Citation
Pest management strategies for storing grains in Florida

Material Information

Title:
Pest management strategies for storing grains in Florida
Series Title:
Florida Cooperative Extension Service circular 873
Creator:
Talbot, Michael T.
Koehler, Philip G. (Philip Gene), 1947-
Affiliation:
University of Florida -- Florida Cooperative Extension Service -- Institute of Food and Agricultural Sciences
Place of Publication:
Gainesville, Fla.
Publisher:
Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Publication Date:
Language:
English
Physical Description:
27 p. : ill. ; 28 cm.

Subjects

Subjects / Keywords:
Agriculture ( LCSH )
Farm life ( LCSH )
Farming ( LCSH )
University of Florida. ( LCSH )
Grain -- Storage -- Diseases and injuries -- Florida ( LCSH )
Granaries -- Florida ( LCSH )
Grain -- Diseases and pests -- Florida ( LCSH )
Grain aeration -- Florida ( LCSH )
Pests -- Control -- Florida ( LCSH )
Agriculture -- Florida ( LCSH )
Farm life -- Florida ( LCSH )
Grains ( jstor )
Pests ( jstor )
Wildlife damage management ( jstor )
Spatial Coverage:
North America -- United States of America -- Florida

Notes

Funding:
Florida Historical Agriculture and Rural Life

Record Information

Source Institution:
Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location:
Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management:
All rights reserved, Board of Trustees of the University of Florida
Resource Identifier:
26846467
AJG5673
001752716

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HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida




/ or
~3ic-
~19


Management
Strategies for Storing
Grains in Florida


Michael Talbot and Phil Koehler


Florida Cooperative Extension Service Institute of Food and Agricultural Sciences
University of Florida, Gainesville John T. Woeste, Dean


Pest


Cent ra,
rib, S/ r,,.
^4'^


Circular 873


7 '-


































Michael Talbot is Assistant Professor Extension Agricultural Engineer, Depart-
ment of Agricultural Engineering; and Phil Koehler is Professor Extension
Entomologist, Department of Entomology and Nematology; Institute of Food and
Agricultural Sciences (IFAS), University of Florida, Gainesville, FL 32611.
Printed June 1991








Introduction

The principle sources of loss in quality and
quantity in grains during storage are fungi, insects,
rodents, mites, respiration, and moisture migra-
tion. Although storage problems are common
during bad harvest years, many also result from
poor dry grain management practices. Employ-
ment of preharvest preventive management prac-
tices including bin sanitation, insect control, and
aeration along with adequate observation will
minimize dry grain storage problems. This paper
will discuss procedures to ensure proper grain bin
sanitation and pest control in order to reduce grain
wastage and profit loss.

Insects

Stored grain of almost any kind is subject to
attack by insects. The insects which attack stored
grain are highly specialized to exploit the stores
man has set aside for himself. Stored products
insects are, in most cases, insects of small size with
a high reproductive potential. Therefore, they are
easily concealed in grain and grain shipments and
have been carried to all parts of the world. Once
established in a commodity they are usually diffi-
cult to control.
In general, stored products pests thrive in warm,
humid environments. Grain with high moisture
stored in warm conditions is usually most suscep-
tible to insect infestations. Stored grain pests are
important since they contaminate food, lower its
nutritive value, and create conditions favorable for
mold growth.
Pests which attack whole grain usually develop
and feed inside the kernels of grain. They can be
easily overlooked in grain shipments since they
cannot be seen. These pests are not usually ca-
pable of existence as immature insects outside the
grain Examples of whole grain pests are the rice
weevil, the granary weevil, the lesser grain borer,
and the angoumois grain moth.
Other insects which attack grain are usually
unable to penetrate whole grain. These insect
pests however can attack grain after it has been
either mechanically broken or attacked by whole
grain insects. Examples of these secondary pests
are the red and confused flour beetles, Indian meal
moth, Mediterranean flour moth, and the
sawtoothed grain beetle.
Grain may become infested in a number of ways.
One of the most common means of infestation
starts in the field. In Florida, it is not uncommon


for freshly harvested corn to have 10% of kernels
infested with insects. Another common means of
infestation is storing grain in or near infested
storage facilities.
It is important to know the stored grain pests
and inspect according to the length of time it takes
an insect to complete a life cycle. Table 1 lists some
stored grain insects and some biological data while
Figures 1 10 illustrate several insects.

Molds
(pathogens)

Storage rots or moldy grain may develop in grain
storage bins if the moisture content of the kernels
is excessive and the air temperature is high enough
to permit fungus growth. More than 150 different
species of fungi have been reported on cereal
grains. The major storage fungi are species of the
common molds, Aspergillus and Penicillium. Some
species of fungi such as Alternaria sp. and
Fusarium sp. can cause infection in the field and
can cause advanced decay in high moisture grains.
Some of the fungi that grow in grains and other
seeds before harvest or in storage produce toxins.
One of the common storage fungi, Aspergillus
flavus, produces several toxins called aflatoxins
which cause problems when fed to animals.
Storage fungi cause loss of germination, dark
germs (in wheat, designated germ damage or sick
wheat), bin burning, mustiness, and heating.
These are the final results of invasion of grain by
storage fungi. Storage fungi are the cause, not the
result, of spoilage.
Depending on the commodity, contamination by
toxin is either a field problem, a storage problem, or
a combination of the two. Since toxins are produced
by fungi, they should be viewed as a potential
danger anywhere fungi grow on materials which
are used as food or feed. Fungal contamination is
necessary for production of toxins, but toxicity is
certainly not the inevitable result of all fungal
invasion. Fungi are almost universally present on
and in cereal grains, nuts and nearly all other plant
materials, but toxicity seems to be the exception
rather than the rule.

Identification
It is sometimes difficult to identify the specific
species of fungi which are causing a particular
problem in a given lot of grain. A laboratory
equipped with a compound microscope and culture
facilities is necessary to confirm the identity of a
fungus species. Many times, however, the signifi-








Introduction

The principle sources of loss in quality and
quantity in grains during storage are fungi, insects,
rodents, mites, respiration, and moisture migra-
tion. Although storage problems are common
during bad harvest years, many also result from
poor dry grain management practices. Employ-
ment of preharvest preventive management prac-
tices including bin sanitation, insect control, and
aeration along with adequate observation will
minimize dry grain storage problems. This paper
will discuss procedures to ensure proper grain bin
sanitation and pest control in order to reduce grain
wastage and profit loss.

Insects

Stored grain of almost any kind is subject to
attack by insects. The insects which attack stored
grain are highly specialized to exploit the stores
man has set aside for himself. Stored products
insects are, in most cases, insects of small size with
a high reproductive potential. Therefore, they are
easily concealed in grain and grain shipments and
have been carried to all parts of the world. Once
established in a commodity they are usually diffi-
cult to control.
In general, stored products pests thrive in warm,
humid environments. Grain with high moisture
stored in warm conditions is usually most suscep-
tible to insect infestations. Stored grain pests are
important since they contaminate food, lower its
nutritive value, and create conditions favorable for
mold growth.
Pests which attack whole grain usually develop
and feed inside the kernels of grain. They can be
easily overlooked in grain shipments since they
cannot be seen. These pests are not usually ca-
pable of existence as immature insects outside the
grain Examples of whole grain pests are the rice
weevil, the granary weevil, the lesser grain borer,
and the angoumois grain moth.
Other insects which attack grain are usually
unable to penetrate whole grain. These insect
pests however can attack grain after it has been
either mechanically broken or attacked by whole
grain insects. Examples of these secondary pests
are the red and confused flour beetles, Indian meal
moth, Mediterranean flour moth, and the
sawtoothed grain beetle.
Grain may become infested in a number of ways.
One of the most common means of infestation
starts in the field. In Florida, it is not uncommon


for freshly harvested corn to have 10% of kernels
infested with insects. Another common means of
infestation is storing grain in or near infested
storage facilities.
It is important to know the stored grain pests
and inspect according to the length of time it takes
an insect to complete a life cycle. Table 1 lists some
stored grain insects and some biological data while
Figures 1 10 illustrate several insects.

Molds
(pathogens)

Storage rots or moldy grain may develop in grain
storage bins if the moisture content of the kernels
is excessive and the air temperature is high enough
to permit fungus growth. More than 150 different
species of fungi have been reported on cereal
grains. The major storage fungi are species of the
common molds, Aspergillus and Penicillium. Some
species of fungi such as Alternaria sp. and
Fusarium sp. can cause infection in the field and
can cause advanced decay in high moisture grains.
Some of the fungi that grow in grains and other
seeds before harvest or in storage produce toxins.
One of the common storage fungi, Aspergillus
flavus, produces several toxins called aflatoxins
which cause problems when fed to animals.
Storage fungi cause loss of germination, dark
germs (in wheat, designated germ damage or sick
wheat), bin burning, mustiness, and heating.
These are the final results of invasion of grain by
storage fungi. Storage fungi are the cause, not the
result, of spoilage.
Depending on the commodity, contamination by
toxin is either a field problem, a storage problem, or
a combination of the two. Since toxins are produced
by fungi, they should be viewed as a potential
danger anywhere fungi grow on materials which
are used as food or feed. Fungal contamination is
necessary for production of toxins, but toxicity is
certainly not the inevitable result of all fungal
invasion. Fungi are almost universally present on
and in cereal grains, nuts and nearly all other plant
materials, but toxicity seems to be the exception
rather than the rule.

Identification
It is sometimes difficult to identify the specific
species of fungi which are causing a particular
problem in a given lot of grain. A laboratory
equipped with a compound microscope and culture
facilities is necessary to confirm the identity of a
fungus species. Many times, however, the signifi-








Introduction

The principle sources of loss in quality and
quantity in grains during storage are fungi, insects,
rodents, mites, respiration, and moisture migra-
tion. Although storage problems are common
during bad harvest years, many also result from
poor dry grain management practices. Employ-
ment of preharvest preventive management prac-
tices including bin sanitation, insect control, and
aeration along with adequate observation will
minimize dry grain storage problems. This paper
will discuss procedures to ensure proper grain bin
sanitation and pest control in order to reduce grain
wastage and profit loss.

Insects

Stored grain of almost any kind is subject to
attack by insects. The insects which attack stored
grain are highly specialized to exploit the stores
man has set aside for himself. Stored products
insects are, in most cases, insects of small size with
a high reproductive potential. Therefore, they are
easily concealed in grain and grain shipments and
have been carried to all parts of the world. Once
established in a commodity they are usually diffi-
cult to control.
In general, stored products pests thrive in warm,
humid environments. Grain with high moisture
stored in warm conditions is usually most suscep-
tible to insect infestations. Stored grain pests are
important since they contaminate food, lower its
nutritive value, and create conditions favorable for
mold growth.
Pests which attack whole grain usually develop
and feed inside the kernels of grain. They can be
easily overlooked in grain shipments since they
cannot be seen. These pests are not usually ca-
pable of existence as immature insects outside the
grain Examples of whole grain pests are the rice
weevil, the granary weevil, the lesser grain borer,
and the angoumois grain moth.
Other insects which attack grain are usually
unable to penetrate whole grain. These insect
pests however can attack grain after it has been
either mechanically broken or attacked by whole
grain insects. Examples of these secondary pests
are the red and confused flour beetles, Indian meal
moth, Mediterranean flour moth, and the
sawtoothed grain beetle.
Grain may become infested in a number of ways.
One of the most common means of infestation
starts in the field. In Florida, it is not uncommon


for freshly harvested corn to have 10% of kernels
infested with insects. Another common means of
infestation is storing grain in or near infested
storage facilities.
It is important to know the stored grain pests
and inspect according to the length of time it takes
an insect to complete a life cycle. Table 1 lists some
stored grain insects and some biological data while
Figures 1 10 illustrate several insects.

Molds
(pathogens)

Storage rots or moldy grain may develop in grain
storage bins if the moisture content of the kernels
is excessive and the air temperature is high enough
to permit fungus growth. More than 150 different
species of fungi have been reported on cereal
grains. The major storage fungi are species of the
common molds, Aspergillus and Penicillium. Some
species of fungi such as Alternaria sp. and
Fusarium sp. can cause infection in the field and
can cause advanced decay in high moisture grains.
Some of the fungi that grow in grains and other
seeds before harvest or in storage produce toxins.
One of the common storage fungi, Aspergillus
flavus, produces several toxins called aflatoxins
which cause problems when fed to animals.
Storage fungi cause loss of germination, dark
germs (in wheat, designated germ damage or sick
wheat), bin burning, mustiness, and heating.
These are the final results of invasion of grain by
storage fungi. Storage fungi are the cause, not the
result, of spoilage.
Depending on the commodity, contamination by
toxin is either a field problem, a storage problem, or
a combination of the two. Since toxins are produced
by fungi, they should be viewed as a potential
danger anywhere fungi grow on materials which
are used as food or feed. Fungal contamination is
necessary for production of toxins, but toxicity is
certainly not the inevitable result of all fungal
invasion. Fungi are almost universally present on
and in cereal grains, nuts and nearly all other plant
materials, but toxicity seems to be the exception
rather than the rule.

Identification
It is sometimes difficult to identify the specific
species of fungi which are causing a particular
problem in a given lot of grain. A laboratory
equipped with a compound microscope and culture
facilities is necessary to confirm the identity of a
fungus species. Many times, however, the signifi-








Introduction

The principle sources of loss in quality and
quantity in grains during storage are fungi, insects,
rodents, mites, respiration, and moisture migra-
tion. Although storage problems are common
during bad harvest years, many also result from
poor dry grain management practices. Employ-
ment of preharvest preventive management prac-
tices including bin sanitation, insect control, and
aeration along with adequate observation will
minimize dry grain storage problems. This paper
will discuss procedures to ensure proper grain bin
sanitation and pest control in order to reduce grain
wastage and profit loss.

Insects

Stored grain of almost any kind is subject to
attack by insects. The insects which attack stored
grain are highly specialized to exploit the stores
man has set aside for himself. Stored products
insects are, in most cases, insects of small size with
a high reproductive potential. Therefore, they are
easily concealed in grain and grain shipments and
have been carried to all parts of the world. Once
established in a commodity they are usually diffi-
cult to control.
In general, stored products pests thrive in warm,
humid environments. Grain with high moisture
stored in warm conditions is usually most suscep-
tible to insect infestations. Stored grain pests are
important since they contaminate food, lower its
nutritive value, and create conditions favorable for
mold growth.
Pests which attack whole grain usually develop
and feed inside the kernels of grain. They can be
easily overlooked in grain shipments since they
cannot be seen. These pests are not usually ca-
pable of existence as immature insects outside the
grain Examples of whole grain pests are the rice
weevil, the granary weevil, the lesser grain borer,
and the angoumois grain moth.
Other insects which attack grain are usually
unable to penetrate whole grain. These insect
pests however can attack grain after it has been
either mechanically broken or attacked by whole
grain insects. Examples of these secondary pests
are the red and confused flour beetles, Indian meal
moth, Mediterranean flour moth, and the
sawtoothed grain beetle.
Grain may become infested in a number of ways.
One of the most common means of infestation
starts in the field. In Florida, it is not uncommon


for freshly harvested corn to have 10% of kernels
infested with insects. Another common means of
infestation is storing grain in or near infested
storage facilities.
It is important to know the stored grain pests
and inspect according to the length of time it takes
an insect to complete a life cycle. Table 1 lists some
stored grain insects and some biological data while
Figures 1 10 illustrate several insects.

Molds
(pathogens)

Storage rots or moldy grain may develop in grain
storage bins if the moisture content of the kernels
is excessive and the air temperature is high enough
to permit fungus growth. More than 150 different
species of fungi have been reported on cereal
grains. The major storage fungi are species of the
common molds, Aspergillus and Penicillium. Some
species of fungi such as Alternaria sp. and
Fusarium sp. can cause infection in the field and
can cause advanced decay in high moisture grains.
Some of the fungi that grow in grains and other
seeds before harvest or in storage produce toxins.
One of the common storage fungi, Aspergillus
flavus, produces several toxins called aflatoxins
which cause problems when fed to animals.
Storage fungi cause loss of germination, dark
germs (in wheat, designated germ damage or sick
wheat), bin burning, mustiness, and heating.
These are the final results of invasion of grain by
storage fungi. Storage fungi are the cause, not the
result, of spoilage.
Depending on the commodity, contamination by
toxin is either a field problem, a storage problem, or
a combination of the two. Since toxins are produced
by fungi, they should be viewed as a potential
danger anywhere fungi grow on materials which
are used as food or feed. Fungal contamination is
necessary for production of toxins, but toxicity is
certainly not the inevitable result of all fungal
invasion. Fungi are almost universally present on
and in cereal grains, nuts and nearly all other plant
materials, but toxicity seems to be the exception
rather than the rule.

Identification
It is sometimes difficult to identify the specific
species of fungi which are causing a particular
problem in a given lot of grain. A laboratory
equipped with a compound microscope and culture
facilities is necessary to confirm the identity of a
fungus species. Many times, however, the signifi-








Table 1. List of Stored Grain Pests and Some Biological Data.


Time Cycle Required
for Complete Life Cycle


Granary Weevil
Rice Weevil


Broad-Nosed Grain Weevil
Coffee Bean Weevil


Lesser Grain Borer
Angoumois Grain Moth
Indian Meal Moth

Mediterranean Flour Moth

Sawtoothed Grain Beetle
Confused Flour Beetle
Red Flour Beetle


4 weeks
4 weeks


4 weeks
4 weeks


4 weeks
5 weeks
6-8 weeks

8-9 weeks

4 weeks
6 weeks
5 weeks


Universal feeder on whole grains.
Universal feeder on whole grains.
Most common stored whole grain pest
in Florida.
Usually attacks soft or damaged grain.
Lays eggs in corn in field; infestations
may continue for 3 months after
storage.
Universal feeder on whole grains.
Most important in stored corn.
Prefers coarse grades of processed
grain.
Prefers finer grades of processed
grain.
Prefers grain products.
Attacks grain and grain products.
Attacks grain and grain products.


Figure 1. Granary Weevil


Figure 5. Lesser Grain
Borer









Figure 9. Sawtoothed
Grain Beetle


Figure 2. Rice Weevil


Figure 6. Angoumois
Grain Moth


Figure 3. Broad-Nosed
Grain Weevil









Figure 7. Indian Meal Moth


Confused Flour
Beetle



Figure 10. Red Flour Beetle


Grain Pests


Remarks


Figure 4. Coffee Bean
Weevil









Figure 8. Mediterranean
Flour Moth


Table 1. List of Stored Grain Pests and Some Biological Data.


\M/


pjj








chance of a fungus in a given bulk of grain can be
judged by observing the color and shape of the mold
growth, and by having a knowledge of the immedi-
ate history of the grain and future plans for the
grain. A fungus that is common on grain in the
field, for example, would be commonly found in
freshly harvested grain. If corn or wheat seeds are
covered with a black mold (likely Alternaria or
Cladisporium), they may be of low germination and
would not be desirable for seed. Corn with exten-
sive white mold growth is likely to be infected with
Diplodia. If the grain is obviously infected with a
white, pink, orange, or red fungus, a Fusarium sp.
is most likely present. Some species of Fusarium
are toxic and can cause problems when infected
grain is fed to livestock. If a large amount of this
mold is present and/or if feeding or reproductive
problems in animals are associated with the feed-
ing of a given bulk of grain, it should be tested for
the presence of Fusarium toxins.
If grain is in storage and has been for some time,
the appearance of a greenish fungi on the germ of
the grain could mean that the grain is on the verge
of severe deterioration. These fungi would most
likely be species ofAspergillus or Penicillium.

Potential damage

Germination reduction
Under conditions that permit fungi to grow, the
germs of seeds may be invaded almost exclusively
by fungi. If the moisture content of the seeds is at
or slightly above the lower limit that permits their
growth, the germs can be invaded to the point of
almost total decay. Frequently, no outward evi-
dence of molding, even with microscopic examina-
tion and little or no invasion of the endosperm
immediately adjacent to the germ, is observed. The
first effect of this invasion is the weakening of the
germ, followed by death. Some strains of Aspergil-
lus restrictus, A. candidus, and A. flavus can cause
severe damage and kill the germs quickly. Usually,
weakening and death of the embryo by storage
fungi precede the development of any discoloration.
By the time discoloration is evident, the germs are
dead.

Discoloration
Both field and storage fungi may cause the
discoloration of whole seeds or portions of them,
including the germ. It is not uncommon to find
seeds with germs ranging from tan to black. Some-
time the fungi that cause this discoloration will be
sporulating in the area between the germ and the
pericarp. When the growth of the fungus is obvious


to the naked eye, it will be graded as damaged
kernel. This condition in corn is known as "flue-
eye." Any discoloration due to molds will be graded
as damaged according to the official U.S. standards
for grain. It is not uncommon to find grain in hot
spots that is brown or totally black due to the
invasion of these micro-organisms.

Heating
Microbiological heating is common in many
kinds of organic materials such as grain, feed, hay,
sugar beet pulp, wood chips, baled cotton and wool,
and manure piles. Storage fungi begin to grow
because some of the grain is moist enough when
stored or becomes moist through moisture transfer
resulting from temperature differences within the
grain mass. Usually, there is a succession of fungi
as the moisture content and temperature increases.
The fungi involved, A. glaucus, A. candidus, and A.
flavus, can raise the temperature up to about 131F
and hold it there for weeks. The metabolic water
produced by these fungi is sometimes dissipated by
the heat of the hot spots and the moisture can
accumulate in grain around the original hot spot.
This is the factor that determines whether the
heating will gradually subside or pass into the next
stage, where a variety of thermophilic (heat-loving)
fungi take over. These fungi may carry the tem-
peratures up to 140 to 1490F and may be followed
by thermophilic bacteria which can increase the
temperature up to 1670F, the maximum tempera-
ture that can be obtained by micro-biological
heating. Under certain conditions, purely chemical
processes take over and carry the heating up to the
point of spontaneous combustion.
It is not uncommon for grain to reach 122 to
131F in a hot spot. It will be caked and black and
appear to have been burned, even though it has not
been exposed to temperatures required for ignition.
This bin burning is common in soybeans and corn
and may take two to three months to occur. Many
times, heating will begin in the fines which accu-
mulated in the spout line while grain was loaded
into the bin. Some fines and accompanying weed
seeds have a high moisture content and would,
therefore, furnish enough moisture to start the
growth of storage fungi in the heating process.

Mustiness, caking, and decay
Mustiness, caking, and decay are advanced
stages of spoilage by fungi and are detectable by
the unaided eye and also the nose. However,
considerable fungal growth occurs in grain before it
becomes apparent to the naked eye. Mustiness may
develop where grain is still relatively sound, but








usually some mold is visible on the kernels. The
clumping or caking of kernels results from the
mycelial growth that occurs in damp grain. The
amount of caking will range from a slight adhesion
observable when unloading a bin of grain to solid
masses that do not break apart during handling.
Bins with uneven internal temperatures can cause
moisture migration and accumulation in the top.
This may cause heavy mold growth and a crust to
form over the grain mass. The crusted layer is
usually only a few inches thick and may consist of
rotted kernels and fungus tissue occupying all of
the spaces between the kernels. Grain in this
condition may be 30 to 35 percent moisture, while
the grain immediately below can be 13.5 percent
moisture. Caked and decayed grain, whether in a
surface crust or in an entire bin of grain, represents
the final stages of mold growth.
Mustiness, caking, and discoloration of kernels
can cause severe losses. A small hot spot will do no
more than plug up the unloading augers, causing
time delays. At other times, caking and severe
discoloration can reduce the grain value in a
particular bin to the point of salvage value.

Rodents

For effective rodent management in and around
grain storage facilities, the rodent must be identi-
fied so that effective measures can be instituted for
control.
The majority of grain-handling facilities must
contend with only two species of commensal ro-
dents, the Norway rat (Rattus norvegicus) and the
house mouse (Mus musculus). Both pests can cause
tremendous damage to both the stored grain and
the storage facilities. They cause a great deal of
damage by their feeding and contaminate even
more of the stored material with their droppings,
urine, and hair.

Norway rat
The Norway rat is a large, robust animal with a
blunt nose, small eyes and small ears, and weighs
about 11 ounces when fully grown. They normally
achieve this weight and are sexually mature three
months after birth. The Norway rat is typically 8
to 10 inches long with a tail that extends another 6
to 8 inches. The tail is hairless while the body is
covered with a black or dark brown fur. The
underbelly is usually lighter than the back.
The Norway rat has excellent senses that ac-
count for its survival in a human environment.
Their eyesight is poor and they are color-blind but
they have excellent senses of taste, smell, hearing,


and touch. Norway rat pathways are usually close
to walls where they can use their sensitive whis-
kers (vibrissi) as feelers to detect objects. Their
acute sense of taste and smell allows them to detect
even small concentrations of toxicant in baits.
The Norway rat is omnivorous. It will consume
almost any food material including meats, but it
prefers grain. The adult consumes about 1 ounce of
food a day which averages out to approximately 23
pounds of food in a year. Simple arithmetic will
show that even a small rodent population can
account for a substantial loss in stored grain. This
doesn't even take into account what the rodent will
contaminate with its fecal material, urine, and
hair.
The Norway rat is quite efficient at establishing
and maintaining a healthy population. Its normal
life span is only nine to twelve months due to
natural predation and man-directed control pro-
grams. However, the female can produce up to
seven litters a year with eight to twelve offspring
per litter.
When developing an effective control program for
the Norway rat, take into account its natural traits
and features. This rat seldom climbs even though it
is quite capable of doing so. It prefers ground level
and will normally build its nests in burrows or in
enclosed, sheltered areas. The Norway rat con-
sumes water daily and is a good swimmer. Pay
particular attention to areas where moisture is
abundant because it prefers to nest close to an
available water source.
The Norway rat is a shy animal and will not
normally explore new areas or objects in its envi-
ronment until it gets used to their presence. For
example, when bait stations are introduced into an
area for these rats, immediate bait acceptance
should not be expected. The rodent must first
become familiar with the station before it will enter
and feed on the bait. The natural range of the
Norway rat is 50 to 100 feet in any direction. They
will range for food and water but will logically
relocate their nest closer to food and water if it is
available.

House mouse
The house mouse is a small, slender animal
which weighs about 1/2 ounce when fully grown.
They normally achieve this weight and are sexually
mature as early as 45 days. The house mouse is
typically 2.5 to 3.5 inches long with a tail that
extends another 3 to 4 inches. It has a pointed
snout with large ears and small eyes. The hair is
usually light brown to light grey and will appear
lighter on the underbelly.







As with the Norway rat, the house mouse's
senses are excellent. Their eyesight is poor and the
rodent is colorblind but the senses of hearing,
touch, taste, and smell are as acute as those of the
rat. This rodent can also detect minute traces of
toxicant and also must be offered palatable baits if
effective control is expected.
The house mouse almost exclusively consumes
cereal grains and will eat about 1/10 of an ounce
per day. It is known for its nibbling habit of eating
small quantities many times during the day. A
single house mouse will eat approximately 2
pounds of food in a year but will contaminate a
much greater amount with fecal pellets, urine, and
hair.
The normal life span of a house mouse is the
same as a Norway rat, nine to twelve months. The
female can have up to eight litters a year with an
average litter of five to six offspring per litter.
With the gestation period being so short and the
animal being sexually mature at such an early age,
the house mouse has an even more dynamic popu-
lation curve than does the Norway rat.
The house mouse is a good climber so control
methods might be necessary on levels above
ground. They are generally loners whereas rats
most often live in larger groups. Nests for the
house mouse can often be found in stored materials.
Whole generations of mice can live within a pallet
of stored materials if food is available. They do not
need the large quantities of water that the Norway
rat does and can usually obtain needed moisture
from the foods they eat.
Whereas the Norway rat is shy, the house mouse
is just the opposite. They will often investigate new
and different objects in their environment. Bait
stations will usually be entered in a short period of
time because of this curiosity.
The natural range of the house mouse is small
and they seldom travel more than 10 to 20 feet
from their nest. This explains why they prefer
nesting in stored materials (often food stuffs).

Integrated
pest management

Integrated Pest Management (IPM) is a rela-
tively new approach to an old problem: How to
ensure protection of stored grain and maintain
quality by controlling pest populations while
minimizing effects on people and the environment.
IPM attempts to make the most efficient use of the
strategies available to control pest populations by


taking action to prevent problems, suppress dam-
age levels, and use chemical pesticides only where
needed. Rather than seeking to eradicate all pests
entirely, IPM strives to prevent their development
or to suppress their population numbers below
levels which would be economically damaging.
"Integrated" means that a broad, interdiscipli-
nary approach is taken using scientific principles of
grain protection in order to fuse into a single
system a variety of methods and tactics.
"Pest" includes insects, mites, nematodes,
pathogens, weeds, and vertebrates which adversely
affect grain quality.
"Management" refers to the attempt to control
pest populations in a planned, systematic way by
keeping their numbers or damage within accept-
able levels.
Effective IPM consists of four basic principles:
1. Exclusion seeks to prevent pests from entering
the storage in the first place, thus stopping
problems before they arise.
2. Suppression refers to the attempt to suppress
pests below the level at which they would be
economically damaging.
3. Eradication strives to eliminate entirely certain
pests whose presence, however minimal, cannot
be tolerated.
4. Plant resistance stresses the effort to develop
grains that will be resistant to certain pests.
In order to carry out these four basic principles,
the following steps are often taken.
1. The identification of key pests and beneficial
organisms is a necessary first step. In addition,
biological, physical, and environmental factors
which affect these organisms must be ascer-
tained.
2. Preventive cultural practices are selected to
minimize pest population development. These
practices include use of resistant grains, bin
sanitation, proper grain drying, aeration, rota-
tion of grain, and others.
3. Pest populations must be monitored by trained
"scouts" who routinely sample grain storage and
fill out an observation report.
4. A prediction of loss and risks is made by setting
an economic threshold. Pests are controlled only
when the pest population threatens acceptable
levels of quality: Remedial action is taken. The
level at which the pest population or its damage
endangers quality is often called the economic







threshold. The economic threshold is set by
predicting potential loss and risks at a given
population density. This estimation takes into
account weather data, condition of the stored
grain, markets, risk-benefit, costs, and kinds of
control available.
5. An action decision must be made. In some cases
pesticide application will be necessary to reduce
the grain threat, while in other cases a decision
will be made to wait and rely on closer monitor-
ing.
6. Evaluation and follow-up must occur throughout
all stages in order to make corrections, assess
levels of success, and project future possibilities
for improvement.
To be effective, IPM must make use of the fol-
lowing tools:
1. Pesticides. Some pesticides are applied preven-
tively, such as empty bin treatments and grain
surface treatments.
In an effective IPM program pesticides are
applied on a prescription basis tailored to the
particular pest, and chosen to have minimum
impact on people and the environment. They are
applied only when a pest population has been
diagnosed as large enough to threaten acceptable
levels of quality. Pesticides are usually chosen
only after all other feasible alternatives have
been considered.
2. Resistant crop varieties are bred and selected
when available in order to reduce pest problems
in the field.
3. Natural enemies are used to regulate the pest
population whenever possible.
4. Pheromone (sex lure) and food-based traps are
used to lure and destroy male insects, thus
helping monitoring procedures. Traps have
control potential and have been used to keep a
population within acceptable levels.
5. Preventative measures such as bin sanitation,
empty bin pesticide treatments, surface residual
pesticide treatments, and effective monitoring
help avoid severe problems.
6. Avoidance of peak pest populations can be
brought about by complete removal of old grain,
prior to storage of new grain, and aeration, to
reduce grain temperature and prevent moisture
migration.
7. Improved application by keeping equipment up to
date and in excellent shape can be achieved
through reliance on accurate pressure, timing,
agitation, and following proper operational
procedures.


8. Other assorted cultural practices such as proper
grain drying and turning grain during storage,
can influence pest populations.

Before-storage

procedures

Cleanup
The most frequent source of insects infesting
new grain is the previous year's old grain residue
remaining in harvest and handling equipment,
within the bin, under the bin's drying floor, and on
the ground around the bin. Insects live from
season to season around farm buildings and in
accumulations of grain, feed, straw, hay, and litter.
Newly harvested grain should never be placed on
top of old grain. It is best to remove all the old
grain and feed it, then sahitize and treat the empty
bin before storing the new grain. If this is not
possible, the old grain must be treated before the
new grain is added. In this case, fumigation is best
since a surface treatment will not be adequate.
All grain-handling equipment including augers,
combines, trucks, wagons, and other farm equip-
ment should also be thoroughly cleaned and grain
residues removed before harvest. These waste
accumulations can be a source of infestation. A
good time to do this is during maintenance of this
equipment in preparation for harvesting.
Cleaning the bin means more than just removing
the grain. All grain missed by the sweep auger
must be removed. Bin walls, ledges, cracks, floor,
and other areas, where old grain and dust can
lodge, must be swept down. Bins equipped with
drying floors require floor section removal to clean
residue underneath. Wooden bins should be
cleaned very carefully, because grain and dust tend
to collect on walls and floors and encourage infesta-
tions. The sweepings along with the spilled grain
and litter outside the bin should be removed and
disposed of (buried or burned) far enough from the
bin site to prevent an infestation of the newly
stored grain. Grain bins should be cleaned thor-
oughly at least two weeks before the addition of
new grain.
Market grain should be stored away from the
farmstead if at all possible. If stored near the farm,
grain should not be stored near feed rooms, stables,
or animal feeders because places where livestock
feed or where pet foods are stored can be serious
sources of infestations. Grain and feed accumula-
tions that are frequently overlooked include empty
feed sacks, dusts created by the feed grinders, seed
litter from the haymowers, feed left in animal self-
feeders, and grain-based rodenticides.








Empty bins should be thoroughly cleaned and
sprayed before new grain is placed in the bin. The
aeration duct and the raised perforated floor that
distribute the air may be infested and are difficult
to reach with normal sprays.

Empty metal grain bins
The increased use of metal bins with perforated
floors for grain drying and aeration has helped
produce a serious insect problem in farm-stored
grain. Grain dockage (broken kernels, grain dust
and chaff) sifts through the floor perforations and
collects in the subfloor plenum creating a favorable
environment for insect development (Figure 11).
Unfortunately, the floors are usually difficult to
remove, making inspection, cleaning, and insecti-
cide spraying in the plenum difficult if not imprac-
tical. An infested plenum may be disinfected using
approved fumigants.
Just because grain is eventually harvested and
stored does not mean it is safe from insects. Any
grain that is to be stored for more than 6 months
can be seriously infested. The key to good storage
is anticipating and preventing potential problems
through good bin management.
Before treating with protectants, make sure that
the storage structure itself is free of insect-infested
grain. Leftover grain should be removed from the
bins, and the walls should be swept and vacuumed.
This cleanup is most effective if done in early
spring or immediately after the bin has been
emptied.

Make needed bin repairs
After the bin is cleaned, all leaks should be
repaired. Screen or seal openings to keep out
rodents and birds, and eliminate places that will
harbor old grain (such as corners or leaks under bin


floors). The structure should be made tight to
prevent water and air leaks. Air vents should be
sealable to facilitate later fumigation, if necessary.
The bin should be equipped with adequate aeration
fans and ducts that are maintained in good working
order.

Mixing old and new grain
New grain should never be placed into a storage
bin which contains old grain unless the old grain is
completely free from insect infestation and mold
contamination.

Pre-storage bin sprays bin
wall, ceiling and floor treatments
Bin sanitation is not complete until the inside
and outside surfaces are sprayed with a residual
insecticide. Surface sprays leave a thin layer of
insecticide that kills insects which remain in the
bin and those that crawl across the surface trying
to get inside. As soon as the bin is cleaned, it can
be treated with protective insecticides. Spraying
without adequate cleaning will generally not be
effective. Treatments should be applied 2 to 3
weeks before new grain is placed in the bin. Grain
should not be added for at least 24 hours in order
for the walls to dry thoroughly. The treatment will
kill insects emerging from their hiding places
(seams, cracks, crevices, corners, under floors and
in aeration systems). Also, insects crawling or
flying in from the outside will be killed. Any dead
insects should be swept out before the grain is
added. Malathion or chlorpyrifos-methyl used for
this purpose in metal bins will remain effective for
4 to 8 weeks at 800F. Methoxychlor may also be
used. Residual bin sprays recommendations are
listed in Table 2.
Apply the spray (2 gallons per 1,000 square feet
of surface area) to as many surfaces as possible,
especially joints, seams, cracks, ledges, and corners
(Figure 12). Spray the ceilings, walls and floors to
the point of runoff. Use a coarse spray at a pres-
sure of over 30 pounds per square inch and aim for
the cracks and crevices.
Spray beneath the bin, its supports, and a 6-foot
border around the outside foundation. Treat the
outside surface, especially cracks and ledges near
the door and fans. In addition, pertinent areas
should be treated after cleaning harvesting equip-
ment, elevators, augers, trucks, or wagons.
Insecticides, formulations, concentrations, and
rates of application approved for this and other
uses are subject to change. Current insecticide


Figure 11. Typical location of Infestation in empty bin.







Table 2. List of Residual Pre-Storage Grain Bin Sprays.

Insecticide Dilution Directions

43.2% Chlorpyrifos- 1/2 pt. per
methyl EC 6.5 gal. water Treat empty bins prior to filling.
After cleaning bins thoroughly,
57% Malathion EC 1 gal. per spray walls, floors and ceilings to
(premium grade) 25 gal. water the "point of run off" (2 gal/ 1000
% Mr E 1 p sq.ft.). Apply the insecticide 2-3
25% Methoxychlor EC 1 gal. per weeks before harvest. Before
4 gal. water storing the grain, sweep the bin to
50% Methoxychlor WP 1 lb. per remove all dead insects.
3 gal. water
.15% pyrethrins + Ready-to use
1.5% piperronyl
butoxide


Figure 12. Empty bin treatment.
recommendations should be obtained from the local
county extension office and labeled directions
should always be followed for approved chemicals.

Loading grain for storage

Condition of grain
A certain amount of insect infestation occurs in
the field prior to harvest. However, grain that is
harvested dry and free of broken kernels and other
dockage is less likely to be attacked by insects and
molds. Harvest should be at the lowest practical
moisture content, and dryers should be used to
further reduce the moisture content to a storable
level of 13 percent or below. Harvesting machinery
should be adjusted to minimize the amount of
dockage in the grain, and the grain can be screened
before being placed in the bin. Clean grain can be
more easily and uniformly aerated, which in turn
minimizes insect and mold problems. Fumigants
and protectants are also more effective in clean
grain.


Bulk treatment equipment
and procedures
After the bin or storage area has been thor-
oughly cleaned and treated, the grain can be
further protected against insect infestation by the
application of an insecticide to the grain as it is
loaded into the storage area. The use of an ap-
proved insecticide is an effective way to control
stored grain insects, providing the grain being
stored is not already heavily infested and the
moisture content is not above 13%. High moisture
grain attracts insects and enhances more rapid
breeding than does dry grain. Grain protectants
quickly lose their effectiveness on grain that is
above 13% moisture content or at temperatures
above 900F.
Gravity flow or "drip-on" application equipment
is shown in Figures 13, 14, and 15. Pressure-type
sprayers are illustrated in Figures 16 and 17, while
power sprayers are shown in Figures 18 and 19. A
special dust applicator used for small lots of grain
is depicted in Figure 20.

Point of application
Protectants should be applied evenly to the grain
as close to the point of final storage as practical.
Protectants can be applied into an auger (Figure
16A) or into the grain stream as it falls into the
hopper of the elevating equipment (Figures 16B
and 18). Protectant also may be applied as grain
falls into the bin. Grain which is treated and then
transferred long distances through numerous grain
handling systems (such as pneumatic systems, belt
augers, conveyors, or spouts and legs) before
storage will have less insecticide residue when the
grain is finally dropped into the bin. However,
insecticide left in the handling system will help
reduce insects in these areas.




























AUGER


Figure 13. Gravity feed or "drip on" applicator.


Rubber gasket
Washer
Reducer


Grain source


Taped
DETAIL OF AUGER
Showing placement of tubing


Figure 14. Schematic drawing of a gravity feed "drip on" system used to apply grain protectants


9

















































Figure 15. Gravity feed or "drum" applicator.


Figure 18. Pressurized sprayer.


Figure. 16 Components of pressurized liquid application of protectants.


Ito--r--
9-p-
S..Fout* 0


Figure 17. Pressurized spray tank.


SHUTOFF VALVE TO


SHUTOFF VALVE TO
STORAGE
NOZZLE

PRESSURE
GAGE


S 3-GALLON
GARDEN TYPE
TO I PIPE SPRAYER
SPRAYER -- (STAINLESS STEEL)
WELD

AUGER



SCALE
(FOR CALIBRATION)
A DETAIL OF AUGER SCREW B. AUGER HOPPER APPLICATION
APPLICATION
































Figure 19. Pressurized sprayer system.


Application pressure
If other than a gravity-flow system is used, the
spray pressure should be as low as possible; 10 to
20 p.s.i. (pounds per square inch) is preferred.
With low spray pressures, larger spray droplets are
produced. The larger droplets fall onto the grain
and are less likely to drift into the air.

Moisture and temperature of the grain
Most failures with residual sprays occur because
of excessive grain moisture and/or temperatures.
For effectiveness for more than 2 weeks, grain
should not be treated if it is above 13% moisture
and the temperature is above 900F. If warm grain
is treated, it should be cooled with an aeration
system as soon as it is practical. The operation of
an aeration system will not remove the protectant
from the grain. Treatment of grain at 14 to 16%
moisture will be effective for short periods depend-
ing on the temperature.

Factors that influence effec-
tiveness of grain protectants
The point of application, application pressure,
and moisture and temperature of the grain influ-
ence the effectiveness of grain protectants as
discussed above. Other factors include proper
mixing and a fresh spray mixture.


Proper mixing
Even application is important, and one disadvan-
tage in using the emulsifiable formulations is that
most of them must be agitated about once every
half hour after mixing with water to avoid settling.
The gravity flow or "drip on" applications (Figures
13, 14, and 15), the garden-type sprayers (Figure
16), and the pressurized spray tank (Figure 17)
must be shaken to insure that the formulation is
applied evenly. The power sprayers (Figures 18
and 19) do not have to be shaken as the formulation
agitates continuously.


Figure 20. Dust applicator.


PRESSURE GAGE
-SMUTOFF VALVE







Fresh formulations


Only enough insecticide for one day's use should
be mixed with cool water and the left over mixture
should not be carried over for the next day's treat-
ment. Concentrate, mixed spray, and dust should
be kept cool and should not be stored in direct
sunlight. Only fresh dust formulations should be .
used and carryover from one year to the next
should be avoided. If the dust must be kept over, it
should be refrigerated (away from food).

Equipment required -
emulsifiable concentrate
Any low-pressure sprayer that can be calibrated
to deliver a known volume of liquid is suitable for
applying liquid protectants. This includes compres-
sion sprayers (Figures 16 and 17) and electric- and
gasoline-engine-driven power sprayers (Figures 18
and 19). The garden-type compression sprayer and
the gravity feed "drip on" system are used to treat
small lots of grain.
Power sprayers and metering-type sprayers are
generally used to treat large lots of grain. In some
areas, insurance terms require totally enclosed fan-
cooled motors in grain elevators.
The correct size of orifice in the sprayer nozzle is
important because orifice size.and pressure are
used to regulate the rate of insecticide flow. Most
manufacturers of spray nozzles have charts that
give the capacity in gallons per minute and the
spray angle for each size of orifice.
A simple gravity or "drip on" applicator that does
not use any moving parts may be purchased
(Figure 13) or constructed (Figure 14). An applica-
tor may be built by fitting two brass valves and
polyethylene tubing in sequence to an opening in
the bottom of a plastic container. These fittings
are obtainable at plumbing supply shops. The
upper shutoff cock on the jug (see "Pipe Fitting
Detail", Figure 14) serves as the on-off valve while
the lower needle valve regulates the amount of
insecticide flowing through the plastic tubing. The
needle valve is first calibrated to the desired flow
for the rate-of-grain delivery into storage. It then
can be kept at the same setting without the need
for fine adjusting each time flow is turned on.
The gravity feed applicator is used as grain is
unloaded from a truck or auger into the hopper of a
portable auger. The tubing is taped horizontally
along the auger tube at the pick-up end, with the
end of the tubing extending one-fourth inch beyond


the end of the auger tube so the insecticide flows
directly into the grain. The plastic container can be
suspended from the top of the grain bin or auger
and must be agitated by hand at periodic intervals.
The following supplies are needed to build the
gravity feed "drip on" applicator:
1 plastic containerl28 to 384 oz.
1 lock nut 1/4" 18 pipe thread (PT)
2 washers 1/2"
1 rubber gasket 1/4"
1 pipe reducer 1/4" 18 PT x 1/8" 27 PT
1 shut-off cock 1/8" 27 PT x 1/8" 27 PT
1 pipe coupling 1/8" 27 PT x 1/8" 27 PT
1 angle needle valve 1/8" 27 PT x 1/4" in OD
Polyethylene tubing 8' x 1/4" outside diameter

Recommended treatment for
grain during loading
Table 3 contains the recommended chemical
treatment for grain during loading.

Proper filling procedures
The grain bin should not be overfilled (Figures
21 and 22). Space (headroom) must be left on top of
the grain for examination and sampling. After the
bin is filled, the grain's surface should be leveled
(Figure 23).
Application of insecticidal treatment, aeration,
and fumigation cannot be effective on uneven grain
surfaces (Figure 23). Moisture condensation and
subsequent mold and insect problems are more
likely to develop in mounded grain.
As with any other type of work, much can be
learned by studying the mistakes that have caused
other treatments to fail. In Figure 22, the farmer
has filled the grain bin to the top. It is impossible
now to get inside and level the grain for proper
treatment. Even if treatments are tried, applica-
tion will be uneven and probably ineffective.
Storing grain this high is not recommended by the
manufacturer of the building and is strongly
discouraged by fumigators. The best solution to
this problem is to pull the grain down to the level
of the sides (Figure 24). This will probably level
the grain considerably but additional leveling will
be worth the effort (Figure 24).








Table 3. Protect Grain When Loading Into Bins

Insecticide Product Directions

57% malathion EC wheat, Mix 1 pint of 57% EC in 2-5 gallons
oats, of water per 1000 bushels of grain.
rice Spray grain evenly as it is loaded or
turned into final storage. Complete
coverage is essential.
1% malathion dust corn, Apply uniformly at 60 lbs/1000
rye, bushels. Use only malathion labeled
barley, "premium grade" on grain. Grain
grain sorghum, treated with protectant can be fed
field & garden seed safely to livestock at any time
following treatment.
43.2% chlorpyrifos- wheat, oats, Mix according to label directions.
methyl EC rice,sorghum, Apply 1-5 gal. per 1000 bushels. Do
barley not use on corn.
3% chlorpyrifos- wheat, oats, Apply 11.5 lb/1000 bushels of wheat,
methyl dust rice, sorghum, 9.2 lb/1000 bushels of oats or barley.
barley Do not use on corn.
Bacillus stored grains Apply at rate of 3/4 Ib per 100
thuringiensis & soybeans bushels. Apply uniformly to grain
(Dipel) (Indian meal moth, stream.
Almond moth)


Figure 21. Overfilled bin.


Figure 22. Peaked grain is hard to treat evenly.


Figure 24. Bin pulled down.


Figure 23. Leveled bin.








In-storage management

Surface treatments
Surface treatments are applied (Table 4) to
prevent insects such as moths from entering the
grain from the outside. This should be done as soon
as the bins are filled and the surface leveled.
Treatments can be repeated if necessary. The
surface treatment is not effective against an
infestation several inches below the surface.
Fumigation must be used when there is an existing
infestation.
A surface treatment may also be applied when
the grain is going to be stored through a warm
season or after a general fumigation to help prevent
insect reinfestation. The surface treatment will
help control insects that enter the grain through
roof openings and will kill insects found in the
surface areas.

Effectiveness
Surface treatments alone generally will not keep
the grain completely insect-free but they will aid in
keeping insect populations lower during the storage
period. Surface treatments are effective if the
following limitations are understood:
1. Surface treatments will not control insects
already in the storage bin; thus, the grain must
not be infested prior to surface treatment.
2. The storage structure must be insect-tight below
the treated 2 inches of grain.
3. The surface treatment should not be disturbed
since it provides the protective barrier against
insect infestations.
It should be noted that the malathion surface
treatment will probably not control or prevent an
infestation of the Indian Meal Moth or the Almond
Moth because of resistance. Malathion-resistant
beetles are also becoming a problem.
The same equipment used for the application of
the wall sprays can be used to apply the surface
spray. The surface treatment should be applied no
more than three times during a storage year. Three
applications during the year should only be made if
the grain surface has been disturbed, or if tempera-
tures are high and the risk of infestation is great.

Indian Meal Moth control
Indian Meal Moths infest areas of grain and
grain residues that are exposed to exterior areas of
the grain mass such as the grain surface (Figure


25), aeration ducts, and materials beneath false
floors. The worst infestations are found on the
grain surface, but anywhere the moth larvae are
found, they will leave a mass of webbing which
constricts air flow and makes fumigation or surface
treatments less effective. Damage by this insect to
farm-stored grain is relatively low compared to the
beetles or weevils. It is considered more of a pest
rather than a serious economic insect except when
they infest seed grains.
Bacillus thuringiensis (BT), a bacterium that
controls moth larvae, has been approved for use in
stored grains and soybeans. This material (see
commercial label for dilution and application rate)
is mixed with the surface 4 inches of grain (Figure
26) either by adding to the last grain as it is
augered into the bin or by applying it to the grain
surface after the grain has been loaded and leveled.
This treatment will not control weevils or other
beetles that infest grain. The B. thuringiensis
formulation is exempt from tolerance restrictions.

Monitoring
It is important to identify the insects that are in
the grain or know which ones are likely to be in the
grain so that scientific control can be based on the
biology, behavior, and habits of the insects.
For example, the Indian Meal Moth has been
determined as the primary problem. This insect
lives in the upper few inches of grain and the adult
moths will often rest in the head space on the walls.
Grain treated with protectants should be in-
spected at monthly intervals to guard against the
possibility of infestation. These inspections should
not be limited to the surface of the grain, but
should extend down into the grain. If treated grain
becomes infested, it can be fumigated.
It is very important that stored grain be in-
spected often to determine its condition and the
extent of pest damage. Early detection of problems
and their elimination can prevent losses. Tempera-
ture, moisture levels, and the biological activity in
stored grain change throughout the storage period.
The grain should be inspected at 2- to 4-week
intervals to monitor these conditions. Samples
should be taken from top to bottom, to obtain at
least 1 pint of grain per 1,000 bushels. Samples
should be screened for insects and dockage. Mois-
ture content and temperature should be measured
throughout the bin to pinpoint spots where conden-
sation or insects may be concentrated. During
inspections, the presence of musty or spoiled odors,
caking, crusting, moisture condensation, elevated







Table 4. Surface Treatments.

Insecticide Product Directions

57% malathion EC stored grain and field Apply 1 pint in 2-4 gallons of water per 1000 sq ft of
& garden seed grain surface. Apply evenly over the grain surface
immediately after grain is loaded into storage. Repeat if
necessary.
1% malathion dust stored grain and field and Apply to grain surface at rate of 30 lb. per 1000 sq. ft.
garden seed

43.2% chlorpyrifos- wheat, barley, oats, Apply 3 oz (wheat), 2.4 oz (barley), 1.6 oz (oats) in 2
methyl EC rice, sorghum gal. of water per 1000 sq. ft. of grain surface.

3% chlorpyrifos- wheat, barley, oats, Use 7 Ib per 1000 sq. ft. ofgrain surface.
methyl dust rice, sorghum

Bacillus thuringiensis stored grains and soybeans Apply 1 lb. of BT in 10 gal. of water per 500 sq. ft. Mix
(Dipel) (Indian meal moth, Almond moth) into top 4 inches.


Figure 25. Typical location of Meal Moth Infestation.

temperatures, insects, or rodents are indications of
problems that must be immediately solved to prevent
grain loss. Additional information on methods for
obtaining samples and for determining moisture
content can be found in the extension publications
entitled, Grain Sampling and Grain Moisture Deter-
mination.

Aeration

Grain should be aerated to help maintain quality in
storage. Aeration is low-volume ventilation (about
1/4 c.f.m. per bushel) to maintain uniform tempera-
ture throughout the grain mass, and to prevent mois-
ture migration. Reduction and equalization of the
temperature is vital to the prevention of insect and
mold problems. Insects and mold develop more slowly
(or not at all) at low temperatures. Moisture migra-
tion and condensation (which favor insects and mold)
do not occur if uniform temperature is maintained.
Aeration while turning, stirring, or otherwise physi-


Figure 26. Key treatment areas for Indianmeal Moth
Infestation.
cally disturbing the grain can aid in controlling crust-
ing or caking that result from insect- or moisture-
induced hot spots. For more information on aeration
of grains, refer to the extension publication entitled,
Management of Stored Grain with Aeration.

Fumigation

If insect infestation occurs in spite of the precau-
tionary measures discussed above, fumigation of the
grain will be required. Fumigation is the most com-
monly used method of controlling insects that infest
stored grain. It kills insects and eggs present at the
time offumigation, but does not protect the grain from
reinfestation. In Florida, grain should be fumigated
as it is being loaded or turned. The grain should be
inspected at least once a month. Repeat fumigations
may be necessary. The spring following harvest is a
likely time for an additional fumigation.
Fumigants are dangerous and should be applied
only by trained, experienced operators working in







pairs. The Environmental Protection Agency has
initiated a "Label Improvement Program for Fumi-
gants" to help minimize occupational exposure to
fumigants. Changes on the label to better define user
information, warnings, and necessary precautionary
measures will directly affect how fumigants are used
and who uses them. Three features of the program
are of prime importance:
1. The label will direct that two "trained persons" be
present during the principal fumigation operation,
especially if entry into the structure under treat-
ment is required for application of the fumigant.
2. The use of approved respirator protection devices
will be required during application of the fumigant
when concentrations of the fumigant exceed pre-
scribed levels or ifthe concentrations are unknown.
3. Specified direct-reading detector devices would be
required to monitor fumigant concentrations to
prescribed levels as a condition of re-entry or
transfer of treated grain.
Effective fumigation is possible when good storage
practices are followed. For example, condensation
and eventually caking and spoilage will occur, if
farmers fail to level grain peaks, as outside tempera-
tures drop during the fall and winter months. This
same peaking will prevent even distribution of fumi-
gants, allowing insects to survive in the areas that
receive an insufficient amount of fumigant.
A fumigant is a tool that may be needed to help
preserve the grain quality.A fumigant should be used
only when needed since it is the most hazardous type
of pesticide treatment that farmers can use. In
addition, fumigation is expensive and provides no
long-term residual protection.
Fumigation is needed when no other pesticide or
control method can reach the insect infestation. If the
insects are already inside the grain mass, no spray or
dust can reach them.
In some parts of the country, field infestations can
be heavy with considerable internal feeding by the
time the grain is harvested and brought in for storage.
In these cases, especially if the infesting insects de-
velop within kernels, the grain should be fumigated at
the time of storage. Later, if the infestation is dis-
covered throughout the grain mass, control could be
difficult. Only a properly applied fumigant gas will
circulate to all points in the grain mass, allowing the
control of the pests.
Insect infestations can also occur in "pockets" deep
within the grain mass. Special fumigation techniques
are available to provide control in this situation
whereas insecticide sprays would not be effective.


Fumigation is not always practical. If grain is
stored in the open, it would have to be covered with
special gas-retaining tarps. This would also be true of
most open slat cribs or even wooden buildings. This
procedure is very expensive and time-consuming.
While it is possible to find dosage recommendations
for wooden buildings, the increased amount of fumi-
gant required and the poor control often achieved
makes this practice cost-prohibitive. Poor control
often results in reinfestationjust as large and damag-
ing soon thereafter.
Grain fumigants are among the most important
and useful agricultural chemicals available to the
owner of stored grain. Fumigants act on all insect life
stages. They control pests by diffusing through the
space between grain kernels as well as through the
kernel itself. Thus, fumigants are able to penetrate
into places that are inaccessible to insecticide sprays
or dusts.
Fumigants exert their effect on grain pests only
during the time in which the gas is present in the
insects' environment. After the fumigant diffuses out
of the grain, no residual protection is left behind and
the grain is again susceptible to reinfestation. The
objective of fumigation, therefore, is to introduce a
killing concentration of gas into all parts of the grain
mass and to maintain that concentration long enough
to kill all stages of insects present.
Fumigants may be applied directly into the fumi-
gated space as gases from pressurized cylinders. Some
gases appear as liquids under pressure but expand to
a gaseous form when released. Fumigants can also be
generated from solids that react with moisture and
heat from the air to release the fumigant.
Regardless of formulation, all fumigants are poi-
sons that are toxic to humans and other warm-blooded
animals as well as to insects and other pests. Because
fumigant chemicals are highly toxic and hazardous to
use, they are classified as restricted-use pesticides.
They should only be used by persons that have been
trained to use them. Although special training and
certification are required before these fumigants can
be purchased, this training is seldom adequate to
qualify the person to conduct a fumigation.
It is often safer, less expensive, and more effective
for farmers to have their stored grain fumigated by a
professionally licensed and certified fumigator. The
most important factor to consider when deciding
whether to hire a professional to do a fumigation is the
personal risk involved in the handling and applica-
tion of these highly toxic chemicals. A professional
fumigator will have the knowledge and experience
required to conduct effective treatment and will also








have the special equipment needed to apply fumi-
gants properly. In addition, professionals will have
safety equipment such as gas masks or other respi-
ratory protection which are expensive but necessary
when applying any fumigant.
However, professional fumigators are not always
available to service farm-stored grains and many
farmers still prefer to handle this phase of pest man-
agement themselves. Therefore, the following dis-
cussion is designed to help the farmer or new com-
mercial fumigator with information needed to better
understand the properties of grain fumigants, the
factors that influence their effectiveness, and the
methods used to apply and distribute them into bulk
stored grain.

Preparing bins
Attention to proper sealing of grain bins prior to
fumigation will often make the difference between
success or failure of the treatment. Many instances of
poor control, charged against the fumigant, are due to
bins that are not tight. A high degree of gastightness
is essential to achieve the required combination of gas
concentration and time of exposure necessary to kill
grain pests.
Metal storage bins are not gastight since they were
originally designed to hold and aerate grain. They
can be used for fumigating if properly sealed. It is
important to recognize, that the bins will vary in
tightness because of how well they are built. If the
corrugated sections were caulked when put together
and then bolted tight, they will be more effective when
sealed. Loosely constructed wooden bins may have to
be covered totally with a gastight tarpaulin to retain
enough fumigant to be effective.
The goal of fumigating is to try to confine a gas for
a sufficient length of time at a proper concentration to


Roof/wall
juncture








Fan


Fill spout


Bin access doors







Door



Slab/wall juncture


Figure 27. Key areas to seal for effective fumigation.


be lethal to the target pests. Sealing is extremely
important and demands study and work but there are
professional techniques that can make the job more
effective (Figure 27).
There are a number of places in a bin where gas can
escape. The roof-wall juncture looks tight from the
outside,.but examination from the inside will show a
gap around the perimeter inn many bins. This gap is
difficult to seal because it is usually dusty and may be
damp. Cracks wider than 1 inch are even harder to
seal. It is necessary to clean the dust from the surface
before it can be taped or sealed with any other mate-
rial.
Professionals will first clean the surface and then
spray it with an adhesive dispensed from a pressur-
ized can. The gap is then sealed with duct or furnace
cloth tape since this is more effective here than
Smashing tape. At least 2-inch and preferably 3-inch
tape should be used when sealing these cracks.
Polyurethane foams can be used to seal this gap but
they are expensive and difficult to remove if the gap
is needed for extra grain aeration. Insects can burrow
into the foams and destroy their effectiveness but
they can provide a good seal for several years.
Another key area to seal is the gap between the
bottom of the wall and the floor. Some manufacturers
design the wall base to accept a special sealant that
can give a long-term seal. Various sealing materials
have been used including one made with polyure-
thane impregnated with asphalt. Plain asphalt has
also been used but does not have as much elasticity.
The use of foam-in-place plastics applied after the
bins were built seem to give a good seal initially, but
still would be subject to problems discussed previously.
Roof ventilators can be covered with plastic bags.
The bags are less likely to tear against sharp edges if
a burlap bag is placed over the ventilator first. The
plastic bag should be gathered in at the base and then
taped in place. Extreme care should be exercised in
this work to avoid falling.
Bin doors are not gastight when merely closed.
They can be cleaned and sealed with masking tape, or
if not used regularly, they can be sealed with foam-in-
place plastic.
Aeration fans and their housing must be sealed to
avoid gas loss. Normally, polyethylene glued to the
air intake will be sufficient. However, the unit should
be examined for other potential leaks.
Professional fumigators long ago found that it was
difficult to get tape or plastic to stick to the dusty
surfaces of grain bins. Cleaning is necessary and
helpful but more was required.








An expensive but useful tool is the pressurized can
of tape primer. This can be obtained from the fumi-
gant distributor or sometimes from an auto paint
store. These materials give the surface a tacky
texture and help hold the tape on much better. They
can be applied to the adhesive surface ofa piece of tape
to improve its sticking power. Although taping of a
damp surface is not recommended, it can sometimes
be done with this material.
Another useful material is called Bondmaster. It is
painted onto a surface and then the plastic tarp is
pressed into the tacky area. This will normally hold
the plastic on even in a high wind.
Bondmaster can be removed from the hands with
mineral spirits since the application is a messy job
that will usually leave some on the hands and maybe
on the clothing. It can leave a stain on the building but
the improved seal is probably worth the effort and
mess.
Another alternative to taping the eaves is to cover
the entire roof with a plastic sheet formed into a
bonnet or cap which drapes over the top of the bin and
extends down past the roofjoint. An adhesive sprayed
or painted in a horizontal band around the outside bin
wall will provide a point of attachment for the plastic
sheet. The bonnet can then be secured by rope using
the corrugation grooves on the bin to reduce slippage.
Obviously, this sealing method can only be partially
completed before application of the fumigant in order
to provide access to the grain surface.
The grain surface must be leveled and any crusted
areas that have formed must be broken up. When
grain is peaked, the action of fumigants is similar to
rain on a hillside. The heavier-than-air gases simply
slide around the peak, resulting in poor penetration
and survival of pests in the peaked portion of the
grain. Moldy or crusted areas near the grain surface
are generally caused by moisture condensation when
warmer air in the grain rises to the surface and
encounters cold air above the grain. These areas are
sometimes hidden from view just below the grain
surface. Failure to locate and break up these areas
will result in uneven penetration of grain fumigants
and may lead to further deterioration of the grain
from mold development and invasion of the grain by
insects that feed on grain molds.

Methyl bromide
Methyl Bromide is an economical fumigant avail-
able for control of stored grain insects. Methyl Bro-
mide fumes are highly toxic to humans and animals.
Methyl Bromide can affect the germination of grain
and grass seeds, particularly at high moisture levels
or high dosages. It should not be used to fumigate


Table 5. Dosage of Methyl Bromide for
Recirculation Systems.


Type of Grain

wheat, corn, rice
wheat, corn, rice
wheat, corn, rice
grain sorghum
grain sorghum


Grain
Temperature
above 80F
60 80F
below 80F
above 80F
below 80F


Dosage
(lbs/1000 cu ft)
1.5
2.0
2.5
3.0
4.0


Precautions: Do not breathe vapors. Read and follow all
directions and precautions on the label and technical manuals.


seed corn. Methyl Bromide will not corrode most
metals. However, it can react with aluminum or
magnesium in the absence of oxygen to form an
explosive mixture. Therefore, aluminum or magne-
sium tubing should never be connected to a methyl
bromide cylinder.
Instructions: For best results, Methyl Bromide
should be recirculated through the grain in a closed
aeration system (Table 5). Ventilating or aerating
systems can be turned into recirculation systems by
returning the air from the storage area to the blower.
Usually savings of 50% on fumigant costs can be
realized by the recirculation method.
Methyl Bromide gas is inserted into the air circu-
lation system with little trouble. After 24 hours,
Methyl Bromide can be removed from the storage
area rapidly.
To apply Methyl Bromide without a recirculation
system, a pan or other receptacle should be placed on
the surface of the grain at the center of the bin (Table
6). Tubing from the receptacle should be stretched to
the outside of the bin. An open crate or other frame
should be placed over the receptacle and a plastic
cover should be spread over the frame and grain
surface. The door should be sealed and preparation to
Table 6. Dosage of Methyl Bromide for Non-Recirculation
Systems (Temperature must be above 600F).

Volume (cu. ft.) Rate (lbs/1000 cu ft)

less than 100,000 1.5 3
100,000- 500,000 1.25-1.5
500,000 1,000,000 1.0 1.25
more than 1,000,000 1.0


Precautions: Do not breathe vapors. Read and follow all
directions and precautions on the label and technical manuals.








release Methyl Bromide should be made. A special
applicator, Star Model 1.5 opener, should be used by
following instructions.

Aluminum phosphide
In recent years Aluminum Phosphide (Celphos,
Delicia, or Phostoxin) has been found to be an effec-
tive fumigant for stored grain insects. The main
advantage of Aluminum Phosphide is the ease of
application.


Instructions: Aluminum Phosphide is available as
tablets, and the fumigant is released due to mois-
ture in the air. Tablets should be kept away from
liquid water. The container should always be
opened in open air.


For treatment of grain pests in rice, wheat, barley,
corn, oats, sorghum, millet and rye, the Aluminum
Phosphide may be injected into grain with a probe or
fed into the grain stream as it is flowing into the bin.
Grain temperature must be 400F for fumigation.
Effective dosages are 6 tablets per ton of grain or 180
tablets per 1000 bushels. The exposure time required
is 5 days (54 590F), 4 days (60 680F), or 3 days
(warmer than 680F).

Effectiveness
Temperature. Temperature influences the dis-
tribution of fumigants in grain and affects their abil-
ity to kill insects. At temperatures below 60F,
volatility of a fumigant is reduced significantly, sorp-
tion of fumigant vapors into the grain is increased,
and distribution is less uniform throughout the grain
mass. Gases move more slowly and insects breath
less at colder temperatures. Thus, it takes longer for
the fumigant vapors to reach insects in the grain, less
gas is actually available for controlling the pests, and
since the insects are less active, less gas enters their
bodies.
Grain Moisture. The moisture content of grain
also influences the penetration of fumigant gases by
altering the rate of sorption. Dry grain of less than 10
percent moisture will extend the time required for
solid fumigant decomposition.
Grain Type and Condition. Various grains have
different characteristics that can affect fumigations.
The surface area of individual grain kernels is an
influencing factor in the dosage required to treat
various commodities. For example, sorghum, be-
cause of its smaller size and more spherical shape, has
higher total surface area than wheat. Increased
surface means greater sorption loss, which reduces


the amount offumigants left in the space between the
grain kernels and further reduces the amount of
fumigant available to penetrate throughout the grain.
To compensate for this increased loss, higher dosage
rates are required in sorghum than in wheat, particu-
larly when fumigants are used that are easily ab-
sorbed by the grain.
The type and amount of dockage in grain has a
pronounced effect on the sorption and distribution of
fumigants. When the grain mass contains large
amounts of dockage such as crust, chaff, or broken
kernels, the fumigant vapors are rapidly absorbed by
this material and further penetration into the grain is
impaired. Unfortunately, such areas are frequently
sites that attract the greatest number of insects.
When isolated "pockets" of dockage occur within a
grain mass such as below grain spouts, fumigant
vapors may pass around such pockets and follow the
path of least resistance down through the inter-
granular area of the grain. Similar changes in fumi-
gant distribution patterns may occur in grain that has
settled or compacted unevenly during long storage
periods or in storage vibrated by nearby traffic such
as a railroad.
Insects. Grain insect pests and their various
developmental stages (egg, larva, pupa and adult)
vary in their susceptibility and resistance to fumi-
gants. Beetles and other insects that develop on the
outside of grain kernels are usually more susceptible
to fumigants than certain moth and beetle species
that develop inside grain kernels. The pupae and
eggs that breath very little are the hardest develop-
mental stages to kill while the young larvae are
relatively susceptible.
Heavy infestations in which large amounts of dust,
damaged grain, webbing, and cast skins have accu-
mulated are more difficult to control because of the
effect these materials have on the penetration and
diffusion of grain fumigants.
Storage. A fumigant, whether applied initially as
a gas, liquid, or solid, eventually moves through
space, penetrates the grain, and is taken in by the
insect in the form of a gas. The "gastightness" of the
grain bin, therefore, greatly influences the retention
of the fumigant. Metal bins with caulked or welded
seams or concrete bins will still lose some gas but are
generally better suited for fumigation than loosely
constructed wooden bins.
Although there are often label recommendations
for fumigation of grain in wooden bins, the high
dosages and poor control usually achieved normally
make this type of fumigation uneconomical.
Winds and Thermal or Heat Expansion. Winds
and thermal or heat expansion are major factors







influencing gas loss. Winds around a grain storage
structure create pressure gradients across its surface
resulting in rapid loss of fumigant concentrations at
the grain surface and on the downwind side of the
storage. The expansion ofheadspace air due to solar
heating of roofs and walls followed by nighttime
cooling can result in a "pumping" of the fumigant from
the bin. Large flat storage that contain more grain
surface than grain depth are particularly susceptible
to gas loss due to wind and heat expansion. The
greatest gas loss frequently occurs at the grain sur-
face, a location that often contains the highest insect
populations. Furthermore, when the grain surface is
uneven with the large peaks and valleys, the distribu-
tion of fumigants through the grain will also be
uneven.
Air Movement. Successful fumigation of stored
grain requires an understanding of air movement
within the grain mass. It is easy to think that the air
in between the kernels of grain in a bin is as immobile
as the grain itself. This is not true and is one of the
reasons that fumigation sometimes fails even when
done by professional fumigators.
Air moves along the path of least resistance, with
warm air moving upward and cold air moving down-
ward. In a bin, there is usually air movement both up
and down because of temperature difference between
the well-insulated middle and the grain near the
perimeter that is affected by the outside temperature.
Air movement upwards can carry moisture that can
condense on the surface and cause crusting. The
resulting crust can also interfere with air and gas
movement. Air will move easier through a grain mass
composed of larger kernels, such as corn, and more
slowly through those composed of smaller grains,
such as grain sorghum. Air may move around a hot
spot and carry a fumigant gas away from the critical
area. Fumigant gases can penetrate these areas
better than normal air but the air movement can
affect how much gas reaches and stays at these
critical areas.

Precautions in fumigation
All precautions given on the label of the insec-
ticide used should be followed precisely. All fumigants
mentioned give off poisonous vapors. They have an
anesthetic action, and a worker may be suddenly
over-come without noticing adverse symptoms.
Therefore, a worker should never fumigate grain
without the assistance of another person, and should
never stay inside the bin unless protected by a gas
mask approved for the type offumigant being used. If
any fumigant is spilled on the skin, it should be
washed off immediately with soap and water.


Rodent control


Rodenticides
Food, water, and harborage are the three factors
that must be controlled to minimum levels for any
effective rodent control program to work. The basic
requirement is to maintain consistent and diligent
sanitation.
Good sanitation is the paramount factor in any list
of guidelines or general principles for rodent control.
Without adequate sanitation practices, rodent control
becomes nothing more than chasing from one problem
area to another.
While each grain storage area has its own unique
geography and design layout, certain common features
can be found at each. Generally, there are large areas
for parking or open space adequate for vehicles to load
or unload grain. Railroad sidings or tracks can be
found at larger grain elevators. Storage sheds,
maintenance areas, office buildings, and other
structures make preplanning a must for effective
control. Drainage ditches or runoff pathways are
usually present. These areas and others will often
determine where control devices or baits will be placed
for maintenance control programs.
To establish a systematic plan for rodent control, a
map or diagram should be drawn to facilitate planning.
The development of the map can be used to determine
prime areas of possible entry by the different rodent
species. It can also be used to keep track of and to
monitor bait stations, bait locations, or mechanical
control devices.

There are numerous points of entry onto the facili-
ties where field rodents or rodents brought in the
grain shipments or other vehicles can enter. Sanita-
tion, as mentioned earlier, will facilitate your rodent
control program. All the potential harborage must be
eliminated, including weeds growing along railroad
sidings, ditches, and alongside buildings and other
structures. Reduction also includes repairing struc-
tures where rodent populations can flourish. An open
floor drain should be sealed by screening to prevent
rodents from using the drain for harborage or path-
ways into the facility. "Build them out" is the best
policy.
Water resources must be eliminated wherever pos-
sible. Drainage ditches and water runoff areas must
flow quickly away from structures with no standing
water allowed to accumulate. Norway rats, the single
largest rodent pest for grain elevators, must consume
water at least once a day. Control will be easier by
removing any water sources or making the water
available away from the structures. Controlling the







available food sources around grain storage facilities
is the most difficult of all the sanitation practices to be
implemented. Spilled grain is an open invitation for
rodent infestation, especially when it is left open and
available. Cleanup must be instituted before night-
fall when the rodents become more active and are
searching for food materials.
Most experts will agree that sanitation is the key to
any pest management program and can account for as
much as 80 percent control of rodent populations
when the rodents are properly built out of an area and
the facility is kept clean. Assuming that sanitation is
at an optimum, there is still 20 percent of the rodent
population that must be controlled using either me-
chanical or chemical control.

Types
Two basic types of rodenticides are available to the
pest control professional for use around grain storage.
They are acute toxicants and chronic poisons.
Acute toxicants are designed for initial clean-out of
heavy, well-established rodent infestations, situations
where speed is of the essence or where results with
standard anticoagulants have been poor.
Acute rodenticides were the mainstay of the pest
control profession for many years prior to the devel-
opment of anticoagulants. Most acute toxicants used
were highly toxic to all life forms and seldom if ever
had antidotes. Such compounds as Antu, DLP 787,
Strychnine, Red Squill, 1080, and zinc phosphide
were commonly used. Only zinc phosphide has sur-
vived the tests of time and safety and is still readily
used in professional pest control and agricultural use.
Zinc phosphide is one of the oldest toxicants still
used extensively in rodent control. It is most effective
for use in cleanout situations and possesses many
safety features. Zinc phosphide is a natural emetic,
causing vomiting in non-target animals but not rodents
since they cannot vomit. It is a stable compound and
breaks down only in the presence of acidic moisture
such as stomach acids. Its natural grey color and
garlic odor make it unattractive to non-target species.
Also, there is no true secondary poisoning associated
with zinc phosphide, a potential problem for other
acute toxicants.
Zinc phosphide differs from anticoagulant baits in
that it produces toxic phosphine gas in the rodent's
stomach. This gas produces mortality generally within
four to six hours, making this compound ideal for
initial cleanout of problem areas. Acute toxicants
must be made palatable to ensure that a lethal dose is
consumed in one feeding.
Acute products that use superior inert ingredients
should be sought in order to achieve a good accep-


tance of the bait. Inferior baits may often be lower in
cost but saving pennies on the bait may prove more
expensive because of the need to remove the poorly
accepted bait and to rework the site.
Chronic poisons or baits are most commonly known
as anticoagulants. Since their introduction in the late
1940s and 1950s, anticoagulant baits have been the
mainstay for most rodent control programs in all
facets of pest control. There are inherent advantages
associated with anticoagulants that have accounted
for their widespread favor and usage.
In the most simple terms, anticoagulants inhibit
the production of clotting agents within the rodent's
blood. Without this blood clotting ability, the rodents
die from internal hemorrhaging. Death usually occurs
from five to fifteen days after consumption of the bait.
The rodent must consume the bait over a number of
days before a lethal dose is consumed. There is little
possibility of bait shyness and an antidote, Vitamin
I1, is readily available in the event of an accidental
poisoning.
Their safety features (delayed time to death and a
readily available antidote) and general effectiveness
have made the anticoagulants the leader in sales for
rodent control. There exists a number of anticoagu-
lants available for pest control. Such toxicants as
Warfarin, Prolin, diphacinone, chlorophacinone,
PIVAL, Isoval, Bromodialone, and brodifacoum are
but a few. There is a wide variety of anticoagulant
toxicants to choose from and manufacturers make
claims of superior effectiveness or safety for each and
every toxicant.
The existing anticoagulant toxicants can be catego-
rized into three distinct families or generations of
toxicants. The first generation of anticoagulants
would be classified as coumarin-type anticoagulants.
This family would include such compounds as Warfa-
rin, Fumarin, and Prolin. They were the first anti-
coagulants to be developed and quickly found favor in
the pest control profession because of their effective-
ness and safety in comparison to other acute com-
pounds being used. In relative toxicity, they are the
"safest" compounds on the market. However, several
days of consumption are generally needed before a
lethal dose has been consumed and thus they are the
slowest of the anticoagulants available today.
Development of stronger and possibly faster-act-
ing anticoagulants was soon begun which accounts
for the second generation of anticoagulants. These
are referred to as the indanione family of anticoagu-
lants which include PIVAL, Isoval, diphacinone, and
chlorophacinone. They are from five to fifteen times
more toxic than the coumarin family of toxicant which
accounts for their claimed increase in effectiveness.








However, it is the third generation of anticoagu-
lants, the brominated hydroxycoumarins, which have
made the biggest news in rodenticides. Whereas the
coumarins and indandione anticoagulants have gen-
erally needed multiple feedings by the rodent to
produce mortality, this third generation of antico-
agulants can make the claim of being single-feeding
anticoagulants.
A basic premise that must be remembered is that
all three generations of anticoagulants work exactly
the same within the rodent. Warfarin works exactly
the same within the body as bromodialone or
brodifacoum. The only difference is the relative
toxicity of the product. For example, the technical
ingredient brodifacoum is 184 times more toxic than
the technical ingredient Warfarin. Its presumed
effectiveness is directly related to toxicity.
Quite logically, as toxicity increases, relative safety
decreases. When determining which toxicant will
work best for a particular control situation, the safety
parameters for a particular baiting program must be
considered. A simple rule to follow is to use the least
toxic material that will still do the job. For example,
if in the past, Warfarin-based rodenticides have not
worked up to par, consider a diphacinone-based ma-
terial. Ifdiphacinone has not worked, then take a step
up to bromodialone.
Price is another consideration. The third genera-
tion anticoagulants cost considerably more than the
older compounds. All effort toward control amounts to
nothing if the toxic material is not eaten. The hard
part of rodent control is getting the rodent to consume
the lethal dose.
With such a wide range of toxicants on the market,
it is difficult to determine which brand names to
select. The Environmental Protection Agency has
well over 100 different registrations on file for roden-
ticides. There are over 70 brand names alone that use
the active ingredient Warfarin. As just mentioned, it
is difficult to determine which product will work best.
One point to remember which makes the choices that
much more difficult is that products with the same
active ingredient are not the same. As shown in


Table 7, products containing the same active ingredi-
ent get markedly different acceptance.
For baits to be effective, they must also be palat-
able to the rodent. In servicing grain storage opera-
tions, this becomes even more important when sani-
tation is not adequate. The rodenticide bait must be
as palatable as the existing food, preferably more
palatable. The key to this is to find a rodenticide bait
that uses primarily human food grade materials.
Baits containing human food grade materials will
assuredly produce results superior to those habits
using animal feeds.

Forms
There are basically six forms of rodenticide prod-
ucts that can be used effectively in and around grain
handling facilities:
paraffinized products,
pelletized baits,
meal formula baits,
place pack baits,
tracking powders,
liquid rodenticides.
Each bait form has its own inherent advantages
and disadvantages. Usually, each form of bait can be
found containing either chronic toxicants (anticoagu-
lants) or acute toxicants.
Paraffinized bait forms are designed primarily for
maintenance baiting in high moisture areas. Their
advantage can also be their disadvantage because the
paraffin is introduced to the bait to make the product
more weather resistant which reduces its acceptance
when compared to a pellet or meal bait. When
choosing a paraffinized rodenticide, products utiliz-
ing human food grade materials and inert ingredients
should be sought. This will ensure the optimum
acceptance for this type of bait.
Paraffinized bait can be used effectively for exte-
rior baiting with bait placement into burrows or other


Table 7. Bait Acceptance Test Results for Rodenticides.

Acceptance Chronic Toxicants Mortality/Acute Toxicants
Rats Mice Rats Mice
Brand A 48% 39% 100% 95%
Brand B 28% 17% 30% 20%
Brand C 19% 5% 50% 0%







inaccessible areas being best. If inaccessible areas
cannot be found, this and other bait forms should be
placed in tamper-resistant bait stations.
Pelletized rodenticides also have their advantages
and disadvantages. The pelletized form is easy to
work with in bulk containers. Pelletization is a crude
form of encapsulation and helps to mask the taste of
offending toxicants. The disadvantage to pelletized
rodenticides is that they are easily carried from one
location to another by the rodent. This is fine if you
can guarantee the rodent will not contaminate other
locations or stored materials with the bait. They
might take the bait back to their nest and consume the
product at a later time, an advantage. Problems occur
when they store the bait in sensitive areas where the
product should not be found.
Meal bait rodenticides have often been found to be
the most palatable bait form. The open loose meal has
air circulating around the bait and has proven quite
attractive in many situations. However, the open
form has a shorter life than other forms because it
absorbs moisture and will turn moldy or rancid more
quickly than pelletized or paraffinized baits.
There is seldom a problem with rodents moving the
bait when using meal bait rodenticides. The rodent
will not move meal products so special care must be
made in placing the bait where the rodent will feel
comfortable while feeding on it.
Place pack rodenticides have found increased favor
in recent years. The product is labeled for safety
purposes, the bait stays fresh until opened by the
rodent and it is easily dispensed. Disadvantages to
their use are the increased cost that the place pack
material adds to the product, the difficulty that some
rodents might have in opening them, and the lack of
a full and comprehensive label upon some manufac-
turers' packaging.
Tracking powders, available as both acute or chronic
products, have many applications in grain handling
and storage areas. They can be dusted into wall voids,
burrows, along runways, in enclosed spaces, and
other areas. However, they do not stand up well to
moisture (they cake and will not cling to the rodent).
They are often messy and cannot be used in areas
where they can become airborne.
Liquid rodenticides are often neglected because of
the added equipment their use requires and their
general reputation of being labor intensive to use.
However, liquid baits work very well in areas such as
grain elevators where natural food is plentiful and not
easily eliminated.
Again, the key element to remember when choos-
ing bait forms is palatability. The simple rodent-


control premise "If they eat, they will die" should be
remembered. The difficult job is finding a rodenticide
that is palatable enough to get maximum acceptance.
The use of superior inert ingredients in the formula-
tion should be sought. Human food grade materials
are always more attractive than animal feeds. When
considering baits, a low price should not be mislead-
ing. The most expensive component in effective ro-
dent control is labor. The job should be done right the
first time with a superior bait.

Mechanical control and
exclusion

Snap traps, glueboards, and multiple-catch traps
are the mainstay of mechanical control available for
use in and around grain storage areas. They are often
used as monitoring devices in areas where baits
cannot be used for fear of contaminating the stored
materials. They also are a last resort for areas where
the rodents have become bait shy.
Mechanical devices can work very well if they are
placed properly but their drawbacks can be many.
With the exception of multiple-catch mouse traps,
they are usually good only for one rodent and must be
checked daily. Glueboards have the drawback of
catching dust and dirt as effectively as rodents. When
the board has been covered with dust or chaff, they
lose their tackiness and are ineffective. Glueboards
cannot be used effectively in areas where there is
standing water. If the rodents' feet are wet or damp,
the glue will not catch the rodents.
Exclusion or building out the rodents from the
grain storage area will be a major tool in a sanitation
program. Sealing offpotential runway and harborage
areas is a necessity.
Like insecticides, rodenticides are poisonous. They
should be used only when needed, and they should be
handled with extreme care. Directions and precau-
tions on container labels should be carefully followed.
For additional assistance with specific problems,
consult the local extension office staff.

General bin safety
The number of human suffocations in grain storage
systems is increasing. There appear to be at least five
basic reasons:
* increased harvesting and handling of grains,
* larger on-farm storage facilities,
* faster grain handling capabilities,







* increased mechanization (operator working alone),
and
* little knowledge of grain movement and safety
precautions.
To avoid the mistake involving a life, know the
dangers of flowing grain and practice safe work habits
at all times.

Caution: There are several reasons for enter-
ing a bin filled with grain
A successful manager of stored grain must check
his investment closely and frequently. He may enter
a grain bin to visually check the grain's condition, and
may probe the bin to determine the grain's temperature
and moisture content to ensure that there are no
developing "hot spots."
Grain being removed from a bin equipped with a
bottom unloading auger may fail to flow because of
clogging or bridging. The manager may feel that the
only option is to go inside the bin and remove the
obstruction or break up the bridged grain.
When drying grain, check the incoming grain
closely. The manager may feel that the wet holding
bin is the best place to make observations.
Children may find that a storage bin filled with
grain is an attractive place to play.

Caution: There are several reasons for not
coming out alive
Flowing grain is dangerous. Why? To better
comprehend the hazard, be familiar with the way in
which most farm storage bins unload. Grain storage


structures should be, and usually are, unloaded from
the center. When a valve opened in the center of the
bin or a bottom-unloading auger is started, grain
flows from the top surface down a center core to the
unloading port or auger. This is called "enveloping
flow" and is illustrated in Figure 28. The grain across
the bottom and around the sides of the bin does not
move. The rate at which the grain is removed is what
makes the enveloping flow so dangerous. A typical
rate for a bin-unloading auger is 1,000 bushels per
hour. This is equivalent to 1,250 cubic feet per hour
or approximately 21 cubic feet per minute. A 6-foot-
tall man (assuming an average body diameter of 15
inches) displaces about 7.5 cubic feet and this means
that the entire body could be submerged in the enve-
lope of grain in approximately 22 seconds. Even more
importantly, an individual could be up to his knees in
grain and totally helpless to free himself in less than
5 seconds (Figure 29). Also, it requires up to 2,000
pounds of force to pull a totally submerged man up
through the grain.
Flowing grain is like water in that it will exert
pressure over the entire area of any object that is
submerged in it. However, the amount of force re-
quired to pull someone up through grain is much
greater than required in water because grain exerts
no buoyant force and has much greater internal
friction. People who have helped pull partially sub-
merged children from grain have commented on how
hard they had to pull and, frequently, that shoes were
pulled off in the grain. This may mean that rescue
efforts will fail unless the movement of grain is stopped.
Grain that bridges across a bin can be another
hazard. Bridging grain may create air spaces in a
partially unloaded bin (Figure 30). This situation


Figure 28. When bins unload, the grain at the top of the bin is removed first.








presents several dangers. The first is that the person
may break through the surface and be trapped in-
stantly in the flowing grain (Figure 31). Another
danger is that a large void may be created under the
bridged grain by previous unloading so that a person
who breaks through the crust may be carried under
the grain and suffocate even though the unloading
auger may not be in operation at the time (Figure 32).
A third hazard is that, if the grain is wet enough to
mold and bridge across a bin, there may be little
oxygen present in the cavity because of microbial
activity. Therefore, a person falling into this void may


be forced to breathe toxic gases and microbial spores
even if his head stays above the level of the surround-
ing grain.
Safety hazards in grain bins are not limited to
those with bottom-unloading augers. Gravity-un-
loaded bins may present a similar danger through
bridging or unloading. A definite danger exists with
wet holding bins that feed automatic-batch grain
dryers. When the dryer completes its drying cycle and
reloads, a person in the wet holding bin can be drawn
below the surface of the grain in a matter of seconds
(Figure 33).


From the time the auger
starts you have 2-3
seconds to react


In 4-5 seconds
you are trapped


After 22 seconds you are
completely covered


Figure 29. 22 Seconds to suffocation.


Before unloading, a
condition may cause
bridging


Air space is created as
unloading begins


Air space remains
after unloading stops


Figure 30. Potential hazard created by bridging. Note also that when the air space becomes large enough, the bins walls
may buckle.


SecondS2-























A dangerous
situation created by
a previous partial
unloading of the bin


As unloading begins,
the bridged grain
falls into the air
space and the man is
instantly trapped.


Before the grain
flow can be
stopped, the man
is covered. In a
matter of seconds
- suffocation.


Figure 31. Two basic principles were violated. First, the person entered a bin of grain that was out of condition without
seriously considering its previous unloading history. Second, he didn't ensure that unloading could NOT occur
while he was inside.


Probing bridged It may very well
grain presents a result in a break
dangerous situation through to disaster...


...with suffocation
occurring in a
matter of seconds


Figure 32. Bridged grain presents a danger, even when the bin is not unloaded.





























Inspecting grain in the wet holding ...may result in death during the
bin during the drying cycle... refilling cycle


Figure 33. In a modern grain facility, bins may load or unload automatically, thereby adding to the suffocation hazard.


Summary
This publication has discussed procedures to mini-
mize dry grain storage problems. Preharvest preven-
tive management and proper grain bin sanitation
should always be the first management strategy.
Other important management strategies discussed
include monitoring/sampling, temperature and mois-
ture control, aeration, and pest and pathogen control.
In all the activities, safety is a very important consid-
eration.





















































































COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES, John T.
Woeste, Director, in cooperation with the United States Department of Agriculture, publishes this information to further the purpose of the May
8 and June 30,1914 Acts of Congress; and is authorized to provide research, educational information and other services only to individuals and
institutions that function without regard to race, color, sex, age, handicap or national origin. Single copies of extension publications (excluding
4-H and youth publications) are available free to Florida residents from county extension offices. Information on bulk rates or copies for out-of-
state purchasers is available from C.M. Hinton, Publications Distribution Center, IFAS Building 664, University of Florida, Gainesville, Florida
32611. Before publicizing this publication, editors should contact this address to determine availability. Printed June 1991


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