Any form of high-proof alcohol can extract a natural chemical called limonene from the peel. You can try using water instead, but it extracts limonene much less effectively. [2] X Research source Limonene (at high enough concentration) is proven to kill silverfish. [3] X Research source Oranges or mandarins are good choices, but just about any citrus fruit peel contains lots of limonene. [4] X Research source This recipe isn’t hard science. The more peel you use and the longer you soak it, the stronger your spray will be, but feel free to experiment.
Not all mint is created equal. Fortunately, spearmint is quite high in limonene, while “mountain mint” is even better if you can find it. [7] X Research source If your local grocery store just sells “mint” with no other description, that’s probably spearmint (at least in the US). [8] X Research source Until some scientists start to focus on this vital course of research, it’s hard to say exactly how many herbs you need. The more concentrated the better, so bunch them up wherever you see the most damage. Replace the herbs once they dry out.
Essential oils may be natural, but they’re also dangerous when they’re not diluted. If you get it on your bare skin, wipe it off with vegetable oil to prevent a burn or allergic reaction. Don’t use them on bookshelves that children or pets can access. [10] X Research source Mint oil is a proven insecticide against silverfish. [11] X Research source Lemon peel oil and celery seed (or “celery fruit”) oil both contain extremely high concentrations of limonene, a known silverfish insecticide. [12] X Research source (Check the details before you buy: essential oil from celery root is about seven times weaker. [13] X Research source ) Neem oil is okay, but weaker than mint. [14] X Research source Cinnamon, cloves, and lavender are all traditional silverfish repellents, but there’s not a lot of evidence behind them. [15] X Research source (Then again, most agricultural scientists are busy studying pests that eat grapes and not Grapes of Wrath. ) It’s best not to use a diffuser as a permanent insect repeller. Being around a diffuser for more than an hour can cause headaches and other unpleasant symptoms. [16] X Research source
Instead of the masking tape, you can tape the short edge of an index card securely to the top of the jar. Arrange the card so the other end touches the ground, forming a ramp the silverfish can climb up. [18] X Research source
Careful—diatomaceous earth and silica gel are forms of fine sand that can irritate your lungs and skin somewhat. [21] X Trustworthy Source National Pesticide Information Center Organization run by Oregon State University providing objective, science-based information about pests and pesticides Go to source Boric acid can be dangerous for infants and pets. [22] X Trustworthy Source National Pesticide Information Center Organization run by Oregon State University providing objective, science-based information about pests and pesticides Go to source These all occur in nature, but the last two can also be factory-produced, so it’s up to you whether you consider this natural enough. Read the label and safety instructions very carefully, as these products can have other added insecticides. [23] X Research source This is sometimes “pyrethrin,” a natural (but still toxic) pesticide from chrysanthemums. [24] X Trustworthy Source National Pesticide Information Center Organization run by Oregon State University providing objective, science-based information about pests and pesticides Go to source However, many other similar-sounding ingredients like “synergized pyrethrin” or “pyrethroid” are synthetic.
Note that the adults can still survive for up to three years. Use deterrents and traps to help protect your books immediately. Try this method alongside them as an investment in your future, to make the infestation less of a problem down the line.
Cedar probably works because it contains limonene, a chemical that can kill silverfish when it’s more concentrated. [30] X Research source A lot of coniferous trees (trees with needle-like leaves) also release at least a little of this, so you could experiment with their leaves or bark if they grow nearby. [31] X Research source
