&
F o j x E s T SERVICE
U. ?.DEPARTMENT O F AGRICULTURE
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O X 245, BERKELEY, CALIFORNIA 94701
C
PREAO OF DWARF M STLETOE rom discrete seed sources
nto young stands o ponderosa and Je
J. R. Parmeter, Jr.
USDA Fo~orestService
Research 10te PSW-269
1972
roun&ng reproduction averaged 120
rinfeclion in young trees decgned as
seed source increased and was gener
dkection of prevazng winds. This p
was simnar to the previously report
acre of pine reproduc~on.Such residud trees left after
fne or logghg should be removed.
Oxfovd: 442.1:176.1 Arceuthbzobz'tlm cumpybpodurn-181.523 [ + 174.7 Binus jeffieyi + 174.7 Rnus
Relrievcal Terms: Arceuthobhtkm campylopodutkm; seed
dispersal; forest dmage ; Rnus jeffreyli; Enus
Robert F. Scharpf
Proper management of fores"ctands ]infested
with dwarf mistletoe requires knowledge of the
distance and pattern of spread from infected overstory trees into young stands. Substantial information
is available on spread of Arcezlfhobium arne~ca~zum
in lodgepole pine (Piazls contortu):"pread in ponderosa pine (P.ponderosa) is less well understood.
Initial ]infection by A. vaginutum f. crypLopoCY~min
the Southwestern United States seldom exceeded 60
feet from overstory seed sources, and wind did not
influence "&hepattern of spread.2 Furthemore, the
logarithmic slope of seed deposition curves ended at
about 50 feet from the seed soulrce, l~lithan abmpt
drop in dope. But A. eumpybpodum infecting
ponderosa and Jeffrey pines (P.jeffreyq in California3 spread 125 to -145 feet. In Oregon, m m h u m
spread was 130 feet and folUowed prevadhg wind
pautens; h e a infection
~
was concentrated withh 33
feet of the overstouy."
Because of these discrepancies and because
hformation on spread under Califoy~a~conditions
is
needed to provide midelhes for the mmagement of
infested stands, we did a study of spread from
discrete overstoy seed sources.
METHODS
Eleven plots for this study were selected by the
crikfia: (a) predo
antly ponderosa or Jeffrey pine
or both species, (b) discrete overstory sources of
dwarf mistletoe, and (c) adequate numbers of understory trees around the mistletoe seed sources. Seven
of the 1I. plots were in Shasta CounQ. Two were in
El Dorado Counlrgr. Nine plots were on old bums
where isolated overstory "Erees had sumived. Heavy
stands of Mmzanita (A~tostuphyEosspp.), w ~ c h
fogowed burnrieag, had been patidly deared by
bundozers, and the areas were planted to ponderosta
pine in.the late 1930's and early 1940's. Some nahral
regeneration of Jeffrey pine was also present. Heavy
brush competition had markedly suppressed many
understory trees, as indicated by average heights
(table I). The remainirag two plots-one in Plums
County, the other in Nevada County-were in natural
regeneration that foUowed clearing.
Table 2-Understory trees in eeach of Seven height classes at
e ~ e hof six distance intemals fmm overstov trees
Distance
interval
(feet)
Understory height classes (feet) . . .
Perktent
Table 1-Pbf location, h e i s t of dwarf mistletoe infection,
and elf understory and oversto~y trees in ponderosa and
Jeffrey pine stand$, northern California
Feet
Shasta County:
1
2
3
4
5
6
4
El Dorado
County:
1
2
Rumas County
Nevada County
(9
91
112
2 20
135
124
No.
Feet
160
24 8
40
53
31
64
197
7.5
6.5
10.6
15.1
10.0
11.7
3.9
Data were tabulated by 20-foot zones from the
stem of the seed source tree. Shce distmce of
m a h u m spread detembed plot limits and was less
than I40 feet on all plots, we andyzed data only to
the most distant complete zone- B 20 feet.
WSULTS
Infec~onIn Rella~onTo $JnnderstovTree Hei&t
110
45
200
125
34
90
9.5
20.0
10.0
6.8
=Eleightof three trees: 90, 100, and 134 feet.
2 ~ e i g hof
t two trees: 124 and 128 feet.
30verstory trees cut before the study. Examhation of C I O
remGns indicated heavy infection high h the eroms, but
exact hei&ts could not be determined. Stumps wePe 30 to 36
inches in diameter.
Plots were centered on residud overstory trees
occurrhg singy or in compact groups of two or three
trees. Ml understory trees were accurately located
and mapped, and the hei&t of each tree and the
amount of mistletoe were recorded. Ponderssa and
Jeffrey pines were considered together, with no
attempt t o record data separately.
All plots were level or moderately slophg.
Because of irreplarities in ground cover and the
dbtribution of small trees, few of the plots were
ideauy circular. Severd plots induded trees o d y in
one general direction from the source of inkction.
We could not, therefore, obtain a complete sample on
d l plots, but a11 trees within the limits s f the mapped
sectors were recorded. These sectors represent a
random sample with respect to size, distance from
seed source, and amount of infection. Plot lines on
each plot were extended from the stem of the
overstow tree to the m a h u m distance of spread or
to 120 feet, which ever was greatest.
~
Heibt-class &stributions were not unifom
with respect to distance from the source trees (table
2), Trees 18 feet and under constituted 74 percent of
dl trees sampled, but they constitu-ted 9.5percent of
the trees at 0 to 20 feet from the source trees, and 87
percent of the trees 21 to 40 feet from the source.
Conversely, few ta%Btrees were found w i t h 4 8 feet
of the source tree. Beyond 40 feet, h e i b t d i s t ~ b u tions did not appear to be makedly rinaauenced by
overstony trees. Average tree hei$ts among the plots
ranged from 3.9 to 20 feet (tgble I).
Pooled data from 11 plots show the relationship of understory tree hei&t to infection (table 3).
In trees up to 15 feet tau, infection increased as tree
he1ib.t kcreagd. In larger trees, this relationship was
obscured becaux few large trees were found near the
seed source, where high rates of infection would be
expected.
Bstance From Seed %uaee In Re1a~onTo Idecgon
The graphed slope of dedine (table 3; fig. 1)in
the percent of (b to ICb-foot trees hrfected at
hcreasirag distances was s h d a s to the slope of dedline
in seed deposition found in preeous seed trapp&g
stu&es." M e n larger trees were included, a nateer
dope of decEne was obtajined, appxendy reflecting
the increase in numbers of large trees fasther from the
overstory trees. 'Ifhe rate of hfection r e m k e d
relatively high even at 101 to 120 feet.
Table 3-Trees infected with d~vharfmistletoe,by hei&P chss and distancefrom seed source
Hei&"iclass
(feet)
No.Pct. N o .
&.fib
Pdo.Pct. No.Pet. Wro,Pe2;
No.
Pcf.
0-5
5.1-10
10.1-15
15.1-20
20.1-25
25.1-30
30.1-9trees
Distances of m a h u m spread on the 11 plots
(table 4) averaged 120 feet. M a h u m spread exceeded the hei&t of overstony trees by 6 to $3 feet
on five plots and was less by 1 to 32 feet on four
plots. Source tree kbeibts were unavagabk on two
plots.
The m a h u m spread distances recorded might
be a result of secondav spread withh the understo~y
as we41 as of primav spread from the o w r s t o ~ .
Opportunity for secondaw spread was evduated by
recordkg the numbers of infections in urrnderstorgr
trees (table 4),shce numerous infections in single
understory trees would sugest secondav bulild-up
and thus i n c r e a ~ dopportukty for secondary spread.
urn spread: 11 28 and 130 feet),
there were no heavily hfected trees-a sign of no
appreciable production of ~ s t l e t o eseed in the
understory. On four plots, hea~lgrinfected trees were
present, but were not in a position or direction to
p r o ~ d einoculum for the most distant infections. On
four plots, heavgy infected trees mi&t have contributed to m a h u m spread; however, average distance
of spread on these plots (120 feet) did not differ
appreeiawly from that (1 17 feet) on the six plots
where secondary inoculum was not involved.
Dhecgon of Spread
Only two of the 11 plots sere sufficientIy
circular and had rates of hfection suitable for
Table 4-Infec~onsper tree and maximum spread of dwarf
mistlefoe on the I I plofs in ponderosa and Jefiey pise
srands,northem Gliforn&
Plot
I
IInfecMons per tree
. ..
I
Shasta County:
1
Seed deposition--]
(magnitude not actual)
Distance from seed source ( f e e t )
Figure I-Pereenta?pr, of O to 10 foot tress
infected, the wrcentage of all undergory trees
infected, and seed dwosihion (from Scharpf
and Parmeter 197 1) in relation to distance from
werstory trees.
2
3
4
5
6
7
El Dorado
County:
1
2
Plumas County
Nevada County
I ~ a x i m u r nspread was not associated with or in the direction
of any heavily infected understory trees.
2 ~ a t aon this plot were recorded on a rating scale rather than
by actuai numbers.
-
anaIyzhg &fferences in the direction of spread. These
plots had also been used for a 4-year study of seed
&spersale4 The pattern of spread could therefore be
compared to the pattern of seed &spersal. Ei&t 45O
sectors were centered on the same compass lines used
to orient seed traps in the earlier study (fig.2). The
percent infection in the NW,N,NE, and E sectors
was two to six times that in the SE, S, SW,and W
sectors. Of the r e m ~ n h gnine plots, the two showhg
the ~hortestdistances of m a h u m spread (90 and
103 feet) had understories only to the south.
DISCUSSION
Precise detemhation of hfection rates at
vanious distances from discrete sources of misaetoe
seed ideally requires unifom levels of inoculum and
understory trees of even size, age, and spacing.
Uneven suwivd of planted trees, random natural
regeneration, inherent differences in grow^ rates,
and overstory suppression of nearby regeneration
vktudly preclude Gndhg or creating ideal plots.
Furthemore, the rate of infection is low in small
trees, m d before a level of infection sufficient for
andysis develops, it is likely that some secondary
buddup from understory infections wdl have occurred. For these reasons, field data provide a basis
only for general statements of relationships and for
probable ma&ematicd expressions of these relationships,
The pattern of infection from a discrete overstory seed source s42ould reflect the pattern of
decrease in seed deposition at increa~ng&stances
from the source. m e n only small trees are considered, infection cuwes approach the slope of the
deposition curve (fig I), and such slopes probably
would be s h d a r under ideal circumstances. M e n
trees of a41 sizes are conddered, the slope of the
infection curare is flatter thm that of the seed
depoGtion cuwe. This &vergence is a p p ~ e n t l yassociated with unequd disbibution of size-classes at
various distances from the overstonry.
Larger u n d e r s t o ~trees are more lkely to be
hfected either because they present a larger target for
seed interception or because they are older and
therefore have been exposed to inoculum for longer
periods than have smaBer or younger
Our
data and those of Gill2 and Hawksworh and
GrAm1h&cate that suppresion by overstory trees
redues the density and heifit of nearby understory
trees. Thus, as the amount of seed deposition
decreases with distance from the overstory, the size
and density of understow trees tends to increase,
Figure 2-The percent o f t r e s infected i n each
o f eight 450 sectors was h i g h e r in the north
and east sectors
leading to greater opportunity for infection and also
to @eater likelihood of adationd secondary infections. These factors appear to account for the
divergence of the slopes of seed depoGtion and
hfection cuwes.
We found no abrup"cecrease either in rate of
infection or in seed depodtion in the California areas
stuaed. Both deposition and inkction dedined regularly to the limits of the distances considered. Our
data indjicated, however, that an abmpt drop in the
rate of hfection must occur bemeen 120 and 135
feet, since the m m h u m spread did not exceed 135
feet.
Our results confirm Woth9s4Gn&ngs that w h d
kfiuences the pattern of spread. The m o u n t of
kfection in generally no&herly directions was several
times "chat in southerly &rections m d followed
prevding wind and seed deposition patterns.
Data on spread from discrete seed sources have
impfications h the management of ponderosa and
Jeffrey pine stan& in California. Each isolated,
mature pine infected with dwzf mistletoe pro6des
linoculum to infest about one acre of p h e reproduction. Such residud trees left after fire or loging
should be removed. Initial spread into young stands
d l Ekely exceed that sugested by Kimmey," since
on five of nine plots for which tree heights were
avadable, maxlimum spread exceeded overstory tree
heigkts by 6 to 63 feet. These data may not apply to
stand margifls, however, Muir V o u n d that spread
from isolated trees or small goups of bees in
lodgepole pin&: stands was father thm that from.
stand margns (45 as oppogd to 28 feet averages). If
s i d a s differences occur with ponderosa m d Jeffrey
pines, average spread from stand mwgns mi&t be
considerably less &am that from isolated trees. To
find out further study is wananted.
AcknswIedment: This study was supported in
p a t by a grant from the Di~sior?of Forestq,
C d i f o r ~ aDepartment of Natural Resources.
NOTES
'Gill, Lake S., and Frank C, Hawhworth. Bwamistletoe of
bdgepole pine. Forest Pest Lean. 18, 7 p. 1964.
b w k s w r t h , Frank G. Rate o f spread and intensification
of dcvarfmistletoe in young lodgepole pine stmds* J. For. 56 :
404407.195 8.
Hawksworth, Frank G., and D. P. Graham. Spead and
intensification of dlyarfmistletoe in bdgepole pine reproduction. J . For. 61: 587-591. 1963.
Muir, J. A. Dwarf mistleicoe spread in young lodgepole pine
stands in relation Po density of i~feclionsources. Can. Dep.
Fish and Foresty Bi-Monthly Res. Notes 26: 49.1970.
* G ~ J , Lake S. DwarfnisPletoe of pnderosa pine in the
16outhwest. US. Forest Sem., Rocky Mt. Forest & Range
Exp. Stn. Paper 14, 9 p. 1954.
Gill, Lake S., and Frank 6;. Hawksworth. Dwarfmistletoe
control in ~2outhweskernponderosa pine forests under m n agemen$. J. For. 52: 347-353.1954.
Hawksworth, Frank 6. Dwa~fmistleQoe
of ponderom pine
in the Southwsl: U.S. Dep. Agric. Tech. Bd. 1246, 112 p,
1961.
3~charpf,R. F., and J. R. Parmeter, Jr. Spend of dworf
mistletoe into Jeffrey pine planta~on. .frees ifected after
22 years. US. Forest Sew*Res. Note 141. Pacific SW. Forest
& Range Ewp. Stn., Berkeley, Calif. 6 p. 1967.
Schar~pf,Robert F,, and J. R. Pameterlr,Jr. Seed producfion hnd dispersal by dwarf mistletoe i~ ooverstory JefPey
pines in inolifomk. USDA Forest Serv. Res. Note BSW-247.
Padfic SW. Forest & Range Exp. Stn., Berkeley, Calif. 5 p.
1971.
'~hilds, T. We,and E. R. Wilcox. Dwarf mistleme effects in
m t u r e ponderosa pine forests ilz south-eenml Oregon. J.
For. 64: 246-250. 1966.
Roth, L. F. Pine dwarfiistletoe on the mg-Ze Falls
Ejcperimental Forest. KS. Forest Serv., Pacific W .Forest I%.
Range Exp. Stn. Res. Note 9, 3 p. 1953.
5~charpf,Robert F. Dwry' misPletoe on Ped fir-infection
and conl"ro1 in understovy stands. USDA Forest Sew. Res.
Paper PSW-50. Pacific SW. Forest & Range Exp. Stn.,
Berkeley, Calif. 8 p. 1969.
6~immey,J. W. Dwnrfmistlefoes of California and their
c o n ~ o l .U.S. Forest Sen., Calif. Forest & Range Exp. Stn.
Tech. Paper 19,12 p. 1957.
The Au&ors
EmR, is professor of plant pathology at the University of
Californh, Berkeley. He earned a bachelor's degree in botany at Oregon
$Late Unkersity (1951) and a doctorate in plant pathology at the
University of Wisconsin (1955). ROBERT F. SCHAWP, a plant pathologist, is studying problems in forest diseases and theh control. He earned a
forestry degee (1954) at the U~versityof Missouri, and a master's degree
in forestry (1957) and a doctorate in plant p a ~ o l o g y(1963) at the
University of California, Berkeley. He joined the Forest Service in 1960,
and has h e n with the StaLion3sBerkeley research staff since then.
-
The Forest Service of the U.S. Department of Agriculkme
. . . Conducts forest and range research at more than 75 locations from Puerto Rico to
Alaska and Hawaii.
. . . Participates with all State forestry agencies in cooperative programs to protect and improve the Nation's 395 million acres of State, local, and private forest lands.
. . . Manages and protects the 187-million-acre National Forest System for sustained yield
of its many products and services.
The Pacific Southwest Forest and Range Experiment Station
represents the research branch of the Forest Service in California and Hawaii.