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Pest control
Fichas del conjunto (22)
- 1What are pests and what do they do?• Pests are organisms that reduce agricultural productivity or the quality of the product.
• This may be done by: eat crops or livestock, compete for resources, be pathogens, carry pathogens and reduce marketability. - 2Endemic and epidemic pests Indigenous and introduced pests• Endemic are always present, usually in small numbers.
• Epidemic are not normally present but there may be outbreaks where they rapidly become a problem.
• Indigenous species are native to the area. Many pests have been introduced so these are often more of a problem as they make not have any predators in the area - 3Cultural pest control. What is it and what are the methods used?• This involves non-pesticide methods where crops or livestock are cultivated to reduce the risk of pest damage.
-Crop rotation
-Companion crops
- Predator habitats
-Biological control
-Sterile male techniques
- Pheromone traps
- Genetic resistance to disease
- GM crops and pest control - 4Crop rotationIf the same crop is grown in consecutive years the pests from the first year may survive. This allows the pest population to increase and cause more damage. Crop rotation means the cultivation of different crops each year so the remaining pests will die off before the crop is grown again.
- 5Companion cropsCrops which if grown together will be more productive. There a number of inter-species relationships between companion crops: legumes can be intercropped among other crops to increase nitrate levels, smell of onions can mask the smell of carrots and reduce damage by carrot root flies, flowering plants support bees which are important for pollinating fruit crops.
- 6Predator habitatsThe populations of pest predators can be increased by providing suitable habitats such as beetle banks and hedgerows for beetles and ladybirds that eat greenfly and black fly.
- 7Biological controlPredator or pathogen species introduced to control pests. Especially important if the pest is a non-indigenous species that has been introduced and has no indigenous predators. Specialist feeders will eat the pest species and if they have a wider diet then they may eat beneficial and other non-target species.
- 8Case study of successful biological controlPrickly pear cactus introduced into Australia from South America where it had no predators. Controlled by Cacoblastis moth from South America.
- 9Case study of biological control that went wrongCane toads introduced to Australia to control beetle pests of sugar can but have eaten a wide range of other species. They are toxic so have few predators and have colonised a huge area. African land snail was introduced to islands of Polynesia in the Pacific Ocean as a source of human food but it spread and ate farmer’s crops. The Florida Wolfsnail was introduced to control the African Land snail but they also ate the indigenous Partulid snails.
- 10Sterile male techniquesMany species females only mate once then store sperm for future egg laying. This method involves producing many sterile males by exposing them to gamma radiation. If enough are released the number of fertile mating’s will be reduced to a level below that needed to produce enough young to compensate for mortality, so the population would decline. Pests that have been controlled by this method include: Mediterranean fruit fly and sweet potato weevil in Japan. Only affects the specific species target but is only successful is the males behave normally.
- 11Pheremone trapsIn many insects species mates are attracted by pheromone. Traps release an artificial scent that attracts the pests and they can be used to show the pest is present so that pesticides can be used, or to kill the pests. They are used for w wide range of pest taxa including moths, weevils and flies.
- 12Genetic resistance to diseaseWith all species there is a range of genetic characteristics for every environmental adaptation. Selective breeding may enhance the resistance to pests or disease. Pathogens can evolve to overcome crop disease resistance so it’s necessary to increase new characteristics to maintain resistance. This may be done through CWR’s and crop breeding programmes. However these genetic resources are threatened by habitat loss and the spread of commercial crop varieties with small gene pools.
- 13GM crops and pest controlthe DNA of a crop can be modified to control pest more effectively.
- 14Pest control using chemical pesticides. What is it and what are the factors?The properties of pesticides influence their effectiveness and environmental impacts.
Toxicity
Specificity
Persistence
Solubility in water/liquids
Mode of action
Antibiotics
Hormone pesticides
Integrated control - 15Toxicitypesticides which have a high toxicity require the use of smaller volumes. Most pesticides act by inhibiting enzyme action.
- 16SpecificityA measure of the range of taxa affected. More specific pesticides are less likely to harm non-target species
- 17PersistenceThese pesticides are chemically more stable and degrade slowly. This reduces the frequency of re-application but increase the risk of it dispersing more widely into the environment and may extend the time it can harm non-target species.
- 18Solubility in water/liquidsPesticides that are water soluble are more likely to be washed off a crop, requiring re-application. Liposoluble pesticides may be absorbed and stored within the crop, possibly entering the human food chain.
- 19Mode of actionThere are two main modes of action y which chemical pesticides kill pests: Contact action: kill plants by the tissue which the herbicide is sprayed onto. Contact insecticides kill plants that come in direct contact with the pesticide. Pesticide only protects the crop surface which it was sprayed on to. Unsprayed surfaces are not protected. The pesticide could also be washed off by train.
Systemic action: these pesticides are absorbed by the plant. It protects all of the plant and all new growth. It can’t be washed off by train but may remain in the harvested crop and be eaten by humans.
Washing food may remove contact pesticides but not systemic pesticides so a good time should be left between application and the harvesting of the crop. - 20AntibioticsThese are chemical that kill microbes such as pathogenic bacteria. They can be used in farming for many reasons:
To treat infections
To prevent infections in a large livestock group. This may be done as a precaution if the stock density is large such as intensive production units
To promote growth. Small doses of antibiotics can kill non-pathogenic gut bacteria which means more of the animals food is used for growth therefore increasing productivity and farm income.
Exposure to high doses of antibiotics can kill all pathogenic organisms but exposure to low doses may only kill sensitive individuals so the rest of the population can still reproduce. The large scale use of antibiotics for growth can increase the risk of antibiotics resistance. Some of these may be zoonoses such E.coli which can humans to become ill. - 21Hormone pesticidesKill pests through their biochemical actions. Not toxic action but increasing or starting natural processes in a way that is harmful to pests. Some cause them to metamorphose into adults before they are large enough to function properly so they die and others prevent the formation of the skeleton when they moult.
- 22Integrated controlEach control technique has advantages and disadvantages. The use of a combination of techniques can maximise effective pest control. Integrated control often has an order based on cost and ease of use, effectiveness and environmental impacts. The principles: use of cultural techniques which make the growth environment less suitable for pests, use of cultural techniques that prevent the build-up of a pest population, cultivating species and varieties that are less likely to suffer from pests, use of appropriate non-pesticide techniques and finally use of pesticides when essential.
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- A level Environmental Studies Fichas sobre Pest control, creado por Mollie Munday el 25/09/2018.
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- Mollie Munday
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