United States Department of Agriculture Dwarf Mistletoe in Red and White Forest Service in 23 to 28 Years after Inoculation Pacific Southwest Forest and Range Experiment Station John R. Parmebr9Jr. Robert F- Scharpf P.O. Box 245 Berkeley California 94701

Research Note PSW-406

June 1989

warf mistletoes are widespread in three methods with freshly collected, local California stands. Losses, in- sources of dwarf mistletoe: (a) in 1960, cluding reductions in growth and clumps of fruiting dwarf mistletoes were quality, predisposition to bark shaken near trees, approximating natural beetles, and damage by secondary decays discharge and deposition, (b) in-1958 and cankers, are mainly functions of the and 1961, freshly discharged were Parmeter, John R., Jr.; Scharpf, Robert F. 1989. numbers of infections and their distribution collected and placed individually on Dwarf mbtletoe in redad whitefirs in Califor- in tree crowns. We have followed the dy- branches? and (c) in 1963-1967, freshly nk-23 to 28 years a$er inoculation. Res. namics of dwarf mistletoe populations in collected seeds were soaked in water and Note PSW-4%. Berkeley, CA: Pacific South- inoculated firs since 1958,1-2when we be- then placed individually on branches.' west Forest and Range Experiment Station, gan inoculations with Arceuthobium abi- Initially, the inoculated trees were moni- Forest Service, U.S. Department of Agricul- ture; 5 p. etinum Engelm. ex Munz on young red firs tored for mistletoe seed germination, pene- (Abies mgnifica A. Murr.) and white firs tration, infection, shoot development, hit Spread and buildup of dwarf mistletoe, Ar- (A. concolor [Gord. & Glendl.] Lindl.) in production, and seed dispersal? After these ceuthobiwn nbietinum, was studied on inoculated the Sierra and southern . early observations, some trees were exam- white fir, Abies concolor,and red fu,A. mgn1j7ca, This note provides an update of popula- ined annually for new infections, shoot and in northern Califomia for 23 to 28 years. At the end of these studies (1986). and in the absence of tion trends in these trees from 1977 to 1986, fruit development,and death of infection^.^ overstory infection, 13 of 23 trees had dwarf with data on additional trees, tree-to-tree For other trees, time and travel constraints mistletoe populations that were the same or spread, changes in dwarf mistletoe ratings, precluded annual monitoring of popula- smaller than the original populations resulting and rate of dieback of infected branches. tions and at times data only on tree height, from inoculation. Mortality of infections was the crown length, and highest infection in the main factor limiting population increases. Live crown ratio of all trees averaged over 0.8. The METHODS crown were taken. Periodically, detailed average ratio of tree height growth to vertical mistletoe population data were obtained for spread rate of dwarf mistletoe was 11.5 to 1 in Five red firs at Latour State Forest near all trees. Thus, dates of data collection and white fir and 7 to 1 in red fu in the . Mt. Lassen in the southern Cascades and 13 kinds and amounts of data varied from tree In the southem Cascades, the average ratio was 1.7 red firs and 11 white firs on the Stanislaus to tree and from year to year and are speci- to 1 in red fir. About onefourth of thetrees became infected in thebole. Of 14 additional trees infected National Forest in the central SierraNevada fied for each factor discussqi. by lateral spread of the parasite, 13 were within 6 were ~tudied.~'All trees were less than 10 Initially, for most trees, the infections m of the source of infection. Evidence continues m tall at the time of inoculation, had resulting from inoculation and subsequent to indicate that losses from dwarf mistletoes will branches to within 1 m or less of theground, secondary infections were individually be small in well-managed young fu stands free and were in areas free from natural infesta- identified with metal tags wired to from infected overstory trees and properly spaced to promote good growth. tion by dwarf mistletoe. Thus, these trees branches. As numbers of infections in- were suitable for studying population build- creased, this method eventually became too Retrieval Terms: dwarf mistletoe, population dy- up, rate of change in dwarf mistletoe rating, cumbersome and time-consuming. Vandals namics, epidemiology, vertical spread, red fir, and distance of vertical and horizontal removed some or all tags from some trees, white fir, Abies concolor, Abies tnagnifica, Ar- spread. and other tags were lost for unknown rea- ceuthobiwn abietinm, Viscocea, Califomia The rest trees were inoculated by one of sons. One red fir was cut, apparently for a , I

1 USDA Forest Service Res. Note PSW-405. 1989. Christmas Wee. At different times, tagging Table I--Idumber of live kfecfionr in 1986 in trees irrocdated between 1958 and 1967 was discontinued, and numbers of live in- Year Initial Live infections fections were recorded for each branch at 1 Host 1 inoculated 1 Trees 1 infections 1 1971 1 I976 1 1981 1 1986 1 each branch whorl. Tagging individual dwarf mistleloe infections wrmitted devel- I I Stanislaus National Forest 1 opment of life tables. Counting live infec- White fir 1960 2 3 7100 tions on branches by whorl provided data on 1961 3 13 6 25 22 23 1963-67 6 111 82 133 129 96 net changes in live populations and their dishbution in tree crowns. As dwarf mistletoe populations in- creased, the intensity of infection within the tree was detemined by the 6-class dwarf mistletoe rating system.5 For the lower, I I Latour State Forest middle, and upperportionsof the living tree / Red fir 1 1958 5 28 596 905 667 1 crown, the mistletoe in each was rated as absent (0); light-less than half the 1 lone tree, cut by vandals in 1978, had only a single infection that produced shoots I branches infected (1); or heavy-more than only twice and never fruited. 'No data recorded. half the branches infected (2). The sum of the numbers is the dwarf mistletoe rating (DMR). Trees with 1 to 3 ratings were Table 2--Cwnulative mortality to 1986 of cohorts of dwarf mistletoe considered lightly infected, trees with 4 to 6 infections detected and tagged at different tinzes ratings, heavily infected. Tree and branch heights were measured Interval of Alive Host observation Infections in 1986 Moitality to 7 m with a telescoping, calibrated pole. Pct Beyond 7 m, heights were determined with Stanislaus National Forest a clinometer. Dwarf mistletoe infections in White fir 1964-67 37 10 73 upper crowns were detected by climbing 1968-71 57 8 86 trees with a 24-foot (7.3-m) extension lad- 1972-76 62 10 84 der or by inspecting carefully with field Red fir 1964-67 40 6 glasses. I 1 85 I

RESULTS I I Latour State Forest I Population Builldup and Decline 1 Red fir 1 1962-65 16 1966-68 223 On the Stanislaus National Forest, popu- 1969-72 731 lation changes were variable and inconsis- tent among 11 white firs and 12 red firs over the 19 to 26 years since inoculation (table rional Forest. From 28 initial infections, she from first detection (table 2). Surviving I). Mistletoe fruit and seeds were produced population increased to 905 (about 32 infections were generally on the bole or on on all but 2 trees, both red firs with single, times) in 1981 and then declined to 667 main branch axes. Since inoculations often male infections. By 1986, the number of (about 24 times) in 1986. involved placing seeds on main branch infections had declined in nine white firs Population data alone do not indicate the axes, survival of early cohorts of infection and three red firs, was unchanged in one red rate of new infections,but rather the balance was slightly higher, likely because later fir, and had increased in three white and six between new infections and mortality of cohorts resulted from natural infections red firs. One red fir with a single, male older ones. For four white firs and four red occurring mainly on secondary, tertiary, infection was cut by vandals. Among the 13 firs on the Stanislaus, we have yearly data and quaternary branchlets. Among tagged trees with static or declining populations, all from 1976 to 1986 on the survival of all infections recorded from 1964 to 1976 on infections had died on three trees, and only infections arising from inoculation. By 10 white and 15 red firs for which data on one infection was still alive on each of five 1986, only 28 (22 percent) of the original branch rank were available, mortality for trees. Population increases on the other infections were alive, but the total numbers primary, secondary, and tertiary or quater- nine trees ranged from less than two times to of live infections increased to 246, indicat- nary branches was, respectively, 48 per- about six times the original population. ing that the change from 1976 to 1986 re- cent, 66 percent, and 80 percent over the 4 to Total populations on 23 trees increased sulted from 100 deaths and 218 new infec- 16 years (to 1980) in which such data were from 301 to 716 (2.4 times) in 19-26 years. tions. Lakcen (fable 3). On Latour State Forest, dwarf mistletoe Mortality among 1326 infections on all Much of the mortality of mistletoe infec- intensified in all five red firs inoculated, and test trees during early population monitor- tions was due to death of branches, caused the rates of population increase were much ing (1962-1976) ranged from 73 percent Lo mainly by the parasitic fungus Cytospora more dramatic than on the Stanislaus Na- nearly 100 percent within 10 to 26 years abietis Sacc. and girdling by rodents.

2 USDA Forest Service Res. Xote PSW-4%. 1989. Tabla d& by I90 04 dwarf l:tkloe hfectbm f~81recorded ow diyere~mh of braaches

RwMinffer:hmx percent Year dad by 1980 am bmckes of aemtrds mdd Rkwy I Secondary I ~edary~at NO. b"Cb No. Pct No. Pet 1964-70 1-42 49 179 88 123 96 1 Msnn height (m) 4.8 7.6 7.0 8.1 11.51 1971-76 69 33 264 53 172 76 Iplfected (pct) 67 38 18 7 0

lSpmd periods ranged fm23 to 28 years from inmlrarim.

spread in&cat& m avemge mnud rate of spread of 2.6 em (rmge of -35.0 to 7.7 ern). five branch mrkrli9 to 1986 at wriouperiOCBT afier defection of fist mi~fiefmi~fecti~w Average mnud gowlh in wee height for the meperiod (23 to 26 yr) was 30 cm, giving an average ratio of height pwlh to veAcal anisdew spread of 11.5: 1. lFor the 12 red fks, vertical misdetor, spread averaged 4.5 cnnlyea (range of -2.2 eo 18.0 cm) and epee height growth was 32 crnlyear (range 14-59 cm), giving arstrio of tree gowlh to vertical misfleloe spread of 7: 1. For the five red firs at the Latow Slate rest, average mistlew verticd spread over 28 years was 20.0 cm/ year (rmge 13 to 24 cm). Height growth averaged 33 crn (range 25 eo 40 cm)/year, Lower uninfecM and hfwa branches averaged0.87 (range 0.75 eo 0.93) for white giving a ratio of height growth to vertical ahdied as bey kcme shd& md f~sand 0.88 (range 0.78 to 0.95) for red firs. spread of 1.7:1. physiologidly weaker as hetrees grew in Percent of live crown infxtd averaged 15 heighb. Why hfecM bmchbls died, thus (rmge 0 to 47) for white firs and 27 (rmge Bole Infections mling h&viduah irmfa~ons.In lime, entire 0 to 45) for red firs. Two red firs with single, Two bole irmfections result& from inocu- bmches died (fcmble41, $iilfingdl hfections male ide~rionswere considered to be min- lations, and 15 resulted from seconw on the bmh. 144s expxted, the longer a fwted, since misfleloe reproduction was idecdons within inoculated trees or from bmch was infwted, the more l&ely it was precludd. The DMR averagd 1.5 (rmge 0 spread t~ smomding trees. Excluding the to die. Over Mofthe bmches infected for to 3) fawhite fis md 2.0 (range 1 to 3) for two fminoculations, bole infeeions de- more &m 16 t~ 18 yeas were dead. Tres rred firs. Combin& raring for the 20 trees veloped in 10 (24 percent) of 42 trees. Bole at Latour were not monibsd regul~ly was 1.8. In none of these eeswas the upper infecdons sccwed mainly from brmch emugh to pmGde conskknt reor& on third of the crown infaed, md only seven infec~onsgrowing into the bole, but some date of higd infm~on of hchdm&, had infwlions in the middle third. were from direct infection of young needle- but for hee mas, he con&bon of dl At Earour after 28 years, KRof five red ng main stems. bmches less than 3 m from the pound was fus averaged 0.79 (rmge 0.61 to 0.92). r~orM.There were 133 live bmhes in Percent of live crown infect& averaged 43 Tree-to-Tree Spread 1968,40 in 4978,7 in 4981, and none in (mge 0 to 70). The ""O" value is an miface Because inoculated trees were in isolated 1986. owing to the fact &at the highest infected areas free of natural infwlion, spread of bmch was also the lowest live brarrch in misdetm to surrounding trees could be Dwarf Mlstletw Rating (DMR) one tree. The avemge dwarE rnisdetw rat- monieorec9. Inocuhred trees separated by On the Smkhus Na~ondForese, rm- ing was 3.0 (range 1 to 5). less than 3 m from one another were consid- or& of cmwn lengLks, md lmabon of in- ered single loci of infecrion. Inoculated fated bmcksprniud de~miimbon of Vertical Spread in Relation to Tree vees in which misdems never hired were live crown ratios (LCR), percent of live Height Gro* not included. By Ekes criteria, 14 loci of cmm iinfectd, md Dmfor 10 white and On the Smislaus Nadond Forest, the infecrion were identified. The rate of infec- 10rdh(3&~haadcukork&enLspsmd rate of vertical spread through me crowns lion decreased with dismce from see64 we= not incluw). AhougR live cmwns was delemined for 11 white firs and 12 red souxe (rQble5).Of the 14 srces hatkme were not mwwdat the the d imuh- fis. I;of white fis, the dsmce fmm the infect&, 13 (93 pxent) were within 4 m of don, only trees with LC23 of 0.8 or more highest bmch infmed by inmulaeiclw to %mi.One of 14 gees ktween 6 to 8 rn and werp: wed. After 2% to 26 ym, Em the highest bmch infxtd by seconw now of 13 tmes &ween 8 to 10 rn fmm loci of hfe~onin me fus are crown mdos (0.61 to 1.O) md light Life~dcfi Iowe2 23 inmnkM trees on the ratings (1 to 3) grew $itelk d&r reles~, Sd&ns N&dFore& mistletoe ppn- None of om trees had a live crown ratio aM~odlocus, but the new Uwtions && below 0.61,and only 5 (20 percart) fad out and qmd was PBjsmfm m~dd ratios below 0.81. fistlebx ratk~gs\veae mmm. light in 96 percent of &Iem9 and hem-7 in es@b&& -9bb ppula~onsapp~enay only 4 peecent.. Since most wes hati gcd bw mks of infection, even when live crown ratios ad.light infixtion 1eveis, DISCUSSION are pducdfor sevend yws. my damage. caused by rnis~emwill 'be Death of infections generally involved srndl. R~omenwonsfor mm@g red or death of bmchm or bmhle~from one or Bole infections develodd in only 2.4 sr- WGEfi~ sm& hfe~t& with dwarf x&&- idly rodent chewing cent d the trees. Since such iwfecuons do tm b~l~dest~~3-b~~ a~lkhent of re- adbmch gb&hg by s~mmfungi and not appear to cause much hxagein young, pducfion h idestd sm&, clmutfing i Smdl secondary ter~ia~njfast-gowing Firs? ,sSignificmt bmage is not foHow& by plm&g or natural regenera- bmcMe& sa~smaywere more liable to expet&. die from gbdhg, hence the higher percent Tnere was some bkerd spread sf mis9e- of early. deaths mong infections on these toe to firs adjacent &e test trees, but higher bmch ranks. Beaus many of the almost di spread was -*vittt-%abut. 4 m 6 m how qidydwdrnisaem might inase on these branches produce very after 23 to 228 yws, Zlerefore, he spread in ymg sm& with satkred iwfeM and have Btde effect on the tree, mong fks in tfls stud.] -+/asslightly kss . Such infma~onnl~maely quhes their loss is sf litrkepnsachd hpmce. In dhan the average of abut 09 ft (0.2'7 m: %mg-mWPQ~@~&; of p1w u*& ZId n which brmeha bameheavily in- lateral spread per yeax reported for ponder- refine data. dm! of entire bmsches was fie- 0% pine in the wutbwest? h&hresults from &me studies in&- quent and often led to eliminadon ass" large re$&@provide furtiler evidence of MBdup md spread numkm of idmdons and to marked de- that 10sses from dv~&mi~tle~w,s shouldbe f yowg firs were. dow."z7 cline in misdetm ppulafions, On hemost smdl in wdl-mmagd young sands free al FuPghemo~,ow rmbnlts &ow aihst after heavily idat& red firs at bmw, virtually infected oa~erstwy,If care is taken to eeErnl- abut 2 d&es sf iniM inaws, dwarf a of brmches less M "4 mom nate overstoq sources sf infw~~ocand misdem pssph~omhave begun to level ground have died. smds are spaced pfoperEy to pro~ob:gd off or d61he in the Ewmder study. For Veddspread on the SB~S~~UScontin- growth, scattered idectmns withha young empBe, for the heow red fm, SmkBZpw ued to lag v~el:%lbhbd height growth in the fii stands snould not affect prcxjcctiia~ty red fis, and Smslms white fm, 19% 29 trees studied. By 1986,ratios of height appreciably. ppul&ons of live infmbms w g~owthto vertical mistletoe spread for red cmk 96 percent, md 79 percent, fmmd whikf~swere'7to 1 md 151.5 m 11, END NOTES AND BL5ZZENCES rap~vely.These ratios represent a slight incr~in the vemcd spread rate for red '%&serpf, Robert P.; Pameter, J&n R., Jr. 1976. fm and a sEghe decrease in spread rate for Popddion btdild~p and vertical sprad of dive enaces in sumpGblity mowg em in &f- white fm since ow ea11ier ~pfi."us* wisthros an young red d white *firsin Cal$iornia. ferent arm (or aferent micmgma~c newly dB the trees on &e Sm~slausNa- Res. Paper PSW-HZ. Be&eHey$I,CA: Wcfic South- weat Fomst Rang2 Exp~hentStation, Forest cm&dom in &ffe=wt ikaw &at influeme thnd Forest continue to outgow the up Sewice, US.Department of Aghcdturn; 9 p. w& ~qpeadof the ite by a wide ma- SWarpf,Ro2wfl P.; Pame%:, J.R., Jr. 1982.Pop&- misdew md (3) rate of death of @. id^& b S. At hmw9 werage rates of vertical We have p~~owstlgr on differ- spread in red firs were gaiter (20.0 cm/ ences in pp~b~ondp dwdmk- yaw) by 1986 than hey were in 1976 (7.3 kpt~rtrnmtd Psgrialtmr; 9 p. dewat the mo FmeskskslOw idmbon data cww),but 'the rate of host height gowh9 JS&i?rpf,R.F.; Pis,mWkrs Z.R., Jr. 1%7. Tke bbl- in &at repa b&mM that the dfferencw (avg, 33 crn&es) still exceded the rate of ogj ad@hilogy ofdv"&~gr~ktietesArceuthabium were due in part to he shorter incubahon ver%cd misdem qr@d by a ratio of 1.7: 1, ~ampjjIopAmf. babiekmm~p~mitizkg trwji51s ii~ period, for dwarf mkdew at lhb~g8.~With the dminkhing d dwarf misdetm Cali,fornh. Tech. Bull, 1362.WssS.hg?nn, E: Fore8 Higher inhid rates of ~mdonfollowing pplahms during the hesever& yaws, it Sewice, U.S. D~p~rtnne~aof jL%gricu&tam; 42 p. 4S&apfs Robert F.; Pameter, LR.,4a. 1952. Tk imuhbali (28 pmnt) were Jm noted on is 1ie1y $pee height growth will con- eollec~ba,storage, adger~&w%bn qa SLC~S oj a red fm at htowPbut not on white fm? The thm to outpace vedcd spd,and bathe dwr-fd-t~~soe.Journal of Fomrtxry GO(8). 551-552. are *H~aspdksisl&h* Fr& 0. 1977. Tbs 5-chs dvwf ut. they might involve ewhn- ge and grow& 10s &om dwuf w&t6etoe ratiag system. Ch.Tech. Rep. RM-48. Pet nces, pvemge Ufermca misaew in firs me relami to live crown &Em, 03 Rocky h4hquh Fast and Rang8 atS~icm* Fomst Sewiicx* U.S. Dqmrbnmt in wq~b&eSor Y ratios and m the mount of live crown in- d Ag~dgasm;7 p. mong pop& fectais s has beaq repdby Sckrpf'? %SSarpfOR&ri P. I&. &wagmistletoe om rsd Ckr =d&h&mk as pGcaly Scmf find that trees with g~dlive fir...i@ectim. ard eo?Jrol im twsrstory &zP&. We.

USDA Fmae SineiceRa. Note P5W424. 1989. B&apfe Robert. P. 1969. &Dw$mbIl~boc on red 'Pmek~,J& R., Jr.; &hWpf, Ro$cJfi F. 1982. The Authors: @r...ifecIk OP~control ia drstory sIQ&. Ra. S6em infictiorn by dwarf m&tletcie in CaliJCOr~kfi. Paper RSW-50. Berkeley, @A: PaciF~ckuhwesr Res. Paper PSW-165. Berkeley, @A: Pacific Soueh- Fmst and Range E~rirnmt&ion, Eiomt Service, west %rest 4 Rmge Exphent Station, Fom81 JOHN pARMmER9 JRe ~mfegr~rof ~hm U.S. wmmeof Agricdmm; 8 p. Service, U.S. kpament of Ag~cdmm;7 p. pathology, Univamity of California, Berkeley. 'S&arpf, R&rt 6;. 1979. h@htZe~m-i@ec8edB %~lrrwkswo&, P& 6.1961. Dwo$~dleimOI ROBERT ni: SCWRW is pmja leder-f~met retip: growth afier release. Res. Papr BW-143. ~~O~FOSO&)kb8 ik ~0~lh~13.96.Tech. Bd. 1246. dime wiphbdoduamm in Bekele~. Be&eley, CA: PaSic ea Fomst md Wmge Washings, LC: Forest Sewice, U.S. kpmmtof Ag~cdm~;% 12 p. of Agridm~;9 p.

Pmms of my race, color, national origins, sex, ap. religion, oz with my handicapping mditions are wdms to we md enjoy dl fwilitiea, pgmr, md services of the U.S. wament of Agricdtum. Dircrirnkatim in my fown is strictly against agency policy, and should be mp*d to the S-~ary of Agniculaum, WashiPlgm, DC 20250.

USDA Forest Service Res. Note PSW-406. 1989.