Editing Pest control (section)

====Pesticides====
{{main|Pesticide}}
[[File:Insecticide pine logs ips sexdentatus.jpg|thumb|Spraying [[pine]] logs with [[insecticide]] against ''[[Ips sexdentatus]]'', a pine engraver beetle]]
<!--aircraft spraying crops: image in lead section-->

[[Pesticide]]s are substances applied to crops to control pests, they include [[herbicide]]s to kill weeds, [[fungicide]]s to kill fungi and [[insecticide]]s to kill insects. They can be applied as sprays by hand, tractors, or aircraft or as [[seed dressing]]s. To be effective, the correct substance must be applied at the correct time and the method of application is important to ensure adequate coverage and retention on the crop. The killing of natural enemies of the target pest should be minimized. This is particularly important in countries where there are natural reservoirs of pests and their enemies in the countryside surrounding plantation crops, and these co-exist in a delicate balance. Often in less-developed countries, the crops are well adapted to the local situation and no pesticides are needed. Where progressive farmers are using fertilizers to grow improved crop varieties, these are often more susceptible to pest damage, but the indiscriminate application of pesticides may be detrimental in the longer term.<ref name=Hill>{{cite book |author=Hill, Dennis S.|title=Agricultural Insect Pests of the Tropics and Their Control |url=https://books.google.com/books?id=Ywc5AAAAIAAJ&pg=PA4 |year=1983 |publisher=CUP Archive |isbn=978-0-521-24638-5 |pages=4–5}}</ref>{{unreliable-inline|date=November 2023}}{{failed verification|date=November 2023}}
The efficacy of chemical pesticides tends to diminish over time. This is because any organism that manages to survive the initial application will pass on its genes to its offspring and a [[Pesticide resistance|resistant strain]] will be developed. In this way, some of the most serious pests have developed resistance and are no longer killed by pesticides that used to kill their ancestors. This necessitates higher concentrations of chemical, more frequent applications and a movement to more expensive formulations.<ref name=Georghiou>{{cite book|author=Georghiou, G.P.|title=Pest Resistance to Pesticides |url=https://books.google.com/books?id=SavaBwAAQBAJ&pg=PA1 |year=2012 |publisher=Springer Science & Business Media|isbn=978-1-4684-4466-7 |pages=1–3}}</ref>

Pesticides are intended to kill pests, but many have detrimental effects on non-target species; of particular concern is the [[Pesticide toxicity to bees|damage]] done to [[honey-bee]]s, solitary bees and other [[pollinating insect]]s and in this regard, the time of day when the spray is applied can be important.<ref name=Carrington/> The widely used [[neonicotinoid]]s have been banned on flowering crops in some countries because of their effects on bees.<ref name=Carrington>{{cite news |title=Pesticides damage survival of bee colonies, landmark study shows |author=Carrington, Damian |url=https://www.theguardian.com/environment/2017/jun/29/pesticides-damage-survival-of-bee-colonies-landmark-study-shows |newspaper=The Guardian |date=29 June 2017 |access-date=27 August 2017}}</ref> Some pesticides may cause [[cancer]] and other health problems in humans, as well as being harmful to wildlife.<ref name="National Institute of Environmental Health Sciences">{{cite web|title=Pesticides|url=http://www.niehs.nih.gov/health/topics/agents/pesticides/|work=National Institute of Health Sciences|publisher=National Institute of Environmental Health|access-date=5 April 2013}}</ref> There can be acute effects immediately after exposure or chronic effects after continuous low-level, or occasional exposure.<ref>{{cite web |url=http://psep.cce.cornell.edu/Tutorials/core-tutorial/module04/index.aspx |title=Toxicity of Pesticides |year=2012 |work=Pesticide Safety Education Program |access-date=27 August 2017 |archive-date=21 July 2021 |archive-url=https://web.archive.org/web/20210721082302/http://psep.cce.cornell.edu/Tutorials/core-tutorial/module04/index.aspx |url-status=dead }}</ref> [[Maximum residue limit]]s for pesticides in foodstuffs and animal feed are set by many nations.<ref>{{cite web |url=https://ec.europa.eu/food/plant/pesticides/max_residue_levels_en |title=Maximum Residue Levels |work=Plants |publisher=European Commission |access-date=27 August 2017}}</ref>