Pyrethrum is a natural insecticide derived from the dried and powdered flowers of the Chrysanthemum plant. It is a highly effective, yet safe, option for controlling a wide variety of insect pests. Pyrethrum is a contact poison, meaning that it only kills insects when they come into direct contact with the chemical. It is a fast-acting poison and works immediately upon contact with the insect, killing it within minutes. Pyrethrum does not persist in the environment and breaks down quickly, making it a safe choice for both people and the environment. Additionally, it is not harmful to honeybees, so it can be safely used in gardens and lawns where bees are present.
Pyrethrum is a natural insecticide derived from the dried flower heads of certain菊花 (jú huā) chrysanthemum species, particularly Chrysanthemum cinerariifolium [1]. It's not a single substance but a complex mixture of natural insecticides called pyrethrins [2]. Here's a breakdown of pyrethrum:
Insecticidal Properties:
- Mode of Action: Pyrethrins act on the nervous system of insects, causing paralysis and ultimately death [2]. They disrupt the flow of sodium and potassium ions across nerve cell membranes, leading to abnormal nerve impulses and eventually insect knockdown and death [3].
- Target Insects: Pyrethrum is effective against a broad spectrum of insects, including flies, mosquitoes, cockroaches, ants, and lice [4].
Use:
- Historically: Pyrethrum has been used as a natural insecticide for centuries [5].
- Modern Use: Due to its fast-acting nature and generally low toxicity to humans and pets when used correctly [6], pyrethrum is still used in some:
- Household insecticides (sprays, foggers) for occasional use
- Food-handling areas (when labeled appropriately)
- Organic gardening (as some organic gardening guidelines allow its use)
Important Considerations:
- Breakdown: Pyrethrum breaks down relatively quickly in sunlight and loses potency over time, so fresh formulations are typically more effective [7].
- Alternatives: Synthetic pyrethroids, chemically similar to pyrethrum but more stable, are commonly used as insecticides today. However, some insects may have developed resistance to these synthetic versions [8].