- control pests by physically, chemically or biologically interfering with their metabolism or behaviour.
- may be natural or synthetically produced
- are registered for use in NSW by the Australian Pesticides and Veterinary Medicines Authority (APVMA)
- are regulated under the Pesticides Act 1999 and Pesticides Regulation 2017.
See the legal definition of pesticide
How pesticides work
Pesticides are often applied by spraying, fumigating and baiting. However, not all pesticides kill the target pest. Some act in other ways, for example
- repel or lure the pest into a trap
- sterilise the pest to prevent them reproducing
- cause leaf drop without killing the plant
- boost the action of another pesticide, for example, piperonyl butoxide adds to the effectiveness of pyrethrum in some insecticides.
‘Contact' pesticides are absorbed through the pest’s body surface. Examples include
- tetramethrin used in household fly sprays
- bipyridillium herbicides such as paraquat that are used on weeds
Contact pesticides have to reach their target directly to be effective.
Other pesticides move from the site of application to another area in the pest, for example
- insecticides that are absorbed by foliage and move through the plant to kill chewing or sucking insects
- blood anticoagulants in baits for rats and mice that move from the digestive system to the bloodstream
Systemic pesticides move from where they are applied to other parts of the plant to reach their target.
Some pesticides are effective for long periods of time. For example
- triazine herbicides remain in the soil and kill emerging weeds over the lifetime of a crop.
- insecticide barriers that stop termites entering buildings are active for several years
How long a pesticide persists in the environment depends on a number of factors including
- how much is applied
- how it is distributed
- environmental factors such as temperature, moisture, soil pH and micro-organisms
- the chemical properties of the pesticide
Many modern pesticides act quickly and then degrade to non-toxic substances. This helps prevent pesticide build-up in crops or plants and animals that are not pests.
One risk of using pesticides is that pests may develop resistance, which means the pesticide is no longer effective. Resistance generally develops when a pesticide is applied and a small percentage of the target organisms survive. These survivors pass their ‘pesticide survival’ characteristic on to each subsequent generation, making them more likely to be unaffected by the same pesticide.
To minimise resistance, pesticide users should
- closely follow the directions on the APVMA approved label (these may include specific resistance warnings)
- have a pest management strategy that does not solely rely on the use of pesticides, such as integrated pest management
- CropLife Australia have an informative video on how rotating pesticides can minimise pest resistance.
- AusVEG provide guidance on managing pesticide resistance in horticultural crops.
- The NSW Department of Primary Industries provides information on how pesticide resistance develops and how to manage it in specific crops. Use the search function to search for a crop or by typing in ‘pesticide resistance’.