As much as 40% of the food grown for human consumption is ruined by pests. Pests such as aphids, mealy bugs, whitefly and red spider mites that make their habitat in fields amongst the plants that we harvest for food. Chemical insecticides are one solution to the pest problem. They are sprayed on to the fields and are usually specific to kill only the insects that are considered pests of the plants. However, this is only a short-term solution of pest control as after a period of time, the pests build up a resistance to the chemicals.
The effect of the pesticide is then diminished, so farmers use a more concentrated pesticide to kill off the pests. Even though increasing the concentration of the chemical pesticide will kill the pests shot term, it will reach a point where it will start to effect insects other than the ones it was specifically designed to kill. The population of other insects, some of which act as natural pesticides because they are predators of the pests, will decrease. This means that the pests have very few predators to keep their populations low.
Some examples of pests and there predators are as follows; ladybirds that attack mealy bugs, phytoseiulus attack red spider mites and aphidolete larvae eat aphids. If they are killed then there is no factor that will prevent the population of the pests increasing. So, by using chemical pesticides farmers have not only increased the pests’ chances of survival but have disrupted the food chain so that their population can increase. Chemical pesticides are also damaging to humans and to the environment. They seep in to rivers and can enter the food chain, poisoning many animals.
However, pesticides do work quickly and are relatively inexpensive. There are other conditions on farms that can help the pest population to increase. Farmers often uproot hedgerows to make more area for growing crops and to make it easier for the manoeuvre of large pieces of machinery. Hedges provide the ideal habitats for predators and without them, they are unable to survive or reach areas in the centre of large fields where pests are inhabitants. Another form of pest control is now being used which does not involve the use of harmful pesticides. It is known as biological control.
It is a way of interfering with a pest’s ecological status. There are companies that package the larvae of useful predators in to sachets, which can be left amongst plants. The predators can then make their habitats, using the pests as their main food source. This form of pest control is eco-friendly but does have its disadvantages. It can take along time (up to 18 months) for the pest to bought under control and then the pests are not totally eliminated. Also if the correct predator is not used there can be catastrophic results whereby the once useful predator becomes a pest itself.
It takes a lot of research for an ideal predator, which must be specific to the pest. Other complications apply if a predator needs to be brought in from abroad, i. e. quarantine. There are pests that have no natural predators and are resistant to pesticides, such as the locust. A way of killing these types of pests is to put a disease in to the population. This is an expensive method of pest control, but it can help pest control national as the disease is spread. To prevent any other species being killed by the disease, it must be specific to the pest.
A problem with spreading disease in to the pest population is that once a disease has been introduced to a natural environment, it is impossible to take it out of the environment if necessary. Screwworm flies are flesh-eating insects that lay their eggs in to the wounds of warm-blooded animals, including humans. The larvae then feed on the flesh, which can then get infected, causing the animal to die. These pests have caused havoc in pastoral farms in tropical countries such as Indonesia. They are resistant to pesticides, have no known predators and have a life cycle that allows them to breed incredibly quickly.
However, a solution to the problem of the screwworm fly has been found. There is a factory that breed screwworm fly in cages. The larvae are collected are collected at a very specific stage in their life cycle and are subjected to a source of gamma radiation. This makes them sterile. The infertile larvae are then put amongst the population. This stops them from breeding so they will eventually die out. This is an expensive procedure but it is very effective. A simple solution to the problem of pest control would be for farmers to stop using chemical pesticides. However many are reluctant to do so, usually due to ignorance.