Plantwise Factsheets for Farmers
Grain storage in metal silos against insect pests
Prostephanus truncatus, E.g. Sitophilus
Recognize the problem
pests include the common maize weevil (also called the greater grain weevil, Busumpe
in Tonga language and Impese in Bemba language) and the larger grain borer (also
called Chidonkola mapwe). These pests eat lots of cereal grains when they
have been in storage for six months or longer. Some grains have feeding holes
when examined. Where grain is stored in bags, a powder is seen outside the
bags. When a hand is passed through the damaged grain, powder will stick to it.
of metal silos can prevent or kill the insect pests that damage the grain. A
metal silo is a cylindrical container in which the air required by insect
pests can be restricted (hermetically closed conditions). The capacity varies
from 100 – 1000 kg. The silo has both an inlet on top and outlet at the
bottom that can be tightly closed with a lid tied with rubber bands to
prevent the entry of air.
technology reduces the need for insecticides. Silos are cheap as they do not
require constant maintenance, and can be easily moved when shifting from one
area to another.
Close the outlet tightly
with a lid and tie with a rubber band
- Load clean and dry maize
into the silo. Maize is dry when is has a moisture content of 13% or less.
This occurs when the maize is fully mature and has been hanging on the plants
or in a shelter for a few weeks in dry weather.
- After filling the silo,
a candle is placed inside the silo on a small tray, to avoid wax from getting
on the grain. Then the candle is lit to use up all of the air (oxygen) in the
silo. The size of the candle depends on the size of the silo but a 10 cm
candle can suffice for 100 – 500 kg capacity.
- The inlet is then
covered and tied with rubber band to avoid air getting into the metal silo.
- The burning candle
inside the silo will go out as soon as all of the air is used up by the
candle. This may take 5 – 20 minutes depending on the size of the metal silo.
Do not move or shake the silo during this period.
- Insects will die due
to the lack of air available for them to breathe.
The recommendations in this factsheet are relevant to:
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