Essay on Biological Control of Gorse
Gorse (Ulex europaeus) was introduced to NZ from Western Europe as a hedge plant before 1838; it grows at a fast rate and has the ability to grow up to 4 meters long in NZ. They have an average life- span of 29 years and can produce 34,000 seeds per meter square per annum. Its seed is extremely long lived and they normally germinate in autumn or spring to mid-summer. Seedpods explode when exposed to full sunlight. The seeds are scattered by water, birds, animals, farm machinery and road equipment. Gorse can be found in flower in almost any month, but the main season is spring. It can grow in almost all soil types because it's a nitrogen fixer, which means it can improve the condition of the soil by itself and this gives the advantage of the plant invading new areas.
The reason that biological control is needed for gorse is because gorse had broke the ecological equilibrium of the environment. Gorse is considered as a pest because it has the ability to invade new areas of pasture and form dense thickets. Its seed can remain germinable up to 30 years in the soil. Since gorse had so many characteristics that would break the balance of the ecosystem, biological control is introduced in order to limit the population growth rate of the gorse. Gorse had invaded the farm area of NZ and it forms dense spiny stems imbedded in sheep's wool lowered wool's value. The dense impenetrable thickets restricts the grazing area and prohibit native plant species or pastoral crop's growth, since the sun light had been blocked by the thickets and the plants growing under it can't carry out the process of photosynthesis. Also it provides habitat for animal pests and presents a fire hazard. Since both chemical and physical removal is costly and ineffective, bio-control is the best solution.
Biological control is a good method of controlling gorse because it's much more effective than the chemical pesticide and less expensive, it's natural and wouldn't pollute the environment, it's cheaper than hiring people to remove the gorse and the seeds in soil then replace the soil to prevent the gorse growing back and it's better than starting a fire and destroy the community living in that environment.
Herbicides had been used in controlling gorse, but most of the herbicide didn't have much effect on gorse and chemicals that work on gorse were expensive to make.
Therefore after a period of time chemical control was abandoned even though it was once considered as the best solution. Chemical control also brings pollution and could harm animals and plants living in the area were chemical control had taken place. Biological control is natural and it wouldn't pollute the environment like the chemical does, but help to reach ecological equilibrium. Also it's cheaper and effective than the chemicals.
Physical removal is expensive and ineffective because the task of removing gorse physically is very hard and takes a lot of time and money. Therefore it's not being widely used. The soil that the gorse had grown on also needs to be removed to prevent the seeds left in the soil have the chance to revive gorse population. As for the bio-control different agents were introduced to attacks different parts of gorse, both gorse seed weevil (Exapion ulicis) and gorse pod moths (Cydia succedana) attacks the seeds therefore there would be no worries about the seed problem. Gorse spider mites (Tetranychus lintearius), gorse thrips (Sericothrips staphylinus), soft shoot moths (Agonopterix ulicetella) and hard shoot moths (Scythris grandipennins) are used to attack stems and leaves. This obstructs the plant to carry out photosynthesis and therefore weakened the plant's growth rate and may cause death.
Manage the gorse by fire had been carry out. But since the wind direction is unpredictable, the fire had often invaded the area that is not related and destroy the communities in the environment although it was claimed as controlled burning. Burning gorses also pollutes the environment because it produces carbon dioxide and nitrogen dioxide, which could cause acid rain and suffocate the animals. Biological control wouldn't have these problems and is more effective because the gorse can survive in the area since fire didn't burn the soil the trees and the seeds can survive and grow.
Even though some people is afraid that the bio-control agents will be out of control and kill other plants and bring diseases, it was not considered as a problem because the agents that are chosen to control gorse were carefully selected to ensure that they will do no/little harm to other plants or animals and they will not bring diseases, so there is nothing to worry about. As for the people that were afraid of the agents becoming over populated they don't have to worry because if all the gorse were destroyed in NZ there would be no food source left for them and they'll die soon after all the gorses were destroyed.
Biological control was once considered as useless because of the failure of the gorse seed weevil. The result of this agent was not as great as what had been expected because the gorse can forms seeds in both spring and autumn, while gorse seed weevil is only active in spring. Therefore although gorse seed weevil can destroy over 90% of the spring seeds there are still seeds remained from autumn. But people did not realize this and said bio-control is useless. Now the statement was known as wrong since the gorse pod moth was introduced which compensate with seed weevil, it can attack the seeds of gorse from autumn to summer and the seeds of gorse were effectively controlled.
The principle of biological control is by using the nature enemy of the of the pest species to control the pest population. In the case of gorse the principles used were parasitism (occurs when one organism live in or on a larger organism and feeding of it) and herbivory (occurs when the herbivore gains the food source from plant) both principles belongs to the interaction of exploitation бV one species benefits at the expense of the other. And by using these two principles gorse is being controlled effectively today. By the principles of parasitism and herbivory the bio-control agents gorse seed weevil, gorse pod moths, and gorse spider mites gorse thrips, soft shoot moths and hard shoot moths were used since all of them feeds on gorse either as a parasite or herbivore.
The result of the bio-control is great by using the gorse seed weevil and gorse pod moths together. They have destroyed over ninety percent of the annual seed production of gorse. The gorse spider mites and gorse thrips had slow down the gorse growth rate by sucking the sap, this bleaches the leaf so it can't carry out the process of photosynthesis and therefore slow down the growth rate. As for the soft shoot moths and hard shoot moths there is not enough information to say if it's a success or not.
In conclusion from the researched information we can see that bio-control is the best solution for the gorse problem because it's much more effective and less expensive than the herbicides and physical removal and it won't cause pollution like the chemical pesticides or controlled burning. Most importantly it will not harm the communities in the environment.
The reason that biological control is needed for gorse is because gorse had broke the ecological equilibrium of the environment. Gorse is considered as a pest because it has the ability to invade new areas of pasture and form dense thickets. Its seed can remain germinable up to 30 years in the soil. Since gorse had so many characteristics that would break the balance of the ecosystem, biological control is introduced in order to limit the population growth rate of the gorse. Gorse had invaded the farm area of NZ and it forms dense spiny stems imbedded in sheep's wool lowered wool's value. The dense impenetrable thickets restricts the grazing area and prohibit native plant species or pastoral crop's growth, since the sun light had been blocked by the thickets and the plants growing under it can't carry out the process of photosynthesis. Also it provides habitat for animal pests and presents a fire hazard. Since both chemical and physical removal is costly and ineffective, bio-control is the best solution.
Biological control is a good method of controlling gorse because it's much more effective than the chemical pesticide and less expensive, it's natural and wouldn't pollute the environment, it's cheaper than hiring people to remove the gorse and the seeds in soil then replace the soil to prevent the gorse growing back and it's better than starting a fire and destroy the community living in that environment.
Herbicides had been used in controlling gorse, but most of the herbicide didn't have much effect on gorse and chemicals that work on gorse were expensive to make.
Therefore after a period of time chemical control was abandoned even though it was once considered as the best solution. Chemical control also brings pollution and could harm animals and plants living in the area were chemical control had taken place. Biological control is natural and it wouldn't pollute the environment like the chemical does, but help to reach ecological equilibrium. Also it's cheaper and effective than the chemicals.
Physical removal is expensive and ineffective because the task of removing gorse physically is very hard and takes a lot of time and money. Therefore it's not being widely used. The soil that the gorse had grown on also needs to be removed to prevent the seeds left in the soil have the chance to revive gorse population. As for the bio-control different agents were introduced to attacks different parts of gorse, both gorse seed weevil (Exapion ulicis) and gorse pod moths (Cydia succedana) attacks the seeds therefore there would be no worries about the seed problem. Gorse spider mites (Tetranychus lintearius), gorse thrips (Sericothrips staphylinus), soft shoot moths (Agonopterix ulicetella) and hard shoot moths (Scythris grandipennins) are used to attack stems and leaves. This obstructs the plant to carry out photosynthesis and therefore weakened the plant's growth rate and may cause death.
Manage the gorse by fire had been carry out. But since the wind direction is unpredictable, the fire had often invaded the area that is not related and destroy the communities in the environment although it was claimed as controlled burning. Burning gorses also pollutes the environment because it produces carbon dioxide and nitrogen dioxide, which could cause acid rain and suffocate the animals. Biological control wouldn't have these problems and is more effective because the gorse can survive in the area since fire didn't burn the soil the trees and the seeds can survive and grow.
Even though some people is afraid that the bio-control agents will be out of control and kill other plants and bring diseases, it was not considered as a problem because the agents that are chosen to control gorse were carefully selected to ensure that they will do no/little harm to other plants or animals and they will not bring diseases, so there is nothing to worry about. As for the people that were afraid of the agents becoming over populated they don't have to worry because if all the gorse were destroyed in NZ there would be no food source left for them and they'll die soon after all the gorses were destroyed.
Biological control was once considered as useless because of the failure of the gorse seed weevil. The result of this agent was not as great as what had been expected because the gorse can forms seeds in both spring and autumn, while gorse seed weevil is only active in spring. Therefore although gorse seed weevil can destroy over 90% of the spring seeds there are still seeds remained from autumn. But people did not realize this and said bio-control is useless. Now the statement was known as wrong since the gorse pod moth was introduced which compensate with seed weevil, it can attack the seeds of gorse from autumn to summer and the seeds of gorse were effectively controlled.
The principle of biological control is by using the nature enemy of the of the pest species to control the pest population. In the case of gorse the principles used were parasitism (occurs when one organism live in or on a larger organism and feeding of it) and herbivory (occurs when the herbivore gains the food source from plant) both principles belongs to the interaction of exploitation бV one species benefits at the expense of the other. And by using these two principles gorse is being controlled effectively today. By the principles of parasitism and herbivory the bio-control agents gorse seed weevil, gorse pod moths, and gorse spider mites gorse thrips, soft shoot moths and hard shoot moths were used since all of them feeds on gorse either as a parasite or herbivore.
The result of the bio-control is great by using the gorse seed weevil and gorse pod moths together. They have destroyed over ninety percent of the annual seed production of gorse. The gorse spider mites and gorse thrips had slow down the gorse growth rate by sucking the sap, this bleaches the leaf so it can't carry out the process of photosynthesis and therefore slow down the growth rate. As for the soft shoot moths and hard shoot moths there is not enough information to say if it's a success or not.
In conclusion from the researched information we can see that bio-control is the best solution for the gorse problem because it's much more effective and less expensive than the herbicides and physical removal and it won't cause pollution like the chemical pesticides or controlled burning. Most importantly it will not harm the communities in the environment.
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