Editing Pyrethrum (section)

==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>