Notwithstanding the desire and well-intentioned efforts of many organic gardeners, there comes a time when insecticides must be used to eliminate bugs that infest and destroy garden crops. Many prefer to use a natural insecticide rather than a synthetically produced chemical insecticide. Rotenone and pyrethrum are both very well known and widely used natural insecticides derived from plants. Other natural insecticides include nicotine, neem oil, and soap.
Rotenone and pyrethrum are commonly used as natural insecticides. Rotenone is derived from the root of tropical and sub-tropical plants of the genus Derris. Rotenone acts as a broad-spectrum natural insecticide that poisons both on contact and by ingestion. Rotenone is typically used as a dust or spray, and while non-toxic to plants, it is highly toxic to fish and moderately toxic to warm-blooded mammals.
Pyrethrum is derived from the Dalmatian chrysanthemum and is used in dust or liquid suspension form. In large concentrations, it acts as a natural insecticide by attacking an insect’s central nervous system. Pyrethrum in small concentrations may not be toxic to insects, but it retains the ability to repel insects. Pyrethrum is toxic to fish, but less toxic to mammals than synthetic pesticides. It is biodegradable and breaks down easily with exposure to light.
Some organic gardeners recommend using soap, which has been used as a natural insecticide for hundreds of years. Diluting liquid dishwashing detergent, such as Ivory, with water to a 1-2% solution that can be sprayed to cover plants has been found effective at controlling insects. However, use caution, as repeated and thorough coverage with high concentrations of soap may cause damage to certain kinds of plants. Soap as a natural insecticide may be far less toxic to humans and animals than other alternatives, but it can also be far less effective, especially when treating an infestation.
While nicotine, neem and other botanical insecticides not discussed here have been found to be effective with minimal to moderate success, any kind of natural insecticide should be used as minimally as possible. Just because you use a natural insecticide rather than a synthetic one does not mean it is any less harmful to animals or humans. Application of any type of natural insecticide should be performed safely and only at the frequency necessary to maintain a healthy crop of fruits or vegetables.
