Food is vital for humans to survive, the population of the world is immense as it approaches 6 billion and all these humans need to be fed on a continual basis. Therefore, a large quantity of food needs to be produced rapidly and on a very large scale. Generally farmers across the western world do produce food very quickly and efficiently and there tends to be a surplus of food, whereas, in less developed countries they have a shortage of food. Due to the size of the world's population and it's high levels of demand for food farmers are unable to leave crops alone and let them grow naturally.
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For example, one-third of the crops that are grown worldwide are spoiled by pests, animals particularly insects and many plants. Certain types of crops grow better in certain set conditions and there are many different factors which effect the crop yield. Crops grow by photosynthesis, the environmental factors affecting the rate of photosynthesis, are light intensity, concentration of carbon dioxide in the air, and the surrounding temperatures.
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All the requirements for photosynthesis need to be available at a good rate and supply, the light intensity which is usually supplied by the sun needs to be at suitable intensity, which means the crop will only grow certain times of the year due to the amount of light available. The same applies to the concentration of carbon dioxide, which usually does not tend to cause a problem, as there is ample supply of carbon dioxide in the surrounding air, however if it is ever to run low the crops will not grow.
The temperature is another factor which has a huge effect on the growth of crops, if the temperature is to get too high this would prevent any growth of the plant as it would not be able to deal with the extreme temperature killing off the chlorophyll that the plant requires to grow. However if the temperature is decreased to a very low temperature this will restrict any growth, as the plant will not be able to function properly. Therefore, all these factors need to be at the correct rate for the crop to be able to grow sufficiently.
Many different types of crops such as maize, corn, wheat, rice, fruit and vegetables are grown at different times throughout the year and most farming is usually based on monoculture. Which is where one type of crop is grown in a certain piece of land, this technique of mass production tends to cause many problems and is not as straight forward as it seems. If crops are growing extremely well and conditions are correct and all the crops have all their requirements at the right rate and intensity there is still one other factor which would still prevent a perfect yield from being produced which are known as pests.
These pests still destroy all crop yields, by destroying the crop its self and restricting growth in certain ways. When crops are grown they are just like plants in that they compete for mineral ions, water from the soil and light, however when crops are grown using the monoculture method there usually isn't a problem because it's the same crop being grown and so the conditions can be controlled.
However, the problems that do arise is that if there is a large concentration of the same crop in one area and they are all in close proximity to each other then there is the potential of the crop being infected by diseases, fungi, unwanted plants and insects which will then lead to the rapid destruction of large areas of the crop. There are a number of different pests, for example, insects, fungi and weeds that effect individual crops in different ways; like insects, fungi and weeds. Weeds are plants that grow in places we do not want them to grow and there optimum growth occurs in ground disturbed by human activity.
They compete with cultivated plants for space, water and minerals. Worldwide, about 10% of crop yield are lost because of weed growth. Weeds tend to come in different sizes and they can be long and the same length as the crops, which means their roots are able to reach deep into the ground and take the nutrients, they require leaving many shortages for the crops. Also weeds can sometimes have broad leafs that cover the crops and so take all the sunlight and restrict the amount of sunlight reaching the crop. The competition between the crops and weed, which is organisms of different species, is known as interspecific competition.
Occasionally you may come across weeds that are very small and do not do any real harm to the crops. The insect pests work in many different ways, each kind of plant has its own species of aphids, and these little creatures have small mouthparts, which they use to suck sap from plants. The loss of sap can be harmful to the plant in many ways in that, it can cause leaves to curl up and become distorted. The leaves are the place where photosynthesis takes place; the curled up leaf leaves the plant unable to photosynthesise efficiently and so can leave the plant stunted.
Another way in which aphids can effect crops are, that as the aphids suck in the sap if that crop was diseased they could pick up the disease or virus and then go suck on another plant which would then pass the disease or virus on, which would spread the disease to many plants, any organism which spreads disease or viruses from host to host is known as a vector. Also if the aphids take in to much sap they tend to secrete it through their abdomens, this is usually a sticky honey dew which forms a sticky droplet which attracts ants, which then attack the crop even further.
So altogether there are a number of ways in which crops are prevented from being grown. The ways in which these pests can be controlled and crops can be grown without too many problems is that we can put into the environment a chemical substance that kills the pest, which is called pesticides, or we can put into the environment another organism, which kills the pest, which is known as biological control. A pesticide is any substance or mixture of substances intended for preventing, destroying, or repelling any pests. Chemical control is the use of pesticides. Insects, which eat crops, can be killed with insecticides.
Fungi, which grow on crops, are controlled with fungicides. Weeds, which compete with crop plants for water, light and minerals, can be controlled with herbicides; pesticides are usually applied as pellets, powders or sprays. Many different chemical substances are used as pesticides; there are contact pesticides, systemic pesticides and residual pesticides. The contact pesticides are used as spray as they are sprayed straight on to the crop where the pests are living and as the contact insecticides spray comes in contact with the insect, the insect tends to absorb it in through its gas-exchange pores, the spiracles, along its body.
This is where it attacks the insects and poisons them. The same process occurs with contact herbicides and fungicides the surface of the plant absorbs the poison through, and so the poison then attacks it there. This method is not very expensive however they need to be reapplied continuously as there are always pests, which are missed out, and the affect of it does not last very long. Systemic pesticides work in a similar way as they are sprayed straight on to the crop where the leaves and surface of the plant absorbs it in and so it is transported all around the plant.
Therefore, whenever a sap-sucking insect comes along it sucks the poison into its body, and this eventually results in the killing of the creature. This method for systemic insecticides is very effective because the spray does not have to come into contact with the insect so it only attacks the insects that attack the crops. Systemic herbicides are also quite effective in that they are able to be sprayed onto the surface of the leaf where they get absorbed and then have that poison transported all along the weed killing off the tissue and even reach the roots.
Residual pesticides can also be quite effective, as they are also sprayed directly on to the soil and instead of attacking the actual insect or weed they attack any insect egg and larvae, and weed seedling as they germinate. All these methods are used for chemical pest control; chemical pest control is very effective in that this is the most popular method in the UK for farming large number of crops, to provide the large population of the UK. However even though chemical pest control is very effective and is very popular there are a number of disadvantages of using chemical pesticides.
Firstly, chemical pest controls involve many chemicals that can be very dangerous if they are not monitored correctly. Therefore, chemical pest controls must be safe for farmers to use and must not damage the environment. To provide this there must be continual testing and development carried out on all pesticides. This can be very expensive and this expense will be passed onto the farmer in the form of the pesticide costing a huge amount of money.
This expense is taken by the farmer on the premise that it will assist in the good growth of his crops, however, the disadvantage being that it may not work at all! It is also known that pesticides damage the environment a great deal, Pesticides can badly affect wildlife through changes in the food web, direct and indirect poisoning. And their harmful effects may show up in animals, which have no direct relationship to the original pest. In that in the 1950's many of the pesticide used did a lot of damage to the environment especially one DDT (dichlorodiphenyltrichloroethane).
It was used to kill insects, however people didn't realise that it is a persistent insecticide, which means it doesn't break down but remains in the body of insects and the soil. So whenever a bird or other organisms ate the insects they ate the DDT too. And so the DDT stayed in their bodies and just began to accumulate. Also as well as being persistent it was also non-specific as most pesticides are. This means that it not only harms the insect it's meant to but also harms other living things. For example in the 1960s, the gannet population in Quebec began to shrink.
The shells of the gannets' eggs were too thin to protect the embryos. Once the egg had been examined they realised DDT was the culprit. Because there where large concentration of DDT in the birds because of all the pests they had consumed which had been sprayed with it. Many other birds such as ospreys, eagles and peregrine falcons also had been affected greatly and populations of those birds had declined. Also all the chemical sprays that are sprayed into the air will have a great effect on the atmosphere.
So many pesticides harm the environment a great deal, even though many tests are done before hand. Pesticides also change wildlife habitat, for example if a herbicide was put down on certain plants or vegetation, animals that depend on that piece of vegetation find it difficult to live any longer and so slowly will begin to die out, and so if they begin to die out then the population of their predator that relies on that particular creature, will begin to decrease. Another problem, that that may arise is if a particular pesticide is used a lot the pest may eventually become resistant to it.
The pesticide no longer kills the pest and so a new one has to be developed at all times which results in more resources and cash flow being ploughed into developing and testing. Also once the pesticides are applied, they can be used up quickly and if it rains they sometimes need to be reapplied which takes much time and effort because special clothing and safety measures need to be carried out each time. The most important disadvantage of using chemical pesticides are that the crops that have been produced using pesticides are now covered with chemicals which we will now eat and which can be very harmful for us.
Another major harm to humans is to farmers, who are using the pesticides and are in contact with it on a continual basis and it has led to them becoming extremely ill, for example, in parts of the UK, farmers and their families are being diagnosed with illnesses, which are associated with pesticide poisoning. Such conditions as multiple sclerosis that are occurring in many of the farmers, especially in the cases where they use sheep dipping as part of their work.
Also in less developed countries the farmers are effected a lot more because they do not have all the specially designed clothing which they require and so in places like Malaysia and Sri Lanka, 7 to 15 per cent of farmers experience poisoning at least once in their lives. The advantages of using pesticides are that all these chemicals do produce the maximum amount of food, which is very cheap for the consumer, because the farmers are able to produce on a mass scale, using the chemicals to make sure they have a high-quality crop yield. Also pesticides work very fast and most of the time instantaneously, once applied to the ground.
With pesticides you usually have a guarantee that they will work and be extremely effective, and solve the pest problem. Chemical pest control is one way to control pests even though there are a number of disadvantages, however the other way to stop pests from destroying crops are by biological control. Biological control is not using chemicals but the use of a specially chosen living organism to control particular pests; the chosen organism may be a predator, parasite or disease, which will attack the harmful insect. It is a form of manipulating nature to increase a desired effect. Examples of this are usually
A bluebird: it eats insects to prevent damage to trees and gardens. They are found throughout the United States, UK and Canada A ladybird beetle: it eats small soft insects, which prevents damage to fruit and crops. They are found throughout North America. A garden spider: consumes insects with wings by catching them in a sticky web that it spins. Usually found in America and UK. Biological control is usually done in three ways known as classical biological control, conservation and augmentation, these are three ways to use these natural enemies against unwanted insect pest population.
Classical biological control is to import which involves travelling to the country or area from which a newly introduced pest originated and returning with some of the natural anomies that attacked it and kept it from being a pest there. New pests are constantly arriving accidentally or intentionally. Sometimes they survive. When they come, their enemies are left behind. If they become a pest, introducing some of their natural enemies can be an important way to reduce the amount of harm they can do.
The second method is conservation; conservation of natural enemies is an important part in any biological control effort. This involves identifying any factors that limit the effectiveness of a particular natural enemy and changing them to help the beneficial species. Conservation of natural enemies involves either reducing factors, which interfere with the natural enemies, or providing needed resources that help natural enemies. The final method is augmentation; augmentation is a method of increasing the population of a natural enemy, which attacks a pest.
This can be done by mass producing a pest in a laboratory and releasing it into the field at the proper time. Another method of augmentation is breeding a better natural enemy, which can attack or find its prey more effectively. Mass rearing can be released at special times when the pest is most susceptible and natural enemies are not yet present, or they can be released in such large numbers that few pests go untouched by their enemies. The augmentation method relies upon continual human management and does not provide a permanent solution unlike the importation or conservation approaches may.
There is also another way in which pests can be controlled using the biological control method, which is known as Biochemical pesticides these are natural occurring substances, which are safe. This is because most plants and animals produce chemicals that can be used, as pesticides, the oils and seeds are usually the substances, which can be pesticides. For example many insects produce chemical substances called Pheromones, which attract the opposite sex. Synthesised pheromones are sometimes used to attract pest insects into traps.
The traps are usually sticky which hold the insects and so enables you to get rid of them by killing off the insects. Another method of biological control is crop rotation this helps to discourage pests. Since different pests affect different crops, crop rotation can be very effective method of pest control. Using crop rotation means that there is high possibility of pests dying out before the same plant is grown on the soil again. In many cases, removing their preferred food and shelter can control pest populations. Examples of crop rotation are below. Year1: potatoes - may be affected by potato cyst eelworm
Year 2: cabbage - may be affected by clubroot and brassica cyst eelworm Year3: beans - root nodule bacteria improve soil nitrate supply All these methods of biological controls can be used however they also have many disadvantages to them, just as chemical control biological control takes more intensive management and planning. It can take more time; require more record keeping, more patience, and sometimes more education or training. Because a successful use of biological control requires a greater understanding of the biology of both the pest and its enemies.
Also often the result of using biological control is not as dramatic or quick as the results of pesticide use, which can react very quickly. The aim is not to wipe out the pest because this could be counter-productive. If the pest were reduced to such an extent that it no longer provided enough food for the predator, then the predator in its turn would be wiped out. The few remaining pest could then increase their population rapidly, in the absence of the controlling agent. The ideal situation is where the controlling agent and the pest exist in balance with one another, but at a level where the pest has no major affect on the crop yield.
Even though biological control has disadvantages it also has many advantages. Biological control, overall is a far safer method as it reduces the environmental and public safety hazards of chemicals, as the food we are eating is not covered with poisonous sprays and the air is not being polluted by sprays which we breath in that can be quite harmful to us. Also biological control is cheaper for the farmer to use overall because like pesticides they don't have to be reapplied continuously, once they have been introduced they begin to work and consume the pest, so together its cheaper and less time consuming and easier to apply.
Another advantage of biological control is that the pest are less likely to become resistant to the control organism then they are to pesticides, which means unlike pesticides a new pesticide doesn't have to be developed on a regular basis. Also unlike most insecticides biological controls are often very specific for a particular pest. The biological and chemical controls of pests work very well individually however the two can be used together, this is known as integrated control.
This method can be very successful as was shown in Indonesia in 1970's, when they began to use large numbers of pesticides to control the pests to produce high yields strains of rice. There where a lot of brown planthopper pests, and so farmers found them selves spraying up to 8 times a season, to get rid of the pests however it was later discovered that the insecticide was the problem of the large number of these pests. This is because the sprays had wiped out all the natural predators of the pest, particularly the spiders and yet only had a limited effect on the pest its self.
So it was here that the integrated control was introduced. With integrated control the use of pesticides is always the last resort with the minimum amount used. This then prevents pests and enables large healthy yields of crops without using too many pesticides, which have many disadvantages. However using integrated pest management is not always easy, the technique requires time, knowledge and dedication on the part of the farmer. Overall when using pest controls there are a number of factors to consider, to get maximum effect and sustain pest control.
The important factors to consider are how efficient each method is at controlling the pest, the cost, damage that might be caused to the environment, and possible health hazards. When considering how efficient each method is at controlling pests I think both are quite good in their own way in that biological control is aimed at the one pest whereas chemical pesticides tend to infect all insects and plants that they are sprayed on. However at the same time chemical works a lot faster and targets the problem more efficiently whereas biological takes a lot more time to establish its self to the environment and take effect.
The cost is a lot cheaper for the biological, because even though it costs a lot to research and develop to make sure everything is correct and working well, it doesn't cost the farmers a lot to get the method started, and once it has been applied it doesn't have to be re-applied continuously like chemical control. Also with chemical control there is the extra cost on top to develop and test the chemical product, also new chemical products need to be developed continuously at all times because pests become resistant to them quickly unlike biological control.
Even though biological requires a lot of development, training and testing it only has to be done once and then there usually is a result, and doesn't have to be repeated over and over again to develop new pesticides like chemical control. Damage that might be caused to the environment is mostly caused by chemical control because there are a number of pollutants sprayed into the air, which infect the atmosphere, and there are a lot of chemicals going in to the soils, which also damages the soil.
Also if pesticides are persistent a large concentration can be built up in different animals, which can cause problems and be dangerous to those animals. Additionally pesticides are not selective and harm creatures that don't need to be infected; also a number of habitats can be destroyed when certain plants are killed. Whereas biological don't have any environmental effects and so biological controls would be a better one to use. Possible health hazards are that chemical controls can be dangerous to the people who have to apply them to the ground and also the food we eat has absorbed the spray and so they can infect us and harm our bodies.
However biological controls do not have any health hazards, therefore, are very safe and is the better one to use. In addition in the developed world we have become increasingly concerned about the long-term effects that chemical pesticides and herbicides may have on us as we eat our well-sprayed food. We have also become progressively greener over recent years, with more and more people expressing concern over the future of the earth and our effect on it. Substituting biological control for chemical intervention therefore seems like a very good idea.
The developing world cannot yet afford such concerns the main struggle for many developing nations is to be able to feed all their hungry mouths. But in these countries too the cost of chemical control and the increasing resistance of pests to the expensive chemicals are adding another powerful voice to the arguments in favour of biological control as an integrated part of pest management. So overall the one I think is best and has least problems and safest to use is the biological controls.
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