campus trees was visiting the scene of one of the have produced. The remainder bike path wipe outs caused by the of the oil will be sold as single combination of rain and squashed varietals. olives. As he stood on the athletic Genito is emphatic that they field on Russell Blvd, he was not compete with other California struck by the smell of... olive oil. producers, so the Davis oil will be “When life gives you lemons...” he sold only through UCD venues thought, and the UC Davis olive oil such as the bookstore, Picnic Day project was born. and the alumni website. Sal sees With back-up from the Harvester mounted on a tractor shakes olives onto tarps the olive oil as an opportunity to Associate Vice Chancellor for support and advance the California Facilities, Operations and Maintenance, the time-honored “whack-em-with-a- olive oil industry as well as to create Maurice Hollman, Sal forged on with rake” approach to get the olives down something Aggies can be proud of an experimental pressing in December onto tarps. There is great attention paid (send as gifts, bring to tailgate parties... of 2004 and another run in January of to harvest timing and swift processing; lots of possibilities). Proceeds from 2005. Flynn figures they made fifteen trips to the oil will be reinvested in olive oil They produced about 100 gallons, Butte View Olive Company for pressing research and education. of four different types: Ascolano, in the 2005-06 season. In this second The UC Davis Olive Project is an Mission, Koroneiki, and the Wolfskill year of the project they produced about inspiring story of garbage to gold. The blend. Their first release was rewarded 400 gallons. project will not only save the university with two gold medals at the Yolo The care exercised by Genito and the $60,000 in olive management, but County Fair. The oil had its public company in the production of their oil will net in the vicinity of $25,000 this debut at Picnic Day 2005, a UC Davis definitely shows. In an informal tasting, year. And that is not factoring in the risk event that draws thousands of visitors five of the six oils tasted were graded avoidance from slippery olive accidents. to campus. People lined up in great good or excellent by all the tasters. The It is a brilliant example of sustainability numbers to taste the oils, which were sixth, a Koroneiki, was deemed a bit too in action; they are simultaneously enthusiastically received. green, but still ranked above average reducing the waste stream, generating The campus olive trees are mostly and without defects. The Wolfskill revenue, and producing a healthful, Mission, Ascolano and Manzanillo, with blend this year is a silky blend of fairly delicious food. Well done, all!

3 Upcoming Educational Events

Sensory Evaluation of Olive Oil–Mar. 10 & 11, 2006 at UC Davis For info or to register: www.extension.ucdavis.edu or call 800-752-0881

Olive Grower’s Meeting–April 4, 2006 in Hollister For information, call Bill Coates, Farm Advisor, 831-637-5346

Olive Pruning Demonstration, Sonoma Valley–April 29, 2006 For info and reservations, call Vivian at 707-565-2303. Space is limited.

Olive Oil Production Olive Fly Control Update Seminars at the Yolo GF-120 Gets New Section 18 County Fair UCCE Farm Advisor Paul Vossen their county Agricultural Commissioner’s will present seminars on producing office, submit Notices of Intent and report olive oil in California at the Yolo their use of the product. County Fair. Yolo County began its The PAC is free, but requires that olive oil competition and education you take a test on pesticide safety. program in 2005, offering classes There is a study guide, Pesticide Safety: in olive oil appreciation before and A Reference Manual for Private Applicators after the olive oil judging at the fair. (pub. #3383), available for $7 from most This year the judging will take place Cooperative Extension offices or directly in March, but the fair educational from ANR Publications (800-994-8849 programs will still be offered during or http://anrcatalog.ucdavis.edu). Call the run of the fair, August 16-20. For Applying bait spray in a commercial orchard the Agricultural Commissioner’s office information call (530) 662-5393 or for more information, clarification or to www.yolocountyfair.net. Bait spray available to homeowners make an appointment. For the first time, GF-120 will be Plan now for control bookmark on your web browser. Go to available to non-commercial olive This is an excellent time to review http://www.ipm.ucdavis.edu/PMG/ growers. Under a new Section 18 your control options. The handout “Olive selectnewpest.olives.html for a wealth emergency exemption, homeowners will Fruit Fly” http:/ cesonoma.ucdavis.edu/ of information on pest identification, be allowed to purchase the product for hortic/pdf/olive_fruit_fly_info.pdf on monitoring and treatment. use on backyard trees from which fruit this website will give you an overview Monitoring for the olive fly in the late will be harvested for their own use. The of the various methods available. winter and early spring can give you an previous Sec. 18, which expired on Dec. 5, There will be a new set of official UC idea of the level of activity. This can help 2005, limited the use of GF-120 on olives guidelines available around March; you time a prophylactic bait spray or just to commercial growers. those will be posted here as well. Just give you a notion of what to expect. You In order to use GF-120, a homeowner in case you haven’t checked it out might want to get those traps ready soon: will have to hold a Private Applicator’s recently, the “UC Pest Management forewarned is forearmed. Certificate (PAC), obtain a permit from Guidelines for Olives” deserves a –Alexandra Devarenne

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