chemical and biological control of agricultural pests
- Created by: laurabrickell
- Created on: 03-12-15 09:20
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- Chemical and Biological control of agricultural pests
- chemical
- herbicides
- only affects weeds as they are broad leafed and have different enzymes to the crops. This means that herbicides can target weeds only. Weeds are killed as they create interspecific competition with the crops.
- insecticides
- some insecticides (contact insecticide) only kill insects that land on them. Systematic insecticides absorbed by the plant/crop so kill any insect that eats the plant/crop
- fungicides
- fungi are the most important plant pathogens that cause disease. Crop seeds are often treated with fungicides before sewing
- good pesticides are selective, non-toxic, biodegradable, have a long shelf life and are cost effective
- some harm the environment (DDT) and so can be banned.
- bioaccumulation is the build up in the body's fatty tissues of substances that are neither used nor excreted by cells
- caused by pesticides being persistent and lipid soluble
- biomagnification is when pesticides are passed from one trophic level to another
- advantages
- acts quickly
- can apply to a specific area
- kills all/ most/ greater variety of pests
- disadvantages
- bioaccumulation
- biomagnification
- kills insect pollination
- effects on human health
- herbicides
- biological
- advantages
- only one application needed as organisms reproduce
- pests don't develop a resistance
- no bioaccumulation
- keeps pest population below threshold
- disadvantages
- cost
- not immediate
- doesn't remove pest completely
- may become a pest species
- when a predator of the pest is released to decrease pest numbers
- if pest numbers dramatically drop then there is less food for the predators so their numbers drop. This means the number of pests will then increase as there is less predators
- integrated pest management (IPM)
- 1. identify pest and population density at which they cause harm (economic threshold)
- 2. use suitable cultural methods to prevent pest reaching their threshold
- 3. if pest population exceeds threshold use biological control
- 4. if biological control doesn't work then use chemical pesticides
- 5. at each stage the effect of the treatment is evaluated before deciding to proceed with the next stage
- advantages
- cultural control is things like weeding, crop rotation, insect barriers, tiling
- chemical
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