earwigs from sweet melon leaves and ornamentals such as lupine and snapdragons, with diatomaceous earth, also called Fossil Shell Flour. But the bumble bees love my snapdragons; I'm worried.
There's more than slight controversy across the internet, regarding whether or not DE harms bees. Yet, the Tui Rose, author of a 2010 book on Diatomaceous earth called Going Green Using Diatomaceous Earth How-to tips says that, the thick coating of hair on the bees' bodies makes it tough for DE to damage the bees. This jives with the method by which DE works, which is to absorb the lipids or waxy outer layer of insects' exoskeletons, causing them to dehydrate.
Rose felt that the bees are smart enough to avoid blossoms with DE. If they are coated with it, will use beating wings to rid itself of the dust. However, one should avoid helping the bees to ingest it, which would certainly damage their innards. Worst case scenario, the inflicted bee would perish before reaching the hive. Furthermore, the presence of granules of DE dust in the hive, should not kill the colony.
To minimize the possibility that DE will harm a bee:
- When sprinkling a plant with diatomaceous earth, avoid the blossoms as much as possible.
- Carefully assess damage to your crop, to see if DE can be avoided all together, with minimal impact to the harvest.
- Sprinkle DE on the ground, rather than on the plant.
- If spraying on the plant, work to make it adhere to the plant, such as spraying the leaves with water first (best done in the cooler hours of the day) and then sprinkle lightly with DE. (I use a flour sifter with a fine mesh, from my kitchen.)
- Finally, offer bees an alternate water source, so they are not tempted to suck up water atop a layer of DE on your plant.
Bear in mind, that though diatomaceous earth may minimally harm your bee populations, it will harm other beneficial insects in the garden, which lack the hairy exoskeleton.