WEEK 10
SUBJECT:
AGRICULTURE
CLASS: 7
TERM: SECOND
TOPIC: CROP PEST
MEANING OF PEST:
Crop pests are animals that destroy crops and crop products either in the field
or during storage and as a result cause economic losses to the farmer. The
pests of crop plants are very many. They include insects, birds, rodents and
monkeys. Pests attack all parts of crop plants- the roots, stems, leaves,
fruits and seeds. Pests attack crops in the field while some of them continue
their attack after the crop has been harvested and stored. Most pests injure
crop plants while feeding on them. They bite the plants or suck the sap from
them. In the process, disease organisms can be introduced to the plants through
the wounds created by the pests. Many crop plants are killed either directly by
pests or indirectly by the diseases which they cause when entering the attacked
crop plants.
BITING AND CHEWING
INSECTS: Insect larvae or caterpillars and some adult
insects bite and feed on plant leaves especially vegetables. Some of these are
locusts, grasshoppers, crickets and biting beetles.
PIERCING AND SUCKING
INSECT: These insects have mouth-parts with which they
pierce and suck juice from the leaves, stems and fruits of plants. This type of
mouth-part is called a ‘proboscis’. Insects in this group include butterflies,
moths, capsids, aphids, mealy bugs, scale insects, white flies, etc.
BORING INSECT:
Another types of insect that causes damage is the ‘boring beetle’ whose larvae
enter the crop stems and eat up their juicy centres. The stems become so weak
that strong winds can break them. Examples of boring beetles are the palm weevil,
the rhinoceros beetle of coconut palm and the stem borers of kola and coffee.
IMPORTANT FIELD AND
STORAGE PEST:
Field Pests: Most of the
field pests of crops are insects, birds, rodents and monkeys. They attack all
the parts of crop plants roots, stems, leaves, fruits and seeds. Pests attack
crop plants in the field at different stages of growth: seedlings, adult and
mature plants and also their fruit at the time of harvest.
Insect
pests which attack crops in the field include moths, caterpillars or
butterflies, beetles, grasshoppers, crickets, locusts, capsids, cotton
strainers, palm weevil, the rhinoceros beetle and stem borers, etc. By and
large, the more the number of insects attacking crop plants, the greater the
damage done. Insect attack may also lower the quality of the final produce of
crop plants.
Rodents
which attack crop plants in the field include rats, squirrels and grass
cutters, etc. Various species of monkeys feed on corn and fruits such as
banana, and plantain, etc. Monkeys are known to eat a lot of cocoa pods in
Sierra Leone and Ondo State of Nigeria. They probably account for 20% of cocoa
loss annually.
Storage Pests: The most
important storage pests of crops are insects. Birds and rodents (rats, cane
rat, cutting grass or grass cutter, squirrels and mice) also attack harvested
crops in storage, if and when they can get at them. Insects do the most damage
to crops in storage. Some of the insects which cause the most serious damage
and losses of stored crops are the following:
(i)
The maize weevil (Sitophilus zeamays)
(ii)
The Bean beetle (Callosobruchus maculatus)
(iii)
Groundnut bruchids and beetles
(iv)
Yam beetle-the greatest pest of yam which causes considerable damage.
(v)
Various other weevils also attack sweet potato tubers, sorghum, kola nuts, etc
in storage.
Weevils,
also known as bruchids, as a group of insects, are responsible for the greatest
damage and losses to crops in storage.
It
is important to dry crops well before storing them. This is because crops, such
as maize and beans, that are wet i.e. that are high in moisture content and are
badly stored, often harbor very many insects.
ASSIGNMENT
1.
What are crop pest?
2.
Explain biting and chewing pest and give two examples.
3.
Explain piercing and sucking insects and give two examples.
4.
What are boring insects? Give two examples.
5.
What are field pest? Give two examples.
6.
What are storage pests? Give two examples.
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