1

151 E. Carmel Street, San Marcos, CA 92078TEL. (760) 752-4711, FAX (760) 752-4725, E-mail: gsbender@ucdavis.edu

The Univ ersity of California prohibi ts discrimination or harassment of any person on t he basis of race, color, national origin, religion, sex, gender ident ity, pregnancy (including childbi rth, and medical conditions related topregnancy or childbirt h) , physical or mental disability , medical condition (cancer-relat ed or genetic charact er isti cs), ancestry , marital st at us, age, sexual orientation, cit izenship, or serv ice in t he unif ormed serv ices (asdefined by the Unif ormed Serv ices Employ ment and R eemploy ment Rights Act of 1994: service in the unif ormed serv ices includes membership, application f or membership, perf ormance of serv ice, application f orserv ice, or obligat ion f or serv ice in the unif ormed services) in any of its programs or activities. Univ ersity policy also prohibi ts reprisal or retaliation against any person in any of it s programs or activities f or making acomplaint of discrimination or sexual harassment or f or using or participating in t he inv estigation or resolut ion process of any such complaint. University policy is intended to be consistent with the prov isions of appl icableSt ate and F ederal laws. I nquir ies regarding the Univ ersity’s nondiscrimination policies may be directed to t he Affirmativ e Action/Equal Opportunity D irector, University of Calif ornia, Agriculture and N atural R esources,1111 F rankl in Street, 6th Floor , Oakland, CA 94607, (510) 987-0096.

Volume 7, No. 4October-December 2009

Editor’s Note:Please let us know if your mailing address has changed, or youwould like to add someone else to the mailing list. Call or e-mailthe farm advisor in the county where you live. Phone numbersand e-mail addresses can be found in the right column.

Please also let us know if there are specific topics that you wouldlike addressed in subtropical crop production. Copies of Topicsin Subtropics may also be downloaded from the countyCooperative Extension websites of the Farm Advisors listed.

Akif EskalenEditor of this issue

Topic Page

The state of Dothiorella Canker on Avocado inCalifornia 2

The Parent Washington navel orange tree- It’sfirst yearsvChester N RoistacherRetired Citrus Virologist, University ofCalifornia, Riverside

3

Mechanical Harvesting of California Tableand Oil Olives 7

Farm Advisors

Gary Bender – Subtropical Horticulture, San DiegoPhone: (760) 752-4711Email to: gsbender@ucdavis.eduWebsite: http://cesandiego.ucdavis.edu

Mary Bianchi – Horticulture/Water Management, SanLuis ObispoPhone: (805) 781-5949Email to: mlbianchi@ucdavis.eduWebsite: http://cesanluisobispo.ucdavis.edu

Ben Faber – Subtropical Horticulture, Ventura/SantaBarbaraPhone: (805) 645-1462Email to: bafaber@ucdavis.eduWebsite: http://ceventura.ucdavis.edu

Neil O’Connell – Citrus/Avocado, TularePhone: (559) 685-3309 ext 212Email to: nvoconnell@ucdavis.eduWebsite: http://cetulare.ucdavis.edu

Craig Kallsen – Subtropical Horticulture & Pistachios,KernPhone: (661) 868-6221Email to: cekallsen@ucdavis.eduWebsite: http://cekern.ucdavis.edu

Eta Takel e – Area Ag Economics AdvisorPhone: (951) 683-6491, ext 243Email to: ettakele@ucdavis.eduWebsite: http://ceriverside.ucdavis.edu

Jeanette Sutherli n for Mark Freeman – Citrus & NutCrops, Fresno/MaderaPhone: (559) 456-7285Email : mwfreeman@ucdavis.eduWebsite: http://cefresno.ucdavis.edu

2

The state of Dothiorella canker on avocado inCalifornia

Akif Eskalen, Virginia McDonaldCooperative Extension Specialist and Plant

PathologistDepartment of Plant Pathology, UC Riverside

akif.eskalen@ucr.edu,http://www.eskalenlab.ucr.edu

Branch and trunk canker on avocado was formerlyattributed to Dothiorella gregaria, hence the nameDothiorella canker. So far Botryopshaeria dothidea(anamorph: Fusicoccum aesculi) is the only knownspecies causing Dothiorella canker on avocado inCalifornia. Symptoms observed on avocado withDothiorella canker include shoot blight and dieback,leaf scorch, fruit rot, and cankers on branches andbark (Fig.1, 2, 3).

Fig. 1. Dothiorella branch dieback and canker symptoms onHass cv. avocado tree.

However, recent studies based on DNA analysessuggest greater species diversity of this pathogengroup than based on morphological characteristicsalone. Thus far, multiple species ofBotryosphaeriaceae have been found to cause thetypical Dothiorella canker (Fig3.) and stem-end rot(Fig 5) on avocado in California. Percent recoveryof Botryosphaeria spp. based on morphologicalcharacters ranged from 40-100% in Riversidecounty, 42-53% in Ventura county, 33% in SantaBarbara county, 60% in San Diego county and 32-60% in San Luis Obispo county.

Fig. 2. Dothiorella branch and shoot dieback symptoms onHass cv. avocado tree.

According to preliminary results from a continuingsurvey throughout avocado growing areas ofCalifornia, multiple species of Botryosphaeria(Neofusicoccum australe, B. dothidea, N. luteum,and N. parvum) were found.

Fig 3. Dothiorella perennial canker on branch

Pycnidia (overwintering structure) ofBotryosphaeriaceae species were also observed onold diseased avocado tree branches. SequencedrDNA fragments (ITS1, 5.8S rDNA, ITS2,amplified with ITS4 and ITS5 primers) werecompared with sequences deposited in GenBank.

3

Fig 4. Dothiorella perennial canker on trunk

Pathogenicity tests were conducted in thegreenhouse on 1-year-old avocado seedlings, Hasscv., with one randomly chosen isolate from each ofthe Botryosphaeriaceae species noted above. Fourreplicate seedlings were stem-wound inoculatedwith a mycelial plug and covered with Parafilm.Sterile PDA plugs were applied to four seedlings asa control. Over a period of 6 months, seedlings wereassessed for disease symptoms that includedbrowning of leaf edges and shoot dieback. Meanvascular lesion lengths on stems were 64, 66, 64,and 18 mm for B. dothidea, N. parvum, N. luteum,and N. australe, respectively. Each fungal isolatewas consistently reisolated from inoculatedseedlings, thus completing the pathogenicity test.To our knowledge, this is the first report of N.australe, N. luteum, and N. parvum recovered frombranch cankers on avocado in California.

Fig 4. Leaf scorch symptoms of Dothiorella canker

Fig 5. Stem end rot symptom of Dothiorella pathogens

These results are significant becauseBotryosphaeriaceae canker pathogens are known toenter the host plant through fresh wounds (pruning,frost, and mechanical). With high-density plantingbecoming more common, which requires intensivepruning, the transmission rate of these pathogenscould increase in California avocado groves. TheEskalen laboratory is currently investigatingcontrol measures for dothiorella canker and stem-end rot pathogens.

Refernces:

V. McDonald, S. Lynch, and A. Eskalen. 2009. Firstreport of Neofusicoccum australe, N. luteum, and N.parvum associated with avocado branch canker inCalifornia. Plant Disease. V.93, No.9. p.967.

Pedro W. Crous, Bernard Slippers, Michael J. Wingfield,John Rheeder, Walter F.O. Marasas, Alan J.L. Philips,Artur Alves, Treena Burgess, Paul Barber and JohannesZ. Groenewald. 2006. Phylogenetic lineages in theBotryosphaeriaceae. Stud. Mycol. 55:235.

F. F. Halma and G. A. Zentmyer. 1953. RelativeSusceptibility of Guatemalan and Mexican avocadovarieties to Dothiorella Canker. Calif. Avocado Soc.Yearb. 38:156.

W. F. T. Hartill and K. R. Everett. 2002. Inoculumsources and infection pathways of pathogenscausing stem-end rots of ‘Hass’ avocado (Perseaamericana) New Zealand Journal of Crop Hortic. Sci.30:249.

4

The Parent Washington navel orangetree- It’s first years

Chester N RoistacherRetired Citrus Virologist, University of

California, Riverside.Part-I

In January, 1995 during my second consultancyvisit to Thailand, I was asked to lecture to the staffof Kasetsart University located in Bangkok. Thelecture was on the problems of the greening diseasein their country where trees die between 4 and 8years and rarely reach 12 years of age. The lecturewas well attended by many young staff andscientists. During the lecture I showed them apicture of a large citrus tree dying with the greeningdisease (Fig.1). While showing this picture, almosthalf the audience raised their hands and one by one,said that picture of this tree could not have beentaken in Thailand for they had never seen a tree ofthis size. In truth, the picture was taken in Thailandby Dr. E.C. Calavan who visited Thailand in 1975and gave me this slide. In truth, all of these youngerscientists assumed that citrus trees lived a shortperiod of time and were replaced. I then showedthem the picture of the Parent navel orange treewhich was 120 years old the time of my lecture andthey could not grasp that a citrus tree could live thatlong. Today, this historical parent navel orange treelocated at the corner of Arlington and MagnoliaAvenues in Riverside is 134 years old (Fig. 2). It isstill bearing large beautiful fruit and is in goodhealth. In this first of two articles I wish to relate alittle of the early history of this important tree.

The first introduction of budwood of the navelorange from Bahia, Brazil to Washington, D.C.A little known history on the introduction of thefirst budwood is contained in a letter in the files ofthe National Archives in Washington D.C. (Mooreand Moore, 1951). It was written by Richard A.Edes, U.S. Consul in Bahia, Brazil and datedJanuary 21, 1871. The budwood was sent to HoraceCapron, Commissioner of Agriculture and reads asfollows: "I have the honor to acknowledge receiptof your communication of December 15, 1870. Thefavorite orange of this part of Brazil, and of whichthis province is celebrated is named the navelorange. This orange contains no seed and fortransplanting, the cuttings of the tree must be used.

Such cuttings are usually put into a basket of earthof the diameter of about 10 inches and the basketsto the number of 8 or 10 are packed in a large casewith a glass top. In the summer season it can beforwarded without much risk. I shall be glad toforward whatever number of cuttings may bedesired and would suggest the month of May asbeing the most suitable for the purpose." Capronreplied to Edes on February 21, 1871 and on April20, 1871, Edes acknowledged the letter and saidthat he would forward the desired navel orangecuttings.

The first successful introduction of thenavel orange. (Dorsett, Shamel and Popenoe, 1917)reported on the recollection of William Saundersmade some 29 years after receipt of budwood of theBahia navel from Brazil. Saunders was thenSuperintendent of the Gardens and Grounds of theUSDA in Washington D.C. and recalled that "Sometime in 1869 the then Commissioner of Agriculture,Horace Capron, brought to my office and read me aletter which he had just received from acorrespondent in Bahia, Brazil. Among othermatters, special mention was made of a fineseedless orange of large size and fine flavor.Thinking that it might be of value in this country, Inoted the address of the writer and sent a letterasking to be the recipient of a few plants of thisorange. This request brought, in course of time, asmall box of orange twigs, utterly dry and useless. Iimmediately sent a letter requesting that someonebe employed to graft a few trees on young stocksand that all expenses would be paid by theDepartment. Ul timately a box arrived containing 12newly budded trees and being packed as I hadsuggested, were in fairly good condition." In anarticle by (Webber (1940), he believed that theBrazilian correspondent was the Reverend F.I.G.Schneider. It is possible that the initial letter wasthat of Richard Edes and the date was not in 1869,but January of 1871. The second shipment ofbudded trees may have been sent by the ReverendF.I.C. Schneider to William Saunders, as suggestedby Webber (1940).

Shipment of the navel orange to Luther andEliza Tibbets (Fig. 3). There is much debate on thearrival of the parent navel orange trees to Riverside,California from Washington D.C. After the trees

5

were received from Bahia, Brazil they were buddedto a rootstock by Saunders in Washington and mostwere sent to Florida, where they did poorly.Accounts put Eliza Tibbets in Washington, D.C. in1873 (McClain, 1976). "She was an old friend ofthe Saunders and while visiting with them, Mr.Saunders showed her the young navel orange trees."McClain further stated "That no one made note ofthis historic event is not surprising since newvarieties were constantly being brought into the areaby the new settlers.

Fig. 1 This photo of a dying citrus was taken by Dr. E.C.Calavan in 1975 near Bangkok, Thailand. When this slide wasshown to a group of faculty and students during a lecture inBangkok in 1995 many in the audience objected and felt thepicture could not have been taken in Thailand since, as theyvoiced, there were no such large trees citrus trees growing inthe country. In truth, the picture was taken 20 years previouslybut since the average age that a citrus tree survives in Thailandis 8 to 12 years before dying from HLB (Grenzebach 1995),most of the people in the audience would not have seen orremembered that before HLB, trees once grew to a large sizein their country.

The new colony of Riverside was only 4 to 5 yearsold when the trees arrived." Esther Klotz, arenowned historian on the tree, in hand writtennotes on the Washington navel cited evidence forthe arrival of the tree on December 10th 1873 afterbeing a month on the way (Klotz, 1972).

Fig. 2. Showing the 136 year old parent Washington navelorange tree, located in Riverside, California. The tree is aliveand healthy and still bearing fruit. This picture was taken inDecember, 2009 and the tree has to be one of the mostimportant, if NOT the most important plant introduction evermade into the United States of America. Possibly allWashington navel orange trees throughout the world arederived from this one parent tree.

Fig. 3.Luther and Eliza Tibbets. Accounts put Eliza Tibbets inWashington, D.C. in 1873. She was shown the navel orangetrees by Mr. Saunders who was then Superintendent of theGardens and Grounds of the USDA in Washington D.C. andwho she had befriended and known when she lived inWashington. She showed an interest in having trees shipped toher home in Riverside. It is believed that Luther Tibbets droveby horse and wagon from Riverside to Los Angeles to pick upthe trees.

6

The two parent navel orange trees at the Tibbets'home in Riverside about 1877 (Fig 4). McClain(1976) reported that the fact that the trees arrivedsafe and sound was a small miracle. The trees wereshipped by rail to Gilroy via San Francisco, andthen by stage coach from San Francisco to LosAngeles, taking 3 days for the stage trip. She wrotethat Luther and Eliza Tibbets drove 65 miles in theirbuckboard wagon from Riverside to pick up theprecious package. It is reported that perhaps threetrees were planted, but that one had been trampledby a cow. It is widely accepted that Eliza Tibbetstook care of these trees and used dishwater to keepthem alive, since they were not connected up to thecanal water (due to the contentious behavior of Mr.Tibbets who refused to pay for water rights).

Fig.4.Showing the two parent navel trees at the Tibbets’ homeabout 1877. It is reported that perhaps three trees wereplanted, but that one had been trampled by a cow. It is widelyaccepted that Eliza Tibbets took care of these trees and useddishwater to keep them alive, since they were not connectedup to the canal water.

The first fruiting of the Washington navel orange.McClain (1976) reported that the first navel orangeswere not produced on the trees at the Tibbets home,but rather from that of the neighbors McCoy andCover who had budded existing seedling trees withbudwood from the Tibbets' trees when they had firstarrived. Commercial exposure came with the areasfirst citrus fair in 1879 where the seedless naveloranges won first prize over all competition. Thiscreated a demand for budwood and a fence had tobe erected around the two original trees at theTibbets’ home to prevent theft. It is said that $1.00 abud was paid by people anxious to get buds.On April 23rd 1902, one of the two parent navelorange trees was transplanted from the Tibbets

homestead to its present location in a small fencedpark at the corner of Arlington Avenue andMagnolia Avenue. The remaining parent navelorange tree was transplanted on May 8th, 1903 tothe courtyard of the Glenwood tavern, now knownas the Mission Inn. Shown in Fig. 5 is PresidentTheodore Roosevelt assisting in the plantingceremony.

Fig. 5. President Theodore Roosevelt assisting in the plantingof one of the two Washington navel orange tree at the MissionInn (then known as the Glenwood Tavern). The fact that aPresident of the United States would transplant this historictree was testimony to its importance and significance

The fact that a President of the UnitedStates would transplant this historic tree wastestimony to its importance and significance. OnDecember 4th, 1922 the Riverside Daily Pressreported that the parent Washington navel orangetree, which had been replanted to the Mission Innpatio in 1903, had been removed following itsdeath. It was noted by local townspeople that thetree had begun to fail rapidly after the death ofPresident Theodore Roosevelt in 1919 who hadassisted in the transplanting ceremony.

7

Fig. 6. The parent Washington navel orange tree in its newhome at the corner of Magnolia and Arlington Avenues about1920. The tree appeared in good health as shown in thispicture.

A new home. Figure 6 shows the parentWashington navel orange tree in its new home atthe corner of Magnolia and Arlington Avenuesabout 1920. It is in a small park dedicated as the`Eliza Tibbets Memorial Park’ under the care of theRiverside Parks Department. The transplanted treeappeared in good health as shown in this picture.The parent Washington navel orange tree in itssmall park in Riverside began to show decline about1915-1917. In Fig. 7 we see the tree in very poorcondition suffering from Phytophthora (gummosis)root rot. The loss of this tree historic tree wouldhave been tragic, since it was one of the twooriginal parent trees still surviving from the firstshipment to California in 1873. To be continued innext issue.

Fig. 7. The parent Washington navel orange tree in its smallpark in Riverside began to show decline about 1915-1917. Wecan see the tree in very poor condition suffering fromPhytophthora (gummosis) root rot. This tree was on a sweetorange rootstock and highly susceptible to gummosis root rot.

References

Dorsett, P.H., A.D. Shamel and W. Popenoe. 1917. Thenavel orange of Bahia with notes on some little knownBrazilian fruits. USDA Bul. No 445, Washington D.C.USDA Bul. No. 445. Washington, 1917.

Klotz, Esther 1972. Riverside and the day the bankbroke. Source Reprinted in Klotz, Esther. Riverside:Rubidoux Press, 1972. From Riverside Enterprise, April20, 1900.

McClain, Cathi. 1976. A new look at Eliza Tibbets.Citrograph 61:(12) 449-454 Oct. 1976.

Moore, Frank and Bill. 1951. When was the navelorange imported? California Citrograph 36:219

Webber, J. H. 1940. Patron Saint California orange.Credit to Rev. F.I.C. Schneider for introducing theWashington navel. California Citrograph 25:224

Mechanical Harvesting of CaliforniaTable and Oil Olives

L. Ferguson1, S. M. Lee3, J.X. Guinard3

U. A. Rosa2, J. Burns4, H. Krueger1, P.M. Vossen1,K. Glozer1

1-Department of Plant Sciences, Wickson Hall2-Department of Biological and Agricultural Engineering,

Bainer Hall3-Department of Food Science and Technology, RMI South

University of California Davis, One Shields Ave. Davis CA95616 USA

4-Department of Plant Sciences, University of Florida

INTRODUCTIONWhen and how olives are harvested are among themost important factors in both the quantity andquality, and therefore value of processed tableolives and olive oil. Efficiency of harvest, thepercent of fruit removed from the total crop on thetree, is the first component of total processedproduct value. Quality of the fruit, partially afunction of maturity for table olives and oil, andsize for table olives, and condition when deliveredto the processing facility is the second componentof total processed oil or table value. Harvesting isthe final step in field production of an olive crop,but if done at the wrong time or in the wrong way itcan markedly affect net return to the grower.However, within limits, depending upon the use ofthe harvested fruit, the two factors are rankeddifferently.

Efficiency of harvest removal and collection is themore important factor in developing mechanicalharvesting for olives destined for olive oil. Fruitquality and condition, within limits, is secondary.Fruit quality and condition, the potential forproducing an acceptable table fruit when deliveredto the processing plant, is the most important factorin developing mechanical harvesting in olivesdestined for table fruit. Efficiency of harvest issecondary. Given the relative size of the world’solive oil and table olive industries, and the relative

8

difficulty of developing mechanical harvesting foroil or table fruit, successful harvesting of olives foroil is being developed sooner and more easily thansuccessful harvesting of olives for table fruitprocessing.

The major reason for developing mechanical oliveharvesting is the high cost of hand harvesting;currently the single most expensive cost in oliveproduction worldwide. In California’s San JoaquinValley the 2009 average hand harvest cost per tonwas approximately 50% of the gross return per ton.Other major olive producing countries report similarpercentages. Further, in most olive producingcountries adequate supplies of harvest labor are lessavailable, and the liability to meet safe working andfair employment standards is becoming moredifficult.

These two factors, the potential for oliveharvesting methods to affect the quantity andquality of the final processed product, and harvestcosts, mean efforts to develop mechanicalharvesting for olives must be dictated by both thequality of the table olives or oil produced and by thereduction in harvest costs. Though, as discussedabove these factors, within limits, rank differentlydepending upon the final use of the harvested fruit.However, reducing the cost of olive harvest is of noadvantage if the harvested olives cannot besuccessfully processed into high quality table olivesor oil.

RECENT OLIVE MECHANICALHARVESTING RESEARCH IN CALIFORNIA

California’s table olive industry is primarily basedupon a single cultivar, the ‘Manzanillo’, processedin a style called “California black ripe”. Muchsmaller amounts of ‘Mission’, ‘Sevillano’ and‘Ascolano’ are also processed in this style. Thename is misleading as the fruit is harvestedphysiologically immature, therefore the abscissionzone is unformed, and the fruit has a higher FruitRemoval Force (FRF) force than oil olives, whichare generally harvested at physiological maturity.Immature ‘Manzanillos’ routinely have an FRF ashigh as 1 kg when harvested. When physiologicallymature the FRF is less than 0.10 kg. Thisimmaturity, combined with the traditionally largetrees, 4 – 6 m tall and 3 - m ft wide, and pendulous,

thick growth habit of California’s irrigated‘Manzanillo’ olive orchards makes mechanicalharvesting difficult.

Mechanical harvesti ng of oil olives has developedmuch more rapidly because new olive oil cultivarshave been bred for slow growth, planted in high tosuper high densities, 486 – 1800 trees per hectare,and trellised or trained in a hedgerow that is easilyharvested by over the row grape, coffee andblueberry harvesters. The olive oil industry pursuedthe long term goal of tree genetics, the mid termgoal of new orchard conformations with hedgerowtree training and pruning, and the short term goal ofadapting existing mechanical harvesters from othercrops..

Similarly, if the California table olive industry is toultimately succeed it must also pursue tree breeding,new orchard conformation with hedgerow trainingand pruning, and mechanical harvesting technology.However, there is no current table olive treebreeding program in California and only onecurrently active in Spain. Therefore, California’stable olive industry must pursue the short andmidterm goals as follows. For the short term thismeans developing a picking technology and treepruning method for the current California tableolive orchards. For the midterm this meansdeveloping a picking technology and new orchardconformations, with new training and pruningmethods.Therefore, the focus of California Black table olivemechanical harvesting research for the last decadehas been on dual objectives; developing successfulmechanical harvesting for current and neworchards. The effort has required the simultaneousinput of University of California’s agriculturalengineers, plant physiologists, food scientists,agricultural economists and horticulturists,California’s two major table olive processors,multiple commercial mechanical harvesterfabricator/contractors, and the support of theCalifornia Olive Commi ttee (COC). The projectincluded research cooperators from Spain andArgentina and has been conducted in California,Argentina and Portugal. The project has had twodistinct phases and a long evolution as newharvesters have been evaluated and modified. Only

Deleted: ¶

9

the most recent summarized 2008 and 2009research results will be given here.

a) Table Olive Mechanical Harvesting Researchfrom 1996 through 1999.The first phase was initiated in 1996 with a callfrom the olive marketing order, the California OliveCommittee (COC) to harvest equipment fabricatorsfor potential olive harvesters. Agright of Madera,CA presented a modified wine grape harvester witha “canopy contact” head. Research trials byFerguson et al. (1999) from 1996 through 1999demonstrated this picking technology was veryefficient if the rods of the harvester head madedirect contact with the portion of the canopy bearingfruit. However, the rounded shape of a traditionalolive tree rendered all but the portion of the treecanopy within the horizontal and vertical range ofthe picking rods, and facing the row middles,unharvestable. The harvest head could remove upto 98% of the canopy fruit facing the middle of therow, but fruit above or below the harvester head, orin the canopy between trees, was removed with lessthan 50% efficiency. Later versions of this machinehave multiple heads that could move along ahorizontal axis deeper into the canopy, slightlyimproving the overall harvester efficiency, (Fig. 1).Additionally, the catch frames with the earlyiterations of the canopy contact head harvesterswere incompetent, losing 19% of the fruit removedby the picking head. This overall removalefficiency put final fruit harvester efficiency atapproximately 60% or less. Additionally, the fruitwas often bruised and cut, Fig. 2, and unacceptablefor processing as California black ripe table olives.With the appearance of the olive fly (Bactorceraolea)) in 1999, mechanical harvesting research wasdiscontinued.

b) Table Olive Mechanical Harvesting Researchfrom 2006 through 2009.Though most California table olive orchards aregenerally part of a diversified ranch operation, theincreasing hand harvest costs, and stagnant oliveprices of recent years, precipitated the removal ofan increasing number of olive orchards. The reasonwas the increasing table olive hand harvest costswere eroding profitability. However, the UnitedStates is still the single largest table olive market inthe world, giving California growers a marketing

advantage. Recognizing this problem, and thepotential opportunity, the remaining olive growersorganized for the resumption of mechanicalharvesting research, again supported by the COC, inlate 2005.

Fig. 1. 2008 version of the canopy contact head oliveharvester originally modified from wine grape harvesters in1996. This harvester can be used as one of a pair, or as asingle that does both sides of the tree. The head is mounted ona catch frame that conveys the fruit back to a field bin.

When research was resumed the in 2006 there weretwo parallel and equal objectives. The first was todevelop an efficient picking technology. Once thiswas defined, how to propel the harvester, catch thefruit, and convey it to a bin could be designedaround the picking technology. The secondobjective was to identify an abscission compoundthat would decrease the FRF, and make theharvester more efficient.As the following results will demonstrate; twoviable picking technologies have been identified.However, development of an abscission compoundremains as elusive as it has for the past 50 years.(Martin; 1994; Burns et al., 2008) As thediscussion of abscission in earlier in this manuscriptconcluded, development of an abscission in agent,much less obtaining a registration for a crop assmall as olives, remains a goal not achievablewithin the next decade. Both the California andinternational research from 2006 through 2009 haveidentified no new potential candidates andconfirmed the earlier results that ethylene releasingcompounds are as unreliable as previouslydemonstrated. (Burns et al., 2008; Martin, 1994) Asa result, the mechanical harvesters being developed

10

for the California table olive industry need toachieve economic efficiency without the use of fruitloosening agents.

The two viable picking technologies currently beingevaluated are canopy contact harvesting heads, andtrunk shakers. The canopy contact harvester can besuccessfully used in existing orchards that havebeen pruned to a hedgerow. It can also be used fornewer high density orchards trained to a hedgerow.The trunk shaking technology can be used in newhigh density orchards with straight trunks but isineffective in older conventionally trained orchards.Interestingly, both have approximately the samefinal harvest efficiency, from 58% to 63%.However, the mechanism of fruit removal isdifferent, the two machines harvest different partsof the canopy more efficiently, and the potential fortree damage is different. However, the final fruitquality as determined by grade at the receivingstation of the olive processor is remarkably similar.

Fig. 2. Bruising and cutting damage produced by Earlyversion of the the canopy contact head mechanical oliveharvester in ‘Manzanillo’ olives destined for California blackripe olive processing.

Improving Harvester Efficiency with OrchardModificationThe new super high density olive oil orchards beingdeveloped in Argentina, Spain, Tunisia andCalifornia among others were all developed asorchards that could be harvested with existingmechanical harvesters; wine grape, blueberry andcoffee harvesters. All are straddle type harvesterswith limited height and width. Figure 3 is an

example of a super high density olive orchard beingharvested by an unmodified grape harvester.

Our early research suggested high density hedgeroworchards could improve the efficiency of bothcanopy contact and hedgerow orchards. (Fergusonet al., 1999) Efficiency would improve with canopycontact harvesters because the olives would be moreaccessible to the harvest head rods as shown infigure 4. Efficiency would improve with trunkshakers because more of the olives would be closerto the axis of shaking, the main trunk, as shown infigure 5.

Based on this concept a high density hedgeroworchard with three different training treatments wasestablished in 2002. The objective was to produce atree no more than 4 m tall, 2 m wide and skirted upto 1 m, and spaced at 3.7 m in the row and 5.5 mbetween rows with 490 trees/ha. The trainingtreatments were a free standing espalier with all themajor structural branches trained within the treerow, an espalier woven vertically through threehorizontal wires at 1, 2, and 3 m, shown in Figure 9,a treatment espaliered and clipped to the trelliswires, and a conventionally trained control. Theobjective was to determine if these training methodsdecreased yields per acre.

This orchard began bearing in year 4. None of thethree trellised training treatments has a significantlydecreased yield relative to the conventionallypruned control. This suggests ‘Manzanillo’ tableolive orchards can be trained and pruned formechanical harvesting with both canopy contact andtrunk shaking harvesters without significant lossesin yield. However, data will be collected until theyields plateau for at least three successive years.

The next step in this ongoing research program willbe to determine if the canopy contact harvesters andtrunk shaking harvesters will have higher finalefficiencies in high density hedgerow orchards, orin conventional orchards that have been topped,hedged and skirted to produce a modifiedhedgerow. These trials will be conducted in 2010.At that time we also hope to determine the fieldoperating parameters of ground speed, acres perhour, tons per hour and cost per ton and per hour toharvest the olives. The final project goal is an

11

online interactive harvest calculator which willallow growers to enter their orchard parameters todetermine if hand harvest or machine harvestproduces a better net return.

Fig 3. Typical super high density olive oil orchard and straddleharvester.

Fig 4. Nine year old high density, 480 tree/ha, trellised‘Manzanillo’ table olive hedgerow planting.

Fig 5. Canopy contact head harvester in hedgerow oliveorchard.

CONCLUSIONSInterestingly, though olives are one of the world’soldest continuously produced tree crops thetechnology of production has remained unchangedthrough even the industrial revolution, a revolutionthat had a greater impact on agriculture than anyother sector. Now however, the changes in oliveorchard development and olive harvestingtechnology are bringing this traditional crop into thetwenty first century. Within ten years all trulycommercial table and oil olives will bemechanically harvested. The research has been anongoing process of defining, and ranking thelimiting factors, while pursuing all of themsimultaneously. For table olives two pickingtechnologies have been developed. The mostlimiting factor, fruit damage, has been eliminated.Now viable harvesting machines must be developedfor both picking technologies and the orchards bestsuited to these harvest technologies must bedefined.

REFERENCES

Arquero, O., D. Barranco, C. Nararro, and R Perez de Torro.1997. Influence of Monopotassium phosphate on oliveabscission. Olea 24:116-118

Banno, K., G. C. Martin, and R.M. Carlson. 1993. The role ofphosphorous as an olve leaf and fruit abscission inducingagent. J. Amer. Soc. Hort. Sci. 118:599-604.

Barranco, D., C.C. de Toro, M. Oria, H.F. Rapoport.2002. Monopotassium Phosphate for olive fruitabscission. Acta Horticulturae 586:263-266.

Ben-Tal, Y. and M. Wodner. 1994. Chemical looseningof olive pedicels for mechanical harvesting. ActaHorticulturae 356:297-304.

Burns, J.K., L. Ferguson, K. Glozer, W.H. Krueger, R.C.Rosecrance . 2008. Screening fruit loosening agents forblack ripe processed table olives. HortScience 43:1449-1453.

Camerini, F., F. Bartolozzi, G. Vergari, G. Fontanazza.1999. Analysis of the effects of ten years of mechanicalpruning on the yield and certain morphological indexesin an olive orchard. Acta Horticulturae 474:203-207.

Castro-Garcia S, UA Rosa , CJ Gliever, D.Smith,JKBurns , WH Krueger, L. Ferguson, K. Glozer. . 2009.Evaluation of table olive damage during harvest with acanopy shake-and-catch system. HortTech 19:260-266.

12

Ferguson, L., H. Reyes and P. Metheny. 1999.Mechanical harvesting and hedging of California blackripe (Olea europea) Cv. ‘Manzanillo’ table olives. ActaHorticulturae 474; 193– 96.

Fridley, R.B. 1969. Tree fruit and grape harvestmechanization progress and problems. HortScience4:235-237.

Fridley, R. B., H.T. Hartman, J.J. Melschau, P. Chen,and J. Whisler. 1971. Olive Harvest Mechanization inCalifornia. California Agricultural Experiment StationBulletin 855.

Gerasopoulous, D., I. Metzdakis, E. Naoufel. 1999.Ethephon sprays affect harvest parameters of‘Mastoides’ olives. Acta Horticulturae 474:223-225.

Klonsky, K.M. 2009. What yield, harvest cost and priceare profitable? 2009. PowerPoint (24 slides)http://groups.ucanr.org/olive_harvest/Statewide_Olive_Days/

Klonsky, K. M., P.M.Vossen, J. H. Connell and P.Livingston. 2007. Sample costs to establish high densityolive orchards and produce oil.Http://coststudies.ucdavis.edu.

Kouraba, K., J. Gil Ribes, G.L. Blanco Roban, M.A. deJaime Revuelta and D. Barranco Navero. 2004.Suitability of olive varieties for mechanical harvestershaking. Olivae 101:39-43.

Krueger, W.H. 2009. California Table olives of theFuture. 2009. PDF. 28 slides.http://groups.ucanr.org/olive_harvest/Statewide_Olive_Days/

Lee, S. H., J.X. Guinard, and L. Ferguson. 2009.Sensory characteristics and consumer acceptance ofmechanically harvested California black olives. PDF. 49slides.http://groups.ucanr.org/olive_harvest/Statewide_Olive_Days/

Martin, G. C. 1994. Mechanical olive Harvest: use offruit loosening agents. Acta Horticulturae 356:284-291.

Metzdakis, I. 1999. Field studies for mechanicalharvesting by using chemicals for the loosening of olivepedicel on cv. Koroneiki. Acta Horticulturae 474:197-201.

Tombesi, A. 1990. Physiological and mechanicaladvances in olive harvesting. Acta Horticulturae.286:399-412.

Tombesi, A., M. Boco, M. Pili and D. Far inelli. 2002.Influence of canopy density on eff iciency of trunkshaker olive mechanical harvesting. Acta Horticulturae586:291-294.

Visco T., M. Molfese, M. Cipolletti, R. Corradetti andA. Tombesi. 2004. Influence of training system, variety,and fruit ripening on eff iciency of mechanical harvestingof young olive trees in Abruzzo, Italy. Abstract; CM 28.Fifth International Symposium on Olive Growing;September 27 – October 2, 2004. Izmir, Turkey.

Vossen, P., L. Diggs and L. Mendes. 2004 Santa RosaJunior College’s super high density orchard. Olint:?October, 2004:6-8