Unequivocally, the best-kept secret that many people have been shouting about for over 190 years is Hypochlorous Acid (HOCl). Commonly referred to as “Electrolysed Water,” HOCl is an aqueous solution with concentrations that range from 1000 ppm to as low as 1 ppm and ideally has a near-neutral pH.
This simple compound that includes hydrogen, oxygen, and chloride can address everything from powdery mildew and smelly shoes to SARS-CoV-2, acne, the eggs of spider mites, and even bad breath! HOCl has never been registered as a pesticide or a fungicide; instead, widespread testimonials have witnessed its efficacy in many pests and pathogens, plant health, and vigor. More likely, HOCl is commonly registered as a disinfectant. The “magic” behind this unicorn transcends agriculture and is routinely used in hospital sanitation, wound irrigation, cosmetics, and the industrial cleaning of commercial spaces.
Hypochlorous Acid Offers More Stability
Despite HOCl being discovered in 1834 and recognized as one of the most potent and safest disinfectants, it has yet to receive favor over other products like isopropyl alcohol and bleach due to its lack of stability. In years past, manufactured HOCl generated from the electrolysis of water containing either non-iodized salt (NaCl) or hydrochloric acid (HCl) would quickly revert into its component parts, making it ineffective.
Proprietary technologies have now created HOCl solutions at various concentrations that can be shelf-stable for over a year. The variability in shelf stability highlights one of the other reasons why HOCl has not garnered widespread acceptance, as not all hypochlorous acids are created equally. People wrongly assume that all HOCl is the same. HOCl in an aqueous solution can have a wide range of pH and purity (i.e., removing much of the NaOH – sodium hydroxide), which can have a bearing on its stability and ability as a disinfectant.
The Hypochlorous Acid Rumour Mill
Misleading information is another major factor that has limited HOCl from being recognized as a disrupter technology. Many have concluded that HOCl in water is no different than a sodium hypochlorite (NaClO) solution, a common bleaching agent. They do not consider that bleach contains harmful chloramines and stabilizers such as sulfates and phosphates that promote algal blooms. Stable HOCl remains as HOCl, while in contrast, NaClO will dissociate into having hypochlorite (ClO-) ions, which can be very corrosive to humans and metals.
Interestingly, many argue that the disinfectant efficacy of bleach comes from the presence of HOCl. The electrical neutrality of HOCl, especially when designed to have a near-neutral pH, can penetrate plant cell walls and enter cell membranes to exert bactericidal effects on pathogens while causing little or no harm to plants and humans.
All Mammals Produce Hypochlorous Acid
When we consider using chemicals as disinfectants or pesticides, we tend to think of these created by people wearing white lab coats and appropriate PPE (Personal Protective Equipment). Ironically, HOCl is something all mammals produce as a first line of defense against pathogens. White blood cells (neutrophils) chase down invading pathogens, releasing chemicals like the most powerful oxidizing agent—HOCl. HOCl produced in our bodies remains stable for seconds but can kill bacteria, fungi, viruses, and perhaps even viroids in plants.
Even more exciting about all mammals producing HOCl is that in appropriate concentrations, many of the beneficial microbes we find on our skin, mouths, and gut microbiome are not impacted by HOCl. Many beneficial microbes are the same as those found in and on our plant leaves and soil. For example, gram-positive endospore-forming beneficial bacteria like Bacillus subtilis are not killed by HOCl when using recommended rates and contact time. This suggests that growers and gardeners seeking the benefits of microbes associated with nutrient cycling and plant protection can use HOCl in moderation.
Hypochlorous Acid in the Garden
The myriad uses for HOCl in other sectors, such as personal, health, and dental care, are ever-increasing. However, agriculture is the focus of this article, and I am sharing information gained through personal experimentation, anecdotal observations, and communication with other growers. Although not a paid advertorial, my comments are based on five Canadian HOCl products registered as disinfectants, foliar fertilizers, fruit and vegetable washes, or cleaners and descalers.
Most adopters of HOCl are initiated by using it in their sanitation program, but it’s not an easy entrance. For many growers, the notion that “something non-toxic is going to disinfect better than something toxic” is hard to swallow. However, the efficacy, albeit vastly superior to alcohol, quaternary ammonium, bleach, or hydrogen peroxide, is not the only factor in their decision. The safety of their workers plays a significant role in choosing HOCl. In contrast, with products like alcohol and bleach, HOCl requires no PPE and leaves no residue or odor. The contact time for most pathogens is relatively short, so using a fogger or mister works well. There is no safety issue as one might have with an electrostatic sprayer and isopropyl alcohol.
Moreover, several scientific papers claim HOCl does not appear to cause pathogens to mutate, like bleach, alcohol, or hydrogen peroxide. This may lead growers to use HOCl to help slow the mutation of plant pathogens. Within the realm of sanitation, HOCl is more readily accepted as an irrigation and filter cleaner, removing biofilm and scale deposits. Many hydroponic, aeroponic, and deep-water culture systems titrate low concentrations that keep fertigation lines clean and provide root protection, allowing for healthy roots.
Hypochlorous Acid on Seeds and Cuttings
The less chartered waters for HOCl, and frankly more interesting than surface sanitation, is what growers and gardeners worldwide have been experimenting with by using HOCl on plants. For some growers, HOCl starts with the seed or the cutting (clone). Low concentrations as a seed soak help reduce pathogens that may have established, like fusarium or botrytis, while having minimal impact on the beneficial seed microbiome. Similarly, in clones, HOCl helps oxidise the wound from the cutting action and reduces the probability of infection. It is important to note that chloride is also an essential element that can help drive good vegetative growth.
The Exciting Rewards of Hypochlorous Acid
Perhaps an expanded interpretation of the fruit and vegetable wash label or using HOCl as a foliar fertilizer, several growers use HOCl as a prophylactic mist throughout the growing cycle and are reaping some exciting rewards. Expectedly, diseases like powdery mildew and botrytis are non-existent, but many growers have noticed fewer pests like aphids, thrips, fungus gnats, and spider mites. Most interestingly, testimonials stating shorter growing cycles and increased flavor and aromas (terpenes) have been commonly reported. Mushroom growers mist cultivation rooms, growing media, and mature fruiting bodies to establish a sterile environment and prolong shelf-life.
Cannabis growers, including tissue culture labs, use HOCl in their quarantine program to establish plant health and vigor pre- and post-transport. Some cannabis producers will mist HOCl just before harvest to ensure a lower pathogen load prior to drying and curing. Similarly, outdoor cannabis growers will use HOCl as a flower wash to reduce the microbial load post-harvest.
Magical Solutions
As a non-mainstream agronomist, you get accustomed to being presented with some truly “magical” solutions that would be game-changers, only to be frustrated by people unwilling to try an alternative but still complain about the dysfunctional status quo. Hypochlorous acid, when generated at pH neutral, is that magical unicorn that shows promise to revolutionize disinfection and, to some extent, cultivation practices, safeguarding crops and consumers alike.
