When I was researching for The Cannabis Terpene Experience, the strange dichotomy that terpenes depict was rather eye-opening. Terpenes carry with them medicinal properties of enormous magnitude, such as anticancer properties , anti-anxiety properties [2,3], and an effectiveness against bacteria , parasites , and viruses  including COVID-19 .
These properties resemble the yin and yang — some kind of cosmic balance of healing (of us) and annihilation (of things that hurt us). All sorts of thoughts danced in my brain because although I was (and am) an avid anthophile, I did not know the full extent of specific plants’ philanthropy, as told by the scientific literature.
And while I knew that plants can defend themselves, I became mesmerized by the weaponized wrath that a plant can wield with its arsenal of terpenes. Juxtaposed to the heavenly or hellish powers of the terpene, depending on a specific organism’s vantage point, is the fact that darling, vital honeybees communicate parent to child and amongst the adults using terpenes. So, terpenes interweave themselves throughout sentient nature, performing all sorts of tasks running the spectrum from aiding to annihilating. It’s some of the functions of terpenes in nature that I’d like to explore in this article.
We’ll start with the love potion and the bewitching scent of the terpenoid nerolidol. Male red spider mites heel to the scent of nerolidol (as well as geraniol and farnesol), which can be found in plants like corn and tomatoes, but also jasmine, magnolias, and cannabis. The male mite dutifully watches over the female about to emerge from her cocoon, drawn by terpenes emanating from within. 
With nerolidol, though, the loveliness in the mite’s story quickly turns to deathly intentions. Nerolidol is a well-known bodyguard of many plants by, for example, signaling to carnivorous mites to come feast upon invading herbivore spider mites. Yin and yang — Earth in harmony — hired bug muscle — however you slice it, nerolidol’s power puts on a display that doesn’t disappoint.
Mother Earth has more wild tales to tell. Some regard another terpenoid called geraniol, common to attractive plants like geraniums, roses, hops, and cannabis. Precious honeybees utilize geraniol as part of a cocktail of molecules collectively known as the Nasanov pheromone.  Worker bees emit this pheromone to help navigate foraging bees back to their homes with the food.
Aphids release β-farnesene to sound the alarm that an attack is imminent, letting other aphids know to disperse.  While β-farnesene might help keep aphids safe, it too has a dark side. The pine sawfly lays eggs on pine twigs, the process of which releases a volatile cocktail in which β-farnesene is the primary active ingredient. A parasitic wasp picks up the scent and flies to parasitize the eggs. 
Plants communicate chemically as well, especially when they are being eaten. Their fragrant cries for help can signal eaters of herbivores to come to their rescue. Such is the case with lima bean plants.  What’s more, evidence points to chemical communication through the air from one plant to neighboring plants cautioning to the presence of predators. Amazingly, some studies have found that plants responded to their neighbor’s aerial messages by bolstering their own chemical defenses.  Who says plants can’t talk!
While the honeybees like geraniol, mosquitoes loathe it. In fact, geraniol has been shown to be a more effective repellant of mosquitoes than citronella.  A study of citronella, linalool, and geraniol diffusers placed six meters (approximately 20 feet) from mosquito-containing traps demonstrated abilities to repel mosquitoes by 22%, 58%, and 75%, respectively. 
Mama and Baby Bee
Another terpene that honeybees use to communicate is ocimene. Human babies cry when they want food, but honeybee larvae produce trans–β-ocimene to express their hunger.  The strongest concentrations of trans–β-ocimene are emanated from the time just after the larvae have hatched to when they are three days old, illustrating the importance of the terpene exchange during fragile periods of growth
Taking a lesson from Mother Nature, farmers can tap into what plants already know. For example, there are various pests that damage vital food crops such as corn and wheat. Borers, weevils, and their friends likely populate the nightmares of farmers given the destruction they can quickly cause. Luckily, there are terpenoids like camphor, which demonstrated its power when applied to filter paper and offered to the wheat weevil, maize weevil, red flour beetle, and the larger grain borer.  Camphor foiled the pests’ plans, repelling 80-100% of the bugs, and had the added ability to inhibit the development of eggs and other immature growth stages, providing a weapon against all stages of beetle and weevil life.
The sumac flea beetle plasters its own back in its feces. It does this to create a cheap shield out of readily available material. Why? The beetle can defend itself with its malodor against ants, who, having wandered within the beetle dung-armor, have been seen fervently cleaning themselves. Researchers fed the beetles just lettuce and found that the beetles were left weaponless.  When the shields were chemically analyzed, fatty acids, tannins, and the terpenoid phytol were detected. These molecules were also found in the sumac tree, once again demonstrating the symbiosis to be found throughout nature, where one form of life helps another.
In the Ocean
The battles involving terpene weapons aren’t just relegated to land, as many marine species utilize terpenes for protection.  For example, green algae contain a sesquiterpene called caulerpenyne that provides defense against mastication by sea urchin.  Sesquiterpenoids in Dysidea sponges help prevent attack by spongivorous fish (Pomacanthus imperator). 
Terpenes are all around us. They amazingly engage in various battles on land, through the air, and in the sea. They provide communication lines between plants and their neighbors for good (warnings) or ill intentions (allelopathy). They repel, eradicate, and terminate, and yet, they are simultaneously, remarkably beneficent for humankind and many other forms of life on our Earth.
While cannabis has popularized these dear molecules in modern society, they’ve been here all the time, spread ubiquitously throughout nature. We already know some of what these selfless substances can offer, but with increasing regularity, we are unraveling even more of the mysteries authored by Mother Nature.
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Image Credits: MartinB29, CC BY-SA 4.0, via Wikimedia Commons; Aleksey Gnilenkov from Moscow, Russia, CC BY 2.0, via Wikimedia Commons; Joao Burini, CC BY-SA 4.0, via Wikimedia Commons; Insects Unlocked, CC0, via Wikimedia Commons; Bernard Dupont from France, CC BY-SA 2.0 via Wikimedia Commons; NOAA Mr. Mohammed Al Momany, Aqaba, Jordan, Public domain, via Wikimedia Commons