The general principles of insect control are based on reducing the pests to such a low level of population that the loss incurred is minimal.
For effective control, the agriculturist needs to be able to recognize the various types of insect pests, the nature of their damage, and the likely time of attack.
Pests should be studied in relation to their ecology; that is, in investigating the effects of certain pests, one should also investigate the entire relationship of the insects with the crop and the crop’s environment.
Control measures take six main forms: cultural, biological, use of resistant varieties, chemical, prohibition and quarantine.
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Pest Control Measures In Nigerian Farms
1. Cultural control
Good cultural practices may enable crops to escape insect attack, or reduce or destroy insect populations.
Such practices include the rotation of crops susceptible to attack with those which are not.
Ploughing buries the eggs and immature stages of some insects.
Adequate-spacing and correct seed rate per hectare can help make the micro-climate (the humidity and aeration around the crops) unsuitable for the development of the pests.
Timing of planting and frequency of weeding are also important. Pests and diseases are more likely to attack crops planted or harvested during the off season. Many weeds are known to harbor insects.
2. Biological Control
This involves the introduction of the natural enemies of the pests. The method has been successfully used to control some insect pests for example, the ladybird beetle (Vedalia cardinalis has been used to control Iceryo purchasi (cushion scale) in the family Coccidae.
A particular plant, African marigold, has been known to reduce the nematode population in the soil.
A fungus, Trichoderma virida, is antagonistic to another fungus, Rhizoctonia solani, which causes disease in potatoes.
Biological control has its own danger in that the new organisms introduced may start to attack crops that have previously been free from attack.
3. Use of resistant varieties
Breeding crops which are resistant to disease, requires cooperation between plant breeders, pathologists, and farmers
There are problems associated with this method. The resistance of the new variety may not last long because both plants and pests are continuously adapting to their environment.
Plants which are resistant to certain species of pests are not necessarily resistant to other species which cause the same damage.
A plant attacked by an insect species in one country may not be attacked by the same species in another
4. Chemical control
This aims at protecting crops by applying pesticides to them before the posts attack. If the attack is established, chemicals are applied to kill the pests at chosen stages of their life cycles.
A risk of chemical control is that it may lead to an increase in pests or pathogens other than those which it is controlling,
The chemicals used for insect control include insecticides and fumigants.
Insecticides may be applied in the form of solids such as dusts or in the form of suspensions, emulsions and sprays, such as Vetox 25, Gammalin 20, and Didimac 25.
Fumigants are insecticides which act in the form of vapour. They are usually enclosed in airtight containers and are used in arresting insect attacks on stored products.
Some common fumigants are ethylene dichloride (C2H2Cl2), hydrogen cyanide (HCN), and methyl bromide (CH3Br).
Soil may also be fumigated with liquid formulations or nematicides, such as formalin and nemagon.
All fumigants are toxic to man and domestic animals. They must be handled by trained people.
This is the practice of forbidding the introduction of certain infective materials into an area.
It can be very effective in communities where local custom reinforces the practice. Prohibition is done on a nationwide basis by legislation.
The most effective method of control of pests, diseases, and weeds is to prevent their introduction (by legislation if necessary) and to test all plants and animals coming into the country by quarantine.
The agricultural development of any country depends upon the introduction of new varieties of crops and animals.
However, such imports bring with them the danger that serious diseases, pests, or noxious weeds may be introduced into countries which have been free of them
To avoid this, a period of isolation and observation is imposed by law on imported seeds, plants, and animals, whether dead or alive, plant products, non-sterilized soil.
During this period of quarantine the materials are kept under observation in sealed compartments for a period long enough for any disease symptoms to be detected.
If symptoms do appear, the materials are destroyed or re-exported at the expense of the importer.
I hope this article has enlightened you about the principles and the methods of pest control in Nigerian farms.