James W. Byler-2 /
Abstract: The Pest Damage Inventory (PDI) i s a survey
procedure used by t h e U.S. Forest S e r v i c e ' s C a l i f o r n i a Region
f o r measuring pest-caused damage over l a r g e f o r e s t e d a r e a s .
Similar procedures a r e followed i n each survey, but photo and
ground sampling techniques may d i f f e r . S i x PDI surveys have
been completed t o date. Results show t h a t dwarf m i s t l e t o e i s
a major c o n t r i b u t o r t o t r e e m o r t a l i t y . The p a r a s i t e i s but
one major c l a s s of t r e e p e s t s , and p e s t management systems
must i n t e g r a t e treatments f o r t h e e n t i r e p e s t complex.
Pest management p r e s c r i p t i o n s should be i n t e g r a t e d with stand
management p r e s c r i p t i o n s .
INTRODUCTION
The Pest Damage Inventory (PDI) i s a
survey system t h a t provides estimates of
damage caused by f o r e s t p e s t s . The PDI
measures t h e damage from a l l p e s t s i n one
survey, r a t h e r than makes, m u l t i p l e surveys
f o r t h e various i n s e c t s and d i s e a s e s . The
t o t a l damage i s p a r t i t i o n e d among pathogens,
i n s e c t s , a b i o t i c f a c t o r s , and complexes of
t h e s e agents.
of t r e e m o r t a l i t y , t o suggest a method f o r
measuring growth l o s s and dwarf m i s t l e t o e
incidence, and t o describe an approach f o r
i n t e g r a t i n g dwarf m i s t l e t o e treatments i n t o
s i l v i c u l t u r a l p r e s c r i p t i o n s t h a t i s being
used i n t h e Forest S e r v i c e ' s C a l i f o r n i a Region.
The PDI provides information f o r i n t e g r a t e d c o n t r o l i n t h e broad sense. Pest
management s t r a t e g i e s f o r each of t h e major
p e s t s and p e s t complexes a r e i n t e g r a t e d with
s i l v i c u l t u r a l treatments t o form stand pres c r i p t i o n s aimed a t achieving t h e d e s i r e d
s t a n d s t r u c t u r e , composition, and productivi t y . The emphasis i s on f o r e s t management
f o r i n s e c t and d i s e a s e prevention, r a t h e r
than on remedial i n s e c t o r d i s e a s e control.
Pest Damage Inventory methods a r e used
f o r measuring t r e e m o r t a l i t y over l a r g e
f o r e s t e d areas. The estimates of l o s s obt a i n e d from t h e surveys a r e used mainly f o r
two purposes.
This paper describes methods and s e l e c t e d
r e s u l t s from i n v e n t o r i e s made i n s e v e r a l
National Forests i n C a l i f o r n i a during t h e
p a s t 5 years. I t c e n t e r s on dwarf m i s t l e t o e s
as causes of m o r t a l i t y and growth l o s s . But
t h e r e s u l t s and discussion a r e not confined
t o dwarf m i s t l e t o e s . My approach w i l l be t o
put dwarf m i s t l e t o e s i n p e r s p e c t i v e a s causes
Ñ'presente a t t h e Symposium on Dwarf Mistlet o e Control Through Forest Management,
Berkeley, C a l i f . , Apr. 11-13, 1978.
Ñ'plan P a t h o l o g i s t , C a l i f o r n i a Region, Forest
S e r v i c e , U.S. Department of Agriculture, San
Francisco, C a l i f .
MORTALITY SURVEYS
1) Biological evaluations : The C a l i f o r n i a
Region's Forest I n s e c t and Disease Management
S t a f f uses t h e PDI f o r b i o l o g i c a l evaluation
surveys where t h e areas of concern a r e l a r g e
and where t r e e m o r t a l i t y i s t h e primary concern.
The S t a f f evaluates s p e c i f i c i n s e c t and/or
d i s e a s e problems i n response t o requests from
t h e National Forest Supervisors and o t h e r
1and managers. These evaluations contain
estimates of t h e l e v e l of damage and cause of
t h e damage t h a t a r e obtained from surveys.
2) Administrative uses: Estimates of t h e
l e v e l of t r e e m o r t a l i t y and t h e cause of t h a t
m o r t a l i t y a r e a l s o used by administrators i n
s e t t i n g a c t i o n and research p r i o r i t i e s . PDI
estimates f o r t h e 12 National Forests i n
northern C a l i f o r n i a a r e being used f o r such
purposes.
To d a t e , s i x t r e e m o r t a l i t y surveys have
been completed: t h e Moore Creek Compartment
of t h e S t a n i s l a u s National Forest i n 1972;
eight townships on the Eldorado National
Forest in 1973; the commercial forest land
of the Stanislaus National Forest in 1974;
the pine and mixed conifer types on the
San Bernardino National Forest in 1976;
Laguna Mountain on the Cleveland National
Forest in 1977; and a drought survey of tree
mortality on 12 National Forests in northern
California in 1977.
The six surveys had three objectives in
common: (1) to measure the tree mortality
that occurred during a one year period; (2)
to identify the insects and diseases, separately or in combination, that were responsible for that mortality; and (3) to identify
the stand and site conditions that are associated with above-normal mortality.
The aerial photos were examined for dead
tree groups by delineating photo plot boundaries on the center photograph of each triplet
and viewing the plots in stereo at 4x to 8x
magnification. Each tree or group of dead trees
within the photo plot that appeared yellow-tosorrel at the time of photography was encircled
on the photograph. Such faded trees were considered to have died within 1 year prior to
the time of photography. For each dead tree
group, the photointerpreter recorded the number
of dead trees, and the species and size class
of each dead tree. Three size classes were
used: less than 50 feet; 50 feet to 100 feet;
greater than 100 feet.
Ground Survey
Loss estimates from four surveys are
given as examples in this report: the
Eldorado National Forest area, the San Bernardino National Forest, Laguna Mountain, and
the drought survey of 12 National Forests.
METHODS
Similar procedures were followed in each
survey. But the surveys differed in the photo
and ground sampling technique and in sampling
intensity.
A stratified sample of photo-detected dead
tree groups was selected for ground sampling.
Trees were stratified by height class for the
drought survey, and by height class and tree
species for the other surveys. The selected
dead-tree groups were visited on the ground to
gather data used to calculate estimates of tree
mortality. These data included number of trees
in the group, the species and size class of
each tree, and the year in which each tree died.
The year of death was estimated primarily from
color and condition of the foliage, and the
condition of the bark.
Photo Plot Selection
Aerial photographs were used to detect
dead trees. One hundred percent photo coverage was used on the Laguna Mountain area.
Random sampling was used for the remaining
surveys: random photo plot placement in
the commercial forest type for the drought
survey, and stratified random sampling by
timber type for the remainder.
Photo plots were square and covered 284
acres unless part of the area was out of the
timber type or was off the forest. Plots with
less than 50 acres of commercial forest type
were excluded from the San Bernardino and
Eldorado National Forest surveys. Plots with
less than 140 acres were excluded from the
drought survey sample.
Each sample plot (or the entire area in
case of 100 percent coverage) was photographed
at a scale of 1:8000 by using 75 percent overlap for stereo viewing. Nine-and-one-halfinch wide Ektachrome MS film (type 2448), a
Zeiss RMK camera with an 8% inch lens, HF 3
or 4 haze filters, and an antivignetting
filter were used.
Stand, tree, and pest data were recorded
for all trees that were found to have faded
within the year prior to photography. Trees
were examined for pests in the following manner:
crowns and upper boles were observed through
binoculars, bark was removed from lower boles,
and axe cuts were made at the root crown and
in the uppermost roots. Pests present in each
tree were rated and recorded. In addition,
those pests that were considered the most important found on all trees in the mortality
group were included in the pest complex for
that group. Only known tree-killing pests or
conditions were included in the pest complex,
and these were listed only when symptoms and
signs indicated that the pest had contributed
to the death of the trees.
Fomes annosus
was included when typical
stain, decay, or conks were found on the tree
or other trees in the same disease center, or
when the presence of the fungus could be verified by incubating wood samples. Wood samples
were collected and incubated whenever Fomes
annosus was suspected but could not be confirmed by stain, typical decays, or conks.
Armillaria mellea is both a parasite and
a saprophyte on conifers in California. It was
included i n t h e p e s t complex only when a dead
oak was p r e s e n t on t h e s i t e n e a r enough t o
provide a food base ( a condition under which
t h e fungus i s a v i r u l e n t pathogen), o r when
symptoms and s i g n s i n d i c a t e d t h a t t h e fungus
had caused r o o t decay and k i l l i n g by t h e time
of t r e e death. Frequently, both A. mellea
and E. annosus were p r e s e n t , e s p e E i a l l y on
t r u e f i r s . In such c a s e s , only E, annosus
was l i s t e d i n t h e p e s t complex, although i t
should be recognized t h a t t h e decay and k i l l i n g was caused by both r o o t pathogens.
Dwarf m i s t l e t o e s were included i n t h e
p e s t complex when a t r e e was r a t e d f o u r o r
more i n Hawksworthfs s i x c l a s s system (Hawksworth and Lusher 1956). Lighter i n f e c t i o n s
tended t o be r e s t r i c t e d t o t h e lower h a l f of
t h e crown, and were n o t considered t o be s e r i ous enough t o be a cause of a t r e e ' s death.
Dendroctonus spp., Scolytus v e n t r a l i s ,
and o t h e r i n s e c t s were l i s t e d a s p e s t s when
t h e i r d i s t i n c t i v e brood g a l l e r i e s i n d i c a t e d
t h e i r presence and s u c c e s s f u l a t t a c k of t h e
tree.
The p e s t complex was used t o c a l c u l a t e
t h e proportions o f t r e e s k i l l e d by i n d i v i d u a l
i n s e c t s , pathogens, and pathogen/insect comb i n a t i o n s ( f i g . 1-5). Tree m o r t a l i t y was
s a i d t o be "induced" by an i n s e c t o r pathogen
i f t h a t i n s e c t o r d i s e a s e was l i s t e d i n t h e
p e s t complex. As it i s used h e r e , t h e term
"induced" does n o t mean t h a t a p e s t was t h e
s o l e cause, but one o f t h e c o n t r i b u t o r s t o
t h e death o f t h e t r e e .
The inventory design was m u l t i - s t a g e sampl i n g with v a r i a b l e p r o b a b i l i t i e s and s t r a t i f i c a t i o n . Unbiased estimates of t r e e m o r t a l i t y
and t h e i r standard e r r o r s were computed using
methods s u i t e d t o t h e sampling design.
RESULTS AND APPLICATION
Northern C a l i f o r n i a National F o r e s t s
Three p i l o t t e s t s o f PDI m o r t a l i t y s u r vey methods were made during y e a r s o f normal
m o r t a l i t y : t h e 10,000-acre Moore Creek Compartment on t h e S t a n i s l a u s National Forest i n
1972, 87,000 a c r e s o f t h e Eldorado National
Forest i n 1973, and t h e e n t i r e timber-producing
lands of t h e S t a n i s l a u s National Forest (about
1 m i l l i o n acres) i n 1974. The t e s t s showed
t h e f e a s i b i l i t y of obtaining r e l i a b l e e s t i m a t e s
of c u r r e n t t r e e m o r t a l i t y f o r l a r g e a r e a s .
Dwarf m i s t l e t o e s were implicated i n t h e
deaths of a s u b s t a n t i a l proportion o f t h e t r e e s
i n each a r e a . M o r t a l i t y e s t i m a t e s from t h e
Eldorado National Forest survey a r e a a r e used
a s an example ( f i g . 1 ) . Twenty-three percent
-
ELDORADO NATIONAL FOREST SURVEY AREA 1973
Figure 1
--
The r e l a t i o n s h i p between dwarf mistletoe-induced m o r t a l i t y and t o t a l m o r t a l i t y o f
yellow p i n e s and t r u e f i r s i n t h e Eldorado National Forest survey a r e a .
of the ponderosa and Jeffrey pines and 14 percent of the red and white firs were heavily
infested with dwarf mistletoe at the time of
death (dwarf mistletoe ratings of 4-6). I
concluded that the heavy infestation was one
o.f the factors that brought about their death,
although the exact level of dwarf mistletoe
infection necessary to kill trees in the presence and absence of other pests is not known.
Nearly all of the dead pines and firs
also showed evidence of successful insect
attack. Brood galleries of tree-killing bark
beetle species were present under the bark of
the trees, and these likely played a role in
killing the trees also.
The apparent association between "insectkilling" and dwarf mistletoe infestation has
been recognized for some time. Miller and
Keen (1960) discussed the role of pathogens,
including dwarf mistletoe, in increasing pines'
susceptibility to insect attack. More recent
survey information from other Forest Service
Regions, for example, Region 2 (Frye and Landis
1975, Johnson and others 1976). Region 3 (Parker
and others 1975), and Region 4 (Parker and
Stipe 1974) indicates that trees with high
mistletoe ratings are more likely to be attacked by insects and killed than are unintested ones.
The PDI was used operationally in 1977 to
survey 12 northern California Forests (6.3
million acres of commercial Forest Service
land) to measure the drought-associated tree
mortality. The survey was designed to obtain
volume loss estimates for administrative purposes. The estimated level of mortality was
4.5 i 0.8 million trees or 1.2 t 0.3 billion
Schribner board feet for the 1 year period
from May 1976 to May 1977 (0.71 trees/acre).
This level was about three times the estimated
normal loss.
Because of the limited ground sampling
the estimates of loss by pest and pest complex
have high standard errors. However, they suggest that dwarf mistletoe was associated with
a sizable proportion of the mortality (fig. 2).
The proportion of the recently killed pines
with dwarf mistletoe ratings of 4 to 6 was
especially high - - 79 percent. Again, insects
infested nearly all of the trees, suggesting
that they too contributed to their deaths.
TWELVE NORTHERN CALIFORNIA NATIONAL
FORESTS - 1977 DROUGHT
Figure 2 - - The relationship between dwarf mistletoe-induced mortality and total mortality
of yellow pines and true firs in the drought survey of 12 northern California National
Forest.
Root pathogens were a l s o important i n i n ducing t r e e m o r t a l i t y i n t h e 12 f o r e s t s . Root
pathogens appeared t o be more important than
dwarf m i s t l e t o e s i n causing t h e death of t h e
t r u e f i r s ( f i g . 3 ) , although they were assoc i a t e d with fewer dead pine t r e e s than was
dwarf m i s t l e t o e . Root damage and heavy crown
i n f e s t a t i o n s of dwarf m i s t l e t o e were both pres e n t on a s i z a b l e proportion of t h e r e c e n t l y k i l l e d f i r s ( f i g . 3).
F. -annosus was t h e predominant r o o t pathA. mellea and F. -annosus
ogen, but s i g n s of were f r e q u e n t l y present on t h e same t r e e .
Some f i r s appeared t o have been k i l l e d by
mellea i n t h e absence of E. annosus, but i n
those cases a dead oak o r oak stump was u s u a l l y
present t o s e r v e a s a food base f o r k. mellea.
A.
t o t r e e mortality. They may be e s p e c i a l l y
important during periods of drought, o r when
stocking d e n s i t i e s a r e high and t h e t r e e s a r e
under a d d i t i o n a l s t r e s s .
But perhaps more importantly, t h e r e s u l t s
i n d i c a t e t h a t o t h e r pathogens and i n s e c t s a l s o
c o n t r i b u t e t o t r e e m o r t a l i t y and should not be
overlooked. The r o l e of each major p e s t must
be understood i f c o n t r o l e f f o r t s a r e t o be
maximized. Stand treatments may and frequentl y should aim t o reduce t h e l e v e l s of dwarf
m i s t l e t o e i n t h e stand. But l i t t l e b e n e f i t
may r e s u l t unless stand treatments a l s o prevent o r reduce t h e damage from r o o t pathogens
and make t h e stand l e s s s u s c e p t i b l e t o i n s e c t
attack.
Southern C a l i f o r n i a National Forests
Recent r e p o r t s on r o o t disease i n Calif o r n i a (Bega and o t h e r s 1966, S t a r k and Cobb
1969, and Cobb and o t h e r s 1974) and i n Idaho
( P a r t r i d g e and M i l l e r 1972, M i l l e r and Partr i d g e 1974) show t h a t r o o t pathogen/insect
a s s o c i a t i o n s a r e common, and i n d i c a t e t h a t
pathogens predispose t r e e s t o i n s e c t a t t a c k .
These northern C a l i f o r n i a r e s u l t s i n d i c a t e
t h a t dwarf m i s t l e t o e s a r e important c o n t r i b u t o r s
ELDORADO NATIONAL FOREST
AREA
- 1973
In southern C a l i f o r n i a , t h e pine f o r e s t s
on Laguna Mountain, Cleveland National F o r e s t ,
were surveyed i n 1977, and t h e pine and mixed
c o n i f e r f o r e s t types on t h e San Bernardino Nat i o n a l Forest a r e now being surveyed. The San
Bernardino survey ( a cooperative e f f o r t among
t h e University of C a l i f o r n i a , Berkeley; Environmental Protection Agency; and Forest Service)
was begun i n 1976 and i s scheduled t o l a s t
TWELVE NORTHERN CALIFORNIA
NATIONAL FORESTS -
1977 DROUGHT
Figure 3 -- The r e l a t i o n s h i p between dwarf m i s t l e t o e and r o o t pathogen-induced m o r t a l i t y of
t r u e f i r s i n t h e Eldorado National Forest survey a r e a , and t h e drought survey of 12 northern
C a l i f o r n i a National Forests. Fomes annosus was t h e major r o o t pathogen.
3 years.
Information from the Laguna Mountain survey and the first year of the San Bernardino
survey are described here. The levels of tree
mortality (0.62 trees/acre/year on Laguna
Mountain and 0.07 trees/acre/year on the San
Bernardino National Forest) are considered at
or below normal for these areas, since rainfall was normal or greater.
Heavy dwarf mistletoe infection was associated with a large proportion of the pine
mortality in both survey areas (fig. 4). Forty
percent of the dead Jeffrey pines on the San
Bernardino and 60 percent on Laguna Mountain
were heavily infested with dwarf mistletoe at
the time of their death. Dwarf mistletoe was
not the only important pine pathogen on the
two southern California Forests. Root diseases
were implicated in the death of nearly as many
pines as were dwarf mistletoes (fig. 5). And
sizable proportions of the pines in both areas
had both root damage and heavy dwarf mistletoe
infestations at the time of death (fig. 5).
F. -annosus was the major root pathogen in
both areas.
Insects were also associated with most
of the pathogen-induced mortality as was the
S A N BERNARDINO NATIONAL
FOREST
- I976
case on the northern California Forests. Pathogen/insect complexes killed 70 percent of the
trees of all species on the San Bernardino
National Forest and 77 percent on Laguna
Mountain.
The mortality survey results indicate that
dwarf mistletoe is one of the most important
causes of tree mortality on these two southern
California Forests. The problem is especially
acute because one of the two primary management
goals is to provide for recreational use. The
desirability of maintaining a tree cover on
presently-forested land indefinitely intensifies the dwarf mistletoe impact. The option
of making large regeneration cuts, thereby
eliminating the parasite from the new stand
is not feasible in such intensively used areas.
In the past, forest management in the
southern California Forests was largely custodial, consisting primarily of sanitation-salvage cutting to reduce the number of insect
high risk trees from the stands. Dwarf mistletoe suppression projects were separate activities, and were carried out only in limited
areas. Insect suppression projects consisted
of falling infested trees and treating them
with chemicals.
LAGUNA MOUNTAIN AREACLEVELAND NATIONS FOREST
1977
Figure 4 - - The relationship between dwarf mistletoe-induced mortality and total mortality
of two yellow pine species on two southern California National Forests.
But i n s e c t and dwarf m i s t l e t o e c o n t r o l
t r e a t m e n t s a l o n e have n o t r e s u l t e d i n t h e
most d e s i r a b l e r e c r e a t i o n s t a n d s . To some
e x t e n t t h e y may have been d e t r i m e n t a l : t h e
removal o f t r e e s f o r dwarf m i s t l e t o e c o n t r o l ,
i n s e c t c o n t r o l , and s a n i t a t i o n - s a l v a g e c u t t i n g
a p p e a r s t o have i n t e n s i f i e d t h e annosus r o o t
d i s e a s e problem by c r e a t i n g stumps s u i t a b l e
f o r i n f e c t i o n . E. annosus i n f e c t s a f r e s h l y
c u t stump by means o f a i r b o r n e s p o r e s , coloni z e s t h e stump and s p r e a d s from t h e r o o t s o f
t h e i n f e s t e d stump t o t h o s e o f a d j a c e n t l i v i n g
t r e e s , t h e r e b y c a u s i n g an e n l a r g i n g c e n t e r o f
r o o t damage and t r e e d e a t h .
The emphasis on s o u t h e r n C a l i f o r n i a
F o r e s t s i s now changing from a holding a c t i o n
t o one o f a c t i v e f o r e s t management. The
management procedure i s t h e one t a u g h t a s a
p a r t o f t h e C a l i f o r n i a Region's s i l v i c u l t u r a l
c e r t i f i c a t i o n c o u r s e ( C a l i f o r n i a Region,
F o r e s t S e r v i c e 1976). A c e r t i f i e d s i l v i c u l t u r i s t examines t h e p r e s e n t s t a n d s t r u c t u r e
i n l i g h t o f management o b j e c t i v e s and p r e s c r i b e s treatments t h a t w i l l achieve
SAN BERNARDINO NATIONAL
FOREST 1976
and m a i n t a i n a s u i t a b l e f u t u r e s t r u c t u r e . Prev e n t i v e and remedial i n s e c t and d i s e a s e t r e a t ments a r e c a r r i e d o u t a s a n i n t e g r a l p a r t of
t h e s t a n d p r e s c r i p t i o n , n o t a s s e p a r a t e suppression a c t i v i t i e s .
The dwarf m i s t l e t o e p r e v e n t i o n and suppression treatments t h a t a r e incorporated
i n t o an i n t e g r a t e d management system need n o t
b e complex. The t r e a t m e n t s i n c l u d e t h e t o o l s
w i t h which we a r e a l l f a m i l i a r : s p e c i e s conversion, c u t t i n g of infected t r e e s during
t h i n n i n g s , and o v e r s t o r y removal. But I bel i e v e t h e key i s t o i n c o r p o r a t e them i n t o one
p r e s c r i p t i o n whose aim i s n o t dwarf m i s t l e t o e
c o n t r o l but f o r e s t management.
GROWTH EFFECTS SURVEY
I n 1977, we began t e s t i n g PDI methods
f o r a survey t o measure t h e i n c i d e n c e o f , and
t h e growth l o s s caused by, i n s e c t s and pathogens. We c a l l e d t h i s s u r v e y a Growth E f f e c t s
Survey. Our approach f o r t h i s survey i s t o
LAGUNA MOUNTAIN AREA
CLEVELAND NATIONAL FOREST
1977
F i g u r e 5 - - The r e l a t i o n s h i p between dwarf m i s t l e t o e r o o t pathogen-induced m o r t a l i t y
and t o t a l m o r t a l i t y o f two yellow p i n e s p e c i e s i n two s o u t h e r n C a l i f o r n i a National F o r e s t s .
Fomes annosus was t h e major r o o t pathogen.
-
collect pe t data during the Compartment Inventory ?/' Trees measured by Compartment
Inventory crews are also rated for insects,
diseases, and defect. Information gained from
Growth Effects Surveys are to be used mainly
for two purposes:
1. Timber management: Estimates of the incidence of specific insects and pathogens and
the damage (growth loss and defect) they are
causing are obtained for compartments, and for
strata within the compartments. These estimates are to be used in setting treatment
priorities between strata, and for formulating
stand prescriptions that include treatments
for the prevention and reduction of insect
and disease loss.
2. Administrative uses: When sufficient data
have been collected from compartments in the
Region, reliable estimates of growth loss and
defect caused by dwarf mistletoes and other
damaging pathogens and insects can be made.
Stratum Treatment Priority
and Silvicultural Prescriptions
To date, data summaries are available for
only one compartment, the Barton Flats Compartment on the San Bernardino National Forest
(table 1). The compartment is divided into
type strata that are sampled for growth and
standing volume as well as pests. Thirty prism
points were selected to represent each stratum
(six randomly selected locations for L-shaped
Table 1. The incidence of pests in the Barton Flats Compartment, San Bernardino National Forest.
(Sampling strata were based on tree species composition (pine or mixed conifers), average
d.b.h. class (1 = 0-4.9"; 2 = 5-10.9"; 3 = 11-20.9"; 4 & 5 = 21" or more), and stand stocking density (percent crown closure: - = 0-19; = = 20-39; = 40-69; 5
- = 70-loo).)
=
Stratum
Type
-
Pine
-
Pine
-
Sample
Size
D.B.H. Stocking (No. Prism
Class - Density Points)
Percentage of Prism Points with:
Pest
Problems
Ozone
Injury
Annosus
Root
Dwarf
True
Disease Mistletoe Mistletoe
Other
Pests
Two
All
Storied
30
33
17
7
0
3
6
3
-
23
43
13
4
26
4
0
Pine
3
-
27
11
0
0
4
0
7
Pine
4 & 5
All
30
67
23
20
0
3
21
MC
3
A11
30
47
7
17
7
10
6
MC
4 8 5
All
28
61
14
7
7
7
26
168
46
14
10
7
4
13
All Strata
à ‘ ~ o m ~ a r t m e nare
t land areas used in the
National Forests of California for vegetative
sampling. Ranging from 3,000 to 8,000 acres,
they have boundaries that are defined by
easily identified physical features.
c l u s t e r s of 5 p o i n t s ) . A few p o i n t s were not
usable and excluded from t h e summaries. Stat i s t i c s on stratum growth, stocking, and p e s t
incidence a r e used t o w r i t e s i l v i c u l t u r a l pres c r i p t i o n s f o r stands within t h e s t r a t a .
Nearly h a l f of t h e prism p o i n t s had p e s t
problems ( t a b l e I ) , thereby supporting t h e
contention t h a t t h e compartment i s one needing
management. A p e s t problem was defined a s a
'damaging l e v e l u of a pest:dwarf m i s t l e t o e
r a t i n g o f 4 o r higher, E. annosus r o o t disease
on t h e p l o t , t h e presence of i n s e c t k i l l e d
t r e e s , o r ozone symptoms on second-year pine
needles.
Differences i n p e s t i n t e n s i t y can be used
t o s e l e c t s t r a t a and stands f o r immediate
treatment -- and those i n which treatment can
be deferred. The proportion of prism p o i n t s
with p e s t problems varied by stratum ranging
from 11 percent t o 67 percent.
Pest d a t a can a l s o be used f o r making
s i l v i c u l t u r a l p r e s c r i p t i o n s . A c l o s e r look
a t t h e p e s t s i n Barton F l a t s Compartment s t r a t a
suggests t h a t treatment options w i l l vary between s t r a t a . For example, t h e two young sawtimber s i z e d s t r a t a appear q u i t e d i f f e r e n t with
regard t o p e s t problems. The P 3: stratum
appears r e l a t i v e l y f r e e of p e s t s . Removal of
dwarf m i s t l e t o e i n f e c t e d t r e e s during thinning
may be t h e only s p e c i a l p e s t management necess a r y t o maintain a r e l a t i v e l y healthy young
stand.
The P 3- stratum, on t h e o t h e r hand, may
p r e s e n t a more d i f f i c u l t management problem.
The stocking d e n s i t y i s already low and t h e
high incidence of dwarf m i s t l e t o e i n f e c t i o n
suggests more t r e e s w i l l d i e . Regeneration
with pine w i l l be a problem, unless t h e inf e c t e d pine overstory i s removed. But, t h e
removal of t h e i n f e c t e d overstory, a subs t a n t i a l number of t r e e s , i s not d e s i r a b l e
on t h i s southern C a l i f o r n i a Forest where
maintaining an a t t r a c t i v e appearance i s i m portant.
The mature pine stratum (P 4 & 5) had t h e
g r e a t e s t incidence of p e s t problems. Additiona l m o r t a l i t y may be expected -- e s p e c i a l l y i n
years of environmental s t r e s s . Stand prescript i o n s should allow f o r t h e i r replacement, e i t h e r
by r e l e a s e o r regeneration c u t t i n g . The d a t a
suggest t h a t dwarf m i s t l e t o e i s not a major
problem, and regeneration with pine appears
f e a s i b l e -- even near pine overstory t r e e s .
Ozone i n j u r y t o pine i s l i k e l y t o be a continuing problem, however, and annosus r o o t d i s e a s e
i s an important consideration f o r both pine
and f i r .
P r e s c r i p t i o n s a r e made f o r stands, not
s t r a t a . Nevertheless, compartment inventory
a n a l y s i s r e s u l t s a r e used t o p r o j e c t average
stand 'growth, and t o p r e d i c t t h e general r e sponse of stands within t h e stratum t o d i f f e r e n t
treatment options. Pest e f f e c t s a r e a l s o r e l e vant t o those p r e d i c t i o n s , and t h e p e s t d a t a
can be e f f i c i e n t l y c o l l e c t e d a s a p a r t of t h e
compartment examination process. I f a d d i t i o n a l
information i s needed f o r s p e c i f i c stands,
a d d i t i o n a l compartment inventory d a t a , including
p e s t d a t a , can be c o l l e c t e d .
Growth Loss
The second major goal of growth e f f e c t s
surveys i s t o provide growth l o s s estimates
associated with each of t h e most damaging p e s t s
f o r administrative purposes. A l a r g e r d a t a
base i s required before v a l i d estimates can be
made. Our approach i s t o compare stand growth
i n stands with p e s t s , and those f r e e of p e s t s .
Growth l o s s from a l l p e s t s w i l l be t h e d i f f e r ence between growth i n i n f e s t e d and uninfested
stands when d i f f e r e n c e s i n stocking d e n s i t y ,
s i t e and species composition have been accounted
f o r . E f f e c t s of individual p e s t s and p e s t complexes w i l l be expressed a s a portion of t h e
t o t a l loss.
CONCLUSIONS
Dwarf m i s t l e t o e s a r e major contributors
t o t r e e m o r t a l i t y . Dwarf mistletoe-induced
m o r t a l i t y i s u s u a l l y not a major problem i n
timber producing f o r e s t s where even-aged
management i s p r a c t i c e d and when t h e pathogen
w i l l be eliminated o r reduced t o low l e v e l s
during thinnings o r eliminated a t t h e end of
r e l a t i v e l y s h o r t r o t a t i o n s . But dwarf m i s t l e toe-induced m o r t a l i t y i s e s p e c i a l l y important
i n r e c r e a t i o n a r e a s , and o t h e r areas where
management options a r e reduced. The value of
t h e t r e e s , t h e r a t e s a t which dwarf m i s t l e t o e s
b u i l d up i n t h e s t a n d s , and t h e goal of maint a i n i n g a t r e e cover f o r long periods makes
t h e dwarf m i s t l e t o e s an important management
consideration. Regeneration with s u s c e p t i b l e
t r e e species i s e s p e c i a l l y d i f f i c u l t i f t h e
removal of i n f e c t e d overstory t r e e s i s precluded.
Dwarf m i s t l e t o e s a r e but one important
c l a s s of t r e e p e s t s , and p e s t management systems
must i n t e g r a t e treatments f o r t h e e n t i r e complex
of p e s t s . F a i l u r e t o do so may l i m i t t h e e f f e c tiveness of dwarf m i s t l e t o e c o n t r o l , s i n c e t h e
a n t i c i p a t e d b e n e f i t s o f reduced m o r t a l i t y and
increased growth may not be r e a l i z e d i f o t h e r
v e s t s a r e a l s o present. A t l e a s t one dwarf
m i s t l e t o e control p r o j e c t , on Laguna Mountain,
aggravated t h e r o o t d i s e a s e problem by c r e a t i n g ,
stumps t h a t served a s F. -annosus i n f e c t i o n
courts.
Stand management o b j e c t i v e s can b e s t be
accomplished through t h e i n t e g r a t i o n of p e s t
management p r e s c r i p t i o n s and stand p r e s c r i p t i o n s . Stand management, not dwarf m i s t l e t o e
c o n t r o l alone, i s u s u a l l y required t o a t t a i n
and maintain t h e d e s i r e d s t a n d s t r u c t u r e .
The process i s most e f f i c i e n t when dwarf m i s t l e t o e (and o t h e r p e s t ) c o n s i d e r a t i o n s a r e b u i l t
i n t o forest/compartment/stand i n v e n t o r i e s ,
s t a n d p r e s c r i p t i o n s , and s t a n d treatments.
I f dwarf m i s t l e t o e l e v e l s a r e reduced during
s t a n d management, dwarf m i s t l e t o e damage t o
t h e s t a n d w i l l be prevented, and fewer s p e c i a l
remedial c o n t r o l e f f o r t s w i l l be required i n
the future.
Acknowledgements: I thank t h e following
persons f o r t h e i r c o n t r i b u t i o n s : F. W. Cobb,
J r . , D. L . Dahlsten, J . R. McBride ( a l l of t h e
University of C a l i f o r n i a , Berkeley) and t h e
s t a f f of t h e U.S. Environmental P r o t e c t i o n
Agency f o r use of unpublished d a t a from a coo p e r a t i v e survey on t h e San Bernardino National
F o r e s t ; R. S. Smith, J r . , and R. E . Wood (Cali f o r n i a Region, Forest Service) f o r d a t a summaries from t h e drought survey, t h e Laguna
Mountain e v a l u a t i o n s , and t h e Growth E f f e c t s
Survey; and Nancy X. Norick and Dennis R. Hart
( C a l i f o r n i a Region, Forest Service) f o r s t a t i s t i c a l analyses and d a t a management.
LITERATURE CITED
Bega, R. V . , D. Dotta, D. R. M i l l e r and R. S.
Smith, J r .
1966. Root d i s e a s e survey a t Boggs Mountain
S t a t e F o r e s t , C a l i f o r n i a . P l a n t D i s . Rep o r t e r . 50 :439-440.
Cobb, F. W-., J r . , J . R. Parmeter, J r . , D. L.
Wood and R . W. S t a r k .
1974. Root pathogens a s agents predisposing
ponderosa pine and white f i r t o bark beet l e s . ~ o u r t hConf. on Fomes annosus.
Athens, Ga. p. 8-15.
C a l i f o r n i a Region, Forest S e r v i c e
1977. R5 compartment inventory handbook.
46 pages. San Francisco, C a l i f .
Frye, R. H . , and T. D. Landis.
1975. Biological evaluation -- mountain
pine b e e t l e and dwarf m i s t l e t o e , Lake
Creek Area, San Carlos Ranger D i s t r i c t ,
Pike-San I s a b e l National F o r e s t . USDA
Forest Serv., Rep. R-2-75-4, Lakewood,
Colo. 10 p.
Hawksworth, F . G . , and A. A. Lusher.
1956. Dwarf m i s t l e t o e survey and c o n t r o l
on t h e Mescalero-Apache Reservation, New
Mexico. J . For. 56(6):384-391.
Johnson, D. W . , L . C. Yarger, C. D. Minnemeyer
and V. E. Pace.
1976. Dwarf m i s t l e t o e a s a predisposing
f a c t o r f o r mountain p i n e b e e t l e a t t a c k of
ponderosa pine on t h e Colorado Front Range.
USDA Forest Serv., Region 2, Tech. Rep.
R2-4. Lakewood, Colo. 7 p.
M i l l e r , D. L . , and A. D. P a r t r i d g e .
1974. Root r o t i n d i c a t o r s i n grand f i r .
Plant Dis. Reporter 5803) :275-276.
M i l l e r , J. M . , and F. P. Keen.
1960. Biology and c o n t r o l of western p i n e
b e e t l e . USDA Misc. Publ. 800. 381 p.
Parker, D. L., and E. L. S t i p e .
1974. Does mountain p i n e b e e t l e s e l e c t and
k i l l dwarf m i s t l e t o e - i n f e c t e d lodgepole
pine? USDA Forest S e r v . , Region 4. Ogden,
Utah. 4 p.
Parker, D. L . , J . W. Walters, and A. H. Smith.
1975. Assessment of f a c t o r s causing pondeross
pine m o r t a l i t y on t h e Lincoln National
Forest. USDA Forest S e r v . , Region 3 ,
Albuquerque, N.M.
19 p.
P a r t r i d g e , A. D . , and D. L. M i l l e r .
1972. Bark b e e t l e s and r o o t r o t s r e l a t e d
i n Idaho c o n i f e r s . Plant Dis. Reporter
56 :498-500.
S t a r k , R. W . , and F. W. Cobb, Jr.
1969. Smog i n j u r y , r o o t d i s e a s e s and bark
b e e t l e damage i n ponderosa pine. C a l i f .
Agric. 23(9) :13-15.