Insect Pest Management

Insect pest Management can be done through various methods. A system, by which the different methods are integrated, is known as Integrated Pest Management (IPM). Insect management methods are discussed below.

Natural control – is concentrated around the environmental factor, which prevents increases in pest numbers and their distribution. It also includes the presence of natural pest enemies in the environment.

Physical control – occurs when physical or mechanical action is taken to control a pest. It includes physical changes in the environment that will lead to the control of the pest. Physical control methods include: Physical removal of the pest by hand, [ which is impossible in a crop situation]

Mechanical exclusion of the pest such as fly screens on windows.

Mechanical traps i.e. those that are non-toxic, such as sticky traps and electric traps.

Manipulation of the environment has limited application but can be used with success in processes such as dehydration, low relative humidity and regulating temperature.

Control through agricultural practices. Pest control through agricultural practices or cultural control is used in the large-scale cultivation of crops. It is relatively cheap and environmentally friendly. Such practices include:

• Ploughing in of host plants for pests
• Sanitation practices
• Destroying remnants of pest-infested crops
• Crop rotation
• Mixed cultivation
• Strip cropping
• Establishment of trap crops
• Cultivation of pest-resistant crops

Biological Control

Biological control is the manipulation of pest enemies such as parasites, predators and pathogens in such a way that pest numbers are reduced. Biological control agents for pests are specific to a pest species, and once established, can increase and spread independently, making the control self-perpetuating. The control is however expensive, slow and the pest cannot be eliminated even for short periods of time.

Genetic Manipulation

Genetic manipulation of the pest or the crop plant can be employed as a pest control strategy. The release of sterile male pest insects into a normal population has been shown effective in parasitic fly pests in Central America. Sterilisation can be achieved through the radiation of chemicals. The process is however expensive.

Manipulation of the genetics of crop plants can produce pest resident crops. This can be achieved by producing a plant that will repel the pest or the production of a crop that produces toxic compounds. An alternative is a crop plant where growth is stimulated through insect attack, the crop thus compensates for the losses due to the pest.

Chemical Pest Control

Chemical pest control is done by using pesticides. The term pesticides refer to the wide spectrum of agrochemicals used in plant protection. Pesticides include herbicides (plant or weed killers), insecticides, rodenticides (rodent killers), avicides (bird killers), molluscicides (snail killers) and acaricides (mite killers).

The compounds are taken up by the plant and translocated throughout the plant. Insects with sucking feeding habits are the primary targets of systemic compounds. Stomach poisons must be ingested and are absorbed in the stomach of the insect. Fumigants are pesticides in a gas form and enter the insect through the respiratory system. Pesticides with trans-laminar action, penetrate the leaves of plants but are not translocated through the plant.

Pesticide Formulations

The first step in the production of a pesticide is the production of the chemical compound, which has insecticide activity. This compound is known as the active ingredient (a.i.). For the compound to be effective it has to be applied to a crop field. Even older compounds are applied at relatively low rates, e.g. 1 kg spread over one hectare (10 000 m2). It is impractical to apply a pesticide as technical material, and an easier way of distributing a pesticide is diluted in water or in a powder. Often the active ingredient is not soluble in water but the compound is formulated in such a way that it can be diluted in water and then applied. A pesticide formulation is made up of the active ingredient, solvents that aid in water solubility or water miscibility, inert additives and adjuvant (compounds that aim uptake of an active ingredient). The relative amount of a.i. in the formulation is indicated on the label as a percentage (g a.i. per 100g or 100 ml).

Pesticides are available either as dry– or liquid formulations:

Dry formulations are sold as dust (applied as is), granules (applied as is), baits (used as is), wettable powders (to be made up in water) and soluble powders (to be made up in water).

Liquid formulations are sold as emulsion concentrates (turn milky when diluted with water), soluble concentrates (used in dilution in water), Oils (used as is), Ultra-low volume formulations (used as is), encapsulated formulations (used in dilution with water).

Click here to view a video that explains pesticide formulations.