Little Rwanda scents big business in pesticide-producing flowers

A poor, landlock African country with a national economy based almost exclusively on subsistence agriculture is about to turn its natural abundance of large white flowers into a big business.

The country is little Rwanda. The flowers are pyrethrum, the source of powerful but biodegradable pesticides.

Rwanda's action could affect food production and public health everywhere.

World demand for pyrethrum -- the source of an environmentally safe but highly toxic pesticide with increasing use in agriculture, forestry, and public health projects -- consistently outstrips supply.

Rwanda, one of Africa's least-developed and most densely populated countries, has just opened a $3.5 million refinery in the town of Ruhengeri intended to turn its pyrethrum flowers into much-needed cash.

This year, the refinery hopes to process an estimated 1,600 tons of dried pyrethrum flowers (Crysanthemum cinerariae-felium), employing more than 8,000 families in the operation.

This will make Rwanda the world's third- largest producer, after neighboring Kenya and Tanzania. The labor-intensive local economy is well-suited for the task, which involves harvesting the large white flowers in full bloom to ensure the highest concentration of pyrethrins, the insecticidal extract.

Pyrethrins are comparable to DDT, with an immediate paralytic effect on flying insects. Yet they have a low toxicity rate on humans, other mammals, and plants -- one of the lowest among all household insecticides. Yet they safely and rapidly decompose as a result of exposure to sunlight and air into a chemical form that is harmlessly absorbed by the environment.

They are active ingredients in many domestic insecticides as well as in livestock and pet sprays. A set of scientifically controlled experiments recently has demonstrated that minute quantities of the substance can effectively control field insects. Improved application techniques intended to extend the residual effect of these insecticides have led to a widening use of pyrethrum.

The flowers were introduced to Kenya early this century. From there cultivation spread to Tanzania and Zaire. Rwanda's pyrethrum region stretches in a semicircle over the high ground between the towns of Gisenyi and Ruhengeri in the northwest, where the cool climate contributes to the local strain's relatively high pyrethrum content of 1.7 percent.

But dried flowers are expensive to transport, especially for a poor and landlocked country such as Rwanda. Industrial production was made possible by the construction of a local extraction plant between 1970 and 1972. The process has been carried further with an advanced research program into means of refining the crude extract. This has led to erection of the present refinery, which has an annual capacity of 80 tons of purified pyrethirns.

The project is supported by the United Nations Development Fund. Dutch and Austrian firms are also involved.

Pyrethrum production is controlled by a local agricultural cooperative. Its members include many formerly landless peasants, who are allocated 3/4-acre plots by the government. Local yields have nearly doubled during the past decade.

Given the rapidly widening world market for a product traditionally in short supply, Rwanda's new industry is expected to yield an assured income in hard foreign currency.