Control Of Pests, Diseases And Weeds 2.1 Flashcards
Physical control
Hand weeding.
Forking out perennial weeds.
Hand picking of pest eggs and larvae.
Pinching out of Broad Beans to reduce aphid infestation.
Pruning out growth of infected growth (eg canker).
Use if physical barriers eg fleece and netting.
Cultural control
Acts carried out to deter, prevent or reduce pest or disease attacks or reduce weed growth.
Mulching Crop rotation. Use if resistant plants. ‘Right plant, right place’ Hygiene Careful watering (not wetting foliage).
Chemical - herbicides
Glyphosate - translocate herbicide.
2,4-D - selective herbicide often used in turf.
Types of insecticide - organochlorines
Organochlorines- containing carbon, hydrogen and chlorine.
Act on nervous system causing spasms and convulsions, pest dies of exhaustion.
Eg DDT which persist in soil and enter food chain.
Types of insecticides - organophosphates
Contain hydrogen, carbon, oxygen and phosphorus or sulphur.
Act on nerve junctions causing constant convulsions and death through exhaustion.
Not persistent and act on contact.
Good for soft bodied pests.
Eg Dimethoate
Types of pesticides - carbamates
Carbamate contain carbon, hydrogen, oxygen and nitrogen.
Jam up nerve junctions causing paralysis.
Eg Methiocarb.
Act on stomach if molluscs, slugs/snails dry up in sun or are eaten by predators.
Non persistent and low mammalian toxicity.
Chemicals derived from plants
Pyrethrum
Non persistent contact insecticide which affect nervous system.
Synthetic pyrethroids include Deltamethrin
How insecticides work.
Some act on contact.
Some are systemic, or translaminar and absorbed by plant - when insect sucks the sap or eat the foliage the pesticide kills the pest.
Fungicides
Include systemic, selective, broad spectrum, eradicate and protectant.
Non systemic - stop growth and reproduction, beat applied before fungi appear eg. Thiram
Systemic - translocated to xylem walls, can be applied to existing fungal infection, generally require less frequent application.
Eg. Carboxin (available in mixes)
Soil sterilisation - steam
Example John Innes Composts.
Loam is sterilised to control pests, diseases and weeds.
80°c for 20 minutes.
Requires specialist equipment - usually only practical in small area eg. Greenhouses and frames.
Reason for sterilising growing medium.
Control of pests, diseases and weeds.
To provide healthy medium for plant to grow in.
Usually dine in small scale.
Chemical sterilisation of soil.
Dazomet is available professionally for indoor and outdoor use in beds to sterilise soil prior to planting.
Metham -sodium -is one of a range of insecticides used as a soil and seed treatment, either as drench or incorporated into soil, often in protected growing situations.
Use of hot water treatment of rootstock
Eradicate stem eelworm in Narcissus bulbs.
Immersed in water - 44°C for 3 hours
Eradicated leaf eelworm in strawberries
Immerse strawberry runners in water
46°C fo 10 minutes.
Biological controls
Use if ‘natural methods’.
Careful research used to ensure that control works and will not cause other environmental problems.
Examples
Encarsia used to control whitefly.
Encouraging indigenous predators eg ladybirds to predate on aphids.
Bacillus subtilis- bacteria used to control Botrytis on crops.
Economic Damage Threshold
Point at which the damage caused by pest or disease to a crop reaches a level that cause significant economic threat to the producer, triggering need for action against pest or disease.
