''Pyrethrum'' was a genus of several Old World plants now classified in either '' Chrysanthemum'' or '' Tanacetum'' which are cultivated as ornamentals for their showy flower heads. 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 Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, i ...

made from the dried flower heads of '' Chrysanthemum cinerariifolium'' and '' Chrysanthemum coccineum''. The insecticidal compounds present in these species are pyrethrins.

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 Asteraceae () is a large family (biology), family of flowering plants that consists of over 32,000 known species in over 1,900 genera within the Order (biology), order Asterales. The number of species in Asteraceae is rivaled only by the Orchi ...

. They are all

perennial plant In horticulture, the term perennial (''wikt:per-#Prefix, per-'' + ''wikt:-ennial#Suffix, -ennial'', "through the year") is used to differentiate a plant from shorter-lived annual plant, annuals and biennial plant, biennials. It has thus been d ...

s with a daisy-like appearance and white

petal Petals are modified leaves that form an inner whorl surrounding the reproductive parts of flowers. They are often brightly coloured or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corol ...

s. * '' Tanacetum cinerariifolium'' is called the Dalmatian chrysanthemum, denoting its origin in that region of the Balkans (

Dalmatia Dalmatia (; ; ) is a historical region located in modern-day Croatia and Montenegro, on the eastern shore of the Adriatic Sea. Through time it formed part of several historical states, most notably the Roman Empire, the Kingdom of Croatia (925 ...

). 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 in height. The plant is economically important as a natural source of pyrethrin

s. * '' C. coccineum'', the Persian chrysanthemum, is a perennial plant native to

Caucasus The Caucasus () or Caucasia (), is a region spanning Eastern Europe and Western Asia. It is situated between the Black Sea and the Caspian Sea, comprising parts of Southern Russia, Georgia, Armenia, and Azerbaijan. The Caucasus Mountains, i ...

and looks somewhat like a daisy. It produces large white, pink or red flowers. The leaves resemble those of

fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...

s, and the plant grows to between 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. Tanacetum cinerariifolium MHNT

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 biodegradable and also 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

, and as a lice remedy in the

Middle East The Middle East (term originally coined in English language) is a geopolitical region encompassing the Arabian Peninsula, the Levant, Turkey, Egypt, Iran, and Iraq. The term came into widespread usage by the United Kingdom and western Eur ...

( Persian powder, also known as "Persian pellitory"). It was sold worldwide under the brand Zacherlin by Austrian industrialist J. Zacherl. It is one of the most commonly used non-synthetic insecticides allowed in certified organic agriculture. The flowers should be dried and then crushed and mixed with water. *

Pyrethroid A pyrethroid is an organic compound similar to the natural pyrethrins, which are produced by the flowers of pyrethrums (''Chrysanthemum cinerariaefolium'' and ''Chrysanthemum coccineum, C. coccineum''). Pyrethroids are used as commercial and hou ...

s are synthetic insecticides based on natural pyrethrum ( pyrethrins); one common example is permethrin. Pyrethrins are often sold in preparations that also contain the synthetic chemical piperonyl butoxide, which enhances the toxicity 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.

Toxicity

Mammals

Rat and rabbit 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. Nevertheless, pyrethrum should be handled with the same caution as synthetic insecticides: safety equipment should be worn, and mixing with other chemicals should be avoided. People can be exposed to pyrethrum as a mixture of cinerin, 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 The Occupational Safety and Health Administration (OSHA; ) is a regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. The United States Congress established ...

(OSHA) has set the legal limit ( Permissible exposure limit) for pyrethrum exposure in the workplace as 5 mg/m³ over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a Recommended exposure limit (REL) of 5 mg/m³ over an 8-hour workday. At levels of 5000 mg/m³, pyrethrum is immediately dangerous to life and health. People exposed to pyrethrum may experience symptoms including pruritus (itching),

dermatitis Dermatitis is a term used for different types of skin inflammation, typically characterized by itchiness, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become thickened ...

, papules, erythema (red skin), rhinorrhea (runny nose), sneezing, and

asthma Asthma is a common long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wh ...

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.

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

References

External links

National Pesticide Information Center: Pyrethrins and Pyrethroids Fact Sheet

EXTOXNET: Pyrethrins and Pyrethroids

"What is Pyrethrum?"

Role of aphid alarm pheromone produced by the flowers in repelling aphids and attracting ladybug beetles
{{Authority control p Pyrethroids Flora of Europe Plant toxin insecticides Biological pest control Garden plants of Europe Household chemicals Anthemideae Plant common names Historically recognized angiosperm genera