Pest control may involve one or a combination of a number of methods. The combination of many methods to control pests is referred to as integrated pest management.
LEARNING OBJECTIVES
By the end of this lesson, you should be able to:
- Explain the meaning of integrated pest management.
- Describe different methods of pest control.
- State and explain the factors considered before using different methods of pest control.
Integrated pest management (IPM) is also known as integrated pest control (IPC). This is a broad-based approach integrating different practices to achieve economic pest control. Its aim is to suppress populations of pests below the economic injury level. The Food and Agriculture Organization (FAO) defines Integrated pest management as the consideration of the available techniques of pest control and subsequent integration of suitable measures to discourage the development of populations of pests. All this is done while keeping pesticides as well as other interventions to levels that minimize human health risks and are economically justified.
CULTURAL PEST CONTROL
Cultural pest control refers to practices that create conditions that are unfavorable for the survival of the pests. Cultural methods of pest control include the following:
- Timely planting: this enables crops to establish at the right time and escape pest attacks, for example, stalk borer attack.
- Timely harvesting: it allows crops that are ready for harvesting to escape pest infestation in the field, for example, grain weevils.
- Trap-cropping: it involves planting a trap crop before or together with the main crop so as to attract pests away from the main crop. The trap crop is then destroyed.
- Intercropping: it includes the planting of a crop that has a repellent effect, an attractant effect, or a combination of the two, on a targeted insect in close proximity to a crop that has the potential to be attacked by the insect.
- Closed season: this involves not growing a crop for a certain period of time to starve and break the life cycle of a particular pest.
- Crop rotation: the crops susceptible to certain pests are rotated with those that are not or are less susceptible.
- Planting resistant varieties: this provides natural protective mechanisms against specific pests. Examples of pest-resistant crops are the goose-necked sorghum and hairy cotton.
- Open pruning: pruning creates a microclimate that is less conducive to some pests. The antestia bug is an example of a pest that can be controlled through pruning.
- Proper crop nutrition: proper crop nutrition enables crops to grow faster and be strong enough to resist pest attacks, for example from piercing and sucking insects.
- Seed quarantine: imported planting materials are not allowed into the country until they are tested to ascertain they are weed-free or pest-free.
- Destruction of alternate hosts like weeds: this breaks the life cycle of some pests by starving them. Destroying the mallow weed, for example, controls the cotton stainer.
- Proper spacing: this helps to reduce the infestation of certain pests such as aphids in groundnuts.
- Use of clean planting materials: this controls the introduction of pests such as nematodes in the field.
- Proper ventilation of storage facilities: this helps in the control of storage pests.
CHEMICAL PEST CONTROL
This involves the use of pesticides to control pests.
Factors to consider before using chemical pest control
- The intended use of the crop.
- The period within which the crop will be used.
- The cost of pesticide.
- Safety of pesticide to the user and environment.
Ways by which pesticides kill crop pests
- As contact poisons.
- By suffocating the pests.
- As stomach poisons after being digested.
Factors that affect the effectiveness of a pesticide
- The weather conditions. Temperature is a very significant factor in the breakdown of pesticides. Rainfall can also wash away chemicals applied to crops. Apply chemicals when the weather conditions are appropriate for their application.
- The concentration of the pesticide in relation to the stage of development. Based on the stage of development, crops may require different levels of concentration of pesticides.
- The persistence of the pesticide. Persistence refers to the inherent stability of the pesticide. This is also referred to as residual time- how long a pesticide effectively lasts. Some chemicals persist for three weeks, others six weeks, and so on.
- The formulation of the pesticide. Pesticides have two groups of chemicals, active ingredients, and inert or inactive ingredients. The active ingredient(s) is the part of the formulation that is designed to control the target pest. Inert ingredients enhance the effectiveness of active ingredients. Pesticide formulation refers to the combination of active and inactive ingredients. Different formulations allow different means of application like granules, dust, and sprays.
- The mode of action of the pesticide. This refers to how an insecticide works. Many people know that pesticides kill insects by they do not know-how. Most pesticides affect the nervous system. They prevent enzymes from working. Poisoned insects show uncoordinated movement and tremors. Some insecticides are insect growth regulators. They cause death slowly and they are specific for insects with low mammalian toxicity.
MECHANICAL PEST CONTROL
This involves the use of physical methods to remove, kill, or make it difficult for the pests to attack a crop. Physical methods of pest control include:
- Use of lethal temperatures (too cold or hot) to control insect pests such as bollworms.
- Drying grains to appropriate moisture content so it becomes hard for pests such as weevils to penetrate.
- Suffocation or irritation using carbon (IV) oxide.
- Flooding to drown pests such as cutworms, armyworms, and moles.
- Use of physical barriers such as metal deflectors and fences to prevent access of pests to crops and stored produce.
- Physical destruction or killing of pests after hand-picking or trapping them, for example, cutworms, rats and moles.
- Use of electromagnetic radiation such as ultraviolet light and X-rays to kill insect pests.
- Use of scaring devices such as scarecrows and catapults to scare away birds and large mammals.
BIOLOGICAL PEST CONTROL
This refers to the deliberate use of a living organism to control a target pest, for example, the use of the ladybird beetle to control aphids and the use of the parasitic wasp to control the whitefly. This method of pest control relies on herbivory, predation, and parasitism, or other natural mechanisms.
- Herbivory is the consumption of plant material by animals;
- Parasitism is the consumption of nutrients by one organism (parasite) from another organism (host), resulting in a decrease in fitness to the host;
- Predation is the killing and consumption of an organism (prey) by another organism (predator)
This method also involves an active management role by humans. Classical methods of biological control involve the introduction of natural enemies bred in the laboratory and released into the environment. An alternative approach is to increase the number of already existing natural enemies by releasing more. Normally, the released organism will breed and provide long-term control.
For example, mosquitoes can be controlled by putting Bacillus thuringiensis, a bacterium that infects and kills mosquito larvae, in water inhabited by mosquitoes. Parasitic wasps can be used to control aphids too. The parasitic wasp lays eggs in aphids. When the eggs come out, the aphids die and the young wasps start to grow, quickly decreasing the aphid population.
