UNIVERSITY OF CALIFORNIA COOPERATIVE EXTENSION GLENN COUNTY P.O. Box 697 (821 E. South St.), Orland, CA (530) FAX (530)

Transcription

1 UNIVERSITY OF CALIFORNIA COOPERATIVE EXTENSION GLENN COUNTY P.O. Bx 697 (821 E. Suth St.), Orland, CA (530) FAX (530) August 1, 2012 Vl. XIII, N. 3 In This Issue Advisr Retirement/New Psitins Alternaria Leaf Spt and Leaf Rust f Almnd New Almnd Cst Study fr the Sacrament Valley 2012 Navel Orangewrm Why are Sme Individuals Trees Turning Yellw, are Weak, r Nt Grwing? Cping with Rain at Harvest Sizing Prunes at Harvest Managing Prunes Thrugh Harvest Distinguishing Between Branch Dieback Disrders New Prune Manual Bill Krueger Farm Advisr In accrdance with applicable State and Federal laws and University plicy, the University f Califrnia des nt discriminate in any f its plicies, prcedures, r practices n the basis f race, religin, clr, natinal rigin, sex, marital status, sexual rientatin, veteran status, age, medical cnditin, r handicap. Inquiries regarding this plicy may be addressed t the Affirmative Actin Directr, University f Califrnia, Agriculture and Natural Resurces, 300 Lakeside Drive, 6th Flr, Oakland, CA (510) T simplify infrmatin, trade names f prducts have been used. N endrsement f named prducts is intended, nr is criticism implied f similar prducts which are nt mentined. Sacrament Valley Almnd/Prune Newsletter Advisr Retirement and New Psitin Prpsals Bill Krueger UCCE Farm Advisr Glenn Cunty th On June 28 I retired after 32 years as a University f Califrnia Farm Advisr. I started as a Tree Crp Advisr in Glenn Cunty in August f Over the years I added lives in Tehama Cunty and Cunty Directr in Glenn Cunty t my respnsibilities. I have seen tree crp acreage in Glenn Cunty grw frm 22,000 acres t mre than 68,000 as many acres f rw crps and, mre recently, rangeland were cnverted t tree crp prductin. It has been great t be invlved with this and I appreciate all f the supprt and cperatin I have received frm grwers, allied industry and my clleagues ver the years. During the same time we have als seen UCCE ranks decline frm arund 500 t less than 200 nw. Within the current advisr ranks, tw thirds are 55 r lder s there are many mre retirements eminent. While the cnslidatin f UCCE resurces is likely t cntinue, UC ANR administratrs put the hiring f new advisrs and specialists as a highest pririty. There are currently 107 prpsed psitins being cnsidered fr administrative apprval. Frm this grup f 56 specialists and 51 advisrs a small number will be selected fr recruitment. Fur f the prpsed psitins culd be f real benefit t the Nrthern Sacrament Valley. They are, a Sustainable Orchard Systems Advisr fr Almnds and Olives #235 t be hused in Glenn Cunty and cvering Glenn and Tehama Cunties nw and ptentially adding Butte Cunty when the current advisr retires; an Orchard Systems Advisr #079 fcused primarily n walnuts and prunes hused in Butte Cunty cvering Butte and Glenn Cunties nw and, ptentially, adding Tehama Cunty when the current advisr retires; an Area IPM Advisr Sacrament Valley #211; and a Small Farms Lcal Fd Systems Advisr #104 t be hused in Butte Cunty cvering Butte, Glenn, and Tehama Cunties. T learn mre abut these r the ther psitins being requested, and, t cmment r make suggestins, g t the fllwing link: (hld dwn the cntrl key and click n the link t make the link wrk). The site will be pen t cmments th until August 7. Cperative Extensin W rk in Agriculture and Hme Ecnmics, U.S. Department f Agriculture, University f Califrnia and Cunty f Glenn Cperating

2 Once yu are n the website, the psitin descriptins will appear when yu click n the psitin. Yu can als see the prpsed psitins frm thrughut the state n the website and see cmments that have been made s far. Yu can make a cmment by clicking n the number f cmments n the website next t the psitin. Thanks fr yur supprt fr ur UC Cperative Extensin prgrams in the Sacrament Valley. Alternaria Leaf Spt and Leaf Rust f Almnd Je Cnnell, UCCE Farm Advisr, Butte Cunty, and Jim Adaskaveg, Prfessr, Department f Plant Pathlgy and Micrbilgy, University f Califrnia Riverside Alternaria leaf spt and almnd rust are fungal diseases f almnd that are becming mre prevalent in the Sacrament Valley. Bth diseases are favred by high humidity and leaf wetness. Often, additinal fungicide treatments are necessary t minimize early defliatin. Recent extended wet springs and changes in cultural practices (higher density plantings and micrsprinkler irrigatin with lnger, mre frequent irrigatins) are cntributing t higher humidity, mre accumulated leaf wetness hurs (e.g., dew, rainfall, irrigatin, etc.) resulting in higher disease incidence. Alternaria leaf spt is a fungal disease caused by a cmplex f Alternaria species including A. alternata, A. arbrescens and A. tenuissima. Alternaria leaf spt appears as up t half inch diameter brwn spts (Fig.1) n leaves. Leaf spts turn black as the fungus prduces spres. Alternaria leaf spt develps mst rapidly in the ht summer mnths, and can almst cmpletely defliate trees by mid-summer. Disease management. Relying entirely n fungicides t cntrl this disease can be cstly and increases the risk f resistance develpment. Cnsider an integrated apprach including: a. Planting less susceptible cultivars. Varieties mst susceptible include Carmel, Snra, Mnterey, Winters, and Butte. b. Select a planting design which allws fr air circulatin. Orchards planted with rws in an east/west directin typically have mre severe disease than rchards with rws in a nrth/suth rientatin. c. Prune and train trees t allw air circulatin and reduce dew frmatin. d. Practice gd fliar disease and mite cntrl t minimize stressed and injured leaf tissue. e. Irrigate less frequently with larger vlumes f water t minimize relative humidity and subsequent leaf wetness. f. Manage the rchard flr t reduce relative humidity and the amunt f senescing tissue clnized by Alternaria species. Disease resistance against QIs (strbilurins FRAC grup 11) and SDHIs (FRAC grup 7) ccurs in the Sacrament Valley. Late-spring/early-summer applicatins shuld alternate materials t manage resistance. New materials (Quash, Inspire Super - bth cntaining FRAC grup 3) and Ph-D (FRAC grup 19) must be used in rtatins and mixtures fr resistance management. Newer SDHI fungicides (different sub-grups) are prving t be highly effective but the ptential fr resistance is als extremely high. Cmbinatin tank mixtures, pre-mixtures, and rtatins will be required fr preventing disease resistance t the newer SDHI cmpunds. Rust is caused by the fungus Tranzschelia disclr and ccurs spradically thrughut almnd-grwing areas in Califrnia. It appears as small, yellw, angular spts n the upper surface f leaves and rusty red pustules f spres n the lwer surface (Fig. 2). The disease is favred by spring and early summer rains and is mre likely t becme serius in rchards near rivers r streams r ther lcatins where spring and summer humidity is relatively high.. Excessive levels f nitrgen are als knwn t increase a tree's susceptibility. The disease causes premature defliatin and will weaken trees, reducing the fllwing year's blm. The rust fungus verwinters in infected leaves that remain n the tree, spres cntaminating buds and tree bark, and pssibly infected twigs. Rust is frequently mre severe in yung vigrus trees, especially in secnd t furth leaf rchards where fungicides have nt been applied.

3 In rchards with a histry f rust, treatments shuld be applied befre symptms appear: 5 weeks after petal fall and and a secnd applicatin 4 t 5 weeks later t cntrl leaf infectins. Tw r three applicatins may be needed in rchards that have had severe rust prblems. A zinc nutritinal spray (zinc sulfate lb/acre) applied in late Octber t early Nvember resulting in defliatin may reduce verwintering rust inculum. Resistance management will be critical t maintain efficacy f currently available fungicides. Resistance develpment in Alternaria species t QI fungicides was first detected in 2003/04. Field Disease resistance was fund in Kern Cunty in 2005 and in nrthern Califrnia in Field disease resistance t SDHI fungicides (grup 7) was fund in the nrthern and suthern Central Valley in Cnsequently, Pristine (grups 7/11 r QI + SDHI) is nt effective in sme lcatins. Fr rust, resistance has nt been detected and the ptential fr resistance against QI (grup 7 r QI) and DMI (grup 3) fungicides is cnsidered lw. The fllwing are general suggestins fr fungicide resistance management. Rtate and mix fungicides that belng t different FRAC grup numbers. Apply per acre label rates, n every-ther-rw spraying (upper label rates fr QIs). Limit a single mde f actin fungicide class (e.g. FRAC Grup) applicatin t 1 r 2 per rchard per seasn. Start yur fungicide prgram with a multi-site mde f actin material (Captan, Brav/Ech, Ziram, Rvral, sulfur). Sulfur can be used in cmbinatin with single-site mde f actin fungicides such as QI and DMI fungicides. Fungicides effective fr Alternaria leaf spt and rust can be fund at Click n Agricultural Pests, then Almnd, and then the individual diseases. Anther resurce is the 2012 Efficacy and Timing f Fungicides Publicatin at Fig. 1. Alternaria Leaf Spt Fig. 2. Almnd Leaf Rust

4 New Almnd Cst Study fr the Sacrament Valley Carlyn DeBuse, UCCE Farm Advisr, Slan & Yl Cunties A new almnd cst study has been published by UC Davis. The cst study shws sample csts t establish an almnd rchard and prduce almnds in the Sacrament Valley, fr the year 2012, under micr-sprinkler irrigatin. This is a great resurce and guide if yu are thinking abut grwing almnds fr the first time, expanding yur current rchards, r just need t determine ptential returns. This cst study assumes a hypthetical farm f 105 acres with 100 acres planted in almnds. In the first pages, the study ges ver the farm s layut, rchard establishment and cultural practices assumed fr the study trying t capture the current practices used t grw almnds. The secnd part f the study is made up f tables which lk at the average current cst f all these practices fr the years f rchard establishment and fr a mature rchard. Each table finishes with estimated ttal cash cst and returns per acre grwn. A sample table f csts per acre at varying yields is shwn belw. Table shwing the cst per acre at varying yields t prduce almnds taken frm the new Almnd Cst Study fr Sacrament Valley (micr-sprinklers) This cst study is a great tl and shuld nly be used as an estimate f current csts and returns. One way t use the cst study is t use it as an utline and create similar tables using yur actual csts. Or anther way is fr new grwers t use them t summarize what practices, machinery, custm hired wrk, and materials they shuld be planning t have when they establish their first rchard. This cst study can be fund at All current and past UC cst studies can be fund at

5 2012 Navel Orangewrm Richard P. Buchner UCCE Farm Advisr, Tehama Cunty Navel rangewrm (NOW) mnitring begins in early April by hanging black egg traps baited with almnd press cake mixed with 3-10% almnd il. Traps mimic ld, mldy mummy nuts attractive t female NOW fr egg laying and larval feeding. Because NOW ppulatins are usually lw in the Sacrament Valley, we typically d nt bserve egg laying n every trap, every year. Winter weather and gd mummy nut remval (rchard sanitatin), practiced in the Sacrament Valley, reduce verwintering larvae and decrease wrm pressure. Multiple traps are a gd strategy t imprve the prbability f bserving egg laying particularly when NOW ppulatins are lw. Fur traps per lcatin is a reasnable cmprmise between time and accuracy and reading NOW egg traps twice per week (Mnday and Thursday) has wrked well. Eggs will be white when first laid and turn range as they mature. Remember, egg traps alne will nt tell yu if a spray is necessary, but if used in cmbinatin with Degree Days (DD) it is pssible t predict NOW activity and egg hatch. Figure 1 shws 2012 NOW egg laying in a Tehama Cunty almnd rchard. NOW bifix is the beginning date f a cnsistent increase in egg laying. Ntice that 5/3/12 is the bifix fr the Tehama cunty rchard (figure1). New crp nuts are a mre nutritius fd surce which speeds up generatin time. Generatin time is 1056 DD n less nutritius mummy nuts and 723 DD n new crp nuts. Using that infrmatin we can predict secnd and third generatin egg hatch. The accuracy f that predictin will imprve as mre infrmatin is cllected. If egg hatch cincides with hull split n susceptible varieties, the chance f damage is increased. Figure 2 shws actual and predicted generatin events fr ne almnd rchard in Tehama Cunty. Since hullsplit is beginning in sme rchards, a prtin f the secnd generatin may be able t feed n new crp nuts and will develp mre quickly. With ur current infrmatin, the earliest third generatin laying culd be expected t begin is 8/14/12 with egg hatch expected n 8/19/12. Additinal data will adjust that predictin. Yu can fllw the Tehama infrmatin by ging t cetehama.ucdavis.edu then click n rchard crps and click n insect update. Spring r hull split applicatins are tw ptins fr spray cntrl. Spray timing and material chices are described in detail at the UC IPM website Click n Ag Pests, Almnd, then navel rangewrm. Tehama Cunty 2012 Navel Orangewrm Mnitring Figure 1. Egg laying activity fr Navel Orangewrm in a single almnd rchard in Tehama Cunty. 5/3/12 was selected as the first bifix and the beginning f the first generatin.

6 2012 NOW Generatin Activity Bifix, start f st 1 generatin st 1 Gen insect activity Bifix, start f nd 2 gen. nd 2 Gen insect activity Bifix fr 3 rd gen. rd 3 gen. insect activity st 1 eggs, st 1 egg hatch n Egg laying n Secnd egg Egg laying if Egg hatch, nut Tehama C. mummies mummies OR n new crp after hull split hatch mth develped feeding n new crp Actual 5/3/12 Actual 5/9/12 Predicted 7/9/12 Predicted 7/14/12 Predicted 8/14/12 Predicted 8/19/12 0 DD 100 DD 1056 DD 100 DD 723 DD 823 DD Figure 2. Actual and predicted NOW activity fr Tehama cunty almnds. Generatin length is 1056 Degree Days n mummy nuts, 723 Degree Days new crp nuts and 100 Degree Days fr egg hatch. Ntice that Degree Day accumulatins reset t zer at each actual bifix. Why are Sme Individual Trees Turning Yellw, are Weak, r are Nt Grwing? Je Cnnell, UCCE Farm Advisr, Butte Cunty When an individual tree turns yellw cmpared t all f its neighbrs it ften indicates there is smething ging wrng in the rt system. The yellwing ften shws up at the time the weather turns ht and the cmprmised rts are unable t keep up with the water needs f the tree. There are a variety f ptential causes fr these symptms and they can t all be fully explred here but I ll cmment n sme f the main things I see n farm calls. Sil brne diseases. The tw mst cmmn diseases affecting the crwn and rt system are Phytphthra and Armillaria. Bth diseases cause similar abve grund symptms: pr terminal grwth, small chlrtic leaves, premature defliatin, and decreased prductivity, branch dieback and ultimately, tree death. Fr Phytphthra, disease severity depends upn Phytphthra species, sil type, climatic cnditins and tree age. Phytphthra affects the inner bark and cambium and typical rt r crwn cankers will be brwnish with a fairly distinct margin as the fungus advances. Remval f the uter bark ften reveals brwn tissue with a water saked znate appearance near the margin between healthy white and infected tissues if the fungus is active. Excessive sil misture favrs infectin. Armillaria mellea r ak rt fungus is identified by cutting int crwn r rt tissue and lking fr whitish fungal plaques grwing between the bark and wd. Whitish fungal strands and gumming are als cmmnly fund in infected bark. Finding rhizmrps, fungus signs that resemble brwn t black shestrings adhering t the uter bark f infected rts is a psitive cnfirmatin f Armillaria. They develp best in mist sil. Armillaria ften prduces clusters f mushrms arund the base f infected trees fllwing rainfall frm Nvember t February. When newly planted in an infected site it usually takes abut fur years fr a susceptible tree t shw symptms f Armillaria. Infected trees may die suddenly when the heat f summer arrives. Anther sil brne disease that can weaken trees, crwn gall, is caused by the bacterium Agrbacterium tumefaciens and is relatively easy t identify. Galls are made up f undifferentiated, disrganized tissue grwths n rts and/r the tree crwn. Galls mst ften develp n rt r crwn tissue undergrund and may nt be nticed. As galls enlarge, the center f the gall dies creating a dead wd area that can be infected by wd

7 rtting fungi. These galls and wd rts were shwn t be related t 85% f the trees lst in windstrms in surveys previusly cnducted in the Chic area. Trees with severe crwn gall infectin and girdling may be stunted and may display pr grwth and yellw fliage. Befre almnd trees succumb t crwn gall itself they ften tpple ver frm structural weakening related t the wd rts. Water lgging. One f the mre cmmn prblems has been water lgging injury due t perids f excessive rainfall at times during the past tw years. Zinc and manganese micrnutrient deficiencies are mre prevalent in sil related areas where sils are wet, cld, and saturated. Reduced rt activity and nutrient uptake can prduce pale leaf clr r interveinal chlrsis. When tree rts are excessively wet they can die frm lack f xygen even withut any majr pathgens present. This may be a transient prblem in sme cases, affecting nly small feeder rts fllwed by tree recvery as new feeder rts grw ut f the prblem. In mre severe cases, larger rts can die and trees may begin a gradual decline. Such trees may make little new grwth, have a canpy that begins t thin ut, may be ff clr, can stress easily between nrmal irrigatins, and may display lwer limb dieback. Once tree rt systems are injured by excessive rainfall it s easy fr the weak rchard areas t be verwatered when irrigating. This cmpunds the prblem making it difficult t vercme. Reducing nzzle sizes in weak areas in an rchard may help mitigate ver-irrigatin. Misture stress. Gd irrigatin management is required fr grwth and vigr. Yung trees are sensitive t misture stress and will stp grwing at mderate stress levels. Rt systems need t be kept mist but nt wet enugh t favr rt rt fungi and/r lw xygen cnditins. Pressure chambers are the mst effective technique fr measuring tree water status. Research suggests yung almnds will slw sht grwth at 12 t 13 bars Midday Stem Water Ptential. Sil augers are useful fr visual sil misture evaluatin and varius sil misture sensrs are available. Vertebrates. Pcket gphers are serius pests especially in yung rchards. Rt damage results in a yellw, stressed canpy, and pr tree grwth. Gpher girdling n the crwn mimics Phytphthra rt rt, ak rt fungus, r mild etch when n Marianna 2624 rtstck. Trees die when cmpletely girdled. Gphers can easily kill tw t fur year ld trees but I ve seen 10 year ld trees girdled and killed by gphers as well. Lk fr missing bark and parallel tth marks n the wd at feeding sites abut 6 inches belw grund where the bark has been chewed away in a girdle abut 4 t 6 inches wide. Vles, als called meadw vles r meadw mice, may mve int rchards and feed n the bark f yung trees at the grund surface particularly when vegetatin arund tree trunks ffers cver and prtectin. Mainly a prblem n first year trees, their girdling prduces symptms similar t gpher damage. Rdents are ptential pests in all rchards, but they are mre likely t invade rchards that prvide gd cver with a cver crp r where they can migrate in frm rangeland r unmanaged areas. Rtstck cmpatibility. Unin mild etch (UME) ccurs n Marianna 2624 plum rtstck when sils are t wet during the grwing seasn. This prblem is mre prevalent n the varieties in an rchard that are the least cmpatible with the rtstck (such as Butte r Mnterey) but ther varieties may be affected as well. On Marianna 2624, nce grwth is affected by UME, leaves turn pale yellw and grwth may stp. When severely affected, leaves rll and scrch n the margins, and trees may defliate. Sme trees die r remain weak enugh t be remved althugh mst affected trees will recver the fllwing year.

8 Cping with Rain at Harvest Franz Niederhlzer, UCCE Farm Advisr, Clusa/Sutter/Yuba Cunties Rain at harvest can increase risk f mld and cncealed damage t nuts. Bth f these cnditins can reduce grwer incme. The increase in acreage f late harvested varieties in the Sacrament Valley, especially Fritz and Mnterey, increases the risk f rain at harvest. Several key pints t remember if rain is frecast r ccurs at harvest are: 1) If rain is frecast, dn t shake. After a rain, wet nuts dry faster n the tree than n the wet rchard flr. 2) If rain is frecast and nuts are harvested but t wet t pickup, blw them away frm the tree trunks but dn t windrw. Rain wetted nuts n the rchard flr ften are very difficult t blw as they tend t stick t muddy sil. 3) Cnditin ( Drp chute ) windrwed nuts after a rain. Remving leaves and ther trash helps the nuts dry faster. Grwer ptins acrss a range f harvest cnditins appear in the fllwing table.

9 Preharvest, 2012 Sizing Prunes at Harvest Franz Niederhlzer, UC Farm Advisr, Clusa/Sutter/Yuba Cunties Rich Buchner, UC Farm Advisr and Cunty Directr, Tehama Cunty Harvest is appraching, perhaps faster than expected. As this is written n July 19, fruit have begun t shw clr and harvest shuld be abut a mnth away. If the ne mnth t harvest frm first clr ballpark rule hlds, then we are abut a week ahead schedule frm where Franz thught we wuld be when a harvest estimate was made in May. If yur prcessr tells yu they dn t want small fruit r will pay less than the cst f prductin, harvest and drying fr small fruit, then field sizing is a way t avid lsing mney delivering small fruit. Successful field sizing depends upn selecting and maintaining the crrect chain r bar size fr individual harvest cnditins. Watch what's ging n the grund and adapt accrdingly. In general, fresh fruit with medium and larger fresh fruit diameter (see table belw) has gd sugar level, but smaller fruit can be lw r high in sugar depending n specific grwth cnditins in the tree (shade vs sun, number f nearby fruit, etc.). The relatinship between fresh fruit diameter and fresh fruit cunt per pund at harvest and dry fruit cunt per pund. Fresh fruit Fresh Fruit Fresh fruit dia (in) Size categry Cunt/lb Dry Fruit Cunt/lb Small < Medium 3/ Large 3/16 6/ Extra Large 6/16 > /8 Infrmatin presented in this table suggests that running a sizer arund 1 inch may be a gd starting pint. Dn t take ur wrd fr it. Check yur fruit befre yu harvest. Talk with yur packer. Be ready t change chain size r remve it altgether if/when fruit sweetens and/r sftens. Here are several suggestins/cautins fr separating ut small and undersize prunes at harvest. Sugar and pressure. As fruit accumulates sugar and sftens, a sizer is mre likely t remve fruit with value. Price schedule affects the value f remved fruit. Decide which sizes t remve and select the crrect pening t remve target prunes. Be prepared t change r remve sizers as fruit cnditins change. Later in the seasn, as fruit sftens and sugar levels rise, using a smaller size chain may pay ff. D yu need t field size? If the amunt f undersize fruit is relatively small it may nt be ecnmical t invest time and energy t remve it. Harvest timing. The later the harvest, generally speaking, the higher the sugar cntent f the fruit. High sugar prunes are mre likely t have value. Equipment lgistics. Flexibility is necessary when using sizers. They need t be kept clean t functin prperly. Overladed sizers can nt be expected t wrk prperly. Maintain the speed f the sizer s that small fruit can drp thrugh the chain. If the sizer chain is run t fast, then small fruit will literally be carried t the bin with the flw f fruit withut having the chance t fall thrugh the chain. Regularly check drpped fruit. Is it t big t thrw away? Is sme f it? Grwers wh use harvest sizers t remve undersized prunes need t carefully mnitr discarded fruit particularly if larger size penings are selected. What is yur fresh cunt per pund? What is the sugar cntent f the drpped fruit? Larger penings are mre typical early in the harvest. As harvest prgresses, sizer penings are ften decreased r sizers are cmpletely remved.

10 Managing Prunes Thrugh Harvest Richard P. Buchner UC Farm Advisr, Tehama Cunty Irrigatin, nutritin, insect/disease management, tree health, harvest management and perhaps harvest sizing are all critical cultural practices t achieve the highest return fr the current crp. Irrigatin 2011 fruit size measurements in Tehama Cunty dcumented that prunes increase in circumference until abut mid August. Irrigatin research with prunes als shwed that water stress during fruit sizing will decrease grwth rate. In summary, t achieve the largest fruit size fr a given fruit lad; avid water stress when prunes are sizing. If yu tag 10 t 20 prunes and measure thse same fruit each week with a tape measure yu can determine when prunes n lnger increase in circumference. Withut measurements, early t mid August wuld be a gd guess. Water stress after fruit finishes sizing is thught t imprve the dry rati. Ptassium nutritin Adequate ptassium nutritin is crucial t grwing large high quality prunes. Ptassium (K) is essential fr phtsynthesis, translcatin f sugars, pening and clsing f stmata, rt grwth and K directly affects fruit size, sugar, dry rati and yield. Three dry tns f prunes exprt abut 80 punds f K. At three dry tns per acre, that is 80 punds f K leaving the rchard in that crp year. K is cnsidered deficient if leaf analysis drp belw 1.3%. That value is prbably accurate; hwever, the gal is t have every tree in the rchard abve that critical level. A 100 leaf sample represents an average. S a cmpsite leaf sample at 1.3% culd have a significant number f trees in the deficient range. Shting fr a leaf sample in the 2.0% range is a mre realistic gal. If K levels are marginal cnsider an applicatin. The new Prune Prductin Manual has an excellent chapter n Nutritin and Fertilizatin written by Sutter/Yuba/Clusa Farm Advisr Franz Niederhlzer. Insect and Disease Prune trees need leaf area t prduce sugar and capture energy thrugh phtsynthesis. Rust and/r spider mites can seriusly damage leaves and reduce available sugar and energy required t th mature a crp. If leaves shw n rust lesins by July 15, the prbability f serius leaf lss is greatly th reduced. Similar t rust, if n spider mites are fund by July 15 treatments are seldm necessary. Mnitring infrmatin can be fund in the Integrated Prune Farming Practices (IPFP) Manual r at the UC Integrated Pest Management website If brwn rt is present, a pre-harvest applicatin may be advisable. Tree Health Heavy crp lads can significantly stress prune trees, break branches and scafflds and sunburn limbs which encurages cytspra infectin. Usually limb dieback begins t shw in the year fllwing a heavy crp. Prpping limbs, kncking ff fruit and summer pruning are typical techniques t remve fruit weight and prtect the tree. Late fruit remval has little effect n fruit size, but it will favr fruit sugar accumulatin and help tree health and crpping next year. Harvest Management Prunes are at hrticultural maturity and at their best quality when pressure required t penetrate the internal flesh with a 5/16 inch diameter tip declines t 3 t 4 punds f frce. Internal flesh pressure is measured after slicing ff a thin disk f skin befre testing the flesh. At this pint, bth maximum sugar cntent and best ptential dry fruit size have been attained. Crp size has a large effect n fruit size and quality. Orchards with light crps may achieve gd sluble slids while fruit is still greater than 4 punds pressure and are gd candidates fr earlier harvest. Orchards with heavy crps will generally have better ecnmic returns when harvest is later than nrmal. Delayed harvest is nt withut risk. Sfter fruit is mre likely t drp particularly if windy and, if present, brwn rt damage culd increase. The new Prune Prductin Manual has an excellent chapter n Fruit Maturity and Harvest Management authred by retired Farm Advisr Steve Sibbett. Field Sizing Undersized prunes have marginal, if any, value and usually represent a net lss because f csts t haul, dry the fruit and market rder assessments. Field sizing at harvest is a last resrt and is nt a substitute fr in-seasn crp sizing cultural practices. The Niederhlzer article in this newsletter cvers the details f field sizing.

11 Distinguishing Between Branch Dieback Disrders Carlyn DeBuse, Farm Advisr, Slan/Yl Cunties At the first appearance f extreme ht temperatures in summer, flagging f branches, yellwing leaves, and branch and twig dieback appear. The cause f the dieback and stress may be due t different reasns and it is gd t be able t distinguish between the prblems s that apprpriate management can be initiated. Small fruit branches and spurs can be killed by brwn rt fungus (Mnilia laxa r M. fruitcla) r they can be killed by blue prune a physilgical reactin t rapid increase f temperatures fllwing the milder spring temperatures. Larger branches r scafflds can begin t decline with yellwing scrched leaves and then die frm either ptassium deficiency r Cytspra canker (Cytspra leacstma). Bth are very serius prblems but are managed differently. This article will help explain hw t diagnsis the cause and distinguishing between the prblems. The table n the fllwing page is a wrking guide t distinguish between the prblems, preventin, and management f each dieback disrder. Blue prune and brwn rt twig and spur dieback are very similar in appearance but different in sme key symptms. Blue prune will shw up just after the first spike in ht temperatures in the summer and is always assciated with fruit that has begun t turn dark blue and shrivel, eventually falling ff the tree. Leaves near the prune will turn yellw and fall ff (pht 1). Branches in the sun r t the suth are mre affected. There may be sme gummsis that is fund but it is usually clear. Brwn rt n the ther hand begins at blm but ften the small spurs and shts are killed later in the spring as the fungus mves thrugh the wd. The flwers and leaves are ften still attached giving the appearance f sudden death (pht 2). Gummsis is ften fund at the bttm f the flwer r seeping frm the cankers in the twig. The gum is a darker clr f red r amber. All areas f the canpy can be affected by brwn rt. T reduce the blue prune in yur rchard irrigate prperly withut allwing trees t be stressed befre the heat hits. Brwn rt shuld be managed with fungicide sprays at blm. Fr mre infrmatin n treatment timing and fungicide efficacy g t Ptassium dieback can be distinguished frm the thers because it starts t shw leaves scrching and yellwing in the tp f the canpy in the late summer. The dieback prgresses dwn frm the smaller branches at the tp t the larger branches and scafflds in severe cases. It is exasperated by a heavy crp. It is caused by ptassium deficiency and can be crrected ver time with applicatin f K. (See adjining article n Managing Prunes Thrugh Harvest fr mre details) Cytspra canker can lk similar t ptassium dieback but usually effects ne limb r scaffld at a time. The pathgen must have a wund t enter s it ften fllws sunburn which can be initiated frm heavy crps bending branches r ptassium dieback. The symptms t recgnize are sunken cankers n the affected limbs and visible pycnidia n lder cankers (pht 3). When bark is remved t expse interir, the canker will have sharp margins and znate grwth (grwth rings where the pathgen has started and stpped grwth during the year). Limbs cmprmised by cankers shuld be pruned ut and the wd remved frm the rchard. Pht 1. Blue prune shwing leaves turning yellw and falling ff. Pht 2. Brwn rt twig dieback shwing dead leaves and flwers. Pht 3. Cytspra canker pycnidia raised bumps that are black then turn white releasing fungal spres.

12

13 New Prune Prductin Manual frm UC Agriculture and Natural Resurces Written in easy-t-read nn-technical language, this manual is the perfect field applicatin guide t grwing prunes. Inside yu ll find the prfessinalism, expertise and science-based answers yu ve cme t expect frm the University f Califrnia with cntributins frm mre than 40 Cperative Extensin prfessinals, UC faculty, USDA scientists, and highly skilled prune industry experts. Chapters include: 1) An industry verview 2) A detailed descriptin f prune bilgy 3) Infrmatin n understanding sils, varieties, irrigatin and fertilizatin 4) Pest management techniques 5) A lessn n harvest and pstharvest management The breadth f expertise and knwledge cntained in the 320 pages f this manual, alng with the mre than 300 phts and 56 clr illustratins make this ne f the mst cmprehensive prune prductin manuals in the wrld. Call the Glenn Cunty Cperative Extensin Office at t rder yur cpy tday pp $45.00 ANR Pub 3507 ISBN:

14 Yu are invited! Nt Yur Ordinary Retirement Celebratin fr Bill Krueger Cunty Directr and Farm Advisr University f Califrnia! Cperative Extensin Glenn Cunty Friday, August 17, :00 p.m. Scial 7:00 p.m. Dinner Live Music and Dancing fllwing Dinner 7782 Cunty Rad 16 Hamiltn City (Between Rad VV and Hwy 45) at Mills Orchards $25 per persn includes dinner, beverages, dancing and gift cntributin. Please make checks payable t Jdy Samns and mail t UCCE, P. O. Bx 697, Orland, CA by August 10. Glenn Cunty Cperative Extensin P. O. Bx 697 Orland, CA Nnprfit Organizatin Permit N. 63 Pstage PAID Orland, CA 95963