Pyrethrin, the active ingredient of pyrethrum powder, kills insect pests. Pure pyrethrin disintegrates quickly after use, so that no lingering toxic residues remain to poison children if used in the home or ecologically beneficial animals if used out of doors. Pyrethrum powder has several natural sources, and attempts have been made to develop alternative sources. Does this Spark an idea?
Dalmatian Pyrethrum
Dalmatian pyrethrum belongs to same plant family as the chrysanthemum and the tansy (Compositae). It has borne various scientific names, including Chrysanthemum cinerariifolium and Tanacetum cinerariifolium. Dalmatian pyrethrum is currently the most common source of pyrethrum powder. The foliage of the plant contains some pyrethrin, but its composite flower head has the most abundant supply, according to "Natural Pyrethrins and Biotechnological Alternatives" by Srdjan Jovetic. The achenes (the tissue that covers the seeds) have an especially rich supply of pyrethrin. Dalmatian pyrethrum grows wild in the Balkan countryside, but commercial supplies come from cultivated fields in such countries as Kenya.
Persian Insect Flower
The Persian insect flower belongs to the same genus as the Dalmatian pyrethrum. Its scientific name is Tanacetum coccineum. Its colorful composite flower head gives it the additional popular name "painted daisy." It ranks second to Dalmatian pyrethrum as a source of pyrethrum powder. Other Tanacetum species, such a s Tanacetum marschalli, contain even less pyrethrin in their flower heads.
Pyrethroids
The extraction of pyrethrin from flower heads requires considerable labor. Many producers have switched to other crops, and the production of pyrethrum powder tends to fall behind the demand. Besides, the rapid disintegration of pyrethrin in sunlight limits its value as an agricultural pesticide. For this reason, there has been a demand for synthetic products similar to pyrethrin but more effective for use in farmers' fields. Synthetic substances called pyrethroids fulfill this need. However, though they are similar to pyrethrins, they are more toxic to the environment.
In Vitro Experiments
In vitro (laboratory) experiments may lead to alternate ways to produce pyrethrin. Some experiments have not succeeded. For example, tissue grown from a pyrethrum callus does not produce pyrethrin. However, cultures with differentiated shoot tissue have produced some pyrethrins. Efforts have also been made to produce pyrethrins by the process of bioconversion. This process starts with precursors of pyrethrins, such as, isopentyl pyrophosphate, and exposes them to the enzymes that convert these precursors to pyrethrin in nature. The enzymes may be applied in the form of a homogeneous pyrethrum plant extract or else by genetically engineering some microorganism to produce the enzymes.
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