Biotic Factors And Their Control Flashcards
What are pests?
Organisms that reduce agricultural productivity or the quality of the product
What ways do pests affect crops/ livestock?
Be predators that eat the crop or livestock
Compete for resources such as water or nutrients
Be pathogens that cause disease
Carry pathogens
Reduce marketability
What are some examples of reducing marketability? (Crops)
Spoiling the appearance of fruit
Weed seeds mixing with the cereal harvest
What are problems caused by weeds?
Competition for nutrients, water, light
Harvested with crop, reducing quality or spoiling taste
Provide food for other pests
Parasitism of crop roots
What are some examples of weeds?
Wild oats compete for light, water and nutrients in cereal crops
STRIGA parasitises maize crops
What are problems caused by insects?
Eat the crop, destroy the crop or reduce harvests
Spoil the appearance of harvested crops
Act as vectors and spread pathogens
What are some examples of insect pests?
Aphids (greenfly and blackfly)
Suck sap and reduce growth of many crops (cotton, sugar cane, fruit, cereals)
Aphids carry many pathogenic diseases (potato blight)
What are some problems caused by fungi?
Caused the growing plants or harvested crop to rot
What are some examples of fungi?
Leaf smut (of rice)
Leaf blight (of sugarcane)
What are some problems caused by bacteria?
Reduce harvests by causing disease
What are some examples of bacteria? (Agriculture)
Bacterial wilt (potato)
Bacterial leaf blight (wheat)
What are some problems caused by molluscs?
Eat the crop, reduce harvests or spoil appearance
What are some examples of of molluscs?
Many snails and slugs
What are some problems caused by nematode worms?
Damage roots and reduce water and nutrient uptake
Increase the risks of fungal and bacterial disease
What are some examples of nematode worms?
Potato cyst nematode
Soybean cyst nematode
What are some problems caused by vertebrates?
Eat the growing or harvested crops
What are some examples of vertebrates?
Mammals- mice, rats, deer, rabbits, birds (sparrows)
What are endemic pests?
Always present usually in small or moderate numbers
What are epidemic pests?
Not normally present but may be outbreaks where they rapidly become a major problem
What are indigenous pests?
Native to the area they are found
What are non-native pests?
Pests introduced from another area not naturally found in that area
What is cultural pest control?
Non-pesticide methods where crops or livestock are cultivated in a way that reduces the risk of pest damage, often by using natural ecosystem services
Why is crop rotation done?
Different crops have unique pest species
If same crop grown in same place for several years pests may survive from year to year allowing pest populations to increase and cause more damage
What is crop rotation?
The cultivation of a different crop each year, usually on a four or five year cycle
Pests remaining at the end of one year will have died off before that crop is grown again
What are companion crops?
Crops that when grown together will be more productive
Sometimes north crops will be harvestable
Some times only one of the plants is grown to boost another
How can crops increase nutrient supply?
Legumes can be intercropped among other crops to increase nitrate availability in the soil
How can barrier crops be companion crops?
Smell of onions can mask the smell of carrots and reduce the damage caused by carrot root flies
How are pests attracted to protect other plants?
Nasturtiums attract blackfly pests that could damage bean crops
How can support of pollinators increase growth?
Flowering plants that support bees which are important in pollinating fruit crops
How can the population of natural pest predators be increased?
By providing suitable habitats
What are some examples of provision for predator habitats?
Beetle banks and hedgerows provide habitats and hibernation sites for pest predators such as black ground beetles
What is biological control?
Predator or pathogen species may be introduced to control pests
When is biological control very important?
When a non-indigenous pest is introduced and has no indigenous predators
What needs to be considered for biological control?
Should be specialist feeders so they only eat the pest and not non-target species
What are some successful biological control examples?
Whitefly in greenhouses have been successfully controlled by the introduction of parasitic ENCARSIA wasp
Prickly pear introduced to Australia controlled by introducing CACTOBLASTIS moth
What are some examples of where biological control went wrong?
Cane toad introduced to Australia to control beetle pest of sugar cane ate large range of species apart from target species
African land snail introduced for human food source but ate farmers crops predatory Florida rose wolf snail was introduced to control African land snail ended up eating indigenous snail species
Why is sterile male techniques used?
In many insect species the females only mate once then store sperm for all future egg laying
If a female mates with a sterile male then she will never produce fertile offspring
How is sterile male technique done?
Producing many infertile males by exposing them to gamma radiation they are then released
What species has sterilisation of males occurred in?
Screw worm fly (parasitic to livestock)
Mediterranean fruit fly
Sweet potato weevil in Japan
What must occur for sterilisation of males to be a success?
If sterilised male behaves normally and succeed in finding mates
What are pheromone traps?
Release an artificial scent that attracts pests
What two ways are pheromone traps used?
To show a pest is present so pesticides can be sued to protect crops
To kill all pest individuals or enough so the population can’t recover (usually in greenhouses)
What insects are pheromone traps used on?
Moths
Weevils
Flies
How can GM crops reduce pest risk?
Can be modified to control pests more effectively by reducing susceptibility
How can genetic resistance to pests or disease be created?
Selective breeding for desirable characteristics
What must be done making organisms resistance to disease?
Pathogens evolve so must introduce new characteristics to maintain resistance
What can be done to increase resistance of commercially grown crops?
Breeding with crop wild relatives
What are the properties of pesticides?
Toxicity
Specificity
Persistence
Solubility in water/ lipids
Mode of action
How does toxicity of a pesticide affect its effectiveness?
Pesticides that have a high toxicity require the use of smaller volumes
Most act by inhibiting enzyme action
How does specificity influence the effectiveness and environmental impacts of pesticides?
This is the range of taxa (animals) affected by the pesticide
More specific pesticides are less likely to harm non-target species
How does persistence affect the effectiveness and environmental impacts of pesticides?
Persistent pesticides are chemically more stable and degrade slowly
Reduces frequency of re-application but can increase the likelihood of a pesticide dispersing more widely in the environment
May extend period where non-target species are harmed
How does solubility in water/lipids affect the effectiveness and environmental impacts of pesticides?
Pesticides that are water soluble are more likely to be washed off a crop (need re-application)
Liposoluble pesticides may be absorbed and stored within the crop possibly entering the human food chain
What are the two types of mode action?
Contact action
Systemic action
What is contact action?
Kills insects that directly come into contact with the pesticide that was sprayed on the protected crop
Only protects the crop surface
Unsprayed surfaces (underside of leaves) are not protected
May be washed off by rain
What is systemic action?
Absorbed by the crop and translocated throughout the plant
Protects all of the plant and will protect new growth
Cannot be washed away by rain
Can be retained in the harvested crop and be eaten by humans
What are antibiotics?
Chemicals that kill microbes such as pathogenic bacteria
Why might antibiotics be used in livestock farming?
To treat infections
Prevent infection
Promote growth
How can antibiotics be used to treat infection?
Course of bacteria may kill pathogen bacteria
How can antibiotics prevent infections?
Regular large doses of antibiotics prevent livestock from being infected with pathogenic bacteria
May be a precaution in high density intensive units
How can antibiotics promote growth?
Used to increase efficiency of livestock growth
To reduce population of non-pathogenic gut bacteria
Increase amount of food that is used for growth
What is the main problem with the use of antibiotics in agriculture?
Can lead to antibiotic resistance in organisms
what is integrated control?
the use of a combination of techniques can maximise effective pest control while minimising environmental impacts
what will affect the order in which integrated techniques are used?
based on cost
ease of use
effectivesness
environmental impacts
what are the principles for intergrated control?
cultural techniques which make the growth environment less suitable for pests
cultural techniques that prevent the build-up of pest populations (crop rotation)
cultivating species and varieties that are less likely to suffer pest attack
use of other appropriate non-pesticide techniques
use of pesticides when essential (carefully timed, specific and non-persistent pesticides)
what % of plant reproduction is assisted by pollinators?
80%
what are some examples of pollinators?
bees
moths
beetles
other taxa
how can pollinators be aided?
provision for food supplies (plants that provide nectar)
flowering plants alongside the crop
restrciting the use of pesticides that harm pollinators (neonectoids)
introduciton of bee hives
what are soil biota important for?
soil fertility and crop productivity
what types of soil biota are particulary important?
detritivores
decomposers
what does soil biota do?
increase nutrinet availablity through the breakdown of dead organic matter
nitrogen fixation
how does decomposition release nutrients from rocks?
organic acids produced increase the weathering of rocks that releases nutrinets into the soil
why are earthworms important?
increase aeration and drainage which aid aerobic processes and water retention
Where uses more antibiotics agriculture or human healthcare?
Agriculture
what will exposure to a high dose of antibiotic do?
kill all of the pathogen population
what is the problem with exposure to a lower dose of antibiotic?
may only kill most sensitive individuals so the surviving population will be less easily controlled by the antibiotic
What are Zoonoses?
antibiotic resistant bacteria which causes disease if transferred to humans
What are some examples of Zoonoses?
E.coli
salmonella
what are hormone pesticides?
these kill pests through biochemical action
|How do hormone pesticides work?
don’t kill by toxicity
increase or start natural processes in a way that is harmful to pests
What are some examples of the effect of hormone pesticides?
can cause insects to metamorphose into adults before they are large enough to function properly
prevent formation of chitin skeleton when they moult
what are the characteristics of hormone pesticides?
low persistence
more specific
