Insecticides are substances that are used to mitigate or eradicate the invasion of insect pests which tend to reduce the quantity and quality of crop in the farm. Insecticide can be organic or inorganic in nature, the organic type are the ones made from natural raw materials. The inorganic are the ones made from the combination of two or more chemical compounds. The organic are not toxic, they cheap and readily available but the inorganic are not cheap and toxic. They are harmful to man and the plants when not used as prescribed.
Organic insecticides are mostly repellents, the emit odour that repels the insect away.
Examples of the organic insecticides are:
• Petroleum products like oil, kerosene etc.
• Neem tree extracts
• Nicotine from tobacco plant.
• Citrus peels.
Insecticides can be classified based on their mode of action on insects. They are classified as
• Contact insecticide:
This type of insecticide has immediate effects on insect when sprayed, they penetrate into the supporting systems of the insect such as nervous system and respiratory system, causing a total break down of the insect. They are available in powered and liquid form which can be applied on the insects when noticed on the farm, they are very effective in action. Examples are Malathion, Decamethrin, Perfecthion, Carbaryl etc.
• Systemic insecticide:
This type of insecticide seems to be slow but also very effective, they are sprayed on the plants. The plant absorbs the insecticide and it is translocated to every parts of the plant after application. The insect that feeds on any part of this plant will die immediately. It is effective against the piercing and sucking insects like Aphids, Leafhoppers, Fruit worms, Mealybugs etc. Examples are Karate, Sherpa-plus, Rigor 40 etc.
• Stomach poison:
This is the type of insecticide acquired during feeding on plant parts by the insects. The insecticide enters through the mouth of the insect and absorbed through the digestive tract of the insect leading to its death. They are effective on biting and chewing insects like beetle, grasshopper etc.
This type of insecticide contains oil, which distorts the breathing mechanism of the pest.
Mode of Application of insecticides
Application of insecticides has different methods depending on the type of pest and nature of the insecticide, it can be applied through:
Insecticides that are usually suspended in water, like Wettable powder(WP), Flowables (F), and Emulsifying Concentrate (EC), and later dispersed either in soils or on crops or seeds to reach targeted pests are sprayed slightly in the particular spot or vicinity of the insect by using spraying equipment like knapsack sprayer, boom sprayers.
Insecticides that are granulated in nature are applied on large scale by broadcasting to the field for incorporation into the soil. It can be mixed with fertilizer and broadcasted together.
Dust-like insecticides are used on seeds or crops by the use of special equipment to ensure full coverage on the crop or seed. Example is the Acetellic dust.
• Soil injection:
Liquid insecticides can be injected into the soil after mixing with water to control soil insect pests. This is to ensure that the insecticide reaches the targeted insect pests. Emulsifying Concentrates are also used for injection..
Precautions to take note when using insecticides.
• Do not spray when it’s raining to avoid wash off.
• Do not spraying in high temperature to avoid degradation by sunlight
• Do not eat, smoke or drink when spraying.
• Do not spray in windy condition to avoid wastage.
• Spray early in the morning or late in the evening for effective action.