I AR Pest control - USAid

moisture, and competition with other,living
organisms.
(1). Food Supply
The poultry and animal feeds stored in farm
buildings, accumulations of waste grain and
feed in litter on floors of these buildings,
on the ground under them or under grain
bins are supplies of foods that are seldom
safeguarded. They provide sustenance for
colonies of insects, mites and rats that may
later invade grain storages.
The stored grains on the farm, in country
storage sites, in elevators, and in warehouses
provide ar almost ideal food for stored
product pests. Apart from the protein or
amino acids which serve in body building,
and the carbohydrates which supply energy,
the most important food constituents are the
vitamins of which the Vitamin Bgroups are
essential. The requirements for these substances
and other special substances varies
with the pest species.
(2). Temperature and Moisture
They are the most important factors affecting
the prevalence of stored grain insects, mites
and microorganisms. In general, the most
favorable temperature for stored grain
insect development and redroduction
appear to be about 80'F. Below 70'F and
above 95'F reproduction almost, if not
completely ceases. Developmental period
(from egg to adult) islonger at lower tem-
peratures and shorter at higher tempera-
tures. As temperature decreases, insects
become less active, cease feeding and may
die of starvation. All of the stored grain
insects vary somewhat in their susceptibility
to cold temperatures.
Most insect pests of stored grains are killed
by temperature above 100'F. All are killed
with exposure to 140'F for only ten minutes,
whereas most stored grain can withstand
freezing for several days. Insects react to
temperatures above 1000F in grain masses
by migrating or moving to cooler areas
where they attack hitherto uninfected areas.
Moisture content of the grain isalso an
important factor in determining the development,
survival and reproduction of insects
in stored grain. These insects depend primarily
on their food supply for the moisture
to carry on their life processes. Insects grow
better on food with a high rather than with
a low moisture content, but they show
quantitative differences in their reactions.
The most favorable range of moisture for
insect development and reproduction is
approximately 12 to 15%. increase in
moisture content of grain, up to apoint,
causes a corresponding increase in the rate
of reproduction.
The requirements of the microorganisms are
also somewhat similar although some of
them are capable of sustaining themselves
even in the absence of oxygen.
Moisture, temperature and grain dust or
dockage interact to provide conditions
favorable for reproduction and survival of
stored grain insects. As temperatures are
increased, insects are able to reproduce in
grains of lower moisture content and when
moisture isincreased the insects are able
to reproduce at lower temperatures.
(3). Competition
Competition between insects (and other
animals) may take the form of competition
for food and destruction by predators and
parasites. The competition for food is more
severe between species which have the
same nutritional requirements, and the
same temperature and humidity preferences.
In stored products the competition between
insect species is more severe than between
insects and birds, or between insects and
mammals.
Parasites (mostly hymenopterous) and predators
(especiall mites and beetles belonging
to the families Carabidae and Staphyliniidaie)
have undoubtedly caused the death
of many insects, but they have not been
observed to be an important factor in
controlling insect infestations. Some insects
such as flour beetles (Tribolium spp.) are
cannabalistic.
D). Storage Insects
The storage insects found in the Philippines
are the same ones that are found associated
with stored products in most parts of the
world. Out of the many hundreds of insects
that are found associated wth grains,
legumes and their by-products in other parts
of the world, only 41 insect and one mite
species have been reported in the Philippines
as shown below. Only eleven of these
forty-one species are destructive pests of
stored grain and legumes.
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