THE
EFFECTIVENESS OF RCO MOLE BAIT
IN CONTROLLING MOLE DAMAGE
University
Study
4th Eastern Animal Damage Control Conference
Madison Wisconsin 1989
by Dale K. Elshoff and Glenn R. Dudderar
Department of Fisheries and Wildlife
Michigan State University East Lansing, MI 48824
ABSTRACT
The tunneling damage caused by eastern moles
(Scaloous aouaticus') and starnosed moles (Condviura
cristata) is well known to professionals in lawn care,
golfcourse maintenance, and turfgrass production, as well
as many private landowners. Present damage control methods,
include trapping, gas and smoke fumigants, and insecticide
applications have a wide variety of limitations and prove
impractical in some situations. As easily applied mole damage
control method is needed that professional and nonprofessional
applicators can use in a variety of environmental and physical
conditions.
This study tested the effectiveness of Orco
Mole Bait, a chlorophacinnone pellet placed in
active tunnel systems. The bait was tested on both mole species,
three soil types (sand, loam and muck), and two watering regimes
(irrigated and not irrigated).
Orco Mole Bait was
equally effective in controlling the damage caused by both
eastern and starnosed moles. Captive moles readily accepted
the dry, hard bait pellets. The average time to control
in fields trials was 30.3 days following first application
(21.5 days on dry soils, 38.7 days on irrigated soils). The
bait was effective on all three soil types, but irrigation
appeared to lesson effectiveness. On untreated control sites
there was no correlation between precipitation, evaporation,
or average maximum or minimum temperature and mole activity.
Multiple occupancy and/or rapid reinvasion of abandoned tunnel
systems and the use of tunnels by other fossorial species
occurred on several study sites such as birdfeeders.
Orco Mole Bait
was a practical, effective mole damage control agent
that was more easily applied then present damage control methods.
INTRODUCTION
Professionals in lawncare, golfcourse maintenance,
pest control, and turfgrass production, as well as many private
landowners, are well aquatinted with the damage that moles
can do. This damage, from disfiguring lawns and greens to
creating hazards for people and machinery, is well documented
(Eadie 19'54, Dudderar 1977, Marsh & Howard 1978, Henderson
1983). Over time, many techniques have been suggested to control
mole damage (Hanawalt 1922 Henning 1952, Eadie 1954, Marsh
& Howard 1978, Ware 1980, Dudderar 1983a, 1983b, 1985,
Henderson 1983, Benjamin 1985, Corrigan 1987). The most popular
of these methods include trapping, gas, and~smoke fumigation,
and insecticide applications. These methods are subject to
a wide variety of limitations and prove impractical in some
situations. Traps are easily mis-set and are conspicuous.
The most effective fumigants are not available to non-professionals,
and there are restrictions on use areas. Insecticides seem
less effective on dry and organic soils, and there are restrictions
on area and vegetation use after application.
Professional and non-professional applicators need an easily
applied mole damage control method that can be used in a variety
of physical and environmental conditions the primary purpose
of this study was to test the efficacy of Orco
Mole Bait and compare it to other mole damage control
methods. Orco Mole Bait
is manufactured by Oregon Rodent
Control Outfitters and is licensed for distribution
within the states of Oregon and Washington.
The development of an effective damage control technique requires
a thorough understanding of the species physiology, population
dynamics, habitat requirements, and habits. In reviewing the
literature it becomes more obvious why we do not have a consistently
reliable mole damage control method despite numerous attempts,
while there is a preponderance of information concerning the
population dynamics, social habits, tunneling behavior, and
food preferences of moles (Slonaker 1920, Hanawalt 1922, Jackson
1922, Hamilton 1956, Godfrey 1957, Conaway 1959, Brown 1972,
Giger 1973, Funnilayo 1976, 1977, Harvey 1976, Hartman &
Gottschang 1983, Hickman 1982), much of this information is
contradictory. Therefore, a second goal of this study was
to collect observations on the tunneling activity and social
habits of the two mole species that occur in mid-Michigan:
the eastern mole (Scalpus aquaticus') and the starnosed
mole (Condviura cristata'), specifically, information
was collected on multiple mole occupancy in tunnel systems,
the use of mole tunnels by other fossorial species, tunneling
habits, and habitat preferences.
Relationships between tunneling activity and rainfall evaporation
and average maximum and minimum temperature were also investigated.
METHODS
SITE DESCRIPTION
All studies were conducted in Meridian Township,
in Ingham County Michigan. Topographical the county lies on
a broad glaciated plain lying 200-600 feet above lakes Michigan,
Eria, and Huron. It is characterized by smooth or gently undulating
topography though some regions are choppy and comparatively
hilly. Swamps and lakes widely distributed. Originally the
area was entirely forested except the 3-4% of marshland and
water (Sommers. 1977). The climate in the county is characterized
by fairly cold winters and mild summers, the mean temperature
is 46.9 degrees Fahrenheit (24.2 in winter, 68.6 in summer).
The average length of frost-free season is from May 3 to October
10 (160 days), but this period is shorter on muck lands. Normal
annual precipitation is 31.43 inches, including melted snow.
Yearly snowfall averages 47.4 inches (Michigan Weather Services,
1974).
Study sites were scattered throughout the county and grouped
into three major soiltypes: 1) muck (Carlisle), 2) loam (hillsdale
sandy loam, Granby sandy loam, Walkill loam, Bellfontaine
sandy loam), and 3) sand (Berrien loamy sand, Beifontaine
loamy sand, and unknown backfill sands).
BAIT EFFICACY
Efficacy testing of Orco Mole Bait (active
ingredient: chlorophacinone) was conducted July 10 to September
16, 1986. Testing was also attempted February 10 to March
15, 1987, but sporadic mole activity made testing impossible.
Only tunnels currently active were used for study. Mole activity
was determined by creating "active assessment points"
every 10 to 15 Et along all visible tunnels. The method by
which the activity assessment points were created depended
on the characteristics of the damage on a particular site.
in shallow system (designated eastern mole system as described
by Dudderar (1985)) the mole tunnel just below the surface
of the ground leaving raised ridges on the turf. These tunnels
were marked by depressing short sections of tunnel or by poking
a 1" hole in the top of the tunnel. In deep systems (identified
as starnosed mole systems) the moles tunnel 4 to 20 inches
below the ground surface
pushing the excavated earth up to the surface through vertical
shafts. This results in large, coneshaped mounds on the surface
of the turf. Deep systems were marked only by poking holes
in the top of the tunnel either directly in the middle of
one mound or between two mounds. Activity assessment points
were marked with spray paint for easy identification on subsequent
visits. A tunnel was declared "active" if the activity
assessment points on that tunnel were repaired 3 times in
5 days.
Ten starnosed mole sites and ten eastern mole sites were identified
by the tunneling characteristics assigned to control and treatment
groups. Bait application varied with species of mole creating
damage. In eastern mole systems a small hole was poled in
the top of the tunnel with a blunt probe. A teaspoonful of
bait was put into the tunnel and the hole plugged with a clod
of dirt, wad of grass, or a piece of paper towel. Care was
taken to keep the bait free of human scent and soil during
application and hole plugging so that attractiveness of the
bait was not reduced. Bait was applied in this manner every
10 to 15 ft in all active tunnels. Starnosed tunnels were
treated by driving the bait probe through the soil between
two mounds until the tunnel was located. A length of rubber
tubing was then inserted into the tunnel and the bait was
fed into the tunnel through the tubing. The tube was removed
and then hole blocked in the same manner as eastern mole systems.
The same process was followed on control sites of both species
but no bait was applied before the holes were plugged.
Activity was monitored on all sites every 2 to 4 days after
initial bait application. New damage was baited as soon as
OT was detected. Bait was reapplied to entire treatment site
if activity did not stop within 10 days. If activity did cease,
activity points were monitored as usual for the remainder
of the study.
WEATHER ACTIVITY CORRELATION
Data to test for correlation between activity
and average maximum and minimum ambient temperature evaporation
and precipitation were collected July 1 to September 15, 1986.
Nine control sites from the bait efficacy study were used
to test for correlation. Activity was measured by using activity
assessment points as described in the BAIT EFFICACY section.
Ambient temperatures, evaporation, and precipitation data
were obtained from the East Lansing post of the National Weather
Service.
Data Analysis
As
the study progressed it appeared that soil type and watering
regime affected bait efficacy. Therefore the number of days
until zero damage occurred on each site was compared by Analysis
of Variance to determine bait efficacy and to detect effects
of species type, soil type, and watering regime. Multiple
regression analysis tested relationships between weather factors
and level of activity. An alpha level of.05 was used to test
for significance in all cases.
RESULTS AND DISCUSSION
Species of mole treated was removed for overall
data analysis for two reasons. First, there was no significant
difference in time to control or percent activity between
designated eastern and starnosed system (Pr > F = 0.51).
Secondly the study showed that in Mid-Michigan one cannot
correctly identify the species of mole in a tunnel system
by the physical characteristics of that system as was previously
thought (Duderar 1985). On two occasions as eastern mole was
collected from a designated starnosed system and once a starnosed
mole was captured in a designated eastern system. There are
two explanations for this phenomenon. 1) These systems were
originally constructed by the designated species then reinvaded
by the "opposite" species, or 2) these moles constructed
tunnels in response to soil type or soil condition, as Slonaker
(1920), Hamilton (1931), and Harvey (1976) found rather than
two species types. Both of these situations are beneficial
from an energy use perspective. Hisaw (1923), Arlton (1963)
and Giger (1973) refer to the tremendous amounts of energy
the moles expend, any energy conservation would be to the
mole's advantage. It would require less energy to invade a
vacant system than to construct a new one. Maintaining surface
tunnels where the soil surface is regularly compacted by mowing,
rolling, or freezing would be extremely intense. In case of
such disturbance it would seem more energy efficient to construct
a deep tunnel system one time rather then rebuild surface
tunnels every 2-3 days.
Orco Mole Bait
was effective. An average of 21.5 days was required to achieve
zero damage on treated dry soil: 38.7 days on treated irrigated
soils. On untreated dry soils and untreated irrigated soils
activity continued for 50 days and 42.3 days respectively.
There was a significant difference in the number of days to
zero damage on muck (Pr>F+0.0351), 1oam(Pr>F+0.0453),
and sand (Pr>F+0.0351) (Table 1).
TABLE I. Average number of days to zero damage.
| |
TREATMENT
|
CONTROL
|
| |
MUCK
|
LOAM
|
SAND
|
MUCK
|
LOAM
|
SAND
|
|
DRY
|
20
|
24
|
20.5
|
50
|
50
|
50
|
|
????
|
34
|
32
|
50
|
36
|
50
|
41
|
Analysis of Variance shows that irrigation significantly
affects bait efficacy on sandy soils (Pr>F+0.0026) but not
on loam soils (Pr>F+0.6477). Irrigation factors on muck could
not be tested because of insufficient sample size. It should
be noted that because the study was not originally designed
to test for soil or water factors small sample sizes make statistical
analysis results of theses factors questionable.
The authors suspect a significant difference between number
of days to zero damage on irrigated and non-irrigated soils
would occur with more repetitions within soil and irrigation
types. An increase in number of days to zero damage due to high
soil moisture might occur for two reasons. First, more earthworms
and other natural food items would be present at the depth where
foraging moles cause detectable soil disturbance. Therefore,
the moles may not consume as much bait as they would when natural
food items are less abundant.
It should be noted that in limited laboratory bait acceptance
tests moles ingested lethal quantities of bait even when given
free choice between the bait and ad libidum earthworm supplies.
A second reason that excess soil moisture may increase the length
of time to reach control is that under these conditions that
bait may become less palatable and therefore not be consumed.
When bait was placed in a container of soil and left outside
in an unprotected area for ten days, it was still intact but
quite mushy.
Multiple mole occupancy or extremely rapid reinvasion of tunnels
increased the number of days to zero damage. On two study sites
activity persisted the day after moles were physically removed
from the systems. On one of the sites an eastern mole was removed
and activity continued at all activity points. This suggests
that either more than one mole was concurrently using all parts
of the tunnel system or extremely rapid reinvasion occurred.
At another site a starnosed mole was removed and 2 days later
an eastern mole was removed from the same site approximately
20 ft. from the point of the first capture. Following the removal
of this second mole the system remained active but a consistent
subset of points was not used again for 14 days. This suggests
that the second mole may have had an established territory within
that larger tunnel system, similar to Giger's (1973) findings
with ScaDanus. Multiple occupancy within a species has been
confirmed by several studies (Hamilton 1931, Arlton 1936, Eadie
& Hamilton 1956, Mellanby 1966, Harvey 1976), particularly
if individuals are part of a family group or early pairs for
the next breeding season. To the best of our knowledge, this
is the first report of two different mole species occupying
the same tunnel system, ruling out family grouping and early
pairing for the breeding season. Rapid reinvasion of the systems
is a possible but unlikely explanation for this situation. While
reinvasion of vacated tunnels occurred on several occasions
(supporting Hartman & Gottschang's (1983) findings); no
site in this study was clearly reinvaded for at least 14 days
after the system was vacated.
In several instances a few sporadic activity points would be
used after a system was evacuated. These intermittent, low levels
of activity appear to be exploratory actions to determine the
possibility of reinvasion. If this mild damage appeared soon
(<10 days) after the system was vacated, damage would cease
without treatment. If the system had been empty more than two
weeks, damage would dramatically increase after 2-3 days. Indicating
successful reinvasion.
Another factor that confounds damage control with Orco
Mole Bait is the presence of other fossorial species
in active and evacuated mole tunnel systems. Thirteen lined
ground squirrels (Citellus tridecimimeatus), meadow vole (Microtus
pennsvlvanicus). short-tailed shrews (Blarina brevicauda). and
two species of Peromyscus were live-trapped in either deep
or shallow mole systems during this study. Hickman (1987) caught
Microtus in Condvlura systems, but this was the only
reference to other species use of mole tunnels found. When moles
and other species were concurrently using the tunnel systems,
it was difficult to detect the other species presence and categorize
damage by species. Only upon closer inspection of root damage
and length of time that activity occurred was there any indication
of additional species. After several bait applications the nature
of the damage changed slightly, indicating that moles were eradicated
from the system but non-target species were not.
Where shrews were co-occupying mole systems tunnels got smaller,
more shallow with more small (>1") holes in the tops
of tunnels, and had more concentrated foraging areas. When ground
squirrels remained in previous mole tunnels, the tunnel diameters
increased slightly and deep travel tunnels were very well maintained
without the mounding typical of mole maintenance. There is some
question why these non-target species were not eradicated during
treatment. Non-target species may not find the bait attractive
or palatable and therefore not ingest it. They may consume some
bait but not get a lethal dose wither because there is an ample
supply of preferred natural food items, they cache the bait
or they require a higher dose of bait than is applied for mole
control. Shrew population levels may be high enough that while
some individuals die, damage continues due to the remainder
of the population. Rapid reinvasion of non-target species may
occur. Whatever the case, the bait controlled mole damage with
no apparent effect on non-target organisms utilizing treated
tunnel systems. It is important to identify all species using
these tunnel systems when treating damage, and damage control
methods for these other species may need to be applied simultaneously
or in succession to mole damage control with Orco
Mole Bait.
Regression analysis showed no relationship between precipitation,
average minimum and maximum temperatures, or evaporation and
level of activity on 7 of 9 sites. A correlation between minimum
average temperature (Pr>F=O.OO, F+0.6918) and activity on
irrigated and site, and between evaporation and activity on
muck site ~r>F=0.001, =0.6489). However, because of the insufficient
sample size we question these results and would assume type
II errors in these cases.
Although moles prefer wooded, shady, moist areas (Arlton 1936,
Godfrey 1957, Funmiiayo 1977, Henderson 1983), they easily adapt
and seen to be somewhat attracted to human alterations of the
environment. Moles used some sort of microhabitat on 17-19 sites
included in this study. Of the two sites that did not include
mircohabitats, one individual migrated to a vacant system with
microhabitats and the other succumbed to treatment within 4
days. These microhabitats are created by natural features such
as the areas under trees, bushes, and rocks, and man-made features
such as gardens and mulched areas, beneath decks and fences,
under woodpiles and along building foundations and driveways.
Several other authors found stumps, logs, etc. included in mole
systems (Hamilton 1931, Arlton 1936, Henderson 1983, Corrigan
1987). These microhabitats are attractive to moles because of
their soil moisture content and less compact soils, a combination
that provides optimal foraging and tunneling conditions. Moles
were highly attracted to the ground beneath birdfeeders and
fruit trees. Under the fruit trees they were probably foraging
on invertebrates that were attracted to rotting fruit on the
ground. Moles were observed on several occasions foraging under
bird feeders and eating the seed that had fallen to the ground.
CONCLUSION
Generally, creating and creating and maintaining
a nicely landscaped lawn is creating and maintaining good mole
habitat. By creating protected areas under trees, shrubs, and
woodpiles and easy travel routes next to foundations and driveways,
prime nesting cover and forage areas are provided for moles.
One way to control the damage of any species is to alter the
habitat to make it less attractive to the animal. Few homeowners
or groundskeepers would be willing to extensively alter lawn
areas to make them less attractive to moles, so they need an
easily applied, method to eradicate moles. This study shows
that Orco Mole Bait is a highly
effective, easily applied mole control technique. However, there
are disadvantages. Two or more successive treatments are often
required particularly where there is multiple occupancy and/or
wet soil conditions. Damage must be correctly identified
because the bait does not appear to be effective in controlling
other fossorial species. Also, it is a toxicant, which is hazardous
if consumed by children or pets. On the other hand, the bait
is inconspicuous and therefore more aesthetic and tamper resistant
then traps. Unlike fumigants and insecticide there are no restrictions
on use areas and it appears to pose minimal hazard to non-target
species.
LITERATURE
CITED
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