I’ve read that, post nuclear holocaust, the only survivors will be cockroaches. I believe that not only is this possible, but they will probably be joined by insects of all kinds, to judge by the total dominion that blackflies, mosquitoes and ticks have over us. As soon as temperatures in Maine rise enough to make gardening a pleasure, swarms of blackflies move in to spoil the party. While they are merely a minor nuisance (as opposed to their relatives, carriers of dengue, West Nile, Zika, Lyme disease, etc.), digging and planting while inhaling clouds of tiny insects that also bite at any area of exposed skin turns spring gardening into a misery of slapping and scratching. I find myself wishing I had a long horse tail to swish continually so my hands could be free to do their work instead of waving away flies. But absent the tail, we depend instead on insect repellent, LOTS of insect repellent, because I only use those that have essential oils as their active ingredient.

Of course I know that repellents containing DEET are the gold standard for woodsmen, fishermen and explorers who hang out in areas where bad bugs live. But DEET has raised lots of red flags concerning environmental and human health risks, and, while those risks must be balanced out with the risk of mosquito- and tick-borne diseases, for forays into more benign garden territory, I choose to go with the more natural products. DEET is thought to work by blocking an insect’s olfactory receptors, which detect elements found in human breath and sweat, so if I can block their receptors with a bit of lavender, citronella or cedar oil, I’ll settle for that. Studies have shown that combining several essential oils from different plants — say, lavender and lemongrass, for example — leads to a synergistic effect, providing a higher repellent activity than if single isolated components were used, and for the most part, these oils are fairly pleasant to smell. The main drawback in using them is that the effects tend to dissipate quickly due to their high volatility. For example, citronella oil is highly volatile and, thus, insect repellents with citronella oil as the major component need to be reapplied every 20 to 60 minutes. The duration of effectiveness in essential oils such as lemongrass, cedar, peppermint, lavender, and geranium oils is estimated to be between 30 minutes and two hours. So in order to repel those pesky blackflies, I end up spraying on lots of my favorite natural repellent, which costs the same per ounce as the finest cognac, every half hour or so.

Fortunately, there is a cheaper DIY alternative. Just as you can make homemade Boursin or Kahlua that rival the originals, you can mix up a batch of a natural insect repellent that will see you through the gardening season. The original outlay for essential oils may be a bit steep, but you only use a few drops per batch, so they last a long time. Further, using a recipe that employs an oil for a carrier for the active ingredients allows them to remain on the skin, and thus actively repelling, for a longer time than a spray that uses water as its carrier. Soybean oil is an excellent base because of its natural bug-repellent properties, but you can substitute any lightweight, organic oil such as sunflower, grapeseed or almond.

E S S E N T I A L   O I L   I N S E C T   R E P E L L E N T

15 drops geranium essential oil
8 drops cedarwood essential oil
8 drops citronella essential oil
6 drops eucalyptus essential oil
6 drops lemongrass essential oil
5 drops peppermint essential oil
12 cup organic soybean (or other) base oil
4-oz. spritzer, pump, or squeeze bottle
Add the geranium, cedarwood citronella, eucalyptus, lemongrass, and peppermint essential oils directly to the storage bottle, then add the soybean oil. Screw the top on the bottle and shake vigorously to blend. Allow the spray to synergize for at least an hour. Store at room temperature, away from heat and light, and use within one year. Shake the bottle prior to each use. If you feel greasy after applying the oil, you’ve used too much.

If you’d like a lighter-weight repellent, which is a good idea in times of higher humidity, you can use the same essential oils, but use a blend of witch hazel and purified water as the carrier.