Chemicals in spices are often noted for deleterious effects on insects. However, these natural chemicals rarely are deployed as commercial insecticides. The insecticidal chemicals in spices are often at low doses making extraction impractical. Many have complex structures that are difficult and expensive to make synthetically. They often degrade too rapidly for long term effect. They may have deleterious effects on beneficial insects or be toxic to plants. The greatest utility of insecticidal plant chemicals is to serve as models for chemists. Chemists can make modifications of a chemical structure to produce new synthetics with more desirable properties such as better efficacy, low environmental impact, appropriate selectivity and minimal adverse human health effects. Many of our modern synthetic insecticides are based on plant toxins.
Turmeric, a spice noted for insecticidal properties has been studied for its toxicity to termites and the insecticidal chemicals elucidated. The toxins are turmerone and curlone which are responsible for the flavoring properties. The mode of action is unknown. Will these lead to new types of commercial insecticides? The odds are against it and it typically requires a decade or longer to go from initial characterization to practical application.