METHYL BROMIDE ALTERNATIVES, FOCUS ON ROOTSTOCKS

METHYL BROMIDE ALTERNATIVES, FOCUS ON ROOTSTOCKS Mihel MKenry ABSTRACT Tolerne to the rejetion omponent of the replnt prolem is otined y swithing rootstoks. We hve found this true with Vitis, Prunus nd now Juglns. When soil rries history of Juglns hindsii its rejetion omponent is nullified y witing one yer nd then replnting on J. thyensis, J. regi or J. mirorp prentge. We ntiipte tht swithing to other Juglns speies will lso suffie ut there must e one full yer of wit during whih the old soil eosystem is strved. A fll pplition of Grlon followed y fllow or growing of non nemtode hosts will suffie. Tolerne or preferly resistne to endoprsiti nemtodes is lso essentil for these rootstoks to ever eome useful. Fortuntely, there is nemtode resistne within Juglns. At Rio Oso we now hve three onseutive yers of yield dt following vrious replited soil fumigtions tht sterilized differing volumes of soil. During their 8 th, 9 th nd 10 th yers, the yield of Chndler on nemtode suseptile prdox seedlings (DN) ws signifintly redued if methyl romide hd not een pplied. More importntly, prdox seedlings hving some nemtode resistne (NX) produed good yields following mediore soil fumigtions. These yield dt onlude our effort to provide quntifition of the importne of nemtode resistne reltive to soil fumigtion. When yields egn to deline in this field we pplied Movento nd in the first yer hve not yet oserved yield enefit. A three yer gthering of nut yields from VX211 nd AX1 lones ws lso ompleted in 2011 nd VX211 ommonly douled the yield of AX1 whether in the presene of nemtodes or not. VX211 lso ppers to e n dequte hoie when replnting fter NCB rootstok. When it omes to other potentil geneti soures of nemtode resistne 20% of the J. thyensis trees imported from Chin still pper resistnt to P. vulnus nd M. inognit in their third yer. This soure hs provided mother-lode of resistnt mteril ut it is lso notle tht the trees diret from Chin pper to e reltively low in vigor. Additionl yers of tree evlution will e importnt to ssess durility of this resistne. We hve lso identified seond soure of nemtode resistne mehnisms nd it emntes from J. mirorp. Our seletion of RX032 remins rootstok of interest ut does possess propgtion diffiulties. We did evlute trees from hrd wood uttings four yers go. At tht time they ppered tolernt of nemtode presene ut did host P. vulnus. More reently Chuk Leslie hs hd some suess with tissue ulturing of RX032 nd two of five trees pper resistnt to P. vulnus fter three yers of study. Prdox lone UZ229 is too good of host for P. vulnus thus we hve stopped ll studies with it. Also of interest, there re now three J. mjor trees from two seedling seletions tht remin nemtode resistnt. In fll 2010 we initited tril to tret replnt sites with: 1) new formultion of Telone, 2) 2, 3-dithioutne nd 3) stem steriliztion utilizing new portle steming unit. All tretments provided remrkle tree growth ginst the rejetion omponent ut eh of these tretments lso ontinues to hve shortomings in terms of ese of delivery. Cliforni Wlnut Bord 331 Wlnut Reserh Reports 2011

OBJECTIVES 1) Mintin the Rio Oso tril for yield dt, rtes of nemtode return nd tree growth with nd without Movento pplitions. 2) Remove up to hlf the trees (6 reps) from the VX211 nd AX1 tril t Kerney Ag Center nd grft over to Chndler for yield dt. 3) Otin for further nemtode nd field evlutions the lones of RX032 nd UZ229 (Wes Hkett). 4) Continue nemtode evlutions of vrious Juglns speies from the USDA Dvis Repository. 5) Explore t our KAC tril site the vlue of Grlon + one yer, Vpm drenh nd/or non-hosts s methods for reduing soil popultions of P. vulnus, Mesorionem xenoplx nd Meloidogyne spp. down to vrious soil depths. PROCEDURES Ojetive 1. The Rio Oso site is now 8 th -lef nd involves pproximtely 8 res with every other tree eing either NX or DN prdox. These rows hve een plnted over soil tht reeived either methyl romide to the 6-foot depth, Telone II t 50 gllons per re stripped with delivery to the 4.5-foot depth or rodst pplition of Metm sodium delivered to the 4-foot depth. Ojetive 2. Within 48 mroplots (1/100 th re eh) t KAC we now hve 4 reps eh of VX211 nd AX1 in eh without nemtodes plus 12 reps with nemtodes. In fll 2006 we ut the trunks within 1/3 of these mroplots nd pplied Grlon. The remining 4 or 8 reps will e grfted to Chndler for purposes of yield olletion. Nemtode smpling of the soil nd trunk mesurements will ontinue twie yerly. Ojetive 3. Seletion RX032 is Juglns mirorp tht we seleted euse it performed well in our erliest nemtode sreens ut it hs not rooted well to this dte. We hve lso oserved it to support high popultions of Ten-lined June Beetle. UZ229 is of interest euse it is now the lrgest of three sved UZ trees. These three trees were originlly seleted euse three out of ten ppered to keep P. vulnus wy from their roots, very similr to wht ws oserved with NX rootstok. RX032 is of interest for its host sttus ginst nemtodes ut lso for its potentil growth hit ginst the rejetion omponent. Ojetive 4. Evlution of more exoti seletions of Juglns from the Ntionl repository initited in 2005. We evluted vrying numers of J. regi, J. mirorp, J. mjor, J. ilntifoli, J. mndshiri, J. thyensis nd J. nigr. Our fous is on J. thyensis. In 2010 we will reeive numerous first-lef trees of J. thyensis olleted during n expedition y Gle MGrnhn. Ojetive 5. Fifty J. thyensis will e plnted into wlnut replnt setting t Kerney in 2010 for evlution of their tolerne to the rejetion omponent of the replnt prolem. Cliforni Wlnut Bord 332 Wlnut Reserh Reports 2011

RESULTS The vlue of pre-infetion resistne The two soures identified in 1999 to hve pre-infetion resistne mehnisms were NX nd UZ seedlings. Three to four of the 10 seedlings exmined from these two soures were unique within the Prdox Diversity Study, ut we did not know the vlue of this type of resistne mehnism within n orhrd setting. This mehnism hs een reported in the literture ut wht is its worth? An 8-re soil fumigtion experiment t Rio Oso, CA provided n opportunity to ompre NX Prdox seedlings with seedlings of DN Prdox seedlings. Yields were olleted in 2009, 2010 nd 2011 nd those findings prllel trunk irumferenes from erlier yers. 2009 yield (l of hulled nuts/tree) of Chndler on NX vs DN seedlings 80 70 60 50 40 30 20 NX prdox DN prdox 10 0 MB rodst Strip Telone Vpm rodst P = 0.05 Eh tretment nlyzed seprtely 2010 yield (l/tree) of Chndler on Two Rootstok Seedlings 120 100 80 60 40 NX prdox DN prdox 20 0 MB Brodst Strip Telone Vpm Brodst P = 0.05 Cliforni Wlnut Bord 333 Wlnut Reserh Reports 2011

2011yield (l/tree) of Chndler on Two Rootstok Seedlings following Movento in fll 2010 nd spring 2011 100 90 80 70 60 50 40 30 20 10 0 MB Brodst Strip Telone Vpm Brodst NX prdox DN prdox P = 0.05 Frm-gte dollrs returned from the orhrd s first three hrvests Tretment NX rootstok DN rootstok MB 400l/, trp rodst Telone II strip 500 l/ + 110 l/ Metm Metm 332 l/ drenh rodst $21,375. $21,943. $20,922. $19,433. $16,440. $15,157. These three yers of yield dt when oupled with previling sles vlues of $1.10, $1.30 nd $1.50/l, respetively for eh yer indite tht rootstok hoie hs long-term importne. The reder lso needs to relize tht fumigtion lso hd vlue euse without it there my not hve een n orhrd fter two or three yers. In the first three yers of hrvesting 22% yield differene seprted the most suseptile seedlings (DN) when replnted to methyl romide ompred to metm sodium. This yield differene ws only 2% when replnted to seedlings (NX) hving gretest inidene of nemtode resistne. After ten yers it is lso pprent tht some of the DN seedlings lso exhiit tolerne to nemtode feeding. Cliforni Wlnut Bord 334 Wlnut Reserh Reports 2011

Prtil vlue of VX211 in the presene of nemtode feeding Our fous hs een VX211 ompred to the modertely vigorous lone AX1. Throughout the first yers tht we evluted these two stoks VX211 exhiited pproximtely 40% more vigor thn AX1. We grfted oth lones to Chndler in their 4 th -lef nd we now oserve in three susequent hrvests tht their extr vigor trnsfers to yield douling in the Chndler sions they support. In the Tle elow we present yield dt from Chndler on VX211 versus AX1 fter eing pled into sites tht initilly hrored 0, 1, 20 or 500 P. vulnus/250 of soil. Yields of Chndler wlnut on two rootstoks plnted t four nemtode popultion levels 60.0 50.0 40.0 30.0 20.0 10.0 d d d d d d d d 2009 2010 2011 0.0 0 500 0 1 20 20 500 1 VX 211 VX 211 AX 1 VX 211 VX 211 AX 1 AX 1 AX 1 Cliforni Wlnut Bord 335 Wlnut Reserh Reports 2011

3yr Men Yields in kg. / Tree Hull, Shell, Met 50.0 45.0 40.0 35.0 30.0 25.0 20.0 15.0 d d d 10.0 5.0 0.0 0 500 0 1 20 20 500 1 VX 211 VX 211 AX 1 VX 211 VX 211 AX 1 AX 1 AX 1 These yield dt prllel our findings from nnul trunk girth mesurements nd the reder must reognize tht these were not replnt settings; totl yield losses eing due only to the presene of the nemtode. Trunk mesurements s well s these yields indite tht higher inoulum levels resulted in improved tree growth nd yield. Our hypothesis for this disrepny is sed on our method of providing inoulum in this experiment. Our inoultion proedure involved seril dilution of soil olleted from round plum trees infeted with P. vulnus. Every 250 of this well-mixed soil ontined 500 P. vulnus plus ny egg stges or iologil ontrol gents present therein. Bent et l. reently reported on the nemtode ontrol vlue of vrious orgnisms within this soil. The mss of soil used to inoulte 500 P. vulnus ws 25 times lrger thn the mss of soil used to inoulte 20 P. vulnus. Likewise, the mss of soil used to inoulte 20 P. vulnus ws 20 times lrger thn the soil mss used to inoulte with one P. vulnus. There were io ontrol gents with our inoulum nd those pper to hve offered nemtode relief when they were in dequte undne. Sreening of dditionl rootstoks of interest In 1999 we set side for dditionl study J. mirorp rootstok known s RX032. This tree is perhps relted to RX1 rootstok ut we set it side euse of its pprent nemtode resistne. Wes Hkett hd diffiulty propgting it from dormnt uttings s well s tissue ultures. Erlier we reeived five individul RX032 trees from dormnt uttings nd our results indited they grew well whether in fumigted soil or not ut they lso supported some P. vulnus fter two yers of evlution. In 2010 we reeived nother five trees of RX032 from tissue ultures nd two of these five trees remin resistnt ut eh is t low popultion level. Two soures of J. mjor were lso reeived nd of 20 totl trees it ppers three of these ontinue to exhiit P. vulnus resistne. Cliforni Wlnut Bord 336 Wlnut Reserh Reports 2011

UZ229 ws seleted in 1999 euse it ppered to offer pre-infetion resistne similr to tht of NX seedlings. Soures from dormnt uttings did not grow dequte root systems ut in 2010 Wes Hkett provided us with 50+ UZ229 trees generted y tissue ulture. The root systems on these hve provided very nie tree with dequte vigor nd reltively fewer P. vulnus in the first yer ut fter the seond yer we no longer hve n interest in UZ229. Seond-yer, P. vulnus/grm of root Rootstok nonfumigted Vpm drenh UZ229,1 yr old 120 30.6 VX211, 2 yr old 31.6 13.2 NCB seed, 1 yr 38.4 64.3 Tulre/NCB, 2 yr 95.9 121. Serr, 2 yr 30.1 60.1 Chndler, 1 yr J. t seed, 1 yr 31.9 98.0 0.1 177. Non signifint RX1, 2 yr 43.0 25.4 In our 2009 report we showed evlutions of J. thyensis seedlings olleted from eh of the four trees in the ntionl repository t Wolfskill. None of the seedlings provided nemtode resistne equivlent to wht we found in J. thyensis #21. In its 7 th lef J. thyensis #21 ws hosting P. vulnus ut its root system lso exhiits some nemtode tolerne. In her expedition to Chin Gle MGrnhn returned with 20 gs of seeds from J. thyensis trees. Four of the gs were roken nd she gve us those unleled nuts for strtifition nd plnting. Fifteen of the seedlings survived three yers nd we note tht ll were resistnt to root knot while only two re now resistnt to P. vulnus. In 2010 Mlli provided us with 33 dditionl seedlings from mong the other 15 or so gs tht still hd lels tthed. After three yers in the ground nine of the 33 still exhiit resistne to P. vulnus nd M. inognit (see elow). None of these seeds hs produed very vigorous tree. These tests will ontinue into 2012 s will field tril tht inludes ll J. thyensis from the repository inluding four lones of J. t #21. Cliforni Wlnut Bord 337 Wlnut Reserh Reports 2011

Soil nd root evlutions indite 9 of 33 J. thyensis provide t lest 3 yrs resistne Shen 0833C2 Shilin 0836i1 Shilin 0837A1 Shilin 0837H1 Shilin 0837G2 Shilin 0837G2 Shilin 0838A1 Shilin 0838A2 Shilin 0838F2 Tolerne to the rejetion nd nemtode omponents of the replnt prolem In 2009 we pplied Vpm within six inhes of wter to every other row of 12 NCB rootstoks. The old trees were ged pproximtely 25 yers. In 2010 we were le to gther 48 eh of vrious Juglns spp. Some were seedlings, most were lones nd those of different ge or size were grouped together down eh row of 12 trees. We rndomly plnted four rows of eh rootstok seletion for totl of 12 single tree replites for eh of eight Juglns seletions. Our gol ws to test for tolerne to the rejetion omponent of RP ut trees with tolerne or resistne to the nemtodes would lso fre est in the longer term. The rejetion omponent of RP is overome y seleting trees of prentge quite different from tht of the previous rootstok nd this is the omponent of RP tht is most ovious in the first yer of growth. NCB following NCB showed visile growth redutions when plnted to non fumigted sites. This ws signifint t P = 0.06% in the first yer. We show elow only those with signifine t P = 0.05. The two prdox lones UZ229 nd VX211 were yer older thn the NCB nd the vlue of fumigtion ws visily pprent s well s sttistilly so. The two English own rooted stoks, Serr nd Chndler, ppered to grow similr whether in fumigted or non fumigted soil ut y Septemer their growth in the non fumigted sites ws ppering grdully diminished. RX1 rootstok ws unffeted y the rejetion omponent of RP ut slowed its growth s nemtodes dmged roots. The rejetion omponent ws unpprent mong J. thyensis seedlings ut vriility did exist from tree site to tree site regrdless of whether fumigted or not. It is highly likely tht the wlnut industry hs the rootstok prentges to swith to in n effort to reple the need for soil fumigtion. Cliforni Wlnut Bord 338 Wlnut Reserh Reports 2011

Seond-yer trunk dimeters (m) mesure of tolerne to root rejetion nd root lesion nemtodes Rootstok n nonfumigted Vpm drenhed % differene UZ229, yr 1 12 4.20 5.55 + 32% VX211 yr 2 12 7.25 8.40 + 16% NCB seed yr1 9 5.50 6.85 + 25% Tulre/NCB yr 2 3 4.75 5.70 + 20% Serr, yr 2 3 5.65 5.65 0 Chndler, yr 1 9 3.50 3.95 +13% J. t seed, yr 1 12 4.40 4.40 0 RX1, yr 2 12 5.10 5.35 + 5% Tree site tretments to oost first yer tree growth Cpility y the wlnut industry to pply Grlon to old trees nd suessfully swith to other rootstok prentge is possile. Soures of interest reltive to the replnt prolem inlude J. thyensis, RX032, RX1 nd there will e others. Muh ttention must now e given to rootstok reeding nd seletion with ttention to grft ffinity. However, we demonstrted dede go tht prtil steriliztion of one ui yrd of soil t plnting sites ould provide first yer oost of growth for ny Prunus root system therein. We suggest tht for wlnuts we need to tret 1 to 2 ui yrds of soil t eh plnting site. In fll 2010 we initited field tril following removl of six rows of Prdox nd Blk wlnuts rootstoks. To this site we instlled 150 k hoed sites with: 1) new formultion of Telone 2) DMDS (2,3dithioutne) pled t one, two or three depths nd 3) stem generted from 3 gllons of propne within 1 to 2 ui yrds of soil using new moile stem genertor tht hets soil within tipsters for replement to individul tree sites. All these soil profile tretments performed similr to stndrd Telone II tretment exept stem-treted soil did not provide ontrol elow 3 foot depth. These tree sites were replnted with NCB in spring 2011 nd ll tretments exept for the untreted provided notle orretion of the rejetion omponent nd nemtode ontrol of t lest 98%. DISCUSSION A method for solving the replnt prolem with miniml fumigtion hs een suggested. We n see the diretion tht reserh efforts must tke whether it is for Vitis, Prunus or Juglns. The tsks eing suggested re muh more omplex thn simple soil fumigtion. Rootstok development tems will e neessry. Possile rootstoks will e slow to eome ville. Fults nd enefits of eh potentil rootstok will need yers of quntifition nd then t lest dede of evlution in severl field settings. We need to get pst the notion tht the replnt prolem is only disese. It hs t lest four prts nd the showy prt is referred to here s root Cliforni Wlnut Bord 339 Wlnut Reserh Reports 2011

rejetion. The soil eosystem eomes quite stle fter dedes of root exudtes hve een imprted y very speifi host. These eosystems, prtiulrly if they re in orser textured soils, re not friendly to introdution of foreign miroes. They re lso unfriendly for time if the new host is of the sme prentge s the previous host. Growers will hope for improved Juglns rootstoks ut if improvements re too slow to develop the lterntive will e rop rottion. Even rop rottion will e indequte if the new rop hoie does not hve resistne to soil pests nd diseses tht remin from the previous perennil rop. One other point! Beyond the ft tht nemtodes n e pthogens, some re reltively non pthogeni ut n still inrese levels of norml root exudtion. Even in medium to fine-textured soils Prtylenhus vulnus is importnt to wlnut growers euse of its feeding nd its pthogeniity. REFERENCES Tom Buzo, J. MKenn, S. Kku, S. A. Anwr, M. V. MKenry. 2010. VX211, A Vigorous New Wlnut Hyrid Clone with Nemtode Tolerne nd Useful Resistne Mehnism. Journl of Nemtology 41(3):211-216. Bent, E., A. Loffredo, M. V. MKenry, J. O. Beker nd J. Bornemn. 2008. Detetion nd investigtion of soil iologil tivity ginst Meloidogyne inognit. JON 40(2): 109-118. Cliforni Wlnut Bord 340 Wlnut Reserh Reports 2011