View source for Pyrethrum

{{short description|Genus of plants and natural insecticide}}
{{more cn|date=May 2011}}

'''''Pyrethrum''''' was a genus of several Old World plants now classified in either ''[[Chrysanthemum]]'' or ''[[Tanacetum]]'' which are cultivated as ornamentals for their showy [[Pseudanthium|flower head]]s. '''Pyrethrum''' continues to be used as a common name for plants formerly included in the genus ''Pyrethrum''. Pyrethrum is also the name of a natural [[insecticide]] made from the dried flower heads of '''''[[Tanacetum cinerariifolium|Chrysanthemum cinerariifolium]]''''' and '''''[[Chrysanthemum coccineum]]'''''. The insecticidal compounds present in these species are [[pyrethrin]]s.

==Description==
Some members of the genus ''Chrysanthemum'', such as the following two, are placed in the genus ''[[Tanacetum]]'' instead by some botanists. Both genera are members of the daisy (or aster) family, [[Asteraceae]]. They are all [[perennial plant]]s with a daisy-like appearance and white [[petal]]s.

{{anchor|Tanacetum cinerariifolium}}
* [[Image:Tanacetum cinerariifolium1.jpg|thumb|''Tanacetum cinerariifolium'']] ''[[Tanacetum cinerariifolium]]'' is called the Dalmatian chrysanthemum, denoting its origin in that region of the Balkans ([[Dalmatia]]). It looks more like the common daisy than other pyrethrums do. Its flowers, typically white with yellow centers, grow from numerous fairly rigid stems. Plants have blue-green leaves and grow to {{convert|45|to|100|cm|abbr=on}} in height. The plant is economically important as a natural source of pyrethrin [[insecticide]]s.
* [[Image:Tanacetum coccineum2.jpg|thumb|''Tanacetum coccineum'']]''[[Chrysanthemum coccineum|C. coccineum]]'', the Persian chrysanthemum, is a perennial plant native to [[Caucasus]] and looks somewhat like a [[Asteraceae|daisy]]. It produces large white, pink or red flowers. The leaves resemble those of [[fern]]s, and the plant grows to between {{convert|30|and|60|cm|abbr=on}} in height. The flowering period is June to July in temperate climates (Northern Hemisphere). ''C. coccineum'' also contains insecticidal pyrethrins, but it is a poor source compared to ''C. cinerariifolium''.
* Other species, such as ''C. balsamita'' and ''C. marshalli'', also contain insecticidal substances, but are less effective than the two species mentioned above.

[[File:Tanacetum cinerariifolium MHNT.BOT. 2012.10.14.JPG|thumb|''Tanacetum cinerariifolium '']]

==Insecticides==
The flowers are pulverized and the active components, called pyrethrins, contained in the seed cases, are extracted and sold in the form of an [[oleoresin]]. This is applied as a suspension in water or oil, or as a powder. Pyrethrins attack the nervous systems of all insects, and inhibit female mosquitoes from biting. When present in amounts less than those fatal to insects, they still appear to have an [[insect repellent]] effect. They are harmful to fish, but are far less toxic to mammals and birds than many synthetic insecticides and are not persistent, being [[biodegradation|biodegradable]] and also [[Chemical decomposition|decompose]] easily on exposure to light. They are considered to be amongst the safest insecticides for use around food. In 1998 Kenya was producing 90% (over 6,000 tonnes) of the world's pyrethrum, called ''py'' for short. Production in Tanzania and Ecuador is also significant.  Currently the world's major producer is Tasmania, Australia.

===Sprays===
Pyrethrum has been used for centuries as an [[insecticide]],<ref>''Bioaromatica'' [https://web.archive.org/web/20100324061424/http://www.aromatica.hr/eng/page.asp?id=buhac&sub=buhac3 The history of pyrethrum]</ref> and as a lice remedy in the [[Middle East]] ([[Persian powder]], also known as "Persian pellitory"). It was sold worldwide under the brand [[Zacherlin]] by Austrian industrialist [[Johann Zacherl|J. Zacherl]].<ref name="US Patent">{{US patent reference| number = 308172|issue-date=November 18, 1884| inventor = Johann Zacherl| title =Pyrethrum Soap}}</ref>  It is one of the most commonly used non-synthetic insecticides allowed in certified organic agriculture.<ref>[http://www.colostate.edu/Depts/CoopExt/4DMG/VegFruit/organic.htm Some Pesticides Permitted in Organic Gardening], by Laura Pickett Pottorff, Colorado State University Cooperative Extension, January 5, 2010.</ref>

The flowers should be dried and then crushed and mixed with water.
* [[Pyrethroid]]s are synthetic insecticides based on natural pyrethrum ([[pyrethrin]]s); one common example is [[permethrin]]. Pyrethrins are often sold in preparations that also contain the synthetic chemical [[piperonyl butoxide]], which enhances the [[toxic]]ity to insects and is faster acting compared with pyrethrins used alone. These formulations are known as ''synergized pyrethrins''.

===Companion planting===
A pheromone produced by these plants attracts ladybug beetles, and at the same time acts as an alarm signal to aphids.<ref>{{cite journal |last1=Li |first1=Jinjin |last2=Hu |first2=Hao |last3=Mao |first3=Jing |last4=Yu |first4=Lu |last5=Stoopen |first5=Geert |last6=Wang |first6=Manqun |last7=Mumm |first7=Roland |last8=Ruijter |first8=Norbert C. A. |last9=Dicke |first9=Marcel |last10=Jongsma |first10=Maarten A. |last11=Wang |first11=Caiyun |title=Defense of pyrethrum flowers: repelling herbivores and recruiting carnivores by producing aphid alarm pheromone |journal=New Phytologist |date=August 2019 |volume=223 |issue=3 |pages=1607–1620 |doi=10.1111/nph.15869|pmid=31087371 |pmc=6772172 |bibcode=2019NewPh.223.1607L }}</ref>

==Toxicity==
=== Mammals ===
Rat and rabbit {{LD50}} levels for pyrethrum are high, with doses in some cases of about 1% of the animal's body weight required to cause significant mortality. This is similar to fatal levels in synthetic pyrethroids.<ref>[http://edis.ifas.ufl.edu/pi091 Pesticide Toxicity Profile: Synthetic Pyrethroid Pesticides] {{Webarchive|url=https://web.archive.org/web/20210422160831/https://edis.ifas.ufl.edu/pi091 |date=2021-04-22 }}, by Frederick M. Fisher, University of Florida IFAS Extension Service, 2013</ref> Nevertheless, pyrethrum should be handled with the same caution as synthetic insecticides:<ref>[http://edis.ifas.ufl.edu/in197#TABLE_1 insecticide (botanical, mineral, synthetic) toxicity to mammals] Electronic Data Information Source of University of Florida</ref> safety equipment should be worn, and mixing with other chemicals should be avoided.<ref>{{cite web |title=Using Pyrethrum |url=https://www.abc.net.au/gardening/factsheets/using-pyrethrum/9434612 |website=Gardening Australia |publisher=[[Australian Broadcasting Corporation]] |access-date=3 November 2018 |date=25 May 2013 |quote="I've also marked my pyrethrum bottle 'for pesticides only'. I have another one for herbicides. It doesn't matter whether you're organic or not, accidents can happen. It's best to keep these chemicals apart."  As a precaution, safety gear should be worn when using pyrethrum.}}</ref>

People can be exposed to pyrethrum as a mixture of [[cinerin]], [[Jasmolone|jasmolin]], and [[pyrethrin]] in the workplace by breathing it in, getting it in the eyes or on the skin, or swallowing it. The [[Occupational Safety and Health Administration]] (OSHA) has set the legal limit ([[Permissible exposure limit]]) for pyrethrum exposure in the workplace as 5&nbsp;mg/m<sup>3</sup> over an 8-hour workday. The [[National Institute for Occupational Safety and Health]] (NIOSH) has set a [[Recommended exposure limit]] (REL) of 5&nbsp;mg/m<sup>3</sup> over an 8-hour workday. At levels of 5000&nbsp;mg/m<sup>3</sup>, pyrethrum is [[IDLH|immediately dangerous to life and health]]. People exposed to pyrethrum may experience symptoms including [[pruritus]] (itching), [[dermatitis]], [[papules]], [[erythema]] (red skin), [[rhinorrhea]] (runny nose), [[sneezing]], and [[asthma]].<ref>{{Cite web|title = CDC - NIOSH Pocket Guide to Chemical Hazards - Pyrethrum |url = https://www.cdc.gov/niosh/npg/npgd0685.html|website = www.cdc.gov|access-date=October 23, 2015}}</ref>

=== Other animals ===
Pyrethrum, specifically the pyrethrin within, is highly toxic to insects including useful pollinators like bees. The risk of killing bees and other beneficial insects is partially reduced by the compound's rapid breakdown (a half-life of approximately 12 hours on plants and on the surface of the soil, with about 3% remaining after five days, but persisting several weeks or more if it enters a body of water or is dug into the soil) and its slight insect-repellant activity.<ref name=NPIC>{{cite web |title=Pyrethrins general fact sheet |url=http://npic.orst.edu/factsheets/pyrethrins.pdf |website=national pesticide information center}}</ref>

==Common names==
Common names for ''Chrysanthemum cinerariifolium'' include:
* Pyrethrum
* Pyrethrum daisy
* Dalmatian pyrethrum
* Dalmatian chrysanthemum
* Dalmatian insect flower
* Dalmatian [[pellitory]]
* Big daisy

Common names for ''Chrysanthemum coccineum'' include:
* Pyrethrum
* Pyrethrum daisy
* Painted daisy
* Persian chrysanthemum
* Persian insect flower
* Persian [[pellitory]]
* Caucasian insect powder plant

==See also==
* ''[[Chrysanthemum]]''
* [[List of companion plants]]
* [[:Category:Plant toxin insecticides|Category: Plant toxin insecticides]]
* [[Permethrin]]
* [[Pyrethrin]]

==References==
{{Reflist}}

==External links==
* [http://npic.orst.edu/factsheets/pyrethrins.pdf National Pesticide Information Center: Pyrethrins and Pyrethroids Fact Sheet]
* [https://www.cdc.gov/niosh/npg/npgd0685.html CDC - NIOSH Pocket Guide to Chemical Hazards]
* [https://web.archive.org/web/20070927005503/http://www.andover.edu/news/documents/B-ChemicalFactSheet.pdf  EXTOXNET: Pyrethrins and Pyrethroids]
* [http://www.pyrethrum.com  "What is Pyrethrum?"] {{Webarchive|url=https://web.archive.org/web/20110124192128/http://www.pyrethrum.com/ |date=2011-01-24 }}
* [http://nph.onlinelibrary.wiley.com/doi/10.1111/nph.15869 Role of aphid alarm pheromone produced by the flowers in repelling aphids and attracting ladybug beetles]

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{{insecticides}}
{{Anti-arthropod medications}}
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[[Category:Chrysanthemum|p]]
[[Category:Pyrethroids]]
[[Category:Flora of Europe]]
[[Category:Plant toxin insecticides]]
[[Category:Biological pest control]]
[[Category:Garden plants of Europe]]
[[Category:Household chemicals]]
[[Category:Anthemideae]]
[[Category:Plant common names]]
[[Category:Historically recognized angiosperm genera]]