Need Some Pyrethrum? Just Turn to This Chrysanthemum
Flowers often have their own way of preventing pests. A recent Sustainable, Secure Food blog from the American Society of Agronomy (ASA) and Crop Science Society of America (CSSA) discusses the history and current research surrounding the compound of pyrethrum, a natural pesticide.
Gardeners may have heard of the common trick to plant chrysanthemums around the garden to deter pests. Marigolds work, too. This is because the flowers naturally are high in chemical compounds that insects don’t like.
A particular type of chrysanthemum, Chrysanthemum cinerariifolium, isn’t typically found in nurseries. Its flowers are very high in the natural compound, pyrethrum. It can be used as both a natural pesticide on organic farms and as an insect repellent for humans. As such it’s been called a green pesticide, and researchers are looking at ways to make more of it.
The use of pyrethrum as an insecticide was a well-kept secret by ancient Persians, for the health of their crops, but its use is documented from around 400 B.C. Japan was the leading producer of pyrethrum before World War II, and later African countries began production.
How can planting chrysanthemums around a garden protect it? Some plants secrete a chemical compound from trichome glands, in this case, pyrethrum. It doesn’t have the best smell.
In the case of Chrysanthemum cinerariifolium, the highest concentration of pyrethrum is in its flowers, which are the focus of the harvest. Growers harvest the flowers at specific stages and dry the flowers. They then grind the flowers and extract the pyrethrum. From there, different products can be made, like powders and liquids.
Current Research About Pyrethrum
In its natural state, Chrysanthemum cinerariifolium doesn’t flower until its second year of growth. Researchers at the University of Minnesota recently published a paper about the work to breed a new type of pyrethrum that can flower in its first year. This would greatly increase the yield to growers, with an early payoff.
They were also looking for varieties that grew more flowers and less of the leaves and stalks. After their initial research using seeds collected from various sources, they will continue their studies and breeding in hopes to create a higher-yielding, first-year flower producer that makes more natural pyrethrum.
Ah, if it were so easy to understand the difference in names of types of pyrethrum. Pyrethrum is the natural compound found in daisies, and Chrysanthemum cinerariifolium is the type of daisy that contains the most and is used commercially.
The compound can also be made in the lab and factories. In this case, they are referred to as pyrethrin and are often mixed with other chemicals to enhance their effects. Permethrin is another synthetic compound based off the chemical structure of the natural pyrethrum. It is used to treat clothing, tents, and outdoor equipment, not skin.
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