3.3 Crop Protection Flashcards
What is the productivity of crops affected by?
competition with weeds
What is a weed?
A weed is defined as simply a plant growing in the wrong place
A field planted with rows of potatoes may be contaminated with weeds growing both between the rows of potato plants, and between the individual plants themselves
TOPTIP
Plant productivity is the rate of new material (biomass) per unit area per unit of time factors limiting the rate of photosynthesis and therefore plant productivity include light intensity, carbon dioxide concentration and temperature.
TOPTIP
When two or more members of a community need the same resources which are in short supply competition occurs. Plants compete for light, water, minerals and root space.
Crop weeds that grow among crop plants reduce what?
reduce yields by competing for resources needed by crops
What two types of plants can weeds be?
annual or perennial plants
Adaptations of annual weeds?
sexual reproduction short life cycle (one year) rapid growth high number of seeds produced dormant seeds remain viable for long periods of time
Examples of annual weeds?
goosegrass, knotweed, sheperd’s purse
Adaptations of perennial weeds?
asexual production long lifecycle (two years +) broken pieces of plant can root and grow into individual plants storage organs provide food for plant in autumn/winter
Examples of perennial weeds?
couch grass, nettles, buttercup
Examples of pests?
Insects cause leaf damage such as greenfly, blackfly and leatherjackets
Nematodes are roundworms in soil that attack roots and storage organs
Molluscs like slugs and snails damage leaves
Examples of Diseases?
Fungi - yellow rust on leaves of cereal plants; brown rot on stone fruits, peaches and plums
Bacteria affect stems, roots and leaves and cause leaf spot, blight and galls
Virus - yellow mosaic of lettuce leaves caused by lettuce mosaic virus reduces photosynthesis
TOP TIP
A vector is any agent such as an animal which carries and transmits a pathogen into another living organism
Some invertebrates are also vectors of fungi bacteria or viruses and so are responsible for transmitting plant diseases
TOPTIP
A weed is a plant growing in the wrong place
TOPTIP
Weeds within a growing crop can
compete with crop plants for nutrients
contaminate crop at harvest time
release chemicals into the soil which inhibit the growth of the crop plant provide habitats for pest species
What are methods that can control crop pests?
prevention
cultural control
chemical control
Explain the method prevention?
preventing the introduction of weeds to the soil can be easier than removing established weeds
Good practice includes the removal of weed seeds and vegetative structures from tools and machinery used to prepare the soil, ensuring seeds are certified to be free of weeds and controlling weeds in the surrounding areas
Explain cultivation control?
cultivation and good management of soil help to prevent the build up of weeds, pests and diseases.
There are 4 methods of cultivation these are?
Ploughing
autumn sowing
weeding
crop rotation
Describe Ploughing?
This destroys perennial root systems in the soil and clears the field of any previous crop residue which may harbour some pests and plant diseases
Describe autumn sowing?
seeds planted in the autumn allow a crop to become established before a surge of pests and diseases in the spring, improving crop tolerance
Describe weeding?
Growing weeds are removed by cultivation between rows of crop plants
Describe crop rotation?
Planting different crops in each field each year helps to break the lifecycle of pest species
What are herbicides, pesticides and fungicides?
chemicals that are sprayed onto a growing crop
What are herbicides?
chemicals that kill weeds and are grouped according to how they attack a weed
contact - non selective kills all green plants on contact e.g. resolva
selective - selective attacks only broad leaved plants, narrow leaved plants such as grass are unaffected e.g. preen
systematic - non selective herbicide absorbed into the transport system of the plant (xylem and phloem) Kills all parts of the plant e.g. roundup
What are pesticides and fungicides?
chemicals that kill pests and fungal species on plants
Describe pesticides by contact and systematic?
contact - kills pests on contact with spray
systematic - spray absorbed by plant to prevent invasion and growth of fungus
Describe fungicides by contact and systematic?
contact - sprayed onto crop to prevent growth of fungus, following consultation with the disease forecast or the region
systematic - spray absorbed by plant to prevent invasion and growth of fungus
Disadvantages of chemical crop protection?
Toxic to wild animals
Chemical remains in the soil and surrounding environment following harvest of crop
Chemical enters the food chain and bioaccumulates in the body tissues of animals. The concentration of the chemical increases through the trophic levels of the food chain, with the final predator containing the highest concentration of the chemical in body tissues such as fat -this is called biomagnification
TOPTIP
An adaptation is an inherited characteristic that makes an organism well suited to survival in its environment or niche
Organisms which are better adapted to their environment are more likely to survive reproduce and pass on their favourable genes to their offspring
this is survival of the fittest and is the basis of natural selection
What are disease forecasts?
plant disease forecasting is used to predict the likliehood of the occurence of a plant disease
Fungal diseases in particular are influenced by climate and weather patterns so collaboration between plant pathologists and meteorologists allows predictions about the risk of disease.
This enables farmers to make decisions about applying a particular fungicide to protect crops applying a particular fungicide to protect crops before they become they become diseased which is more effective than treating a diseased crop
What is biological control?
no chemicals are used
pest population is reduced by the deliberate introduction of a natural predator
A greenfly infestation in a glass house can be biologically controlled by introducing ladybirds which eat greenfly
Introduction of a natural parasite or disease may also reduce pest numbers
Example 1 Glasshouse Whitefly?
glasshouse whitefly is a common pest in greenhouses and has a large range of host plants including tomatoes, cucumber, peppers, grapes and beans
The flies suck sap from the phloem, which results in reduced plant vigour, stunted growth and leaf fall
They also secrete a sticky fluid called honeydew on the host plants allowing mould to grow on the leaves
Insect populations reproduce rapidly and many pesticide resistant strains have evolved, making biological control more effective
The tiny parasitic wasp encarsia attacks whitefly nymphs
Example 2 Red Spider Mites?
Red spider mites pierce leaf cells and suck plat juices, resulting in discolouration of the leaves, stunted growth and death of the plant.
A natural predator of the red spider mite is the predatory mite
Pesticide control would also kill the natural predator of the red spider mite and make the problem worse long term
Example 3 Butterfly Caterpillars?
The bacterium bacillus thuringiensis occurs naturally in the soil and on plants producing a protein that is toxic to specific groups of insects including butterfly caterpillars
TOPTIP
biological control is a method of reducing numbers of pests using their natural enemies such as predators, parasites or pathogens
A parasite is an organism which lives in or on the body of another organism its host. the parasite benefits and the host is harmed.
What are the risks with biological control?
possible risks associated with biological control include harm of non target insects or crop damage by control species - the control agent may itself become a pest.
Example Cane toad?
The cane toad was introduced into Australia to control the population growth of cane beetles on which it feeds
However the cane toad itself became a pest as it kills many other small invertebrates
The cane toad has poisonous skin which kills any predator which tries to eat it.
What is integrated pest management?
Integrated pest management (IPM) is a process for controlling pests while minimising any risks to other organisms including humans and the environment.
It involves a range of techniques, using pesticides as a last resort.
What are the techniques and processes used in IPM?
identification of the pests
monitoring the number of pests and the damage caused
long term pest prevention by controlling environmental factors to create unfavourable conditions for the pest
using a combination of control methods which may be more effective than a single method of control
TOPTIP
Many IPM programmes combine cultural chemical and biological control
TOPTIP
Integrated pest management IPM uses a combination of chemical and biological techniques to control the population size of a pest
Instead of killing the whole population
