Cooperative Extension University of California Santa Barbara and Ventura Counties Coast Counties Subtropicat 9{ezvs Fall 1990 m Introducing Ben Faber On Marc±i 1 of this year I took the position of Soils/Water/Subtropical Crops Farm Advisor for the counties of Santa Barbara and Ventura. It is a big, beautiful place and 1 am glad to be here. 1 am a U.C. Davis graduate of the Land Air Water Resources Department, and also have a background in fomology as a result of a Master's "egree and 3 years work in commercial nurseries. 1 work out of the Ventura office, but my responsibilities are for both counties and am available for aU subtropical grower's calls. A message left in the Santa Barbara or Ventura offices will gladly be answered. Santa Barbara office: (805)681-5630, Ventura office: (805)654-2952. A New Disease of Avocado Recently, U.C. plant pathologists have identifiea a disease of avocado that has been fotmd in most of the CTOwing areas of the state. The disease. Bacterial Canker, is thought to be caused by Pseudomonas syringae in South Africa, but this agent has not been verified here. Symptoms can be like Black Streak, with a dark streaking of the upper anker m scaffold branches, but the canker goes into the wood, unlike Black ' treak, and when a fresh canker is cut, an exudate appears. When the cariker dries, a suriken pit is left about the size of a silver dollar. The disease normally does not kill the tree, but yield reductions of 50% are found in South Africa. To date, trees with these symptoms have been found in Goleta, Carpinteria, Santa Paula and Saticoy. We would like to get an idea of the extent of the disease, so if you suspect a problem, f)lease call the Ventura office and eave a message. Thrips Greenhouse thrips are frequently the most apparent with the summer and fall seasons with damage to fruit. The insect builds up its population during the summer months and, if fruit from last year has been left unpicked, the bugs travel to young fruit. U.C. has released the parasitic Thripobius wasp the last two years, and it has become established in the release orchards. Rates of release were found to be effective with 2000 wasps per acre. Although they have become established it is not dear how rapidly they are spreading. If you are having thrips problems, would you please contact us. Use Less Pesticide Most pesticides work best at a given pH of the mixing solution, that is, it requires less material to get the job done if the pH of the water is appropriate for the material. The waters in the Ventura/Santa Barbara area range in pH from 6 to 8.4, with the majority m the 7.5 - 8.2 range. For many pesticides the ideal PH IS more add, around pH 6.5. requently, addition of as little as one cup of buffer (sold under various labels as an adjuvant or water modifier) per 100 gallons will suffice to improve the activity of the material. Pestiddes vary in their efficacy at different pH s so it is important to consult the product representative to determine the correct pH to which water should be adjusted. Simple, inexpensive test strips can be used to determine water pH. These test strips have various ranges in which they work. Some are wide range, pH 1-14, and others are narrow, such as pH 2-4 or 6-9. The accuracy declines the wider the range, so test strips with ranges of 6-9 are the best to use. What's Inside Page 2 Avocado Rootstock Trial Leaf Analysts Time Irrigation with Evapotranspiration Data Page 3 U.C. Publications Available for Drought Relief Upcoming Meetings
Transcript
Cooperative Extension University of California Santa Barbara and Ventura Counties
Coast CountiesSubtropicat9{ezvs
Fall 1990
m
Introducing BenFaber
On Marc±i 1 of this year I took theposition ofSoils/Water/SubtropicalCrops Farm Advisor for thecounties of Santa Barbara andVentura. It is a big, beautiful placeand 1 am glad to be here. 1 am aU.C. Davis graduate of the Land AirWater Resources Department, andalso have a background infomology as a result of a Master's"egree and 3 years work incommercial nurseries. 1 work out ofthe Ventura office, butmyresponsibilities are for both countiesand am available for aU subtropicalgrower's calls. A message left in theSanta Barbara or Ventura officeswill gladly be answered. SantaBarbara office: (805)681-5630,Ventura office: (805)654-2952.
A New Disease ofAvocado
Recently, U.C. plant pathologistshave identifiea a disease of avocadothat has been fotmd inmost of theCTOwing areas of the state. Thedisease. Bacterial Canker, is thoughtto be caused by Pseudomonassyringae in South Africa, but thisagent has not been verified here.Symptoms can be like Black Streak,with a dark streaking of the upper
anker
mscaffold branches, but the cankergoes into the wood, unlike Black' treak, and when a fresh canker is
cut, an exudate appears. When thecariker dries, a suriken pit is leftabout the size of a silver dollar. Thedisease normally does not kill thetree, but yield reductions of 50% arefound in South Africa. To date, treeswith these symptoms have beenfound in Goleta, Carpinteria, SantaPaula and Saticoy. We would like toget an idea of the extent of thedisease, so if you suspect a problem,f)lease call the Ventura office andeave a message.
ThripsGreenhouse thrips are frequentlythemost apparent with the summerand fall seasons with damage tofruit. The insect builds up itspopulation during the summermonths and, if fruit from last yearhas been left unpicked, the bugstravel to young fruit. U.C. hasreleased the parasitic Thripobiuswasp the last two years, and it hasbecome established in the releaseorchards. Rates of release werefound to be effective with 2000wasps per acre. Although they havebecome established it is not dearhow rapidly they are spreading. Ifyou are having thrips problems,would you please contact us.
Use Less Pesticide
Most pesticides work best at a givenpH of themixing solution, that is, itrequires less material to get the jobdone if the pH of the water is
appropriate for the material. Thewaters in the Ventura/SantaBarbara area range in pH from 6 to8.4, with themajoritym the 7.5 - 8.2range. Formany pesticides the idealPH IS more add, around pH 6.5.requently, addition of as little asone cup of buffer (sold undervarious labels as an adjuvant orwatermodifier) per 100 gallons willsuffice to improve the activity of thematerial. Pestiddes vary in theirefficacy at different pH s so it isimportant to consult the productrepresentative to determine thecorrect pH to which water shouldbe adjusted.Simple, inexpensive test strips canbe used to determine water pH.These test strips have variousranges in which they work. Someare wide range, pH 1-14, and othersare narrow, such as pH 2-4 or 6-9.The accuracy declines the wider therange, so test strips with ranges of6-9 are the best to use.
^^Four years after establishment,differences in yield performancehave been noted in Hass" avocadoon ten clonal rootstocks. These areresults from the fourth year of atrial headed byMary Lu Arpaia andGary Bender. The trial is located atthe University's South Coast FieldStation in Irvme. The data ispresented in Table 1.Themost distinctive result is the
relatively poor performance of theG755 series at this site. Duke 7, themostwidely planted clonalrootstock, on the other hand, seemsto give the neatest yield andnumber of fruit per tree. ToroCanyon appeared to be the most
precocious. There was no differencein the average fruit size from thedifferent rootstocks. These are stillpreliminary results and may not beapplicable to all avocado growingareas.
LeafAnalysisTime
This is the season to take thoseleaves in for tissue analysis. This is arelatively cheap way to determinefertilLzer requirements. The leavessampled should be those from thespring flush, not the summer.Healtny, fully expanded, leavesfrom non- flushing and non-fruitingterminals at chest height should betaken from around the tree. Leafanalysis from trees prior to coming
into commercial production aremore difficult to interpret,especially for nitrogen. Table 2 givesthe ranges of elements for themostfrequently foimd deficiencies andtoxicities in our area.
Irrigation withEvapotranspirationData
Currently, calling the GoletaWaterDistrict (967-8605), reading the"Montecito Life" or calling theVentura CounW ResourceConservation District (388-8425)will give you a value which isrelated to the water use of a crop.This value is called referenceevapotranspiration (ETokEvapotranspiration is the amoimt ofwater evaporated from the soilsurface or transpired from a tree orother crop. ETo values are given ininches, like rainfall, but in this caseit is inches of water lost from a
given area. Multiplying ETo by acoefficient that adjusts the ETovalue for a specific crop wiU givethe actual crop water requirement.For example:
Daily ETo=.2 in. Avocado crop coeficient=.650.2 in. X 0.65= 0.13 in. for that day.
Howmany gallons of water per treedoes that mean? For amatureorchard where 70% or more of theorchard floor is shaded and thereare 100 trees per acre:
27.000 gal X acre X 0.13 in= 35 gal./dayacre-in 100 trees day tree
With less than 70% cover, smallertrees, evapotranspiration isrelatively proportional to thedecrease in cover. With a yoimgorchard where only about 10% ofthe ground is shaded, trees wiU useonly about 10% of that of a matureorchard, or as in the example: 3.5gallons per tree.Guidelines from U.C. publications#21454 and #21428 below can befollowed to more fully exploit theuse of ET-based irrigationscheduling.Reference ET needs to be adjustedto your specific climatic conditions,a south facing slope, a wnndy vaUey,etc. ET is t)eing measured currently
Table 1. "Hass" Avocado Clonal Rootstock Trial
Yield (kg/tree) Number of fruit/treeYears after planting Years after planting
Values followed by the same letter wdthin a column are not statisticallydifferent. All trees were planted in 4/86, except Thomas and G1033
Table2. Ranges of Elements in Avocado Leaves
Ranges for Mature Trees
Element UnitDeficientless than
Adequate Excessmore than
Nitrogen N % 1.6 1.6-2.0 2.0Boron B ppm 10-20 50-100 100-250Iron Fe ppm 20-40 50-200 7Zinc Zn ppm 10-20 30-150 300Chloride CI ppm ? 7 0.25-0.50
There are a total of 17 elements important in the metabolism of trees, butthese 5 are of primary concern in our area.
y^aamo Coast CmmtksSuStropicaCO^vJs 2
•only in Santa Paula and Goleta, butsoon there will be data available forPiru, Ojai and Port Hueneme. Thestations are relatively inexpensive,but they still costmoney andrequire maintenance.With thediverse growing conditions foundin our area it would help if we hadmore detailed measurements.
A cheap way to obtain these ETorates, is to takemaximum andminimum temperatures and relatethese to the data from the fixedweather stations. Temperature is anitmortant, but not the only part ofET, wind and relative humiditybeing very important. The valuesobtamed would not be highlyaccurate, but would be extremelyuseful inmapping our area fordifferences relative to the weatherstations.
If anyone hasmax/mintemperature readings for theirrandr, would you please send themto me with the details of where theywere obtamed.
®U.C. PublicationsAvailable forDrought ReliefOur two counties are struggling invarious degrees with the effects ofbelow normal rainfall. TheUniversity has a variety ofpublications which can helpgrowers cope with the drought. Thepublications are available for anominal charge and cover a widerange of topics. These publicationsinclude:
Irrigation Scheduling: A Guide forEfficient On-Farm Management(#21454) $6.
Drip Irrigation Management ((#21259)$2.50.
Irrigation on Steep Land (#2825) $1.00.Measuring Irrigation Water (#2956)$1.00.
Even/body's Guide to Water Terms(321403) $0.50.
Determining Daily ReferenceEvapotranspiraiion (#21426) $1.00.Using Reference Evapotranspiraiionand Crop Coefficients to Estimate CropEvapotranspiraiion: Trees and Vines(#21428) $1.00.
To order these publications contactPublications, University ofCalifornia, ./Wiculture and NaturalResources, 6^1 San Pablo Ave.,Oakland, California 94608-1239.
UpcomingMeetingsSecondWorld Avocado
CongressThe Second World AvocadoCongress wiU be held in Orange,California from April 21-26,1991.Themeeting is being sponsored byThe University of California andThe Cahfomia Avocado Society.Final preparations for the meetingare underway and already there hasbeen tremendous internationalinterest. To date over 100 abstractshave been received.
Themeeting will be a uniqueopportunity for California growersto hear about the latest innovationsin avocado research, productionpractices and marketmg worldwide.There are three components to theCongress. There will be an optionalpre-congress tour to Mexico andCuatamala. In Mexico the tour willvisit the birthplace of the Fuerteavocado, the Iwchoacan productionwhich produces over 1 biUionpounds a year, and Cictamex, anavocado research center which hasdeveloped several new andinteresting avocado cuMvars. The
trip to Cuatamala wiU emphasizethe origins of the avocado and wiUinclude a visitwith Dr. EugenioScheiber who has contributedimmensely to the University's rootrot resistance program.
The second phase is the Congressitsdf in Orange. The Congress willbe a series of technical sessions andgrower oriented workshops. On thefinal day there will be a specialsession on worldwidemarketing,organized by the President of theC^omia Avocado Commission,Mark Affleck.
The final phase of the Congress willbe a tour of the Cahfomia avocadoindustry. This portion of themeeting will provide anopportunity to interact withgrowers and researchers fromaroimd the world.
If you wish to receive registrationmaterial or further information,please contactMary Lu Arpaia(714)787-3335 or Cindi McKeenan(714)787-3423.
Avocado Festival
Carpinteria, October 6 & 7Revel in the largest Cuacamole evermade.
California CherimoyaAssociation Field Trip
October 20,10 am - mid-aftemoon6790WorthWay, SomisCome see different varieties ofcherimoya and other types of rarefruits.
