Pyrethrum is a perennial herb that grows up to a height of anything between 30 cm and 75 cm (12 inches to 30 inches) having lean stems that are covered with hair and grows deep green leaves that are profoundly slit open and separated into seven different sections. The pyrethrum herb produces a single, white flower that has resemblance to daisy in appearance between early summer and early autumn.
Pyrethrum is native to Yugoslavia and Albania and belongs to the gorgeous daisy family and is extensively cultivated for its attractive flowers that produce one of the finest natural pesticides available. Pyrethrum is also widely grown in gardens mostly as a decorative plant and it creates a luxuriant knoll with lacey, green undergrowth. The herb bears numerous solitary, yellow-eyed, white daises in bunches during the period between summer and the fall. Pyrethrum is a hardy plant that is able to withstand harsh cold weather up to 10° F. Pyrethrum is a beautiful plant that can be grown in any kind of soil in the gardens. However, when the plant is cultivated in inferior and dry soil, it creates the utmost concentration of insecticides. When the leaves and flowers are massaged on the skin, they help to keep away from insect bites.
It is interesting to note that the Persians were the first to find out and ascertain that an associated species of pyrethrum flowers possessed the characteristics of exterminating insects. Afterward it was discovered that the pyrethrum herb was even more effectual as an insecticide and presently it has turned out to be among the most popular, natural insect killers to control insects invading the outdoor as well as indoor plants. The vigorous chemicals present in pyrethrum are known as pyrethrins and these are considered to be deadly for the nervous system of the insects.
Habitat and cultivation
As mentioned earlier, pyrethrum herb is indigenous to the coastal regions of Yugoslavia and the islands of the country. In fact, the plant thrives best in chalk-like or rock-strewn shores, but it also grows in the interior hilly regions where the land is dry and stony. Presently, pyrethrum is commercially grown in countries such as South Africa, Japan and California.
Side effects and cautions
Remember, pyrethrum encloses toxic elements and hence it is effective as a natural insecticide. Thus, when low dosage, less than two grams, of pyrethrum is massaged on the skin, it not only helps us to avoid insect bites, but is also considered to be safe for majority of the people. Since pyrethrum possesses low measures of toxicity at small dosages, it may often lead to side effects, including nausea, respiratory troubles, headaches, ringing of the ears, itching of fingers and toes, and other symptoms related with the toxicity of the nerves. There are numerous people who have allergic reactions on the application of pyrethrum and they should strictly avoid the use of the substance. In fact, people who face the greatest risk of allergic reactions from pyrethrum are those who are also allergic to plants belonging to the Asteraceae/ Compositae family, including chrysanthemums, ragweed, daises, marigold and a number of other similar herbs.
WARNING: It is not advisable to apply pyrethrum on children who are below two years old as the substance may lead to adverse side effects on their tender skins. In addition, pregnant and lactating women should not take pyrethrum. Pyrethrum is also injurious to people who have allergic reactions on using ragweed, marigold, chrysanthemums, daises and other plants belonging to the same genre. Even people suffering from asthma should keep away from pyrethrum.
The chemical pyrethrins enclosed in pyrethrum are toxic substances that function as a natural insecticide. This toxic substance is produced by some species of the chrysanthemum plant and is commercially used as a natural insecticide. The flowers of these species of chrysanthemum are of use as natural pesticides and they are usually harvested soon after they bloom. There are two processes of extracting the pyrethrins contained in these flowers - either they are plucked, dried and stored as powders or the oils enclosed by the flowers are extracted with the help of dissolvable substances.
In fact, two elements of pyrethrins are of utmost significance - pyrethrin I and pyrethrin II. Both, pyrethrin I and pyrethrin II are structurally linked esters that have a cyclopropane core. The basic difference between these two important elements of pyrethrins is their oxidation state of one carbon. Both these pyrethrin elements are thick and sticky liquids in form and they react with oxygen to become inactivated. Being biodegradable, these pyrethrins are very unstable and break down when exposed to oxygen or light. It is important to note that the chemical composition of these pyrethrin forms the basis for an assortment of artificially manufactured insecticides known as pyrethroids, including permethrin, bifenthrin and cypermethrin. In addition to pyrethrin I and pyrethrin II, the pyrethrins also enclose four other vigorous elements called Cinerin I and II and Jasmolin I and II.
Basically, the pyrethrin amalgams have been made use of to manage mosquitoes, human lice, cockroaches, flies and beetles. Even ‘pyrethrin dusts' are useful as some of them are used to control insects in horticulture. These ‘pyrethrin dusts' enclose mere 0.3 per cent to 0.5 per cent pyrethrins and are normally used in the measure of up to 50 lb/A. In addition to theses, there are some other pyrethrin compounds that are usually used in the storage of grains and in poultry pens. They are also made use of in controlling lice and fleas that invade the furs of dogs and cats. In fact, the natural pyrethrins are called contact poisons as they are able to break through the nervous system of the insects eventually render them inactive. They are so powerful that the insects are rendered incapable of moving or flying just a few minutes after applying these natural pyrethrins. However, a ‘knockdown dose' of pyrethrin does not essentially denote a killing dosage. In fact, the enzymes secreted in the insects are able to detoxify the effects of natural pyrethrins very quickly and within minutes.
As there are some insects that are able to recover fast from the effect of natural pyrethrins and hence it is often essential to use a lethal dosage to delay the action of the enzymes secreted by the insects. In order to enhance the lethal power of pyrethrins and make the compounds more potent, one may add substances such as synergists, carbamates or organophosphates to the pyrethrin dosages.
Over the years, researchers have succeeded in developing partially synthetic by-products of the chrysanthemumic acids and today they are being widely used to control insects and pests. Such partially synthetic by-products of the chrysanthemumic acids are called pyrethroids and more effective compared to the natural pyrethrins. Pyrethroids are not only more potent than the natural pyrethrins, but they are also less harmful for the mammals. Allethrin is among the synthetic pyrethroids that is used extensively to control insects and pests.
It may be noted here that although pyrethrum is native to Yugoslavia and Albania, Kenya supplies most of the world's requirements for pyrethrin and Chrysanthemum cinerariaefolium. It was during the latter phase of the 1920s that the pyrethrum flowers were first brought into Kenya and the mountainous regions of Eastern Africa. And within a span of less than a century, today Kenya is the largest producer of pyrethrum and supplies almost 70 per cent of the world's pyrethrum requirements. In Kenya, a large number of farmers grow pyrethrum in small quantities in their fields and this is a major source of income for most of them. In addition, pyrethrum also comprises a major export item for Kenya earning the country millions of dollars.
As discussed earlier in this article, pyrethrins are primarily used in an assortment of insecticides, a number of pet products and fogging products. A word of caution, one ought to be extra careful while using pyrethrins or products prepared with them near humans and animals. Application of pyrethrins in excess dosages as well as their toxicity may sometimes lead to a range of symptoms, particularly in pets. Such conditions may include weariness, muscle tremors, nausea, drooling, convulsions and even death of the pets. On the other hand, humans are also not free from the adverse side effects of pyrethrins. Toxicity of pyrethrins may lead to asthmatic breathing, nasal stiffness, sneezing, headache, tremors, nausea, spasms, swelling and facial reddening as well as inflammatory and itching sensations among humans.
It must also be noted here that pyrethrin is also tremendously poisonous to aquatic life, especially bluegill and lake trout. On the other hand, the chemical is somewhat toxic to many bird species like mallards. Interestingly, the toxicity of pyrethrins enhances when the water temperature is high as well as the increase in the intensity of acids. Usually, natural pyrethrins are extremely soluble in fat, but they disintegrate easily and hence they are not able to build up in the body. Pyrethrins are also toxic to bees and hence should never be used near the hives.