An organic interest in Pyrethrum


Probably ever since the beginning of growing crops for food some 10,000 years ago, farmers have been battling hungry insects.

Sulphur, mercury and arsenic were used by ancient Chinese, while Romans and Greeks tried religious and folk magic rituals and smelly smoke from burning stinky objects such as fish and dung.

Then, maybe 2,000 years ago, the Persians discovered that a powder, Pyrethrum, made from grinding the dried blooms of a species of Chrysanthemum flower would protect stored grain from insect damage.

Bordeaux mixture (lime and copper sulfate), sodium arsenate, creosote, and nicotine derivatives, such as Black Leaf 40 which my parents used in our large garden, were prevalent in this country.

After World War II, chlordane, DDT, and other very effective chemicals were developed and widely used until they were found to be unsafe for humans and other animals and most were banned.

Today, insect control is safer and more sophisticated, even to the point of genetically engineered crops that are boll weevil and corn borer resistant.


However, the growing demand for “organically grown” food has revived interest in the ancient Persian pesticide pyrethrum.

Pyrethrum is organic, has a very low toxicity to mammals (except in large concentrations), and biodegrades quickly — although it is toxic to fish as well as pollinators such as bees.

Native to the Caucasus area of far southwestern Europe, pyrethrum began to be grown in Japan in the 1880s and, by the early 1930s, the Japanese were supplying most of the chemical used in this country — although Kenya in Africa was then becoming an active supplier as well.

About this same time, attempts were made to grow pyrethrum in Colorado, Pennsylvania, Maryland and a couple of other states.

While the plants grew OK, the only way to harvest the flowers, which look almost exactly like the common daisy we’re all familiar with, was by hand picking — a process that required “a tremendous amount of labor,” according to an account at the time.


It was deemed that hand picking costs in this country would be prohibitive, so the USDA decided to develop a mechanical harvester.

A bluegrass stripper was tried but tended to pull the plants out by the roots, while mowing or cutting with a reaper or grain binder were not entirely satisfactory.

The flower heads and stems cut this way were allowed to cure and then put through a threshing machine with carefully adjusted screens and air blast and a fair separation of stems and flowers resulted.

There was still enough stem and leaf debris that the resulting product could be used only for certain purposes.

A cotton stripper was also tried and, while not very successful in its original configuration, it furnished the basis for a more or less efficient pyrethrum harvester.

Trialled during the late 1930s at several locations in this country the one-row machine used the cotton stripping rollers mounted at an angle on a corn binder frame and utilized the binder’s gathering snouts and chains and bull-wheel drive.

Instead of a binding deck, a bin in which to collect the flowers was attached at the rear. The harvested flowers, which still contained a lot of stem pieces and leaves, were then run through a fanning mill which, it was claimed, removed most of the debris.


Apparently, even with the new harvesting machine, pyrethrum production never caught on in the United States, probably due to the war and because of the proliferation of chemical insecticides developed during the ’40s and ’50s.

Kenya continued to supply the bulk of the pyrethrum used here, and in the 1980s the Australian state of Tasmania undertook to get into pyrethrum production in a big way.

An island state, Tasmania’s main island is located about 150 miles south of Melbourne on the southeast edge of Australia and is surrounded by the 334 smaller islands of the state.

The main island contains 24,911 square miles and the northwest part is where pyrethrum is grown. Kenya, Rwanda and Tanzania in southeastern Africa, where the plants are transplanted and harvested by hand, still provide a percentage of the world’s pyrethrum.

Tasmania, however, has developed a highly mechanized system of growing the stuff — since 2004 when production in Kenya dropped drastically — and now produces more than 75 percent of the world market.


Instead of hand seeding, and then separating and transplanting the seedlings by hand each spring, as is the practice with African producers, Tasmanian farmers drill the seeds directly into the soil where they come up in two or three weeks.

The crop isn’t harvested until the following summer and, being a perennial, will often yield two or three more harvests before beginning to decline.

When ready to harvest, the crop is cut with a windrower and allowed to dry, after which it is gathered with combines equipped with special pick-up heads, separating the flower seeds which contain the greatest concentration of pyrethrum.

Botanical Resources Australia (BRA) is a Tasmanian company that has contracts with some 900 farmers, who grow more than 3,000 hectares (about 7,500 acres) of pyrethrum, which yields 10,000 metric tons of pyrethrum flowers per year.

These flowers are harvested by a contracted fleet of around a dozen windrowers, 25 to 35 combines and around 40 grain trucks, and then hauled to BRA plants where the oil is extracted, refined and put into drums for shipment all over the world.

I came across this subject while leafing through a 1942 issue of Farm Machinery And Equipment Magazine that contained two photos of a horse-drawn pyrethrum harvester.

I’d never before heard of pyrethrum, but once I started the research it proved fascinating.

I wonder if any of those old corn binder-like machines are still out there in a fence-row or junkyard. It would be so cool to have one all fixed up and take it around to the shows.

Wouldn’t that cause some wild speculation among the “experts”?


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Sam Moore grew up on a family farm in Western Pennsylvania during the late 1930s and the 1940s. Although he left the farm in 1953, it never left him. He now lives near Salem, where he tinkers with a few old tractors, collects old farm literature, and writes about old machinery, farming practices and personal experiences for Farm and Dairy, as well as Farm Collector and Rural Heritage magazines. He has published one book about farm machinery, titled Implements for Farming with Horses and Mules.



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