Crop Protection Flashcards
What is a monoculture?
A monoculture is a vast population of a single species of crop plant cultivated over a large area
Often the members of the population are genetically identical providing ideal growing conditions for pests
Describe competition
Plants growing side-by-side will compete for light, water, nutrients and space
Describe competition in a monoculture
Competition among members of the monoculture is reduced by spacing the plants out however weeds can grow in these gaps and cause competition
What is the effect of weeds as competition?
Weeds reduce productivity because they cause competition and release chemical inhibitors which reduce crop growth
Characteristics of perennial weeds
Asexual reproduction
Storage organs provide food without the need for photosynthesis
Characteristics of annual weeds
Rapidly produce flowers due to the short life span
Produces a large number of seeds
Produces which can lie dormant for very long periods of time
Grow very quickly
Harmful effects of invertebrate pests
Damage to leave reduces photosynthesis, hence less sugar produced
Lots of sugary sap reduces energy supply to tissues
Describe plant diseases
Plant diseases are caused by pathogens such as fungi, bacteria or viruses which are often carried by invertebrates
Diseases cause poorer yield, Reduced market ability (blemished), reduced storage life (degrade too quickly)
Methods of crop protection/ control of pests through cultural means
Crop rotation
Ploughing
Removal of alternative hosts
Describe crop rotation as a cultural method of controlling pests
Crop rotation helps put nitrogen back in the soil
It is the practice by which each of a series of very different types of crop plant is grown in turn on the same piece of ground
Pests will be unlikely to survive in the time it takes for its host plant to return to the same plot of land
Crop rotation works best against soil inhibiting pests that are only able to attack a narrow range of host plants
Describe ploughing as a cultural method of controlling pests
Ploughing is we are the top 20 cm of soil is turned over and many of the perennial weeds are buried to a depth at which they die and decompose
The crop seeds can be planted and become established before the weeds return
Describe removal of alternative hosts as a cultural method of controlling pests
In the absence of their favourite host plant many insect pests are able to survive and breed on alternative hosts such as weeds bordering the field so removing these helps to control pests
Methods of crop protection/ control of pests through chemical means
Herbicides which kill weeds
Pesticides which kill invertebrates
Fungicides which kill fungal parasites
Types of herbicides
Selective
Systemic
Contact
Types of pesticides
Contact
Systemic
Types of fungicides
Contact
Systemic
Describe Selective herbicides
Mimic the action of plant growth hormones
Speeds up metabolism of broad leaved plants which uses up food and kills them
Narrow leaved plants aren’t affected by selective herbicides
Usually biodegradable
What should a plant protection chemical be ideally?
Specific to the pest concerned
Short left (shouldn’t persist in the environment and should be broken down into harmless byproducts)
Safe for animals and humans
What are the problems with using chemicals for crop protection and pest control?
Toxicity - plant protection chemicals can be poisonous to more than just the pest
Persistence – Some are not biodegradable so remain in the environment for long periods of time
Bioaccumulation - when concentrations of chemicals increase as you go up trophic levels
Producing a resistant population
What is biological control?
Biological control is the reduction of a pest population by the deliberate introduction of one of its natural enemies
However it may not kill all the best (but it would cause economic damage)
What is integrated pest management?
A combination of techniques including chemical control, biological control and cultural means
It sets out to reduce the need for pesticides while bringing pest populations down to a level at which they can no longer cause economic damage
What are fungicides?
Fungicides can be used to protect crops when environmental conditions and disease forecasts suggest that infection is likely
Prevention is more effective than treatment
What are contact chemicals for control of pests?
Kills pests which are in direct contact with chemical
What are selective chemicals for control of pests?
Designed to only affect one type of pest and leave other organisms unharmed
Describe systemic herbicides
Kills all plant matter and can clear an area before planting crops
Effective as they reach storage organs and root systems
Describe systemic fungicides
Sprayed onto crops and absorbed by plant tissues giving them protection from disease causing fungus
Not washed away by rain giving better protection
Only kill fungi
Describe systemic pesticides
Sprayed onto crop plants and absorbed by plant tissues and will kill pests when they feed on the plant tissues
Describe contact herbicides
Kill all green plant tissue that they come into contact with
Biodegradable- their effect is short lived
Roots survive so plants with storage organs can regrow
Describe contact pesticides
Work in two ways:
- kills invertebrates coming into contact with spray
- leaves a protective layer on plant which will kill future invertebrates
Describe contact fungicides
Sprayed onto crops and absorbed by fungal spores when germination starts casting the fungi to die
Easily washed away by rain so needs to be reapplied regularly
