Editing Weed control (section)

== Methods ==
{{See also|Pesticide#Alternatives}}
Weed control plans typically consist of many methods which are divided into biological, chemical, cultural, and physical/mechanical control.<ref>{{cite web|url=https://www.agric.wa.gov.au/pests-weeds-diseases/control-methods|title=Control methods|publisher=Department of Agriculture and Food, Government of Western Australia|access-date=11 December 2015}}</ref>

===Physical/mechanical methods===
{{See also|Mechanical weed control}}
==== Coverings ====
In a domestic gardens, methods of weed control include covering an area of ground with a material that creates an unsuitable environment for weed growth, known as a ''weed mat''. For example, several layers of wet [[newspaper]] prevent light from reaching plants beneath, which kills them.

In the case of black plastic, the [[greenhouse effect]] kills the plants. Although the black plastic sheet is effective at preventing weeds that it covers, it is difficult to achieve complete coverage. Eradicating persistent perennials may require the sheets to be left in place for at least two seasons.{{Citation needed|date=September 2022}}

Some plants are said to produce root exudates that suppress [[herb]]aceous weeds. ''[[Tagetes minuta]]'' is claimed to be effective against couch and ground elder,<ref>{{cite web|url=http://www.pfaf.org/user/Plant.aspx?LatinName=Tagetes+minuta|title=Tagetes minuta Muster-John-Henry PFAF Plant Database|work=pfaf.org}}</ref> whilst a border of [[comfrey]] is also said to act as a barrier against the invasion of some weeds including couch.
A {{convert|5|–|10|cm}} layer of [[Woodchips|wood chip]] [[mulch]] prevents some weeds from sprouting.

[[Gravel]] can serve as an inorganic mulch.

[[Irrigation]] is sometimes used as a weed control measure such as in the case of [[paddy fields]] to kill any plant other than the water-tolerant rice crop.

==== Manual removal ====
[[File:Weeding (499719425).jpg|thumb|Tools used for amateur weeding include spades and gloves]]
[[File:Weeding.jpg|thumb|Weeds are removed manually in large parts of India.]]

Many gardeners still remove weeds by manually pulling them out of the ground, making sure to include the roots that would otherwise allow some to re-sprout.

Hoeing off weed leaves and stems as soon as they appear can eventually weaken and kill perennials, although this will require persistence in the case of plants such as bindweed. Nettle infestations can be tackled by cutting back at least three times a year, repeated over a three-year period. Bramble can be dealt with in a similar way.

A highly successful, mostly manual, removal programme of weed control in natural bush land has been the control of [[sea spurge]] by [[Sea Spurge Remote Area Teams]] in [[Tasmania]].<ref>{{cite web |url=http://www.parks.tas.gov.au/file.aspx?base=41336 |title=EVALUATION REPORT DECEMBER 2015 - Wildcare SPRATS volunteer weed eradication project |publisher=Tasmanian Parks and Wildlife Service |access-date=19 June 2017}}</ref>

==== Tillage ====

[[File:00DI0874 - Flickr - USDAgov (1).jpg|thumb|Weed control through tilling with hoes, circa 1930-40s]]

[[Plough]]ing includes tilling of soil, intercultural ploughing and summer ploughing. Ploughing uproots weeds, causing them to die. Summer ploughing also helps in killing pests.

[[File:Dwarswieder.jpg|thumb|A mechanical weed control device]]

Mechanical tilling with various types of [[cultivator]]s can remove weeds around crop plants at various points in the growing process.

An [[Aquamog]], an [[aquatic weed harvester]], can be used to remove weeds covering a body of water.<ref>{{cite web |title=Aquamogs |date=21 June 2011 |url=http://aquamog.net/aquamogs/aquamogs/ |access-date=November 22, 2018}}</ref>

==== Thermal ====
[[File:Speicherkoog Kartoffelacker Abflammgerät Envo-Dan.jpg|thumb|Pesticide-free thermic weed control with a weed burner on a potato field in [[Dithmarschen]], Germany]]
Several thermal methods can control weeds.

{{visible anchor|Flame weeding}} uses a [[flame]] several centimetres/inches away from the weeds to singe them, giving them a sudden and severe heating.<ref name="Vougioukas-2019">{{cite journal | last=Vougioukas | first=Stavros G. | title=Agricultural Robotics | journal=[[Annual Review of Control, Robotics, and Autonomous Systems]] | publisher=[[Annual Reviews (publisher)|Annual Reviews]] | volume=2 | issue=1 | date=2019-05-03 | issn=2573-5144 | doi=10.1146/annurev-control-053018-023617 | pages=365–392| s2cid=242732172 | doi-access=free }}</ref> The goal of flame weeding is not necessarily burning the plant, but rather causing a lethal [[wilting]] by [[denaturation (biochemistry)|denaturing proteins]] in the weed. Similarly, hot air weeders can heat up the seeds to the point of destroying them.  Flame weeders can be combined with techniques such as stale seedbeds (preparing and watering the seedbed early, then killing the nascent crop of weeds that springs up from it, then sowing the crop seeds) and pre-emergence flaming (doing a flame pass against weed seedlings after the sowing of the crop seeds but before those seedlings emerge from the soil—a span of time that can be days or weeks).

Hot foam causes the cell walls to rupture, killing the plant. Weed burners heat up soil quickly and destroy superficial parts of the plants. Weed seeds are often heat resistant and even react with an increase of growth on dry heat.

Since the 19th century [[soil steam sterilization]] has been used to clean weeds completely from soil. Several research results confirm the high effectiveness of humid heat against weeds and its seeds.<ref>Research report of DLR Rheinlandpfalz, September 2010: [http://www.soil-steaming-steam-boiler-blog.com/wp-content/uploads/2010/10/steaming-research-results_dlr2010.pdf ''Weed control in seed cultures, especially arugula''] {{Webarchive|url=https://web.archive.org/web/20150924103450/http://www.soil-steaming-steam-boiler-blog.com/wp-content/uploads/2010/10/steaming-research-results_dlr2010.pdf |date=2015-09-24 }}, Author: Dr. Norbert Laun, Institute "Queckbrunnerhof", Schifferstadt (Germany). Viewed on 14. February 2011.</ref>

[[Soil solarization]] in some circumstances is very effective at eliminating weeds while maintaining grass. Planted grass tends to have a higher heat/humidity tolerance than unwanted weeds.{{citation needed|date=January 2021}}

==== Lasers ====
In [[precision agriculture]], novel [[agricultural robot]]s and machines can [[agricultural technology|use lasers]] for weed control, called "laserweeding".<ref name="interestingengineeringPapadopoulos">{{cite news |last1=Papadopoulos |first1=Loukia |title=This new farming robot uses lasers to kill 200,000 weeds per hour |url=https://interestingengineering.com/innovation/farming-robot-lasers-200000-weeds-per-hour |access-date=17 November 2022 |work=interestingengineering.com |date=21 October 2022}}</ref> Their benefits may include "healthier crops and [[soil conservation|soil]], decreased herbicide use, and reduced chemical and labor costs".<ref name="interestingengineeringPapadopoulos"/>

==== Seed targeting ====
In 1998, the Australian Herbicide Resistance Initiative debuted. gathered fifteen scientists and technical staff members to conduct field surveys, collect seeds, test for resistance and study the biochemical and genetic mechanisms of resistance. A collaboration with [[DuPont]] led to a mandatory herbicide labeling program, in which each mode of action is clearly identified by a letter of the alphabet.<ref name=s1408/>

The key innovation of the Australian Herbicide Resistance Initiative has been to focus on weed seeds. Ryegrass seeds last only a few years in soil, so if farmers can prevent new seeds from arriving, the number of sprouts will shrink each year. Until the new approach farmers were unintentionally helping the seeds. Their combines loosen ryegrass seeds from their stalks and spread them over the fields. In the mid-1980s, a few farmers hitched covered trailers, called "chaff carts", behind their combines to catch the chaff and weed seeds. The collected material is then burned.<ref name=s1408/>

An alternative is to concentrate the seeds into a half-meter-wide strip called a [[windrow]] and burn the windrows after the harvest, destroying the seeds. Since 2003, windrow burning has been adopted by about 70% of farmers in Western Australia.<ref name=s1408/>

Yet another approach is the Harrington Seed Destructor, which is an adaptation of a coal pulverizing cage mill that uses steel bars whirling at up to 1500 rpm. It keeps all the organic material in the field and does not involve combustion, but kills 95% of seeds.<ref name=s1408/>

===Cultural methods===
==== Stale seed bed ====
Another manual technique is the ‘[[stale seed bed]]’, which involves cultivating the soil, then leaving it fallow for a week or so. When the initial weeds sprout, the grower lightly [[Hoe (tool)|hoes]] them away before planting the desired crop. However, even a freshly cleared bed is susceptible to airborne seed from elsewhere, as well as seed carried by passing animals on their fur, or from imported [[manure]].

==== Buried drip irrigation ====
[[Drip irrigation|Buried drip irrigation]] involves burying drip tape in the subsurface near the planting bed, thereby limiting weeds access to water while also allowing crops to obtain moisture. It is most effective during dry periods.<ref>{{cite web|url=http://anrcatalog.ucanr.edu/pdf/7250.pdf|title=Weed Management for Organic Crops|author=Richard Smith, W. Thomas Lanini, Mark Gaskell, Jeff Mitchell, Steven T. Koike, and Calvin Fouche|publisher=Division of Agriculture and Natural Resources, University of California|page=1|year=2000|access-date=11 December 2015}}</ref>

==== Crop rotation ====
Rotating crops with ones that kill weeds by choking them out, such as [[hemp]],<ref>{{cite web
| url=http://www.gametec.com/hemp/WEED.CTRL.htm
| title=HEMP AS WEED CONTROL
| publisher=www.gametec.com
| access-date=2008-07-09}}</ref> ''[[Mucuna pruriens]]'', and other crops, can be a very effective method of weed control. It is a way to avoid the use of herbicides, and to gain the benefits of [[crop rotation]].

=== Biological methods ===
A biological weed control regiment can consist of [[Biological pest control|biological control agents]], [[bioherbicide]]s, use of grazing animals, and protection of natural predators.<ref>{{cite book|first1=Merrill A.|last1=Ross|first2=Carole A.|last2=Lembi|title=Applied Weed Science: Including the Ecology and Management of Invasive Plants|publisher=Prentice Hall|year=2008|page=123|isbn=978-0135028148}}</ref> Post-dispersal, weed seed predators, like ground beetles and small vertebrates, can substantially contribute to the weed regulation by removing weed seeds from the soil surface and thus reduce seed bank size. Several studies provided evidence for the role of invertebrates to the biological control of weeds<ref>{{Cite journal|last1=Westerman|first1=Paula R.|last2=Liebman|first2=Matt|last3=Menalled|first3=Fabián D.|last4=Heggenstaller|first4=Andrew H.|last5=Hartzler|first5=Robert G.|last6=Dixon|first6=Philip M.|date=June 2005|title=Are many little hammers effective? Velvetleaf (Abutilon theophrasti) population dynamics in two- and four-year crop rotation systems|journal=Weed Science|language=en|volume=53|issue=3|pages=382–392|doi=10.1614/WS-04-130R|s2cid=86362489 |issn=0043-1745}}</ref><ref>{{Cite journal|last=Bohan D.|display-authors=etal|date=2011|title=National-scale regulation of the weed seedbank by carabid predators.|journal=Journal of Applied Ecology|volume=48|issue=4|pages=888–898|doi=10.1111/j.1365-2664.2011.02008.x|bibcode=2011JApEc..48..888B }}</ref>

==== Animal grazing ====
{{main|Conservation grazing}}
Companies using goats to control and eradicate [[Euphorbia virgata|leafy spurge]], [[knapweed]], and other toxic weeds have sprouted across the [[American West]].<ref>{{cite news|url=http://www.brownalumnimagazine.com/content/view/3251/40/|title=American Pastoral|date=Sep–Oct 2012|publisher=Brown Alumni Monthly}}</ref>

===Chemical methods===

==== Herbicides ====
{{main|Herbicide}}
[[File:LPCC-733-Aplicació d'herbicides en arròs.jpg|thumb|A tractor spraying herbicide onto a field of crops]]
The above described methods of weed control use no or very limited chemical inputs. They are preferred by [[Organic gardening|organic gardeners]] or [[Organic farming|organic farmers]].

However weed control can also be achieved by the use of herbicides. Selective herbicides kill certain targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often based on plant [[hormone]]s. Herbicides are generally classified as follows:{{citation needed|date=December 2022}}

* '''Contact''' herbicides destroy only plant tissue that contacts the herbicide. Generally, these are the fastest-acting herbicides. They are ineffective on perennial plants that can re-grow from roots or [[tuber]]s.
* '''Systemic''' herbicides are foliar-applied and move through the plant where they destroy a greater amount of tissue. [[Glyphosate]] is currently the most used systemic herbicide.
* '''Soil-borne''' herbicides are applied to the soil and are taken up by the roots of the target plant.
* '''[[Preemergent herbicides|Pre-emergent]]''' herbicides are applied to the soil and prevent germination or early growth of weed seeds.

In [[agriculture]] large scale and systematic procedures are usually required, often by machines, such as large liquid herbicide 'floater' sprayers, or [[aerial application]].

These are thought to likely have several substantial detrimental impacts (e.g. on soils, health and insects)<ref>{{cite journal |last1=Sánchez-Bayo |first1=Francisco |title=Indirect Effect of Pesticides on Insects and Other Arthropods |journal=Toxics |date=30 July 2021 |volume=9 |issue=8 |pages=177 |doi=10.3390/toxics9080177|pmid=34437495 |pmc=8402326 |doi-access=free }}</ref><ref>{{cite journal |last1=Bourdineaud |first1=Jean-Paul |title=Toxicity of the herbicides used on herbicide-tolerant crops, and societal consequences of their use in France |journal=Drug and Chemical Toxicology |date=4 March 2022 |volume=45 |issue=2 |pages=698–721 |doi=10.1080/01480545.2020.1770781|pmid=32543998 |s2cid=219726947 }}</ref><ref>{{cite journal |last1=Meena |first1=Ram |last2=Kumar |first2=Sandeep |last3=Datta |first3=Rahul |last4=Lal |first4=Rattan |last5=Vijayakumar |first5=Vinod |last6=Brtnicky |first6=Martin |last7=Sharma |first7=Mahaveer |last8=Yadav |first8=Gulab |last9=Jhariya |first9=Manoj |last10=Jangir |first10=Chetan |last11=Pathan |first11=Shamina |last12=Dokulilova |first12=Tereza |last13=Pecina |first13=Vaclav |last14=Marfo |first14=Theodore |title=Impact of Agrochemicals on Soil Microbiota and Management: A Review |journal=Land |date=23 January 2020 |volume=9 |issue=2 |pages=34 |doi=10.3390/land9020034|doi-access=free |hdl=2158/1364313 |hdl-access=free }}</ref> – which may partly explain the development of alternatives described here – and there are also systematic procedures using herbicides that have lower impacts such as robots and machines that apply low amounts [[precision agriculture|with high precision]].<ref>{{cite web |title=Verdant Robotics launches multi-action agricultural robot for 'superhuman farming' |url=https://roboticsandautomationnews.com/2022/02/23/verdant-robotics-launches-multi-action-agricultural-robot-for-superhuman-farming/49471/ |website=Robotics & Automation News |access-date=17 November 2022 |date=23 February 2022}}</ref><ref>{{cite magazine |title=Small Robot Company Tom, Dick, and Harry farm robots: The 200 Best Inventions of 2022 |url=https://time.com/collection/best-inventions-2022/6225155/small-robot-company-tom-dick-and-harry/ |magazine=Time |access-date=17 November 2022 |language=en}}</ref>

===Organic approaches===

Organic weed control involves anything other than applying manufactured chemicals. Typically a combination of methods are used to achieve satisfactory control.

[[Sulfur]] in some circumstances is accepted within British [[Soil Association]] standards.

=== Bradley method ===
The [[Bradley method of bush regeneration|Bradley Method of Bush Regeneration]] uses ecological processes to do much of the work.

[[Perennial plant|Perennial]] weeds also propagate by seeding; the airborne seed of the [[dandelion]] and the [[epilobium|rose-bay willow herb]] parachute far and wide. Dandelion and dock also put down deep [[tap root]]s, which, although they do not spread underground, are able to regrow from any remaining piece left in the ground.

=== Hybrid ===
One method of maintaining the effectiveness of individual strategies is to combine them with others that work in complete different ways. Thus seed targeting has been combined with herbicides. In Australia seed management has been effectively combined with [[trifluralin]] and clethodim.<ref name=s1408/>