Pyrethrum Kills MosquitoesBy Adina Dosan (adinamiti)
August 23, 2012
This spring, tons of snow melted fast in the hot sun and they formed small lakes where mosquitoes grew and reproduced. It seems they've never been as thirsty as this year, nor have they attacked with more fury and in such numerous numbers. Before I had time to go to the store and buy a repellent, I was covered with mosquitoes bites which were itching so badly! I tried burning ground coffee which seemed to work, if I stayed very close to the smoke. But nothing worked as well as a repellent. I figured I need to spray myself all over my body, because mosquitos seem to find any repellant-clear spot and bite it! It's not too comfortable to be sticky with the repellent on, but it's safe. I was so relieved I've found the best solution to this serious problem. Not repellent but another solution, easier and more comfortable appeared later: Pyrethrum. It is a member of the daisy family that I have in my garden, and it is a natural insect repellent, if grown in large clumps. Had I known this summer would bring millions of mosquitoes, I would have divided this plant before and made more clumps in my garden to have a natural protection from these bugs or any other bugs.
Pyrethrum, or Tanacetum cinerariifolium (syn. Chrysanthemum cinerariaefolium) grows wild on the field, but has been cultivated since old times for its insecticidal properties. Its flowers were used in the Napoleonic wars by the soldiers to control flies. It is also called Dalmatian pyrethrum because it originated on the Dalmatian coast in Croatia, Europe - which is probably why it's growing in Romania; we are closely situated to Croatia. It used to be cultivated in China and Japan, but other countries were prefered lately, for their temperate climate and better volcanic, well-drained soil which can produce more crops per year. The best regions for cultivating pyrethrum are now East Africa, China and Australia where the plant can grow as a perennial. Romania has a commercial production of Pyrethrum which can also grow here as a perennial because it is frost resistant, but only in the warmer southern regions of our country.
Pyrethrum came to grow on the field around my house thanks to the former landlord who had sowed herbs all over the field. Because of its scent I first thought it was chamomile and I brought a clump in my garden. First spring after that it bloomed beautifully, but with tall stalks which showed it wasn't chamomile as I thought. This spring, with all the freeze and snow we had last winter, it barely formed a few stalks each with a flower on top. It seems that the flower bed I planted it in isn't well-drained enough for the pyrethrum to grow at its best. I need to move it to another location, with fewer plants around it so it can grow and divide. Then I will be able to say, "Watch out, mosquitoes!" It's worth trying, if it's only for experiencing what I've learned, but if it keeps the mosquitoes away, all the better.
Pyrethrum acts against insects through the six esters known as pyretrins which are active ingredients contained in the Pyrethrum's flowerheads within the flower parts called achenes - the future seeds. Pyrethrins are susceptable to UV light and changes in pH that's why they don't survive too much in the environement and need to be combined with synthetic compounds so they can be better stored for commercilizing. It's very interesting how many insect control products for pets, for home and garden and for environment have pyrethrins as a main active ingredient. In order to obtain the pyrethrins, the Pyrethrum flowerheads need to dry first, then ground and the pyrethrins are extracted from that powder. In the past people mixed the powder with water and use it to repel insects around the house, even on animals. But even if it is a natural pesticide it can be harmful to humans. Pyretrins' effect on insects is very interesting. It acts on the insects' nervous system, making them increase movement so they can make contact with the insecticide plant and stops the female mosquitoes from biting.
If mosquitoes are hiding on this wall, behind some plants in my garden, this means a big clump of a dozen Dalmatian pyrethrum would mess with their nervous systems and make them fly towards the plants, where they would be killed. That is what I am calling a cheap bargain; don't you agree? All I need is to take care of the few plants I have so they can grow bigger and divide themselves and this time next summer, I will be able to report that I don't have any mosquitoes hiding around my house or in my garden.
So now you all know, I've spread the word. I would like to chat more, but I have to go and find the small pyrethrum plants I have and move them to a better location, with more sun and well-drained soil. Mosquitoes, here I come!
 - http://www.pyrethrum.com/About_Pyrethrum/History.aspx
 - http://www.pyrethrum.com/About_Pyrethrum/Agronomy.aspx
 - http://www.pyrethrum.com/About_Pyrethrum/Agronomy/Pyrethrum%20Farming%20Conditions.aspx
 - http://www.pyrethrum.com/About_Pyrethrum/Pyrethrins_Pyrethroids.aspx
 - http://www.pyrethrum.com/Uses.aspx
 - http://www.pyrethrum.com/About_Pyrethrum/Processing.aspx
 - http://en.wikipedia.org/wiki/Pyrethrum#Sprays
 - http://www.pyrethrum.com/Uses/Professional.aspx