The flowers of Tanacetum cinerarifolium, more commonly referred to as the pyrethrum daisy, have been used for hundreds of years as a form of natural insecticide. It was eventually replaced by synthetic chemical insecticides that are more effective. As time went on, however, many of these newer insecticides proved to present significant health risks. Recent interest in more natural and organic insect control has brought pyrethrum insecticide back into use. It is relatively easy to make at home using dried pyrethrum daisy flowers.
Grow your own pyrethrum daisies. Pick the flower heads just as they are opening. Dry them thoroughly. You can also purchase dried pyrethrum daisies. Grind the flowers heads coarsely.
Place 1/4 ounce of the ground flowers in a stainless steel pot with 1 gallon of water and bring to a boil. Place a lid on the pot and reduce the heat to a simmer for a half-hour. Cool the solution to room temperature.
Insert the coffee filter into the funnel and place it in the 1-gallon container. Strain the flowers from the water through the filter. Dispose of the used flowers.
Add one tablespoon each of kerosene and dishwashing detergent to increase the efficacy of the mixture. Shake thoroughly.
Place the mixture in a standard pump garden sprayer for use. Apply liberally to all parts of the plant and the ground around it.