`Natural' Insecticide Research: Still Working Out The Bugs

R.G. McDaniel, a University of Arizona plant geneticist, holds a patent on a flowering plant that grows in Arizona. The plant produces a "natural insecticide" that is lethal to insects yet is relatively safe for consumption by humans and warm-blooded mammals. Meanwhile, in Independence, Oreg., Krishen Bhat, the vice president for research at an agricultural company called Botanical Resources--a subsidiary of John I. Haas Co., the major hops refinery in the United States--is hurriedly working to cultivate his company's patented species of the same flower, which has been adapted to grow in California. What these two scientists are independently trying to do with the plant in question, Chrysanthemum cinerariaefolium, commonly known as pyrethrum, is to eventually grow large enough quantities of this natural insecticide-producer--at least 10,000 pounds per year--to create a viable American crop amenable to mechanical harvesting. While America uses 75 percent of the world's supply of pyrethrum, U.S. farmers grow it only in experimental, low-yielding plots. Today East African farmers provide 85 percent of the pyrethrum to the world market, most of it harvested by hand-picking. The rest comes from South America, Australia, and New Guinea. The pyrethrum plant is a long-stemmed perennial producing yellow, daisylike flowers that bloom from spring to summer. The source of the plant's insecticide, pyrethrin, is dried seeds located under the flower's button. Currently, pyrethrin is extracted from the dried flowers with petroleum-based solvents. Many people think that the flower originated in the Middle East. Centuries ago, the story goes, the Persians used it as a remedy for body lice. It was carried to Dalmatia, on the coast of Yugoslavia, in the early 1800s and was commercialized in Europe. According to folklore, a housewife noticed dead flies accumulating around a bouquet of withering flowers, and the rest is history. But Cecil Still, a professor of plant physiology at Rutgers University's Agricultural Station in New Brunswick, N.J., says that story is slightly exaggerated. The flowers, he says, would first have to have been crushed to be insecticidal. Dan MacIver, senior scientist at Fairfield American Corp. in Rutherford, N.J., a worldwide distributor of pyrethrum extract, has a different theory about pyrethrum's roots. He thinks the plant was carried to the Middle East from China along the silk routes. The plant is known in parts of China today, he says. It was--and still is--used as sweet-smelling incense in temples. "Although it is a conjecture, I feel the incense could have been seen to be effective against mosquitoes," he says. Today, in fact, 100,000 tons of mosquito coils made from pyrethrum are sold throughout the world, he says. After Yugoslavia, pyrethrum made its way to France and then to the United States, says MacIver. In 1873, it was grown in Stockton, Calif., and sold as "buhach," or insect powder. The only other insecticides available at the time were sulfur, arsenic, and nicotine, all toxic chemicals. The English also developed a pyrethrum industry. In the early part of the 20th century, pyrethrum was grown in many states in the union. Although synthetic pesticides took over, American industry maintained ties with African suppliers--ties that had been established by the British--and with the Japanese growers. After World War II broke out, American insecticide manufacturers did most of their business with Africa and have done so ever since. Crops from Ecuador, New Guinea, and Australia also recently have been sold. In the U.S., there are currently two major distributors and refiners of imported pyrethrum: MGK Co. of Minneapolis and Fairfield American Corp. --R.E. Pyrethrin, the generic name for the six related active compounds derived from pyrethrum, is considered one of the more environmentally correct insecticides for a number of reasons: It is naturally produced by plants; it decomposes rapidly in sunlight; humans and mammals show few bad effects after eating it or its byproducts of degradation; and insects do not develop resistance to it. Most other insecticides and their degradation products last longer and pose hazards to humans and the environment. "I see a lot of future for pyrethrin," says Bhat. "Not because I am personally involved in it, but [because] this is one of the safest insecticides as far as humans are concerned. Since environmental consciousness is coming to the minds of more people, I think more and more uses will be found for it." Owing to foreign climatic and political vicissitudes, pyrethrum can be expensive, so at present, U.S. insecticide manufacturers tend not to use it in as many applications as they could. But McDaniel and Bhat, among very few other U.S. researchers, aim to stabilize world supply by establishing an inexpensive American source of pyrethrum and carve a market sector and expand its world sales, which currently total $100 million. Their job will not be easy. At one time, pyrethrum grew throughout the U.S., but synthetic insecticides overtook the market in the 1930s. Since then, the U.S. has relied on foreign pyrethrum supplies. Although it would seem that, given the environmental safety of this kind of pesticide, there would be a huge demand for it today, people in the insecticide business doubt whether U.S. scientists could create a crop that will ever be able to effectively compete with the foreign breeds of pyrethrum. They say that if U.S. scientists could have produced a cheap product, they would have invested in domestic production years ago. A major hurdle for pyrethrin research, according to Cecil Still, a professor of plant physiology at the New Jersey Agricultural Station at Rutgers University in New Brunswick, N.J., who also works with pyrethrum, is that the only research that could potentially lead to lucrative licensing arrangements involves creating either new strains or new processes to extract pyrethrins. The Wonder Insecticide Because of its safety--which is being reevaluated by the Environmental Protection Agency, along with the safety of all other pesticides used in the U.S.--pyrethrin is often used as a pre- or postharvest spray to protect foodstuffs on their way either to food processing facilities or to storage in the dark, where the pyrethrin is less susceptible to breakdown. Veterinarians prescribe pyrethrin for intestinal parasites in livestock. Pyrethrin compounds are contained in head lice shampoos, and in many indoor roach and insect sprays. Farmers use pyrethrin on their crops to flush out insects from hiding, but, because it is also expensive, the farmers use it sparingly and then kill the exposed bugs with another insecticide. Some household insects, though, can detoxify modest amounts of pyrethrin poison in their bodies. But when insecticide manufacturers combine a little bit of pyrethrin with a synergist, piperonyl butoxide (PBO), the insect's metabolism is fooled: It can't break down the pyrethrin, and it dies. Most indoor formulations of the product contain PBO, which is extracted from a Brazilian species of sassafras and was originally discovered as a component in sesame oil. PBO is also being evaluated by the EPA. Scientists have tried to protect pyrethrin from breakdown by placing it in a sunscreen-like material so it can be used as a crop spray. 3M Co., in St. Paul, Minn., has a product on the market that coats the insecticide powder in a gelatin. San Diego-based Mycogen Inc., a pesticide company that uses biotechnological techniques in other product applications, is developing a fatty acid-protected pyrethrin. "With our combinations, you can use a quarter of pyrethrin to get the same insecticidal effect," says Leslie Hickle, manager of entomology and nematology at Mycogen. "Currently, there is an opportunity to use this product on high-value crops to increase their value even further," she says. "But to make it more available economically, there has to be [lower] cost of the starting materials." The high cost of the imported natural pyrethrin and its quick degradation has inspired U.S. chemists to try to synthesize pyrethrin for the past 30 years. Their efforts produced "pyrethroids," which are also marketed worldwide. Pyrethroids are similar to the natural product, although they don't break down rapidly, they can't flush out hiding insects, and insects develop resistance to them. "Synthetics don't reproduce the natural product because in the test tube, scientists make all geometric forms of the compounds, and it is difficult to purify the precise ones that are efficacious. In the plant, only the six active geometric forms are created, and they are what is extracted," says Don MacIver, senior scientist at Fairfield American Corp. of Rutherford, N.J., an international distributor of pyrethrins and a subsidiary of Wellcome Foundation Ltd., Research Triangle Park, N.C. Where Are All The Flowers? Given all of pyrethrin's positive attributes, it would seem that many scientists would be rushing to join those already engaged in pyrethrum research, or that the federal government would be interested in sponsoring this work. But that does not seem to be the case. McDaniel's research in Arizona is financed by a small group of independent investors who work in the food processing industry, who hope that he can establish a domestic source. Rutgers' Still says that he hopes the U.S. Department of Agriculture (USDA) will consider a grant application he just sent to the agency. "They stopped funding pyrethrum research years ago because they assumed synthetics would be very successful," says Still. In the early part of the 20th century, the USDA fostered pyrethrum research. "But then DDT came along, and pyrethrum went by the wayside," says Marc Sims, a chemical engineer who patented a pyrethrin extraction method using carbon dioxide instead of petroleum. Sims says he believes a domestic crop can take root if the federal government or industry would commit resources to it over a long period. In fact, he says, a pyrethrum crop that has been established in Tasmania has been supported for the last 10 years by Commonwealth Industrial Gases Ltd. (CIG) of England. This new crop should boost pyrethrin production on that island from 15 percent of the world's supply to 25 percent, according to George Hinkson, director of manufacturing for Fairfield American. The British company invested in the insecticide because it sells the gases used in its application on stored food. Scientists hope to replicate in the U.S. the success of the Tasmanian experiment. CIG, with some Australian government tax support, put together a team of people who are knowledgeable in pyrethrum plant selection and started to lease land from the Tasmanian farmers to grow their plant. "Tasmania has some of the richest farmland in the world. The farmers ride around in Mercedes," says Hinkson. Initially, in field trials, CIG scientists used pyrethrum as a resting crop for poppies. "Poppies take a lot out of the land, so they can only grow for two years. Pyrethrum lends organic [material] to the soil and takes little from it." Then the company expanded to using pyrethrum as an alternate for other crops. All CIG asked of the farmers was the use of their underground irrigation. Exploiting all the latest agricultural methods available, CIG's team planted the high-yield crop, cared for it, and mechanically harvested it. They paid the farmers for their land and added some royalty, based on yields. Today CIG has about 2,500 acres growing after about an $8 million to $10 million investment. But, according to Hinkson, the cost of the Tasmanian product is still much greater than the cost of the East African crop. In East Africa, he says, cost-effective, low-tech sowing and reaping predominate. "About 30 times a year, an East African mother and her children will pick the pyrethrum from their third-of-an-acre plot that they keep in their 2 acres of land," explains Hinkson. "They let it dry, collect the flowers, and place them in 30-kilo sacks--around 66 pounds--and the father carries it approximately five miles from the farm to a collection point. It then gets sorted, graded, and extracted. Most refinery and formulation of the finished product occurs in the States." About 195,000 families maintain 65,000 acres of the flower. Although Hinkson applauds the efforts of the U.S. scientists who are trying to duplicate the accomplishments of the researchers in Tasmania, he says that, had his company thought it could be done, it would have invested in domestic production years ago. and pyrethrum distributors agree that it would be cost-prohibitive to start an industry in the U.S. using "peasant" labor similar to East Africa's. American labor is too expensive, they say. "But if anyone can do it at a significant cost below the Tasmanians, they may have a chance," says Hinkson. Furthermore, some people allege that if the East Africans discovered an American company was supporting U.S. growth of the flower, they would become vindictive and cancel all their shipments. "This could wreak havoc in the American insecticide industry," says a scientist speaking on condition of anonymity. Nevertheless, the U.S. scientists are continuing their research. But they have a long way to go. Bhat has only about 50 acres growing in California but hopes to double that number next year. McDaniel claims he has a plant that can grow in high altitudes and in the dry climate of Arizona. "Insecticides based on plant chemistry is an emerging industry," he says. "I still think there will be many opportunities in the near future."

`Natural' Insecticide Research: Still Working Out The Bugs

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