University of Nebraska - Lincoln
DigitalCommons@University of Nebraska - Lincoln
Eastern Pine and Meadow Vole Symposia
Wildlife Damage Management, Internet Center for
3-4-1981
AN APPROACH TO DETERMINE THE
ECONOMIC THRESHOLD LEVEL FOR PINE
VOLES
Stephen B. White
Cornell University, Ithaca, NY
Theodore L. Huller
Cornell University, Ithaca, NY
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PINE VOLES" (1981). Eastern Pine and Meadow Vole Symposia. Paper 61.
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AN APPROACH TO DETERMINE THE ECONOMIC THRESHOLD LEVEL FOR PINE VOLES
Stephen B. White and Theodore L. H u l l a r
Cornell University
I t h a c a , NY 14853
The e f f e c t i v e n e s s of o r c h a r d management, a s i n any a g r i c u l t u r a l
system, i s judged on t h e t o t a l q u a n t i t y and q u a l i t y of t h e produce and
on t h e f i n a n c i a l r e t u r n p e r u n i t of investment. D e c i s i o n s a f f e c t i n g
o r c h a r d management a r e based u l t i m a t e l y on economic f a c t o r s .
T h i s economic c r i t e r i o n should, t h e r e f o r e , be a p p l i e d t o a l l
o r c h a r d p e s t management decisions--including c o n t r o l of t h e p i n e v o l e
(Pitymys pinetorum). The purpose of t h i s paper is t o d e s c r i b e an
approach we a r e t a k i n g t o i d e n t i f y f a c t o r s u s e f u l i n e s t i m a t i n g t h e
economic t h r e s h o l d which can form t h e b a s i s f o r c o s t - e f f e c t i v e
management of t h e p i n e v o l e and t h e meadow v o l e (Microtus pennsylvanicus)
i n apple orchards.
Dyer and Ward (1977) and Dolbeer (1981) s t a t e t h a t t h e d e c i s i o n s
i n management of p e s t s p e c i e s should be based on economics. Key
f a c t o r s i n economics-based p e s t c o n t r o l i n c l u d e : e s t i m a t i o n of l o s s e s
caused by s h o r t - and long-term damage a s a f u n c t i o n of p e s t p o p u l a t i o n s ;
c o s t of measures t o c o n t r o l t h e p e s t w i t h i n d e f i n e d p o p u l a t i o n l e v e l s ;
and t h e o p p o r t u n i t y c o s t s of t h e c o n t r o l measures. When t h e s e f a c t o r s
a r e known t h e p e s t c o n t r o l s p e c i a l i s t , t h e orchard manager, and t h e
r e s e a r c h e r c a n make wise judgements on a c t i o n s t o t a k e a g a i n s t t h e
depredating species.
Rodent damage c o n t r o l i n a p p l e o r c h a r d s h a s evolved l a r g e l y
through u s e of s t a n d a r d o r c h a r d p r a c t i c e s . S t u d i e s a r e n o t a v a i l a b l e
t o q u a n t i f y t h e l e v e l s of damage n e c e s s a r y t o determine what c o n t r o l
measures a r e economically j u s t i f i e d , o r even t o i d e n t i f y t h e range of
damage t h a t would e s t a b l i s h c o s t - e f f e c t i v e n e s s .
There a r e s e v e r a l r e a s o n s f o r t h i s l a c k of knowledge. The damage
done t o a p p l e t r e e s i s n o t e a s i l y observed, d e s c r i b e d , o r measured.
There i s probably n o t a simple l i n e a r r e l a t i o n s h i p between b a r k removal
and economic damage. I n a d d i t i o n t o t h e s e d i f f i c u l t i e s and because
t h e t r e e i s a p e r e n n i a l , t h e r e i s cummulative damage a s w e l l a s
r e c u p e r a t i v e and compensatory p r o c e s s e s .
In numerous s i t u a t i o n s ,
compensatory growth h a s been suggested and a c t u a l l y demonstrated
(Dyer 1973, 1975, 1976, Dyer and Bokhari 1976, H a r r i s 1974, Hutchinson
1971, Pearson 1965, Vickery 1972, Westlake 1963, and Woronecki
&.
1376).
To d a t e , o n l y a few a t t e m p t s have been made t o a d d r e s s t h e
economics of ? i n e v o l e o r meadow v o l e damage i n o r c h a r d s . Pearson
(1976, 1977) and Pearson and Forshey (1978) examined t h e r e l a t i o n s h i p
between t h e p r e s e n c e of v o l e s and t r e e damage expressed a s a r e d u c t i o n
i n c r o p v a l u e . A few a u t h o r s have made some t h e o r e t i c a l and
s p e c u l a t i v e e s t i m a t e s of damage (Kennicott 1957, Hamilton 1938,
Garlough and Spencer 1944, B i s e r 1967, and Syers 1974). Recently
S u l l i v a n g &. (1980) have r e p o r t e d some s t a n d a r d survey work
examining t h e magnitude and c a u s e s of t r e e m o r t a l i t y .
T h i s g i v e s some
concept of economic damage, but cannot b e used t o i s o l a t e even t h e
b e n e f i t s of c u r r e n t r o d e n t c o n t r o l techniques.
Ferguson (1980) and
L u t t n e r (1978) have a l s o produced some v e r y broad economic
g e n e r a l i z a t i o n s by e x t r a p o l a t i n g form r o d e n t i c i d e u s e f i g u r e s . These,
however, a r e o n l y measures of s t a n d a r d a c c e p t a b l e o r c h a r d p r a c t i c e , and
cannot form t h e b a s i s f o r v o l e management i n o r c h a r d s .
A s i m p l e d e s c r i p t i o n of damage t o a n a p p l e t r e e r o o t system i s
n o t a v a i l a b l e . The d e p t h t o which damage e x t e n d s i s a v a i l a b l e o n l y
a s a n t e d o t a l i n f o r m a t i o n (Benton 1952). Even t h e s i m p l e s t u n d e r s t a n d i n g
of r o d e n t damage, and t h e response of t h e t r e e t o such damage, i s n o t
c u r r e n t l y a v a i l a b l e . No s t u d i e s a r e a v a i l a b l e which r e l a t e t h e d e a t h
of t r e e s t o t h e removal of r o o t t i s s u e . There i s no i n f o r m a t i o n t o
s u g g e s t a t what l e v e l t i s s u e removal may b e g i n t o impair growth, o r
a t what l e v e l growth impairment may begin t o reduce c r o p y i e l d s and
t h e p r o d u c t i v e l i f e - s p a n of t h e t r e e .
Such i n f o r m a t i o n is e s s e n t i a l t o w i s e management, and might
s u g g e s t t h a t 100% c o n t r o l , an i n d u s t r y s t a n d a r d , may b e n e i t h e r
n e c e s s a r y nor d e s i r a b l e . We have proposed t h r e e s t u d i e s t h a t should
h e l p d e f i n e t h e economic t h r e s h o l d l e v e l o f p i n e v o l e s and improve
o u r u n d e r s t a n d i n g of and recommendations f o r t h e moderately damaged
t r e e . These t y p e s of s t u d i e s should a l s o a i d i n i d e n t i f y i n g methods
u s e f u l f o r making c a r e f u l damage assessments t h a t a r e now l a c k i n g i n
pine vole control l i t e r a t u r e .
The f i r s t s t u d y w i l l a d d r e s s t h e u n s u b s t a n t i a t e d h y p o t h e s i s t h a t
v o l e d e n s i t y i s a most important f a c t o r i n r o o t damage. T h i s s t u d y
w i l l i n v o l v e e n c l o s i n g known v o l e p o p u l a t i o n s w i t h i n 0.008 ha fenced
p l o t s which c o n t a i n e i g h t a p p l e t r e e s . The t r e e s a r e McIntosh on
M-26 r o o t s t o c k and a r e i n t h e i r n i n t h l e a f . Vole p o p u l a t i o n s
e q u i v a l e n t t o 247, 494, and 74% ( f a m i l y group) v o l e s per ha w i l l
b e p l a c e d w i t h i n e n c l o s u r e s . Harvest r e c o r d s , s h o o t growth and l e a f
a n a l y s e s , which have been c o l l e c t e d d u r i n g p r e v i o u s r e s e a r c h p r o j e c t s ,
w i l l c o n t i n u e t o b e done f o r a l l t r e e s i n each e n c l o s u r e . When shoot
growth, l e a f n u t r i e n t a n a l y s i s , and t r e e s p e c i f i c c r o p l o a d s a r e
c o r r e l a t e d w i t h v o l e d e n s i t i e s , t h i s s t u d y should y i e l d i n f o r m a t i o n
d i r e c t l y r e l a t e d t o t h e economic t h r e s h o l d .
I f r o o t systems w i t h i n
t h e enclosed p l o t s a r e excavated, an even f u l l e r understanding of
v o l e damage on t r e e s should b e gained.
To s t u d y t h e long-term, c u m u l a t i v e e f f e c t s of p i n e v o l e damage,
a second s t u d y w i l l examine t h e r o o t systems of damaged mature t r e e s .
By s e l e c t i n g t r e e s of poor, moderate, and h i g h v i g o r , a c o r r e l a t i o n
between l e v e l s of r o o t damage and t h e v a r i o u s d e g r e e s of t r e e v i g o r
A few t r e e s w i l l b e removed by e x c a v a t i n g a l l
may b e e s t a b l i s h e d .
r o o t m a t e r i a l g r e a t e r t h a n 1 cm i n diameter. Root m a t e r i a l w i l l
b e s e c t i o n e d i n t o approximately s t r a i g h t c y l i n d r i c a l segments. The
d i s t a n c e between t h e r o o t crown and each segment w i l l b e recorded,
and t h e s u r f a c e a r e a w i l l b e e s t i m a t e d ( n ' d i a m e t e r ' h e i g h t ) .
The
p o r t i o n of t h e s u r f a c e a r e a which h a s been damaged w i l l b e e s t i m a t e d
u s i n g a h e l i c a l l i n e - t r a n s e c t t o sample damaged and undamaged b a r k on
e a c h r o o t segment. The amount of damaged t i s s u e , recorded w i t h i n 0.5-m
zones of t h e r o o t crown, w i l l b e c o r r e l a t e d a g a i n s t shoot growth,
l e a f n u t r i e n t a n a l y s i s , and t r e e s p e c i f i c h a r v e s t r e c o r d s . It i s
expected t h a t most r o o t systems would n o t be t o t a l l y excavated b u t
w i l l be sampled by c u t t i n g a 2-m deep t r e n c h a c r o s s t h e d i a m e t e r of
t h e d r i p l i n e ( t h r o u g h o r immediately a d j a c e n t t o t h e t r e e b a s e ) . A
15-cm segment of each r o o t exposed w i l l b e removed and handled a s
d e t a i l e d above. The l o c a t i o n ( v e r t i c a l and h o r i z o n t a l ) of each exposed
segment w i l l a l s o b e noted.
The t h i r d and l a t e r s t u d y would examine t h e p o s s i b i l i t i e s t h a t a
damage l e v e l accumulated over y e a r s of exposure would c a u s e a
s i g n i f i c a n t l y d i f f e r e n t r e d u c t i o n i n y i e l d t h a n does a one-time
exposure t o t h e same damage l e v e l . T h i s q u e s t i o n can b e approached
by e x c a v a t i n g t h e r o o t crown and proximal p o r t i o n of a l l r o o t s
a t t a c h e d t o t h e crown. The d e s i r e d p e r c e n t a g e of damage w i l l b e
o b t a i n e d by measuring t h e t o t a l circumference of t h e exposed r o o t s and
t h e g i r d l i n g of t h a t p o r t i o n of t h e t o t a l circumference which i s
p r e s c r i b e d by t h e damage c a t e g o r y . The l e v e l s of damage chosen f o r
each c a t e g o r y w i l l correspond t o t h e l e v e l s of r o o t g i r d l i n g observed
i n t h e second study.
CONCLUSIONS
The t h r e e s t u d i e s w i l l improve o u r knowledge of t h e dynamic
r e l a t i o n s h i p between v o l e s , damage, and a c t u a l economic l o s s . The
expected i n s i g h t s a r e numerous and may form t h e b a s i s f o r new c o n t r o l
techniques.
I t i s d i s c o n c e r t i n g n o t t o have a good, even simple,
u n d e r s t a n d i n g of t h e a c t u a l damage ( r o o t t i s s u e removal) done by
p i n e v o l e s . A s y s t e m a t i c examination of t h i s f i r s t o r d e r damage i s
important because i t h a s never been done, and i n i t s absence we may
be missing important understandings r e l a t i n g t o t h e functional
mechanisms and more i m p o r t a n t l y t h e c o n t r o l of p i n e v o l e damage.
Through a simple comparison of r e s u l t s from o u r t h r e e s t u d i e s ,
s e v e r a l a d d i t i o n a l o b s e r v a t i o n s should b e p o s s i b l e . By comparing
r e s u l t s from t h e second and t h i r d s t u d i e s , t h e importance of damage
l o c a t i o n (e.g., r o o t h a i r v e r s u s r o o t g i r d l i n g ) and secondary damage
(e.g., fungus) should b e understood. Comparisons from t h e s e s t u d i e s
should a l s o i d e n t i f y damage l e v e l s of no o r o n l y temporary s i g n i f i c a n c e .
The r e s u l t s from t h e f i r s t s t u d y w i l l be t h e most d i r e c t a t t e m p t t o
d e t e r m i n e a n a c t u a l economic t h r e s h o l d p o p u l a t i o n a v a i l a b l e t o d a t e .
T h i s should a l s o p r o v i d e a d d i t i o n a l understanding of t h e r e l a t i v e
importance of r o o t hair f e e d i n g v e r s u s r o o t g i r d l i n g .
Dolbeer (1981) urged animal damage c o n t r o l r e s e a r c h e r s t o spend
h a l f t h e i r e f f o r t i n t h e s t u d y of t h e economic i m p l i c a t i o n s of
damage and damage c o n t r o l . Although s t u d i e s proposed h e r e do n o t
r e a c h t h i s g o a l , t h e y w i l l begin t o improve o u r understanding of t h e
economics of p i n e v o l e damage p a r t i c u l a r l y f o r t h e s o i l t y p e s , and
age c l a s s e s of t r e e s i n t h e s e s t u d i e s . Only through a f u l l e r
u n d e r s t a n d i n g of t h e r e l a t i o n s h i p between v o l e s , t r e e s , c r o p l o s s and
c o n t r o l e f f i c a c y , c a n we r e f i n e o u r a b i l i t y t o c o n s i s t e n t l y make t h e
most a p p r u p r i a t e a n d economically-sound management recommendations f o r
t h e c o n t r o l of p i n e v o l e damage i n commerical a p p l e o r c h a r d s .
LITERATURE CITED
BENTON, A.H.
1952. A s t u d y o f t h e n o r t h e r n p i n e mouse Pitymys
p i n e t o r u m s c a l o p s o i d e s (Audubon and Bachman). Ph.D. T h e s i s ,
C o r n e l l U n i v . , I t h a c a , NY. 7 3 pp.
1967. Hammal damage t o o r c h a r d s i n New York S t a t e .
BISER, D.L.
t1.S. T h e s i s , C o r n e l l Univ., I t h a c a , NY.
8 1 pp.
BYERS, R.E.
1974. P i n e mouse c o n t r o l i n a p p l e o r c h a r d s . Annual
West Va. S t a t e H o r t . Soc. Mountaineer Grower 335:3-13.
DOLBEER, X.A.
1981. C o s t - b e n e f i t d e t e r m i n a t i o n of b l a c k b i r d damage
control for cornfields.
W i l d l . Soc. E u l l . 9:44-51.
DYER, Pi.1.
1973. P l a n t - a n i m a l i n t e r a c t i o n s : t h e e f f e c t s o f redwinged
b l a c k b i r d s on c o r n growth. P r o c . B i r d C o n t r o l Sem. Bowling
Green S t a t e Univ., Bowling Green, OH. 6:229-241.
.
1975. The e f f e c t s o f red-winged b l a c k b i r d s ( A g e l a i u s
p h o e n i c e u s L . ) on biomass p r o d u c t i o n o f c o r n g r a i n s (Zea mays L.)
J . Appl. E c o l .
57:762-772.
.
1976. S i m u l a t i o n o f b i r d damage on c o r n e a r s . P r o c .
B i r d C o n t r o l Sem. Bowling Green S t a t e Univ., Bowling Green, OH.
7~173-179.
, AND U.G. BOKHARI. 1976. P l a n t - a n i m a l i n t e r a c t i o n s :
s t u d i e s o n t h e e f f e c t s o f g r a s s h o p p e r g r a z i n g o n b l u e grama
grass.
Ecology 57:762-772.
, AND P. WARD. 1977. Management o f p e s t s p e c i e s . P a g e s
J . P i n o w s k i and S. C. Kendeigh, e d s . G r a n i v o r o u s
267-300
b i r d s i n e c o s y s t e m s . Cambridge Univ. P r e s s , Cambridge.
431 pp.
1980. R o d e n t i c i d e u s e i n a p p l e o r c h a r d s .
Proc.
FERGUSON, W.L.
E a s t . P i n e and Pteadow V o l e Symp. H e n d e r s o n v i l l e , WC. 4:2-8.
GARLOUGH, F.E., AND D.A. SPENCER. 1944. C o n t r o l o f d e s t r u c t i v e
mice. U.S. Dept. I n t . F i s h and W i l d l . S e r v . Con. B u l l .
36.
37 PP.
HAEIILTON, W . J .
1938. L i f e h i s t o r y note;
J . Xammal.
19:163-170.
on t h e n o r t h e r n p i n e mouse.
HARPHARPIS,
P.
1374. A p o s s i b l e e x p l a n a t i o n o f p l a n t y i e l d i n c r e a s e s
1:219-225.
f o l l o w i n g i n s e c t damage. Agro-Ecosystems
HUTCHINSON, K . J .
1371. P r o d u c t i v i t y and e n e r g y f l o w i n f o d d e r
c o n s e r v a t i o n / g r a z i n g s y s t e m s . Herb. A b s t r . 41:l-10.
KENNICOTT, R. 1957. The q u a d r e p e d s of I l l i n o i s i n j u r i o u s and
b e n e f i c i a l t o t h e f a r m e r . Rep. Comm. o f P a t e n t s (Agr.)
1856:52-110.
LUTTNER, H.A.
1978.
apple orchards.
B e l t s v i l l e , MD.
P r e l i m i n a r y b e n e f i t a n a l y s i s of e n d r i n u s e on
Proc. E a s t . P i n e and Meadoxi Vole Symp.
2:18-22.
PEARSON, K.J.
1976. Some economic a s p e c t s o f p i n e v o l e damage i n
a p p l e o r c h a r d s o f New York s t a t e . M.S. T h e s i s , S t . Univ. o f
NY C o l l e g e of E n v i r . S c i . and F o r . , S y r a c u s e , NY.
55 pp.
.
1977. The i n f l u e n c e o f p i n e v o l e damage on a p p l e t r e e
v i g o r and f r u i t y i e l d .
Proc. E a s t . P i n e a n d :leadow Vole
S p p . W i n c h e s t e r , VA. 1:29-32.
, AND C.G. FORSHEY. 1978. E f f e c t s of p i n e v o l e damage
o n t r e e v i g o r and f r u i t y i e l d i n New York a p p l e o r c h a r d s .
H o r t S c i e n c e 13:56-57.
PEARSON, L.C.
1965. P r i m a r y p r o d u c t i o n i n g r a z e d and ungrazed
d e s e r t communities o f e a s t e r n Idaho. Ecology 46:278-285.
SULLIVAN, W.T., J R . , T.B. SUTTON, AND D.W. HAYNE. 1980. Apple
t r e e m o r t a l i t y , r a t e and c a u s e s . Proc. E a s t . P i n e and ?leadow
V o l e Symp. H e n d e r s o n v i l l e , NC. 4:62-65.
VICKERY, P . J .
1972. G r a z i n g and n e t p r i m a r y p r o d u c t i o n o f a
t e m p e r a t e g r a s s l a n d . 3 . Appl. Ecol. 9:307-314.
WESTLAKE, D.P.
1963.
39:385-425.
Comparison of p l a n t p r o d u c t i v i t y .
B i o l . Res.
WORONECKI, P . P . , C.R. INGRAEI, AND R.A. MLBEER. 1976. Response o f
m a t u r i n g c o r n t o s i m u l a t e d b i r d damage. Proc. Bowling Green
B i r d C o n t r o l Sem. Bowling Green, OH. 7:163-172.