Government
of Canada
Gouvernement
du Canada
Canadian
Service
ISSN 08^6-0532
canadien des
torets
Forestry
Service
Forest
No. 3
Pest
Management
Laboratory Methods]
January 1985
EVALUATING SPRAY DATA USING ABBOTT'S
The data obtained
acy,
usually consists
treatment
and
check
variance,
which
different plots
in a spray
is
trial,
Abbott's
related
(Sower et
to
al.
the
formula
nature
1982).
One
(1925)
If
the populations are
densities
reduces
plots,
the
of
the pre-requisites
not matched,
in
of
of the target insect in
the
of
this formula is that the pre-spray population densities
are identical.
FORMULA
when a pesticide is evaluated for its effic
of pre- and post-spray population
plots.
Institute
effect
of
population
the
for
the
check and
a serious bias is
any
bias
levels
or
between
correct use of
treatrrent plots
introduced,
as can
be seen in the following example and the discussion that follows.
Abbott's
1980),
formula
can
be
written
in
the
form
of
a
simple
equation
(Retnakaran
which is easy to use in any hand-held calculator with keys for brackets.
'Post-spray population
Pre-spray populations
in treatment
in check
% Population
reduction
1
-
X
■Pre-spray population
in treatment
Hypothetical
sets
of
to illustrate the effect of
data
treatment and
tion in check
check
plots are
shown below
varying the pre-spray population density in the check plot on
the percent population reduction.
Canada
from paired
100
Post-spray popula
-
In
set
number
3,
plots are identical and
the
pre-spray
therefore
2
-
population
satisfy
the
densities
in
the
treatment
and check
requirement for applying Abbott's
formula.
The 80% population reduction obtained is the unbiased value.
If
the pre-spray
population
density
in
the
check
is
different from
treatment but the post-spray density in the check is proportionally low,
2,
then the results are unaltered.
requires a
Such
a situation,
check plot with a pre-spray population
however,
identical
that of
as in sets
1
the
and
cannot be predicted and
to
that of
the
treatment
to
confirm the proportionality.
If
the
pre-spray
in
the
overestimated.
If
population
population
treatment,
the
as
pre-spray
in
in
the
set
check
4,
population
plot
then
in
the
is
the
check
lower
%
than
the
population
plot
is
hiqher,
pre-spray
reduction
is
as
5,
in
set
then the % reduction is underestimated.
The
post-spray
reasonable
from
an
competition is severe,
population is
population
ecological
densities
in
standpoint.
the
check
When
the
plots
resulting in relatively high mortality.
relatively
low,
the converse
is usually
(sets
population
On
the
4
and
density
5)
is
other hand
are
hiqh,
if
the
true.
Conclusion
(i)
When
the
it is
plot
estimate
not possible
with
of
the
to
match
higher
population
the
populations
population
reduction
than
as
the
to
of
2
control
do
the
plots,
and
it
is
obtain
reverse
and
better
a
to use
conservative
overestimate
the
result.
(ii)
Examining the pre-spray population densities
of
spray data can alert the reader as
to whether the results are optimistic or conservative.
References
Abbott,
W.S.
1925.
Econ.
Entomol.
Retnakaran,
A.
A
1980.
Effect of
spruce budworm.
Sower,
L.L.,
T.W.
J.
Overhulser,
1982.
attractant.
method
of
computing
Econ.
effectiveness
D.L.,
3 new moult-inhibiting insect
Entomol.
Daterman,
Control of Eucosma
J.
the
of
an
insecticide.
J.
18:265-267.
Econ.
Entomol.
growth
regulators
Laws,
D.E.
on
the
73:520-524.
G.E.,
Sartwell,
sonomana by
C,
and
Koerber,
matinq disruption with synthetic sex
75:315-318.
Arthur Retnakaran
1219 Queen St. East
Sault Ste. Marie
#
P.O.
Box 490
Ontario,
P6A
5M7