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The team also used chemical analysis to determine how two of pyrethrum’s molecular components—EBF and pyrethrin—elicit the repellent response.

Although each product has the same effect on insects — and presents the same risks to beneficial insects — pyrethrin usually is more potent and lasts longer.

It’s the naturally derived form of pyrethrin, which, like boric acid, is deadly to insects, but has very low toxicity to humans and other mammals.

Pyrethrum is extracted from chrysanthemum flowers; pyrethrin is created in a lab.

Pyrethrin and its synthetic derivatives are used in garden insecticides, pet sprays, mosquito repellents and lice shampoos.