Pyrethrum is an extract from chrysanthemum (Tanacetum cinerariifolium). It is one of the oldest pesticides known, and is also the strongest insecticide allowed under organic standards guidelines. Made from died flowers, pyrethrum insecticides are known for their fast knock-down of unwanted insects. Insects are typically paralyzed as soon as they come into contact so it is often used in wasp sprays (nothing worse than a cranky wasp).
Pyrethrum insecticides are highly toxic to bees and other beneficial insects as well as fish so really it should be treated as a last case call in control of problem ants, aphids, caterpillars, whitefly and thrips.
Products often contain piperonyl butoxide for added effectiveness and are available as Beat-A Bug Naturally (Richgro), Nature’s Way Bug Gun (Yates) and Pyrethrum Insect Killer (Kendon)
These products are broken down by sunlight so are best applied later in the day when light is less intense and when susceptible non-target insects have finished foraging for the day.
Please read instructions and guidelines thoroughly and pay particular attention to withholding period.