The insect fauna of Canada thistle, Cirsium arvense (L.) Scop. in southern Montana
by Hilde De Smet-Moens
A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE
in Biological Sciences
Montana State University
© Copyright by Hilde De Smet-Moens (1982)
Abstract:
Insects associated with Cirsium arvense (L.) Scop, in southern Montana are reported. Fifty-six
phytophagous species and 47 visiting insects were collected, identified and tabulated.
Four insect species, Corythucha distincta Osborn and Drake (Hemiptera: Tingidae), Bans sp., poss.
cirsii Gilbert (Coleoptera: Curculionidae), Vanessa cardui L. (Lepidoptera: Nymphalidae), and Orellia
ruficauda (Fabricius)(Diptera: Tephritidae), were considered conspicuous, because of their damage
inflicted to the thistle plant.
More insects were found associated with the developing seed heads than with foliage, stems or roots.
The information gathered on this local survey can be valuable for future introductions of insect
biological control agents. It forms the foundation for follow-up studies with indigenous insect species.
Augmentation and redistribution of established monophagous insects, such as Ceuthorynchus litura and
Baris sp. should be considered. Transmission experiments are necessary to evaluate the potential of
these monophagous insects as thistle pathogen vectors. The combination of two stress-factors will
increase the impact on the thistle plant in the field. STATEMENT OF PERMISSION TO COPY
In p r e s e n t i n g t h i s t h e s i s in p a r t i a l f u l f i l l m e n t o f t h e r e q u i r e ­
ments f o r an advanced de gre e a t Montana S t a t e U n i v e r s i t y , I agree t h a t
t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r i n s p e c t i o n .
I further
agree t h a t pe rm is si o n f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y
purposes may be g r a n t e d by my major p r o f e s s o r , o r , in h i s abse nc e, by
t h e D i r e c t o r of L i b r a r i e s .
I t is understood t h a t any copying or p u b l i ­
c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l ga in s h a l l not be allowed witho ut
my w r i t t e n p e r m is s i o n .
S i g n a t u Ie
Date
THE INSECT FAUNA OF CANADA THISTLE, CIRSIUM ARVENSE (L .) SCOP
IN SOUTHERN MONTANA
by
. .
HILDE DE SMET-MOENS
A t h e s i s sub mit te d in p a r t i a l f u l f i l l m e n t
of t h e re q u ir e m e n ts f o r t h e degree
of
' MASTER OF SCIENCE
in
B i o l o g i c a l Scie nce s
Approved:
MONTANA STATE UNIVERSITY
Bozeman, Montana
August, 1982
/
/
iii
. ACKNOWLEDGMENTS
I wish t o acknowledge and e x p r e s s my a p p r e c i a t i o n f o r t h e c o n t r i ­
b u t i o n s of t h e f o l l o w i n g people:
Dr. W. L. M o r r i l l , my major p r o f e s s o r , f o r h i s p r o f e s s i o n a l a s s i s t ­
ance th ro u g h o u t t h i s r e s e a r c h p r o j e c t ;
The members of my t h e s i s committee. Dr. P. K. F a y , Dr. S. R.
Eversman, and Mr. J . M. S t o r y , f o r t h e i r tim e and i n v a l u a b l e a dvice ;
Mrs. S. D. Rose, C u r a t o r of t h e M.S.U. Entomological C o l l e c t i o n ,
f o r h e r taxonomic a d v ic e and he lp ;
All t h e s y s t e m a t i c i s t s who i d e n t i f i e d t h e i n s e c t s mentioned in t h i s
r e p o r t : t h e t a x o n o m i s t s . o f t h e Sy s te m a ti c Entomology L a b o ra to ry , USDA,
B e l t s v i l . l e , MD; and t h e N a ti o n al Museum of Na tural H i s t o r y , Smithsonian
I n s t i t u t i o n , Washington, DC; J . L a t t i n , P. Oman, K. A. P h i l l i p s , and
G. M. S t o n e d a h l , Oregon S t a t e U n i v e r s i t y , C o r v a l l i s ; L. A. K e l t o n , Bios y s t e m a t i c s Research I n s t i t u t e , Ottawa; M. W. N ie ls o n , Forage I n s e c t s
Research L a b o r a to r y , Tucson, AZ; G. J . M ic he ls , J r . , Texas A&M Univer­
s i t y , A m a ril lo ; R. J . B e s h e a r , The U n i v e r s i t y of Ge orgia, Experiment;
J . A. Onsager and E. A. Oma, U.S.D.A. Rangeland I n s e c t La b o ra to ry ,
Bozeman; R. M. B o h a r t , U n i v e r s i t y o f C a l i f o r n i a , Davis; D. K. Young,
Michigan S t a t e U n i v e r s i t y , Ea st Lansing;
. The Western A g r i c u l t u r a l Research C en t er and t h e Montana weed
d i s t r i c t s f o r t h e fun din g of t h i s r e s e a r c h p r o j e c t .
TABLE OF CONTENTS
Page
VITA ....................................................
ACKNOWLEDGMENTS
i.i
......................
iii
LIST OF TABLES.....................................................................
LIST OF FIGURES
.
. . . ..............................................................................
vi
ABSTRACT .................................................................
vii
INTRODUCTION....................................................
LITERATURE REVIEW
....................
I
. . . . . . . .
3
CO
(T i
The Host P l a n t ............................................ .....................
B i o l o g i c a l Co ntrol of Canada T h i s t l e ..................
B i o l o g i c a l Co ntrol of Canada T h i s t l e in Montana
MATERIALS AND METHODS
v
. , ...................... - . ....................... ....
12
Study S i t e s .....................................................................................................
C o l l e c t i n g M e t h o d s ...........................................
Experimental R e a r i n g s ................................................ .... . ' ..................
F i e l d S t u d i e s .....................
I n s e c t I d e n t i f i c a t i o n ..................
RESULTS AND DISCUSSION..................................
.
Phytophagous I n s e c t s .. ............................................
.
V i s i t o r s , P r e d a t o r s and P a r a s i t o i d s . . . . . . . . . . . .
Summ ary......................
.....................................................■
LITERATURE CITED ..........................................................................
12
12
15
16
16
18
18
38
42
46
V
LIST OF TABLES
Table
1.
2.
3.
4.
5.
6.
7.
Page
In fo rm a tio n on t h e i n s e c t s r e l e a s e d in Montana
f o r t h e b i o l o g i c a l c o n t r o l of Canada t h i s t l e ...............................
10
S e l e c t e d c o l l e c t i o n s i t e s of t h e 1981 i n s e c t
survey on Canada t h i s t l e ...................... ...................................... ....
14
Phytophagous i n s e c t s c o l l e c t e d from Canada
t h i s t l e , Cirsium a ry e ns e (L .) S c o p . , in
s o u th e r n Montana, 1981 . . . . ............................... ..............................
19
Average p l a n t h e i g h t s o f e i g h t B a r is i n f e s t e d
and e i g h t uni n f e s t e d t h i s t l e p l a n t s in s i t e s
5 and 6, June 19, 1981 ............................... . . ...................................
30
I n f e s t a t i o n o f Canada t h i s t l e heads by O r e l l i a
r u f i c a u d a ( F a b r i c i u s ) , September 3, 1981 . . . ...........................
37
V i s i t o r s , p r e d a t o r s , and p a r a s i t o i d s c o l l e c t e d
from Canada t h i s t l e , Cirsium a rv e nse (L .) Scop.
in so u th er n Montana, 1981 T ...................... ..................... .....................
39
P a r a s i t i s m of O r e l l i a r u f icauda ( F a b r i c i u s )
pupae in Canada t h i s t l e seed head s, S e p t e m b e r ^ , 1981
43
. . .
vi
LIST OF FIGURES
F ig u r e
1.
Page
C o l l e c t i o n s i t e s o f t h e i n s e c t survey on
Canada t h i s t l e , 1 9 8 1 ...............................................................................
13
2.
Emergence t r a p in s i t e 5 . . . ................................. ........................
17
3.
Corythucha d i s t i n c t a a d u l t s f e e d i n g on
Canada t h i s t l e le av e s . . ............................................ .....................
23
Feeding damage o f Corythucha d i s t i n c t a
on Canada t h i s t l e
.
.
...............................................
23
4.
5 . • Aggregation of Corythucha d i s t i n c t a nymphs
on t h e u n d e r - s i d e o f Canada t h i s t l e le ave s . . . . . . . .
25
6.
B a r is sp. a d u l t fe e d i n g on t h i s t l e r o s e t t e ...............................
28
7.
Feeding damage o f B a r is sp. a d u l t s on p o tt e d
t h i s t l e p l a n t s in t h e i n s e c t a r y ...................... ....
31
8.
B ar is s p. l a r v a in Canada t h i s t l e r o o t ...................... 31
9.
Wilted t h i s t l e p l a n t in s i t e 5, i n f e s t e d
with B ar is s p . l a r v a e ..........................................................................
31
L i n e a r r e g r e s s i o n of p l a n t h e i g h t v e rs us
l a r v a l f r e q u e n c y , August 19 8 1 ........................................................
33
Feeding damage o f O r e l l i a r u f i c a u d a . l a r v a e
on Canada t h i s t l e seeds. . -................................... .. ...........................
36
P a r a s i t i z e d O r e l l i a r u f i c a u d a pupa . . . ...................................
44
10.
11.
.12.
. ABSTRACT
I n s e c t s a s s o c i a t e d with Cirsium a rv e nse ( I . ) Scop, in south ern
Montana a r e r e p o r t e d . F i f t y - s i x phytophagous species, and 4 7 . v i s i t i n g
i n s e c t s were c o l l e c t e d , i d e n t i f i e d and t a b u l a t e d .
Four i n s e c t s p e c i e s , Corythucha d i s t i n c t a Osborn and Drake
(Hemiptera: T i n g i d a e ) , B a n s s p . , p o s s . c i r s i i G i l b e r t ( C ole opte ra :
C u r c u l i o n i d a e ) , Vanessa^cardui L. ( L e p i d o p t e r a: Nyrnphalidae),. and
O r e l l i a r u f i c a u d a ( F a b r i c i u s ) ( D i p t e r a : T e p h r it i d a e ) , were c o n s i d e r e d ,
c o n s p ic u o u s , because of t h e i r damage i n f l i c t e d t o t h e t h i s t l e p l a n t .
More i n s e c t s were found a s s o c i a t e d with t h e - d e v e l o p i n g seed heads
th a n with f o l i a g e , stems or r o o t s .
The i n fo r m a t io n g a th e r e d o h . t h i s lo c a l survey can be v a l u a b l e f o r
f u t u r e i n t r o d u c t i o n s of in s ec t, b i o l o g i c a l c o n t r o l a g e n t s . I t forms t h e
fo u n d a ti o n f o r fo ll o w - u p s t u d i e s with indigenous i n s e c t s p e c i e s .
Augmentation and r e d i s t r i b u t i o n of e s t a b l i s h e d monophagous i n s e c t s
such as Ceuthorynchus l i t u r a and B a r is sp. should, be c o n s i d e r e d . Trans
mi ssi on ex periments a r e n e c e s s a r y t o e v a l u a t e t h e p o t e n t i a l of these '
monophagous ins ects, as t h i s t l e pathogen v e c t o r s . The combination of .
two s t r e s s - f a c t o r s w i l l i n c r e a s e t h e impact on t h e t h i s t l e p l a n t in .
the f i e l d . -
INTRODUCTION
C u l t u r a l and chemical c o n t r o l p r a c t i c e s have h i s t o r i c a l l y been t h e
main approaches t o weed c o n t r o l .
Both methods a r e aimed a t removing
unwanted p l a n t s as q u i c k l y as p o s s i b l e , a s h o r t term approach r e q u i r i n g
c o n s i d e r a b l e annual e x p e n d i t u r e s of r e s o u r c e s and energy (Andres and
Gpeden, 1971).
B i o l o g i c a l c o n t r o l o f weeds has become a p o p u la r a l t e r n a ­
t i v e because i t i s a means o f c o n t r o l l i n g weeds w i t h o u t t h e high energy
c o s t s o f c u l t u r a l p r a c t i c e s and w i t h o u t t h e r e s i d u e and p o l l u t i o n prob­
lems o f h e r b i c i d e s .
B i o l o g i c a l c o n t r o l o f weeds i s t h e d e l i b e r a t e use of i n s e c t s or
o t h e r p l a n t p a r a s i t e s t o reduce t h e d e n s i t y o f a weed t o an a c c e p t a b l e
l e v e l ( H a r r i s , 1971b).
B i o c o n t r o l , when e f f e c t i v e , i s r e l a t i v e l y in e x­
p e n s i v e , l o n g - l a s t i n g and t h e b e n e f i t s a r e c u m u la ti v e .
This approach
has s t r e n g t h s and weaknesses d i f f e r e n t from o t h e r methods and hence i s
advantageous under c e r t a i n c o n d i t i o n s ( H a r r i s , 1971b; Maw, 1982).
c ro ps of^arablle land lhave many s p e c i e s of weeds as c o m p e t i t o r s .
c o n t r o l l i n g one s p e c i e s through b i o l o g i c a l
Most
Thus,
c o n t r o l would r e q u i r e s p r a y ­
ing o r c u l t i v a t i o n f o r c o n t r o l o f t h e o t h e r s p e c i e s .
On t h e o t h e r hand,
dominance o f one weed s p e c i e s i s t y p i c a l on range lan d.
Such a domi­
na nt weed i s a very s u i t a b l e s u b j e c t f o r b i o l o g i c a l c o n t r o l .
Even a
s l i g h t i n c r e a s e in p r e s s u r e can have a s i g n i f i c a n t e f f e c t ( H a r r i s , 1971b).
One o f t h e i n i t i a l s t e p s in de vel opin g a b i o l o g i c a l weed c o n t r o l
program i s t o de te r m in e t h e n a t u r a l enemies a t t a c k i n g t h e weed s p e c i e s ,
2
in both i t s n a t i v e and i t s p r e s e n t geog raphic ranges (Maw, 1980; H a r r i s ,
1971a).
I n i t i a l surveys expand i n s i g h t and un de rs ta ndi ng o f t h e weed
e co lo gy , h o s t r a n g e s , e t h o lo g y and i n s e c t - h o s t i n t e r r e l a t i o n s h i p s .
The
i n fo r m a t io n g a t h e r e d in t h e l o c a l s u r v e y s . i n d i c a t e s t h e n i c h e s occupied
\
'
■
by indigenous s p e c i e s ^ so t h a t chances of i n t r o d u c i n g a b i o c o n t r o l agent
t h a t may d u p l i c a t e o r compete with an a l r e a d y p r e s e n t s p e c i e s a r e m i n i ­
mized (Maw, 1976).
The o b j e c t i v e s of t h i s study were:
I) t o det ermi ne t h e endemic
i n s e c t fauna a s s o c i a t e d with t h e d i f f e r e n t growth s t a g e s of Canada
t h i s t l e , Cirsium a rv e ns e ( I . ) S c o p . , in Southern Montana, and 2). t o
e v a l u a t e t h e damage i n f l i c t e d by t h e most conspicuous s p e c i e s .
LITERATURE REVIEW
The Host P l a n t
Cirsium a rv en se ( L , ) Scop, i s a troubl eso me p e r e n n i a l weed in
Montana.
Indigenous t o Europe, Western Asia and Northern A f r i c a , i t was
pr ob a bl y in tr odu ce d t o North America in t h e 17th Century (Detmers, 1927;
Pe sch ke n, 1971).
I n f e s t a t i o n s o f Canada t h i s t l e now o c cu r th rou ghout
t h e a g r i c u l t u r a l a r e a s of Canada and t h e n o r t h e r n h a l f o f t h e United
S t a t e s ( Pes chk en , 1971; H itc hco ck , e t a l . , 1973).
A r e c e n t survey i n d i ­
c a t e d t h a t t h i s troubl eso me weed i n f e s t s 1.5 m i l l i o n a c r e s in Montana.1
Canada t h i s t l e damages a wide v a r i e t y of crops by c o m p e t i t i v e use
o f l i g h t , m o i s t u r e and n u t r i e n t s (Hodgson, 1977).
Heavy i n f e s t a t i o n s in
p a s t u r e s and ranges reduce f o r a g e y i e l d s c o n s i d e r a b l y .
The weed a l s o
h a r b o r s i i n s e c t s t h a t a t t a c k economic crops and is an a l t e r n a t e ho s t f o r
some p a th oge nic organisms (Moore, 1975).
Cirsium a rv e ns e ( L . ) Scop, i s a polymorphic s p e c i e s .
and f l o w e r c h a r a c t e r i s t i c s vary c o n s i d e r a b l y .
Stem, l e a f
B o t a n i s t s u s u a l l y reco g­
n i z e t h r e e o r f o u r morphological v a r i a n t s , a l l i n t e r b r e e d i n g f r e e l y
(Moore and F r a n k t o n , 1974; Hodgson, 1964; Detmers, 1927).
Canada t h i s t l e
i s d i o e c i o u s and r e p r o d u c t i o n occurs from seed and rhizome p i e c e s .
Detmers (1927) s t a t e d t h a t honey bees were t h e c h i e f p o l l i n a t i o n a g e n t s .
I
Jackson,: M. J . ,
1982.
Perso na l communication.
4
In Montana, t h e t h i s t l e p l a n t s emerge in e a r l y May, when t h e mean
weekly a i r te m p e r a t u r e reach es 5°C (Moore, 1975).
R o s e t t e s a r e formed
followe d by stem e l o n g a t i o n app rox imate ly t h r e e weeks a f t e r emergence
(Moore, 1975).
September.
Flowering be gin s in mid-June and c o n t i n u e s i n t o
Growth be gi ns d e c r e a s i n g in J u l y , and c e a s e s by e a r l y August
The obnoxious c h a r a c t e r of t h i s weed is due mainly t o t h e rapid
v e g e t a t i v e p r o p a g a t i o n o f i t s c r e e p i n g h o r i z o n t a l rhizomes, giv in g r i s e
t o numerous a e r i a l sh oots (Moore, 1975).
This e x t e n s i v e branched
rhizome system makes Canada t h i s t l e d i f f i c u l t t o c o n t r o l ,
Cultural,
mechanical and chemical c o n t r o l methods can be e f f e c t i v e in c u l t i v a t e d
f i e l d s i f used p e r s i s t e n t l y in a long range c o n t r o l program (Hodgson,
1977).
Where Canada t h i s t l e i s a p r e v a l e n t weed in range la n d , f a ll o w
f i e l d s , waste l a n d s , r o a d s i d e s o r r a i l w a y s , b i o l o g i c a l c o n t r o l by i n ­
s e c t s can be a re a s o n a b l e a d j u n c t .
These h o s t s p e c i f i c i n s e c t s are
harmless t o n o n - t a r g e t p l a n t s and may be a b l e t o m u l t i p l y and d i s p e r s e
to adjacent in f e s ta tio n s .
B i o l o g i c a l Control of Canada T h i s t l e
The p r i n c i p l e s and proc ed ures o f b i o l o g i c a l weed c o n t r o l have been
well d e f i n e d and i l l u s t r a t e d with some s p e c t a c u l a r s u c c e s s e s (Be Bach,
1964; Van den Bosch, e t a l . , 1982).
B i o l o g i c a l c o n t r o l s t r i v e s to
reduce t h e abundance of a weed s p e c i e s by i n tr o d u c in g o r augmenting t h e
weed's n a t u r a l enemies.
Huffaker (1959) l i s t s examples in which
5
n a t u r a l l y o c c u r r i n g i n s e c t s have played an impor tant r o l e in a f f e c t i n g
t h e abundance o f a p a r t i c u l a r p l a n t s p e c i e s . . The i n t r o d u c t i o n of ho s t
s p e c i f i c phytophagous organisms has r e c e i v e d t h e most emphasis t o d a t e
(Andres, e t a l . , 1976).. The s t e p s involved in such a t e c h n i q u e are
d e s c r i b e d by H a r r i s (1971b).
■ Cirsium a rv e ns e ( L.) Scop, i s a prime c a n d i d a t e f o r b i o l o g i c a l con
t r o l (Hume,.1982; H a r r i s , 1971b, A ndr e s , e t a l . , 1976) because:
1.
The p l a n t has l i t t l e o r no va lu e t o people o r w i l d l i f e .
2.
I t t e n d s t o grow in dense p o p u l a t i o n s , r e p r e s e n t i n g a
dominant weed in p a s t u r e and waste a r e a s .
3.
I t i s an in tr o d u c e d weed, and has very few p a r a s i t e s and
predators.
4.
I t i s not c l o s e l y r e l a t e d t o major economic crop; p l a n t s ;
however a r t i c h o k e (Cynara scolymus I . ) and s a f f l o w e r
( C a r t h amus t i n c t o r i us L.) belong t o t h e same Cyhareae
tribe.
5.
Many of t h e t h i s t l e i n f e s t a t i o n s occu r in i n a c c e s s i b l e
. a r e a s and th u s lend th em sel ve s t o b i o c o n t r o l e f f o r t s
( S t o r y , 1980).
6.
The widespread d i s t r i b u t i o n of t h e weed w i l l r e s u l t in
low c o s t p e r a c r e of c o n t r o l .
T h is.c o st per acre will
be lower tha n t h a t of o t h e r c o n t r o l methods ( H a r r i s , 1979).
6
B i o l o g i c a l c o n t r o l w i l l i n c r e a s e t h e environmental p r e s s u r e on
Canada t h i s t l e .
At. b e s t , t h e n a t u r a l enemies may e l i m i n a t e t h e need f o r
o t h e r c o n t r o l methods o ve r much o f t h e p l a n t ' s range and form a sound
b a s i s f o r f u t u r e weed management schemes.
At l e a s t , t h e y would augment .
e x i s t i n g c o n t r o l p r a c t i c e s ('Batra-, e t a l . , 1981) .
The Commonwealth I n s t i t u t e of B i o l o g i c a l Control began work on t h e .
c o n t r o l o f Canada t h i s t l e in 1961, with a stu dy of i t s p a r a s i t e s in
Europe ( Pe sch ken , 1971).
Eighty i n s e c t :s pe c ie s were found t o feed on
t h e weed, A l t i c a c ar d u o ru m -Guer. ( C o l e o p t e r a : Chrysomeli d a e ) ,
Ceutorhynchus l i t u r a (F ab. ) ( C o le o p te ra : C u r c u li o n id a e ) and Urophora
c a r d u i ( I . ) ( D i p t e r a : T e p h r i t i d a e ) were s e l e c t e d f o r f u r t h e r study b e ­
cause o f t h e i r a p p a r e n t h o s t s p e c i f i c i t y (Peschken, 1971; Z w o lf e r , 1964).
Al I t h r e e i n s e c t s have been r e l e a s e d in Canada and t h e United S t a t e s . .. A l t i c a carduorum Guerin f a i l e d t o . e s t a b l i s h in a l l r e l e a s e s i t e s
due t o c l i m a t i c s t r e s s and a t t a c k by i n s e c t p r e d a t o r s ( P es c hk en , e t a l . ,
1970).
Ceutorhynchus l i t u r a ( F .) i s e s t a b l i s h e d in a wide range o f c l i ­
mates in Canada (Peschken, e t a l . ,
1980), Montana and Idaho; however,
t h e range of i n f e s t a t i o n i s i n c r e a s i n g very slo wly .
While t h i s weevil
e x e r t s s t r e s s on i t s h o s t in t h e l a b o r a t o r y (Peschken and Beecher, 1973)
t h e r e i s no ev ide nc e t h a t C,. l i t u r a c o n t r o l s Canada t h i s t l e in t h e f i e l d
(Peschken, et, a l . ,
19Q1).
7
Urophora c ar du i ( L . ) has. become e s t a b l i s h e d and i s sp re ad in g in
e a s t e r n Canada ( P es c hke n, e t a l . , 1980).
A microsporidian disease of
LL c ar du i (Nosema s p . ) i s one o f t h e causes le adi ng t o f a i l u r e of
e s t a b l i s h m e n t in t h e Western s t a t e s .
Other r e a s o n s , such as i n f e r t i l i t y
o f t h e f l i e s , o r s p r i n g f r o s t k i l l i n g o f t h e l a r v a e may have been a d d i ­
t i o n a l causes of m o r t a l i t y (Peschken, e t a l . , 1982).
Ap pa rentl y t h e t w o . e s t a b l i s h e d in tr od uce d i n s e c t s w i l l not c o n t r o l
Canada t h i s t l e .
F u r t h e r s t r e s s f a c t o r s from o t h e r i n s e c t s , pathogens
o r p l a n t c o m p e t it io n a r e needed t o c o n t r o l t h i s weed.
Few p o t e n t i a l l y e f f e c t i v e and h o s t s p e c i f i c i n s e c t s from Z w o l f e r 's
l i s t (1964) a r e s t i l l a v a i l a b l e .
T i n g i s am plia ta H.-S. ( H e t e r o p t e r a:
T in gi da e ) was r e c e n t l y t e s t e d f o r h o s t s p e c i f i c i t y in t h e l a b o r a t o r y .
I t was c o n s id e r e d uns af e f o r i n t r o d u c t i o n in Canada, because i t s h o s ts
i n c lu d e s a f f l o w e r and globe a r t i c h o k e .
Lema c y a n e l l a ' ( I . )
The approval f o r r e l e a s e of
( C o le o p te r a : C u r c u l i o n i d a e ) has been w it h h e ld be­
cause i t a t t a c k s s e v e r a l Cirsium spp. indigenous t o North America
(Peschken, e t a l . ,
1980).
The p r e s e n t concern f o r n a t i v e Cirsium s p e c ie s has become a c r i t i ­
cal issue.
Had such s t r i n g e n t host s p e c i f i c i t y req u ir e m e n ts been
a p p l i e d in t h e p a s t , a number of i n s e c t s would never have been r e l e a s e d .
This f e a r f o r n a t i v e f l o r a could lengthe n t h e s c r e e n in g p r o c e s s con­
s i d e r a b l y and many promising agen ts could be r e j e c t e d .
B i o l o g i c a l con­
t r o l could th e n become i m p r a c t i c a l a n d .v e r y ex p en s iv e .
Peschken (1982)
8
reviewed s u c c e s s f u l b i o l o g i c a l weed c o n t r o l p r o j e c t s and concluded t h a t
no t a r g e t weed has e v e r become r a r e .
He s t a t e d t h a t i t i s very u n l i k e l y
t h a t n a t i v e p l a n t s , which a r e in e q u i l i b r i u m with t h e i r own i n s e c t fa u n a ,
would su p p o rt a d d i t i o n a l i n s e c t s p e c i e s .
P o p u l a t i o n s of Canada t h i s t l e a r e a l s o a t t a c k e d by numerous in d i g e n ­
ous i n s e c t s and pa th o g en s .
Nat ura l enemies, a s s o c i a t e d with Canada
t h i s t l e in North America have been r e p o r t e d by Moore (197 5) , Maw (1976),
Watson, e t a l . (198 0) , Detmers (1927), and Andres (1980).
Among t h e
most imp or tan t s p e c i e s were:
a.
The p a i n t e d lady b u t t e r f l y , Vanessa c a r d u i L. ( =Pyrameis cardui
L . , =Cynthia c ar du i ( I . ) )
( L e p i d o p t e r a : NymphaTidae).
The
l a r v a e o c c a s i o n a l l y cause s p e c t a c u l a r d e f o l i a t i o n o f t h i s t l e s
in l o c a l a r e a s . .
I t i s a m i g r a to r y b u t t e r f l y , and i t s numbers
f l u c t u a t e a n n u a l l y , making i t u n r e l i a b l e as a n a t u r a l c o n t r o l
agent.
I t can be a p e s t of sunf lower and soybean (Morihara.
and. Balsbaugh, 1976) and many o t h e r p l a n t s .
b.
The Canada t h i s t l e midge Dasyneura g ib s o n i F e l t ( D i p t e r a :
Cecidomyii d a e ) , which a t t a c k s t h e de vel opin g seed
c.
heads.
O r e l l i a r u f i c a u d a ( F . ) ( =Trypeta f l o r e s c e n t i a e L.) ( D i p t e r a :
T e p h r i t i d a e ) which a t t a c k s up t o 70% o f t h e t h i s t l e he ads .
This seed head f l y was probably a c c i d e n t a l l y in tr oduc e d from
Europe ( H a r r i s , 1971a).
9
d.
Cassida r u b i g i n o s a MuelI . ( C d le o p te ra : Chrysomeli d a e ) :
This
b e e t l e was a c c i d e n t a l l y in tr od uce d i n t o t h e United S t a t e s
(Ward, 1976), and d e f o l i a t e s Canada t h i s t l e a t high po p u la ­
tions.
This f l e a b e e t l e has become widely e s t a b l i s h e d in t h e
E a s te r n United S t a t e s (Ward, 1976).
e.
The systemic a u to e c io u s r u s t P u c c in ia obtegens (Link) T u l . is
an endemic patho gen , h o s t s p e c i f i c t o Canada t h i s t l e .
N a tu r­
a l i n f e c t i o n i s no t high enough f o r economic c o n t r o l .
Since host
r e s i s t a n c e i s an im por tan t f a c t o r l i m i t i n g r u s t i n f e c t i o n , an
a g g r e s s i v e s t r a i n may be more e f f e c t i v e as a b i o c o n t r o l agent
o f Canada t h i s t l e (T u r n e r , 1981).
None o f t h e l i s t e d s p e c i e s su pp re ss Canada t h i s t l e p o p u l a t i o n s below
t h e economic l e v e l .
However, i n v e s t i g a t i o n s of t h e bio lo g y o f t h e most
d e s t r u c t i v e organisms could r e s u l t in t h e development o f approaches
whereby p o p u l a t i o n s o f t h e s e n a t u r a l enemies a r e augmented t o i n c r e a s e
t h e i r damage t o Canada t h i s t l e (Watson, e t a l . , 1980; Ward, 1976;
Tu r n e r , 1981).
B i o l o g i c a l Co ntrol of Canada T h i s t l e in Montana
The b i o l o g i c a l c o n t r o l program o f Canada t h i s t l e in Montana began
with t h e l i b e r a t i o n of A l t i c a
carduorum Guerin in 1964.
Sub se quen tl y,
t h e stem weevil Ceutorhynchus l i t u r a ( F . ) was r e l e a s e d in 1973 and
Urophora c ar du i (L.), in 1978 ( S t o r y , 1979) (Table I ) .
Of t h e t h r e e ,
Table I .
In f orm a tio n on t h e i n s e c t s r e l e a s e d in Montana f o r t h e
b i o l o g i c a l c o n t r o l o f Canada t h i s t l e . a
Insect
A ltica
carduorum Guerin
Date
Insects
Released
No.
Insects
Released
County
where
Released
Source
of
Insect
Status
.
of
Insect
1964
1966
200
200.
R av a ll i
Gallatin
USDA
USDA
No recovery
No rec overy
Ceutorhynchus
litu ra (F .)
1973
200
Gallatin
. USDA
Inc. slowly
Urophora
c ar du i ( I . )
1978
92
R a v a ll i
USDA
No recovery
^Data from S t o r y , J . M., 1979.
11
onl y Ceutorhynchus l i t u r a ( F . ) has su rv iv e d and become e s t a b l i s h e d .
Attempts t o r e d i s t r i b u t e t h e weevil were made in 1977. a t t h e Bozeman
s i t e , when 95% of t h e s hoo ts were found t o be mined ( S t o r y , 1980).
P l a n t s i n f e s t e d with C_. l i t u r a l a r v a e were c o l l e c t e d in June from t h e ■
r e l e a s e s i t e and t r a n s p l a n t e d in o t h e r a r e a s of Montana.
The re a so n s f o r f a i l u r e of A I t i c a carduorum Guerin and Urophdra
c a r d u i ( L . ) t o e s t a b l i s h in Montana a r e not known.
t o e s t a b l i s h jJ. c a r d u i
A d d i t i o n a l a tt e m pts
w i l l be made as more i n s e c t s become a v a i l a b l e
( S t o r y , 1980).
The b i o l o g i c a l weed c o n t r o l . p r o g r a m in Montana i s i n c r e a s i n g in
momentum.
I n t e r e s t and awareness by t h e p u b l i c and academic communities
a re growing.
Endemic p l a n t pathogen's, p a r t i c u l a r l y P u c c in ia obtegehs
I
(T ur ne r, 1981) and S c l e r o t i n i a s c l e r o t i o r u m (Simmonds, 1982) a re being
i n v e s t i g a t e d as p o t e n t i a l b i o c o n t r o l ag en ts a g a i n s t Canada t h i s t l e in
Montana.
The use of p l a n t pat hogen s may extend t h e a p p l c i a t i o n of b i o ­
l o g i c a l weed c o n t r o l t o i n c lu d e c u l t i v a t e d a r e a s .
MATERIALS AND METHODS
Study S i t e s
A t o t a l of 50 s i t e s were surveyed th ro ughou t t h e 1981 growing s e a ­
son, s t a r t i n g A p ri l 15 and ending September 30 (F ig ur e I)..
This pe ri o d
co ver s r o s e t t e , v e g e t a t i v e , f lo w e r in g and f r u i t i n g s t a g e s o f t h e t h i s t l e
plant.
Most o f t h e l o c a t i o n s r e p r e s e n t o c c a s i o n a l c o l l e c t i o n s i t e s .
Seven were s e l e c t e d f o r more i n t e n s i v e weekly o r bi-m onthl y sampling
(T able 2 ) .
S e l e c t i o n o f t h e s e s i t e s was based on e x t e n t o f t h i s t l e
i n f e s t a t i o n , h a b i t a t - t y p e , a c c e s s i b i l i t y and absence o f h e r b i c i d e and
p e s t i c i d e u s e.
C o l l e c t i n g Methods
The samples were c o l l e c t e d by t h e f o ll o w i n g methods:
1. .
Stand s .of Canada t h i s t l e p l a n t s were examined c a r e f u l l y f o r
i n s e c t i n f e s t a t i o n s and e x t e r n a l symptoms of endophagy.
Feeding o r o v i p o s i t i o n damage was recorded in t h e f i e l d and '
whenever p o s s i b l e c o r r e l a t e d with t h e i n s e c t s p e c i e s p r e s e n t .
2.
Most of t h e i n s e c t s were c o l l e c t e d by h a n d p i c k i n g , t h e only
method a llo w ing c o r r e c t l o c a l i z a t i o n of t h e sampled specimens.
Sweeping d i s t u r b e d t h e i n s e c t s and did not always d i s l o d g e
i n d i v i d u a l s on upper and lower p a r t s o f t h e p l a n t .
3.
O c c a s i o n a l l y , a simple p o l y e t h y l e n e - b a g s a m p l in g .t e c h n iq u e
was used (Trumble, e t a l . , 1975).
A l a r g e p o l y e t h y l e n e bag
M ' W O u I*
# : occas ional c o l l e c t i o n s i t e s
O : s e le c te d c o l l e c t i o n s i t e s
Fi gu re I .
C o l l e c t i o n s i t e s of t h e i n s e c t survey on Canada t h i s t l e , 1981.
14
Table 2.
Site
S e l e c t e d c o l l e c t i o n s i t e s o f t h e 1981 i n s e c t survey on Canada
thistle.
Location
Habitat.
I
Agronomy Farm, Bozeman
( G a l l a t i n County)
Mowed g r a s s l a n d with n a t u r a l r u s t
i n f e s t a t i o n (P. ob te ge ns ) o f 52%.
(T u rn e r, 198IT.
2
Fort E l l i s
( G a l l a t i n County)
Fallow f i e l d p l a n t e d with wheat
and b a r l e y in 1980
3.
Southern Research Cent er
Fallow f i e l d , b o r d e r in g b a r l e y
Huntley (Yellowstone County) f i e l d .
4,
Waste a r e a , shaded by high t r e e s
Southern. Research C en te r
Huntley (Yellowstone County)
5
Billings
(Yellowstone County)
H ills id e , natural h a b ita t
6
Columbus
( S t i l l w a t e r County)
D is tu rb e d a r e a , r o a d s i d e
7
Park C it y
( S t i l l w a t e r County)
Roadside, bord e ri n g p a s t u r e l a n d
15
was i n v e r t e d o ve r t h e t a r g e t p l a n t s and f a s t e n e d a t t h e open
end.
P la n ts , were then upr o o te d , la b e l e d and t r a n s p o r t e d , t o
t h e l a b o r a t o r y ' f o r exami nat ion .
4.
Two t o f i v e t h i s t l e p l a n t s were s e l e c t e d a t random and uprooted
. a t each s i t e .
Roots, crowns and stems were d i s s e c t e d arid ex­
amined f o r endophagous i n s e c t s .
5.
Flower heads and buds were d i s s e c t e d in t h e f i e l d .
By t h e end
o f t h e growing s ea s on , c o l l e c t i o n s o f seed heads were made a t'
different site s.
Approximately 50% o f t h e seed heads were ex­
amined in. t h e l a b o r a t o r y and t h e r e s t were s t o r e d in po ly e th y Iene bags t o r e c o v e r emerging a d u l t s o f endophagous s p e c i e s .
Experimental Rearings
.
Immature i n s e c t s were r e a r e d t o t h e a d u l t s t a g e on p o t t e d p l a n t s
o r f r e s h c u t Canada t h i s t l e f o l i a g e in the. i n s e c t a r y .
Conspicuous i n s e c t s such as B a r is s p . , p os s. c i r s i i G i j b e r t 1
and Corythucha d i s t i n c t a Osborn and Drake were c o l l e c t e d in c o n t a i n e r s
and c on fi ne d t o p o t t e d p l a n t s in the. i n s e c t a r y .
Canada t h i s t l e p l a n t s was observed d a i l y .
T h e i r impact on p o t t e d
Cages used t o c o n f i n e i n s e c t s
were c y l i n d r i c a l in shape (22 x 38 cm), and had wooden frames covered by
a f i n e mesh c l o t h .
---------------- - r — --------- :------------------------ :-----------------------------
Whitehead, D. R. (S yst em at ic Entomological L a b o r a to r y , USDA) .
could not supply a p o s i t i v e i d e n t i f i c a t i o n . . We w i l l r e f e r t o i t . as
Baris sp.
-
16
Field
Studies
S i t e s 5 a n d . 6 (Table 2) were s e l e c t e d f o r o b s e r v a t i o n s of Baris
sp. ( C o le o p te r a : C u r c u l i o n i d a e ) on Canada t h i s t l e .
Both s i t e s were
h e a v i l y i n f e s t e d with t h e weevil and i t s h o s t .
1.
He ights of e i g h t damaged t h i s t l e p l a n t s were rec ord ed in mid-June
a t each s i t e and compared with h e i g h t s o f e i g h t u n i n f e s t e d p l a n t s
a t t h e same s i t e .
D i f f e r e n c e s were t e s t e d f o r s i g n i f i c a n c e with
t h e t - t e s t (P < 0 . 0 1 ) .
2.
At t h e end of t h e growing sea so n, 17 damaged t h i s t l e p l a n t s were
u p ro o te d , d i s s e c t e d , and pupal counts were made.
A regression
a n a l y s i s was performed o f t h e p l a n t h e t g h t over t h e l a r v a l f r e ­
quency ( P<- 0 . 0 1 ) .
3.
Emergence t r a p s , each co verin g ap proxim ately two p l a n t s , were
p la ce d in s i t e 5, in e a r l y September, 1981.
These c a g e s , ma de,.,
o f f i n e w i r e - n e t t i n g , were c o n i c a l in shape with a dia m e te r of
80 cm.
A small t r a p was a t t a c h e d on t h e top ( F ig u r e 2 ) .
These
t r a p s made i t p o s s i b l e t o c o n t r o l seaso nal a c t i v i t y of B aris
a d u l t s and t o c o l l e c t o t h e r i n s e c t s p e c i e s emerging from t h e
same t h i s t l e p l a n t s .
Insect Id e n tifica tio n
I n s e c t specimens were s o r t e d and s e n t t o taxonomic a u t h o r i t i e s
for identification.
17
Fi gu re 2.
Emergence t r a p in s i t e 5.
RESULTS AND DISCUSSION
The i n s e c t s c o l l e c t e d on Canada t h i s t l e were grouped as I) phyto­
phagous i n s e c t s (Table 3 ) ; 2) i n s e c t s c o l l e c t i n g p o l l e n o r n e c t a r , i n ­
s e c t s which a r e i n c i d e n t a l v i s i t o r s , p r e d a t o r s and p a r a s i t o i d s o f o t h e r
insects.
I n s e c t s c o l l e c t e d a r e l i s t e d by o r d e r acc ord ing t o B o rr o r , De
Long and T r i p l e h o r n (1976).
Phytophagous I n s e c t s
Table 3 l i s t s 58 s p e c i e s , r e p r e s e n t i n g s i x o r d e r s , 22 f a m i l i e s
and 51 g e n e r a .
food p l a n t .
tiv e host.
All of t h e s e s p e c i e s have adopted Canada t h i s t l e as a
Twenty-six s p e c i e s a l s o use t h i s a l i e n weed as a repro duc ­
However, none of t h e s e i n s e c t s a re r e s t r i c t e d s o l e l y t o
Cirsium a r v e n s e , w ith t h e e x c e p ti o n o f Ceutorhynchus l i t u r a ( F a b r i c i u s ) ,
which has been p u rp o s e ly in tr oduce d f o r t h e c o n t r o l of Canada t h i s t l e .
On t h e c o n t r a r y , one t h i r d o f t h e i n s e c t s found f e e d in g on Canada
t h i s t l e in so u th er n Montana a r e e i t h e r minor o r major p e s t s of economic
crops.
Four s p e c i e s , Corythucha d i s t i n c t a Osborn and Drake (Hemiptera:
T i n g i d a e ) , B a r is s p . p o s s . c i r s i i G i l b e r t ( C o l e o p t e r a: C u r c u l i o n i d a e ) ,
Vanessa c ar du i L. ( L e p id o p t e r a : Nymphali d a e ) , and O r e l l i a ru f ic a u d a
( F a b r ic iu s )(Diptera:
T e p h r i t i d a e ) , were c onsi de re d c onsp ic uous , because
of t h e damage th e y i n f l i c t e d t o t h e t h i s t l e p l a n t .
They can be very
19
Table 3
Phytophagous i n s e c t s c o l l e c t e d from Canada t h i s t l e , Cirsium
a rv e ns e ( L . ) S c o p . , in so u th er n Montana, 1981.
Insects
Orthoptera
Acndidae
Chortophaga v ir ld if a s c ia ta (DeGeer)
E ri t e t t i x simplex (Thomas)
Melanoplus b i v itta tu s (Say)
M. femur-rubrum (DeGeer)
M. packardii Scudder
M. sanguinipes (Fabricius)
Gryllidae
Allonemobius allardi (Alexander
and Thomas)
Hemiptera
Miridae
Chlamydatus associatus (Uhler)
Lygus lineolaris (Palisot de Beauvois)
L. robustus Uhler
L. schulli Knight
Tingidae
Corythucha d istin cta Osbom and Drake
Pentatomidae
Euschistus euschistoides (Vollenmolen)
Euschistus sp .
Rhytidolomia sp.
I unidentified sp.
Homoptera
Membracidae
Ceresini sp.
Publilia modesta (Uhler)
T ortistilu s wlckhami (Van Duzee)
Cercopidae
Aphrophora permutata Uhler
Philaenus spumarius (L.)
Cicadellidae
Aceratagallia sp.
Agallia sp.
Cuerna prob. s t r i a t a (Walker)
Empoasca sp.
Euscelidius variegatus (Kirschbaum)
Macrosteles fascifrons (Stall
Xerophloea v i r id ls (FabricIus)
I unidentified sp.
Frequency in
Collection6
Plant Association
Plant Growth
Stage)s r
Stages6 Feeding0 Part(S)6
Recorded Literature
Hosts'
Source
A
A
N1A
N1A
A
A
ECT
ECT
ECT
ECT
ECT
ECT
L
L
L
L
L
L
R
R
F
F
F
F
A
ECT
L
F
A
A
N,A
A
ECT
ECT
ECT
ECT
F
F
V1F
F
C
F
F
F
P
(29)
(29)
(29)
(29)
C
E.N.A
ECT
L
R1V1F
P
(13,15)
O
O
O
O
A
N
A
E
ECT
ECT
ECT
-
L
L
L
L
R
F
F
F
P
(8.15)
O
C
R
N
A
A
ECT
ECT
ECT
S
S
L
F
R1V
F
P
-
(15)
O
C
A
N.A
ECT
ECT
S
L.S
V
R1V1F
P
P
(15)
(18)
R
O
O
R
R
LC
R
R
A
A
N.A
A
A
A
N
E
ECT
ECT
ECT
ECT
ECT
ECT
ECT
L
L
L
L
L
L
L
S
F
V
R.V
R
F
F
F
F
P
(43)
P
P
P
(6.44)
(6,44)
(6,15)
LC
O
LC
C
C
C
R
R
R
LC
R
-
P
P
P
P
P
(15,38)
(15)
(15.38)
(15.38)
(15)
-
P
C
-
20
Table 3. (con ti n u e d )
Insects
Aphididae
Aphis fabae Scopoli
Aphis SP.
Brachycauduscardul (L.)
Capitophorus carduinus (Walker)
DdCtynotus sp.
Pseudococcidae
Chnaurococcus t r i f o l l i i (Forbes)
Phenacoccus solani Ferris
Coleoptera
Mordel Iidae
Mordellistena sp.
Mordellistena sp. "A"
Mordellistena sp. "B"
Chrysomelidae
Criocens duodecimpunctatus ( I.)
Deloyala guttata (Olivier)
Oiachus auratus (Fabncius)
Pachybrachys melanostictus Suffnan
Systena blanda Melsheimer
Tnrhabda prob. convergens LeConte
Curculionidae
Baris s p . , poss. c i r s i i Gilbert
Ceutorhynchus l itu ra (Fabncius)
Dysticheus sp.
Macrorhoptus sp.
Notaris bimaculatus (Fabricius)
Otiorhynchus ovatus (L.)
Tychlus p i c i r o s t r is (FabrIcius)
Rhinocyllus conicus Froelich
Lepidoptera
Pterophoridae
P la ty p tilia carduidactyla (Riley)
, Relative
Frequency in
ColIectiona
Plant Association
P T a n l “ Plant Growth
Stage(s)e
Stages6 Feeding0 P art(s)d
Recorded Literature
Hosts'
Source
O
O
O
R
R
N1A
N1A
N1A
N1A
N1A
ECT
ECT
ECT
ECT
ECT
S
S
S
S
S
F
F
F
F
F
P
t
t
(46)
R
R
N1A
N1A
ECT
ECT
R
S
F
V
P
P
C
O
O
L
A
A
END
ECT
ECT
S
L
L
F
V
V
P
-
(53)
R
R
O
O
R
R
A
A
A
A
A
A
ECT
ECT
ECT
ECT
ECT
ECT
L
L
L
L
L
L
V
R
R
R1V
F
F
P
P
P
P
P
C
(23)
(23)
(23)
(23)
(15)
(23)
C
LC
R
R
R
O
R
C
L1A
L.A
A
A
A
A
A
L.A
END1ECT
END1ECT
ECT
ECT
ECT
ECT
ECT
END1ECT
R1S
S1L
L
L
L
L
L
F1L
R1V1F
R1V
F
F
R
V1F
R
R1V1F
t
t
(17)
(48)
O
L
END
S
V
(45)
(45)
(16)
(15,16)
P
C
t
(15,23)
(23)
(5)
C
(15)
21
Table 3.
(c o n ti n u e d )
Insects
Tortrlcldae
I unidentified sp.
I unidentified sp.
Arctlidae
Apantesiswilliamsii (Dodge)
Noctuidae
I unidentified sp.
Nymphalidae
Vanessa (Cynthia) cardul L.
Diptera
Sciaridae
I unidentified sp.
Cecidomyiidae
I unidentified sp.
Tephritidae
Orellia ruficauda (Fabricius)
Lauxaniidae
Camptoproscopella sp.
„ Rela tive.
Frequency in
Col lection®
Association
Plant Growth
Stage(s)e
Stages6 Feedlngc
Recorded Literature
Hosts'
Source
R
R
L
L
ECT
ECT
L
L
V
V
-
R
L
ECT
L
V
C
O
L
END
R
F
-
O
L
ECT
L
V
P
O
L
END
R
V1F
O
L
END
F
F
_
C
L1A
END,ECT
F
F
C
A
ECT
L.F
V.F
-
LC
aNumber of sites in which the species appears/50 si t e s ; R * Rare (species found in I collection s i t e ) ,
0 = Occasional (species found in 2-5 collection s i t e s ) , LC = Locally coimon (species found in 2-5 collection
s i t e s , and present in high density), C = Common (species found in more than 5 collection s i t e s ) .
bE = eggs, L = larvae, N * nymphs. A = adults.
cECT = ectophagous, END = endophagous.
bR = roots, S = stems, L = leaves, F = flower heads or buds.
eR = rosette stage, V = ver tical growth stage, F * flowering and fru itin g stages.
f t - t h i s t l e s (host plants apparently restricted to closely related genera as Carduus, Clrsiun, and Silybun)
c = Composltae (host plants apparently restricted to the Compositae), p * poIyphagous (attacking plants belonging
to d iffe rent fam ilies ), - * no information.
(60)
(15,60)
(39)
22
e f f e c t i v e in lo c a l a r e a s , although d e n s i t i e s were too low t o a f f e c t t h e
weed p o p u l a t i o n s .
Grasshoppers were c o l l e c t e d in most of t h e s a m p l e s , with t h e
h e a v i e s t i n f e s t a t i o n d u ri n g f lo w e ri n g and f r u i t i n g s t a g e s o f t h e p l a n t .
These i n s e c t s a r e g e n e r a l f e e d e r s and t h u s have l i t t l e i n f l u e n c e in t h e
n a t u r a l c o n t r o l of t h i s t l e s .
pests.
In a d d i t i o n , they a r e c o n s i d e r e d ; economic
T h i s t l e r o s e t t e s were examined f o r fe e d in g damage in s i t e I
(Table.2).
The g ra s sh o p p e rs p r e f e r r e d r u s t i n f e s t e d over h e a l t h y
t h i s t l e plants.
Lewis (1979) s u g g e s ts t h a t such p r e f e r e n c e s a re due t o
f a v o r a b l e a l t e r a t i o n s in t h e n u t r i t i o n a l a n d / o r d e f e n s i v e chem is tr y of
the plant.
The most common Hemiptera c o l l e c t e d from Canada t h i s t l e p l a n t s
were Corythucha d i s t i n c t a Osborn and Drake and s e v e r a l Lygus s p e c i e s .
The l a t t e r a r e common s a p f e e d e r s on g r a s s e s , weeds and a wide v a r i e t y
of economic p l a n t s ( K e l t o n , 1975).
C_. d i s t i n c t a appeared in lo c a l popu­
l a t i o n s , p a r t i c u l a r l y in mo is t h a b i t a t s .
This lace bug was found f e e d ­
ing on t h e t h i s t l e le av e s from e a r l y May th r oug hout t h e growing season
of t h e p l a n t (F ig ure 3 ) .
Adults and nymphs were h ig h ly aggregated on
t h e t h i s t l e le aves and caused brown o r bla ck fee din g s c a r s (Fig ure 4),.
When l a r g e numbers o c cu r re d p e r p l a n t , t h e le av e s became n e c r o t i c .
A du lts .w er e c o l l e c t e d in e a r l y May from s i t e s 4, 5 and 7 (Table 2) and
co nf in ed t o p o t t e d t h i s t l e p l a n t s in t h e i n s e c t a r y .
A f t e r two weeks,
most o f t h e p l a n t s showed a g g r e g a ti o n o f nymphs, c l u s t e r e d ne ar t h e s p o t
23
Fi gu re 3.
Corythucha d i s t i n c t a
a d u l t s f e e d i n g on
Canada t h i s t l e l e a v e s .
Fig ur e 4.
Feeding damage of
Corythucha d i s t i n c t a
on Canada t h i s t l e .
24
where t h e eggs were l a i d , on t h e u n d e r - s i d e o f t h e l e a f (F ig u re 5 ) .
A f t e r a p e r io d of s i x week s, t h e la ce bugs were p r e s e n t in such d e n s i t y
t h a t a l l t h e le av e s were c u r l e d and n e c r o t i c .
produce fl o w e r buds.
These p l a n t s f a i l e d t o
£ . d i s t i n c t a i s m u l t i v o l t i n e and has two o r more
g e n e r a t i o n s p e r y e a r , depending on t h e c l i m a t i c c o n d i t i o n s (Drake and
R u h o ff , 1960).
However, n a t u r a l Corythucha p o p u l a t i o n s were too small
t o cause s u b s t a n t i a l d e f o l i a t i o n o f t h e t h i s t l e p l a n t s .
Lamp and
McCarthy (1982) r e p o r t e d t h a t nymphaI p o p u l a t i o n s o f (X d i s t i n c t a on
Cirsium canescens N u t t , caused n e c r o s i s o f t h e l e a v e s , but did not
reduce t h e seed p ro d u c ti o n o f t h e p l a n t s .
Hosto p l a n t s of C_. d i s t i n c t a
a r e rec ord ed as being Carduus l a n c e o l a t u s , Cnicus s p . , Cirsium
pulc herrimum, £ . c a n e s c e n s , Lathyrus n u t t a l l i i , and Alth a ea s p . , In
a d d i t i o n , Ess ig (1958) r e p o r t e d i t s o c c u r re n c e on balsam r o o t , beans,,
c o r n , l e t t u c e , l u p i n e , p a r s n i p , squash, and t u r n i p .
The s p i t t l e b u g , P h il a e n u s spumarius (L .) was found t o be very
abundant in a wide v a r i e t y of h a b i t a t s .
The nymphs were observed on
t h e t h i s t l e r o s e t t e s in e a r l y May, surrounded by a mass o f s p i t t l e - l i k e
froth.
The a d u l t s fe d on t h e upper p a r t of t h e t h i s t l e stem th rou ghout
t h e r e s t of t h e summer.
FX spumarius i s c onsi de re d a n . i m p o r t a n t eco­
nomic p e s t o f f o r a g e crops in e a s t e r n United S t a t e s (Halkka, e t a l . ,
1967).
plants.
However, th e y appeared t o have l i t t l e e f f e c t on t h e t h i s t l e
A c o in c i d e n c e o f high r u s t (£. o b t e g e n s ) i n f e s t a t i o n (52%) and
a high d e n s i t y o f s p i t t l e b u g nymphs was observed in s i t e I .
In June,
25
F ig ure 5.
Aggregation of Corythucha
d i s t i n c t a nymphs on th e
u n d e r - s i d e of Canada t h i s t l e ,
leaves.
26
1981, a t o t a l of 425 t h i s t l e p l a n t s were examined in s i t e I f o r s p i t t l e bug a t t a c k .
An average o f 2 % p l a n t s were found t o be i n f e s t e d with
spittlebugs.
'
-
P u b l i l i a modesta (Uhler) was c o l l e c t e d only as an a d u l t on
Cirsium a r v e n s e .
Like t h e s p i t t l e b u g s , t h e y fed on t h e upper p a r t of
t h e stem from June t o September and were a t t e n d e d by s e v e r a l an t s p e c i e s
The aphid c o l o n i e s on Canada t h i s t l e were common in l a t e J u l y and August
I n d i v i d u a l c o l o n i e s did not reach damaging d e n s i t i e s .
The most numerous phytophagous group in t h e Montana survey was
r e p r e s e n t e d by t h e o r d e r o f t h e C o l e o p t e r a .
As in t h e European survey
( Z w o l f e r , 1964), t h e l a r g e s t b e e t l e f a m il y c o l l e c t e d in south Montana
was t h e C u r c u l i o n i d a e .
Four of t h e 15 b e e t l e s p e c i e s fe e d i n g on Canada
t h i s t l e a r e endophagous in t h e i r l a r v a l s t a g e s .
Of t h e s e ,
M o r d e l l i s t e n a sp. ( M o r d e l l i d a e ) , B a r i s s p . , po s s. c i r s i i G i l b e r t and
Rhynocyllus conicu s F r o e l i c h ( C u r c u li o n id a e ) occu rr ed in a t l e a s t e i g h t ,
d i f f e r e n t c o l l e c t i o n s i t e s , with a r e l a t i v e high fr equ en cy a t each
site.
The f i r s t M o r d e l l i s t e n a sp. l a r v a e mining in t h e t h i s t l e stems
were observed by m i d - J u l y .
These l a r v a e o v e r w in te r in old t h i s t l e
s t a l k s , and pupate t h e fo ll o w i n g s p r i n g .
The a d u l t s , pro ba bl y emerging
in l a t e May, were found f e e d in g on Canada t h i s t l e in Ju ne .
The l a r v a l
f e e d i n g th ro u g h o u t t h e summer a p p a r e n t l y did not a f f e c t t h e normal
growth and r e p r o d u c t i o n of t h e t h i s t l e p l a n t .
27
A ro o t- b o r in g , w e e v i l , B ar is sp. p o s s . c i r s i i G i l b e r t , n a t i v e t o .
North America, a t t a c k e d Canada t h i s t l e in s o u t h e a s t e r n Montana.
This
w e e v i l , a l s o rec ord ed on o t h e r C i r s i u m .spp. ( G i l b e r t , 1964), i s probably
t h e only indigenous i n s e c t approaching t h e monophagous h a b i t .
Gilbert
(1964) c l a s s i f i e s j3. f u t i l i s , j3. c i r s i i , B_. bru nnei pe s and Bv monticola
as f o u r s p e c i e s of t h e same subgroup, comprising a. complex o f c l o s e l y
r e l a t e d s p e c i e s which a r e a l l r e s t r i c t e d t o h o s t s in t h e genus
C ir s iu m .
B a r is c i r s i i has been recorded on s i x d i f f e r e n t Cirsium h o s t s
in C a l i f o r n i a :
Cv q u e r c e to r u m , Cv o c c i d e n t a l e , Cv c o u l t e r ! , Cv
c a l i f o r n i c a , C_. cymosum and £ . f o l i o s u m .
In our su rv e y, B a r is sp. po s s.
c i r s i i was o nly observed on Cirsium a rv e nse and was found e s p e c i a l l y in
d i s t u r b e d a r e a s , r o a d s i d e s and g r a s s l a n d s .
Both a d u l t and l a r v a l
feeding, were observed in s i t e s 5 and 6 and in t h e i n s e c t a r y .
■ B a r is a d u l t s o v e r w i n t e r as unemerged a d u l t s in t h e r o o t s o f
t h e i r h o s t s and emerged in e a r l y s p r i n g by making t h e i r way through old
l a r v a l g a l l e r i e s t o t h e base of t h e stem.
There was no i n d i c a t i o n of
a c t i v i t y in t h e c e l l s of o v e r w i n t e r i n g . a d u l t s .
t h e t h i s t l e s were about
f i v e t o 20 cm t a l l .
At t h e time of emergence,
The w e e v il s s t a r t e d f e e d ­
ing between t h e newly formed d i s t a l l e a f l e t s of t h e young t h i s t l e s
(F ig u re 6 ) ; l a t e r in middle and lower l e a f a x i l s of t a l l e r p l a n t s .
G e n e r a l l y , two specimens p e r p l a n t were obser ve d, up t o f o u r on t a l l e r
plants.
The f e e d i n g on t h e young p l a n t s u s u a l l y damaged t h e primary
v e r t i c a l shoot.
Damaged p l a n t s produced new s i d e s h o o t s , r e s u l t i n g in
Fig ur e 6.
B ar is s p . a d u l t fee din g on
th is tle rosette.
29
a g e n e r a l bushy a ppea rance , which were d i s t i n c t i v e in t h e f i e l d .
Heights of e i g h t damaged t h i s t l e p l a n t s were recorded a t s i t e s 5 and
6 and compared with h e i g h t of e i g h t u n i n f e s t e d p l a n t s a t t h e same s i t e .
Adult fe e d i n g reduced t h e v e r t i c a l growth o f t h e t h i s t l e p l a n t s i g n i f i ­
c a n t l y (Table 4 ) .
In e a r l y May, B a r i s a d u l t s were t r a n s f e r r e d from
s i t e 5 t o t h e i n s e c t a r y . a n d confine d t o p o t t e d t h i s t l e p l a n t s , where
t h e i r impact on t h e p l a n t s was ob s er ved .
Most o f t h e s e p l a n t s , a lr e a d y
under heavy s t r e s s due t o low l i g h t i n t e n s i t y , did not s u r v i v e t h e
a t t a c k o f t h e weevil (F ig u re 7) and t h e p l a n t s died w i t h i n two weeks.
F i e l d o b s e r v a t i o n s in Montana i n d i c a t e d t h a t emerged a d u l t s l iv e d from
two t o f o u r months, were h i g h l y l o c a l i z e d in d i s t r i b u t i o n and d i s p e r s e d
by ambulation o r o c c a s i o n a l l y by f l i g h t .
G i l b e r t (1964) r e p o r t s t h a t
t h e r e i s a p e r i o d o f about t h r e e weeks between emergence and o v i p o s t i o n
O v i p o s i t i o n s i t e s , always in t h e lower h a l f o f t h e p l a n t , vary during
t h e s e a s on , becoming p r o g r e s s i v e l y lower on t h e main stem.
The f i r s t
B a r i s l a r v a e were d e t e c t e d in s i t e 5 by mid J u l y .
The l a r v a e were f e e d i n g a c t i v e l y in t h e t h i s t l e r o o t s , about
15 cm below ground l e v e l .
The c e n t r a l v a s c u l a r c y l i n d e r , as well as
t h e c o r t i c a l t i s s u e of t h e r o o t s , were e i t h e r consumed o r used f o r t h e
c o n s t r u c t i o n o f t h e pupal chamber (F ig u re 8 ) .
By t h e end o f J u l y , t h e
small bushy p l a n t s w i l t e d and f a i l e d t o produce fl ow e r buds (F igu re 9 ) .
A t o t a l o f 17 w i l t e d p l a n t s were uprooted by t h e end of t h e growing
season and unemerged a d u l t s were c ounte d.
I found an av erage of
Table 4.
Site
Average p l a n t h e i g h t s (cm) o f e i g h t B ar is i n f e s t e d and e i g h t
uni n f e s t e d ' t h i s t l e p l a n t s in s i t e s 5 and 6, June 19, 1981.
*
P l a n t H eight, cm
Weevil P r e s e n t
Weevil Absent
5
. 29 . op
6
32.25
58.10 •
71.00
* P l a n t h e i g h t s were s i g n i f i c a n t l y d i f f e r e n t , t - t e s t (P < 0 . 0 1 ) .
31
F ig ure 7.
Feeding damage of B aris
s p. a d u l t s on p o t t e d
t h i s t l e p l a n t s in t h e
insectary.
Fi g u r e 9.
F ig ur e 8 .
B ar is sp. l a r v a in
Canada t h i s t l e r o o t ,
Wilted t h i s t l e p l a n t in
s i t e 5, i n f e s t e d with
B ar is sp. l a r v a e .
32
1.6 unemerged a d u l t s p e r Canada t h i s t l e p l a n t and d is c o v e r e d a s i g n i f i ­
c a n t c o r r e l a t i o n between p l a n t h e i g h t and l a r v a l fr equ en cy ( r = 0 . 7 6 6 ,
P < 0.01 ) (F ig u re 10).
This could be due t o a h i g h e r l a r v a l s u r v i v a l
r a t e in t a l l e r p l a n t s o r t o a h i g h e r imaginal freque ncy on t h e l a r g e r
p l a n t s e a r l y in t h e seaso n.
The damage i n f l i c t e d by t h e weevil i s both d i r e c t and i n d i r e c t ,
c ov er in g t h e e n t i r e growing season o f t h e p l a n t .
Adults s t r e s s t h e
p l a n t in e a r l y s p r i n g by d e s t r o y i n g t h e m e r i s t e m a t i c t i p and a f f e c t i n g
t h e v e r t i c a l growth o f t h e p l a n t .
Larvae burrow i n t o t h e v a s c u l a r
t i s s u e of t h e r o o t and block t r a n s p o r t , s t u n t i n g t h e o v e r a l l growth of.
t h e p l a n t and p r e v e n t i n g seed p r o d u c t i o n .
Both a d u l t and l a r v a l f e e d ­
ing r e n d e r t h e p l a n t s u s c e p t i b l e t o inv asi on by o t h e r org anisms.
e a s e s a s s o c i a t e d with weevil damage have not been i d e n t i f i e d .
o b s e r v a t i o n s showed t h a t o t h e r i n s e c t s invade damaged r o o t s .
i n s e c t s , Chnaurococcus t r i f o l i i
D is ­
Field,
Two s c a l e
(Forbes) and Phenococcus s o l a n i F e r r i s
(Homoptera: P s e u d o c o c c i d a e ) , and u n i d e n t i f i e d S c i a r i d a e (D ip te r a ) l a r v a e
were c o l l e c t e d from t h i s t l e r o o t s damaged by B ar is l a r v a l f e e d i n g .
U n i d e n t i f i e d f a c t o r s a p p a r e n t l y p r e v e n t t h e b u ild up o f high den­
s i t i e s of Baris populations.
p a r a s i t e s of t h e genus B a r i s .
Very l i t t l e i s known about p r e d a t o r s and
None have been observed in t h e s u r v e y ,.
with t h e e x c e p ti o n of one C a n t h a r i s sp. l a r v a found a s s o c i a t e d with a
B a r i s l a r v a in t h e t h i s t l e r o o t .
The r o l e of i n q u i l i n e i n s e c t s i s not
y e t known, b u t i t i s a p p a r e n t t h a t t h e s e i n s e c t s could be c o m p e t it o rs o r
33
1
2
3
N o.
.Figure 10.
4
OF LARVAE
Li near r e g r e s s i o n of p l a n t
h e i g h t (cm) v e rs us l a r v a l
f r e q u e n c y , August 1981.
The b va lu e ( b = l I .183,
S. E .= 2.43) is s i g n i f i c a n t l y
d i f f e r e n t from zero
(P < 0 . 0 1 ) .
34
may i n t e r r u p t o r impede o v i p o s i t i o n .
In a l l c o l l e c t i o n s i t e s i n f e s t e d
. with B a r i s , M o r d e l l i s t e n a l a r v a e were found fe e d in g in t h e stem p i t h of
t h e same p l a n t ;
In s i t e 6, R hin oc yll us conicus and B a r i s were p r e s e n t
on t h e same p l a n t .
G i l b e r t (1964) r e p o r t e d t h a t w h e n .la r v ae of O r e l l i a
a r e abundant in C i r s i u m , l a r v a e of B a r is a re s c a r c e o r wa ntin g.
This
was su pported by my o b s e r v a t i o n s .
R hin oc yll us c on ic us F r o e l i c h i s a t h i s t l e seed he ad - fe e din g
w e e v i l , in tr od uc e d from France f o r t h e c o n t r o l of Carduus nutans L.
(musk t h i s t l e ) .
This weevil a l s o a t t a c k s Canada t h i s t l e .
Larvae of
R:, c on icu s in Canada t h i s t l e seed heads f r e q u e n t l y e a t through, t h e wall
of t h e bud, and t h e r e b y become v u l n e r a b l e t o pre d a ci o u s i n s e c t s and
s p i d e r s (Rees, 1982).
observed in our su rv e y.
A maximum of t h r e e l a r v a e p e r fl o w e r bud were
Growth c r a c k s in i n f e s t e d Canada t h i s t l e seed-
heads and stems were very common.
Two s p e c i e s o f Le pid op te ra were found t o d e f o l i a t e t h i s t l e p l a n t s .
The most common, Vanessa c ardui L . , t h e p a i n t e d la dy, s t a r t e d fe e d in g on
t h e t h i s t l e le ave s in l a t e May, causing c o n s i d e r a b l e d e f o l i a t i o n in
local a reas.
Because i t i s a m ig r a to r y b u t t e r f l y , i t s numbers f l u c t u a t e
widely from y e a r t o y e a r and make i t u n r e l i a b l e as a n a t u r a l c o n tr o l
agent.
I t can a l s o be a p e s t of sun flowe r and soybean (Morihara
B al sb au gh, 1976).
and
The a r t i c h o k e plume moth, P l a t y p t i l i a c a r d u i d a c t y l a
R i l e y , was r e a r e d on f i e l d c o l l e c t e d t h i s t l e stems.
I t i s c onsid ered
a troubl eso me p e s t o f globe a r t i c o k e in C a l i f o r n i a ( E s s i g , 1958).
35
Most, a d u l t D i p t e r a c o l l e c t e d in t h e Montana survey were c onsid ered
o c c a s i o n a l v i s i t o r s , with the. e x c e p ti o n of t h e seed-head f l y , O r e I l i a
r u f i c a u d a ( F a b r i c i u s ) , r e p r e s e n t i n g one of t h e most common i n s e c t s in
our su rv e y.
A dul ts appeared on t h e fl o w e r buds from e a r l y summer
th ro u g h o u t J u l y .
The l a r v a e fee d on t h e t h i s t l e seeds (F ig u re 11) and
weave a coccoon of pappus h a i r s , in which th e y o v e r w i n t e r .
By t h e end
of t h e summer a t o t a l o f 350 seed-h ead s were c o l l e c t e d a t f o u r d i f f e r e n t
sites.
Of t h e s e , 170 were d i s s e c t e d in t h e l a b o r a t o r y and 0. r u f icauda
pupae were cou nte d.
The remaining seed-he ads were s t o r e d t o re c ov er
emerging £ . r u f icauda a d u l t s and p o s s i b l e p a r a s i t e s .
Our stud y showed
an upper l i m i t o f 38% heads a t t a c k e d by £ . r u f icauda with an average of
1.5 l a r v a e per. head (Table 5 ) .
This i s 32% l e s s th a n V i r l y and Watson
(1977) r e p o r t e d from s t u d i e s a t Macdonald Col le ge (Quebec).
A high .
oc cu r re n c e of jR. c on ic us in s i t e s A a n d . B, and B ar is s p . in s i t e s . C and
.D, a r e pro ba bly reducing o r i n h i b i t i n g t h e 0. r u f icauda i n f e s t a t i o n .
An u n i d e n t i f i e d Cecidomyiidae l a r v a
c o l l e c t i o n s th ro u g h o u t t h e summer.
young f lo w e r buds.
f r e q u e n t l y o c cu r re d in my
The l a r v a e were.found f e e d in g in t h e
All a t t e m p t s t o . r e a r t h i s i n s e c t f a i l e d .
This could
p o s s i b l y be Dasyneura g ib s o n i F e l t , as r e p o r t e d by Detmers (1927) i n ­
f e s t i n g both s t a m i n a t e and c a r p e l l a t e t h i s t l e heads.
36
Fi g u r e 11.
Feeding damage o f O r e l l i a r u f i c a u d a ,
l a r v a e on Canada t h i s t l e se e ds .
37
Table 5.
I n f e s t a t i o n of Canada t h i s t l e heads by O r e I l i a ru f i c a u d a
( F a b r i c i u s ) , September 3, 1981.
%
. Heads Attacked
Mean Number
of Pupae/Head
Site A
(n=60)
38.30
2.04
Site B .
(n=37)
33.30
2.16
Site C
. ( n=52)
. 7.70
1.00
9.50
1.00
S ite D.
(n=21)
. .
n = t o t a l number o f seed heads examined f o r each c o l l e c t i o n s i t e .
38
V i s i t o r s , P r e d a t o r s and P a r a s i t o i ds
The v i s i t o r s included in Table 6- a r e p o l l e n c o l l e c t o r s , n e c t a r
f e e d e r s , o r i n s e c t s t e n d i n g on aphids and membracids.
Most o f t h e predaceous i n s e c t s c o l l e c t e d in t h e Montana survey
a r e common p r e d a t o r s p re yi ng on immature o r small i n s e c t s , such as
aphids o r t h r i p s .
Larvae of Phyllobaenus s p . were observed fe e di ng on
0. r u f i c a u d a l a r v a e in Canada t h i s t l e s e e d -h e a d s .
Formica po d z o lica
Fr ancoeur was found t e n d i n g aphids on Canada t h i s t l e .
This s p e c i e s i s
known t o h a r v e s t R. c onicu s l a r v a e on Canada t h i s t l e (Rees, 1982).
Of t h e p a r a s i t i c Hymenoptera, l i s t e d in Table 6, two s p e c i e s ,
Pteromalus s p . and Eurytoma sp. were c o l l e c t e d from pupal chambers of
Rv c on icu s in t h i s t l e seed he ads .
In e a r l y August, a t o t a l of 615 seed
heads were c o l l e c t e d in s i t e 2 and examined in t h e l a b o r a t o r y .
c on icu s i n f e s t a t i o n was based on pupal chamber c o u n t s .
Rv
One hundred
twenty-two (20%) s eed -he ads were found t o be i n f e s t e d with Rv c o n i c u s .
Of t h e s e , 20% c o n ta i n e d a d u l t P t e r o m a l i d s , i d e n t i f i e d as Pteromalus sp.
None of t h e s e were r e a r e d from Rv c onic us l a r v a e and have not been r e ­
corded as p a r a s i t o i d s of Rv conicu s in t h e United S t a t e s (Dowd and Kok,
1982; Rees, 1982).
S u r l e s (1974) r e p o r t e d Eurytoma sp. (Eurytomidae)
as a l a r v a l p a r a s i t o i d o f Rv conicus in Europe.
The p a r a s i t o i d s r e a r e d from O r e l l i a r u f icauda pupae and l a r v a e in
t h e i r i s e c t a r y were i d e n t i f i e d as Eulophidae (Hymenoptera).
At t h e end
o f t h e summer, Canada t h i s t l e , s e e d - h e a d s , c o l l e c t e d a t f o u r d i f f e r e n t
39
Table 6
V i s i t o r s , p r e d a t o r s , and p a r a s i t o i d s c o l l e c t e d from Canada
t h i s t l e , Cirsium a rv e nse (L .) Scop, in so ut her n Montana, 1981.
Relative
Frequency in
Collection^
Stages
Collectedb
Plant
P a rt(s)c
Plant Growth
Stage(s )d
Hemiptera
Anthocoridae
Orius t r is tic o lo r (White)
O
N1A
F
F
Nabidae
Nabis altern ates Parshley
LC
N1A
L
R.V.F
Insects
predaceous on mites
aphids, th rip s ,
other small insects
and eggs
R
A
L
F
Lygaeidae
Geocoris sp.
R
N1A
L
V1F
O
A
L
F
O
A
L
A
L
Coleoptera
E lateridae
Ctenicera gIauca (Germar)
Cantharidae
Cantharis sp.
Drob. Canthans sp.
Anobiidae
Tricorvnus productus White
Dermestidae
Attagenus canadensis Casey
Cleridae
Phyllobaenus or lsohydnocera sp.
Phyllobaenus sp.
Trichodes ornatus Say
R
Source
(1,30)
predaceous on aphids,(30)
th rip s and other
small insects
Reduviidae
Sinea diadema (Fabncius)
Neuroptera
Hemerobiidae
Micromus vanolosus Hagen
Chrysopidae
Chrysopa carnea Stephens
Habits
predaceous on so ft
bodied insects
(8,30)
F
pollen and nectar
feeder
(7)
R
flower v is ito r
(15)
predaceous on Aphis
(15,23)
O
R
A
L
L
R
R
F
R
A
L
R
R
A
L
R
flower v is ito r
(23)
O
L
F
F
Feeding on 0.
ru fIcauda leaves
predaceous on woodboring insects
Pers. observ
R
R
A
A
L
F
V
F
-
flower v isito rs
larvae predaceous on
bees and wasps
(23)
(15.23)
40
Table 6.
(c o n ti n u e d )
Insects
Melyndae
Collops bipunctatus Say
Collops tric o lo r (Say)
Malachius aeneus L.
Coccinel Iidae
Brachyacantha ursina (Fabricius)
Coccinella transversoguttata
transversoguttata Falderman
Hippodamia convergens Guerin
H.
parenthesis (Say)
Keiative
Frequency in
Collection*
Stages
Collectedb
Plant
P a rt(s)c
O
R
. R
A
A
A
L
L
L
V.F
V.f
V
R
A
L
V
A
E.L.A
L
L
F
F
A
L
F
O
LC
R
H. quinquesignata
qumqueslgnata (Kirby)
LC
Hyperaspis undulata (Say)
Scymnus (Pullus) postpinctus Casey
Lepidoptera
PyralIdae
I unidentified sp.
Blastobasidae
I unidentified sp.
Diptera
Chironomidae
Cricotopus sp.
Sciaridae
Bradysia sp.
Bombyllidae
Systoechus vulgaris Loew
Syrphidae
Sphaerophoria p hilanthus (Meigen)
S y rltta piplens (L .)
Anthomyiidae
Delia platura (Meigen)
Plant Growth
Stage(s)d
E.L.A
L
R.V.F
R
A
L
F
R
A
L
R
LC
A
L
V
R
A
L
V
R
A
L
R
R
A
F
F
LC
A
F
F
LC
O
A
A
F
F
F
F
O
A
F
F
Habits
Source
flower v isito rs
(15.23)
-
.
predaceous on Aphis
s p ., eggs and larvae
predaceous on Aphis
sp.
predaceous on Aphis
sp
predaceous on various unarmored
scales
(15)
(15)
(15)
(15)
.
predaceous on grasshopper egg pods
(9)
-
larva is a pest of
vegetables
(9)
41
Table 6.
(con ti n u e d )
Insects
Keiative
Frequency in
Collectiona
Stages
Collectedb
Plant
P a r tts lc
Scathophagidae
Scathophagastercorarla (L.)
O
A
L
Tachinidae
Hyalomya a ld rich it Townsend
P eleteria sp.
R
R
A
A
R
Plant Growth
Stage(s)d
Habits
Source
V
predaceous on blow­
fly and house fly
F
F
p arasite of Hemiptera (9)
F
A
F
F
-
R*
A
F
F
-
R
A
L
V
I unidentified sp.
I unidentified sp.
Eulophidae
I unidentified sp.
R
R
A
A
L
F
V
F
O
L
F
F
I unidentified sp.
C
L
F
F
L.A
F
F
-
A
F
F
-
Hymenoptera
Xyelidae
Xyela obscura (Strobl)
Braconidae
Bracon sp.
Ichneumonidae
Thyrateles sp .. poss. Iugubrator
(Gravenhorst)
Pteromalidae
Pteromalus sp.
EuryLomidae
Eurytoma sp.
Chrysidldae
Hedychrum sp iloventer French
Formicidae
Formica neoclara Emery
F. o b scunventris c l Ivia Creighton
F. podzolica Francoeur
Formica sp.
Hyrmica Incompleta Provancher
Pompilidae
PomplIus sp.
Apidae
Apis m ellifera L.
Bombus sp.
LC
O
F
(15)
-
p arasite of several
Nymphalldae
(31)
-
p arasite of 0.
ruficauda larvae
p arasite of 0.
ruficauda larvae
(pers. observ)
(pers. observ)
R
A
F
F
O
LC
R
R
S.L
S1L
S.L
S.L
S.L
R.V.F
R.V
V.F
O
A
A
A
A
A
R
A
F
F
predaceous on spiders (31)
LC
A
F
F
O
A
F
F
feeding on nectar and (31)
pollen
feeding on nectar and (31)
pollen
F
V
p arasite of Cecerine
wasp
(Bohart, R.M.
pers. comm.)
Tending
Tending
Tending
Tending
(66)
aphids
aphids
aphids
Membracids
(6 6 )
(pers. observ)
(pers. observ)
-
aNumber of s ite s in which the species appears/50 s ite s ; R « Rare (species found in I co llectio n s i t e ) , O = Occasional
(species found in ?-5 collection s ite s ) . LC = Locally common (species found in 2-5 collection s ite s , and present in high
d en sity ). C = Common (species found in more than 5 collection s ite s ) .
bE = eggs, L = larvae. N = nymphs. A = adults.
cR = roots, S = stems. L = leaves, F = flower heads or flower buds.
dR = ro sette stage. V = v ertical growth stage, F * flowering and fru itin g stages.
42
s i t e s were examined f o r 0. r u f i c a u d a i n f e s t a t i o n (Table 5 ) .
At t h e same
time p a r a s i t i z e d 0. r u f icauda pupae were counted (Table 7, Figure 12).
An average in c id e n c e o f 49% p a r a s i t i s m was obser ved .
Summary
Whenever Canada t h i s t l e i s f o u n d , i t has a l a r g e number of i n s e c t s
a s s o c i a t e d with i t .
Although,many o f t h o s e i n s e c t s a r e s t r a y s from
o t h e r p l a n t s , many o f them can be c o n s id e re d as i n c i d e n t a l v i s i t o r s and
about one t h i r d of t h e l i s t e d phytophagous s p e c i e s a l s o a t t a c k economic
plants.
Only a few i n s e c t s were c o n s id e re d conspicuous because of t h e i r
damage i n f l i c t e d t o t h e t h i s t l e p l a n t and because o f t h e i r commonness
to the c o lle c tio n s .
The i n s e c t survey in so uth ern Montana i n d i c a t e s t h a t Cirsium
a rv e ns e has been e x p l o i t e d by t h r e e seed he ad - fe e d in g i n s e c t s , t h r e e
s tem -bo rin g i n s e c t s , one r o o t - b o r i n g i n s e c t , and two d e f o l i a t i n g a g e n t s .
C on sid erin g t h e i r in c id e n c e of a t t a c k , more i n s e c t s were a s s o c i a t e d
with t h e . d e v e l o p i n g seed heads than with f o l i a g e , stems o r f o o t s .
Although some i n s e c t s caused c o n s i d e r a b l e p l a n t s t r e s s , f u r t h e r
s t r e s s f a c t o r s from o t h e r i n s e c t s and pathogens a re needed t o c o n t r o l ■
t h i s weed.
Few p o t e n t i a l l y e f f e c t i v e and h o s t s p e c i f i c i n s e c t s from
Zwolfer's l i s t . a r e s t i l l a v ailab le f o r fu tu re introd u ctio n s.
Thus, t h e
in fo r m a t io n g a th e r e d in t h i s survey could form t h e f o u n d a t i o n f o r
f ol lo w - up s t u d i e s on endemic s p e c i e s .
Stenophagous i n s e c t s , as
43
Table 7.
P a r a s i t i s m of O r e l I l a r u f i c a u d a ( F a b r i c i u s ) pupae in Canada
t h i s t l e seed he ad s , September 3, 1981.
Tot al #
Heads Attacked
Site A
(n=60).
Site B
(n=37)
■
23
■
To ta l #
Pupae
Tot al #
P a r a s i t i z e d Pupae
47
21
26
7
.
.
12 -
S i t e C(n=52)
4
4
3
S i t e D.
(n=21)
2
2
I
h = To ta l number of seed heads examined f o r each c o l l e c t i o n s i t e .
44
45
Ceuthorynchus I i t u r a and B a r is s p . , which a r e e s t a b l i s h e d , b u t a re
sp re ad in g s lo w ly , could be augmented and r e d i s t r i b u t e d over t h e s t a t e .
The p o t e n t i a l o f t h e combination o f two s t r e s s - f a c t o r s , t o i n ­
c r e a s e t h e impact on t h e t h i s t l e p l a n t s in t h e f i e l d , should be i n v e s t !
gated.
I n s e c t damage and a pathogen form a p e r f e c t comb ina tion.
In
t h e i r stu dy of i n s e c t involvement in pathogen t r a n s m i s s i o n , H a r r i s and
Maramorosch (1980) s t a t e d :
"We o f t e n ove rlo ok t h e f a c t t h a t i n s e c t i n ­
vad ers of p l a n t s a r e a l w a y s , w it h o u t any e x c e p t i o n , accompanied or f o l ­
lowed by fun gi and b a c t e r i a . "
Endemic pathogens of Canada t h i s t l e a r e
p r e s e n t ; two fung al d i s e a s e s , P u c c in ia obte gen s and S c l e r o t i n i a
.
s c l e r o t i o r u m and an a s t e r yellow caused by a mycoplasma-1 ike organism.
The w e ev ils Ceuthorynchus l i t u r a , Rh in oc yllu s c onic us and B ar is s p . a re
p o t e n t i a l v e c t o r s of b o t h , v i r a l and fung al d i s e a s e s .
Transmission,
exp erimen ts a r e n e c e s s a r y t o e v a l u a t e t h e i r p o t e n t i a l as t h i s t l e p a th o ­
gen v e c t o r s .
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