The interest in using natural substances for pest control is growing, especially to avoid harming beneficial insects like bees. Cinnamon, a common household spice, is often cited as a natural remedy for deterring various pests. Understanding its effect on honey bees requires distinguishing between the powdered spice and the concentrated oil. We must determine if its action is to eliminate the bee or simply to make an area unappealing.
Is Cinnamon Lethal to Bees?
Common household cinnamon powder is not considered acutely lethal to adult honey bees under typical exposure conditions. The powder itself is largely inert and does not contain the necessary concentration of active compounds to cause immediate toxicity. Bees can tolerate contact with the ground spice with no observed ill effects.
The concentrated essential oil does contain insecticidal properties, but only at high doses. The active compound, cinnamaldehyde, is required in high concentrations to cause mortality. The oral lethal concentration 50 (\(text{LC}_{50}\)) for cinnamaldehyde in honey bees is approximately \(9.6 text{ mg/mL}\), which is categorized as practically nontoxic. These fatal concentrations are far higher than what a bee would encounter in a typical garden setting.
How Cinnamon Acts as a Bee Repellent
Cinnamon’s repelling action stems from its potent aroma, which is primarily due to the compound cinnamaldehyde. This chemical is responsible for the spice’s strong, distinct scent, which bees find disagreeable. Bees rely heavily on their sense of smell to navigate, communicate, and locate food sources, making them particularly sensitive to intense, unfamiliar odors.
The mechanism of repellency involves the cinnamaldehyde interfering with the bees’ sensory systems. The powerful, spicy scent can mask the floral pheromones that bees use to identify foraging locations, effectively making an area undesirable to them. This aversion confirms its role as a deterrent rather than a poison.
Safe Use of Cinnamon in Gardens and Hives
Cinnamon is employed in integrated pest management primarily as a localized repellent against specific nuisance insects. Its most effective use in the garden is creating a barrier against pests like ants. Sprinkling ground cinnamon along entry points or around plants disrupts the pheromone trails ants use to navigate, causing them to avoid the area.
In beekeeping, cinnamon oil is sometimes used to target the parasitic Varroa mites, which are a major threat to honey bee colonies. However, the concentrations required to kill the mites are often close to the levels that can harm the bees, requiring careful, controlled application. For the average gardener, the focus should be on using the powder as a barrier and avoiding the highly concentrated oil.
To protect foraging bees, avoid dusting cinnamon powder directly onto flowering plants or near hive entrances. Applying the powder only on the ground, around the base of plants, or along windowsills keeps the repellent effect localized to ground-crawling pests. If using cinnamon essential oil, it must be significantly diluted, as undiluted oil can be phytotoxic to plants and increases the risk of harming beneficial insects.