There are articles all over the Internet that tout just dumping some household product on your yard or garden in the name of pest control. The problem is, they often are not based in reality or scientific studies. I would wager that some of the folks writing the suggestions may not have even tried their advise on their own yard.
In this article I examine some of the more common suggestions and provide links to some of the fact-based and scientific information I have been able to find.
Epsom Salt for Pest Control
There are some anecdotal indications that applying Epsom salt around the base of plants may deter crawling insect and slugs. Applying Epsom salt as a foliar spray may discourage beetles. If you also have a magnesium deficiency in your soil, applying Epsom salt can be a beneficial nutritional supplement. The thing is that many people who have a bug problem don’t have a magnesium problem, so repetitive applications of magnesium sulfate can cause soil toxicity.
The only way to know for sure if you have a magnesium deficiency is to do a soil test. For more details about that please see our article about The Benefits Of Using Epsom Salt In Your Garden.
Rock Salt for Pest Control
A little bit of salt diluted in water is probably not going to hurt your growing things too much. So salt runoff from de-icing your driveway or water splashed out of a saltwater pool will have a limited effect on nearby vegetation, especially if you live in an area where it rains periodically.
Rain is actually part of the problem with using salts for pest control. Instead of staying where you put it, when it rains, the salt dissolves and runs downhill. If ‘downhill’ is directly into the gutter where it goes to a storm sewer, municipal waste treatment systems are accustomed to dealing with a small amount of salt. However, if ‘downhill’ means running through an area with sensitive plants, that is a problem. Repeated application of the sodium chloride (the primary contents in Rock Salt) can cause the soil to salinize.
While Rock Salt is indeed cheaper and less toxic than chemical pest control products, it really is not something I can recommend for your garden. For more scientific commentary of soil salinity and its effect on crops and vegetation in general see this article Nutrient and mineral excesses, salinity, and salt toxicity.
Where Is It Safe to use Salt for Pest Control?
There is one specific case I can think of where salt makes sense for pest control. In Koi ponds, low concentrations of salt is actually recommended. The salt discourages parasites, often resulting in healthier fish. Since the pond systems circulated the same water and are maintained to balance the salt concentration through evaporation and precipitation cycles, the salt benefits the fish without harming the surrounding plants.
Koi Ponds are an example of a ‘closed system’ – in other words, a place where the salt will not get dissolved and drain away. For more about how exactly to use salt in a Koi pond, and most importantly what kind of salt to use, please see The Secret To A Healthy Koi Pond: Just Add Salt.
Other Urban Myths on Salt for Pest Control
Here are a few other prevalent myths regarding salt for pest control:
Salt for Mosquito Control – Studies show that it is ineffective.
Salt for Ant Control – Salt may temporarily repel ants on the surface of a hive. Worker ants will not bring the salt to the queen ant though (they know it’s bad!) and as long as the queen ant is in a hive, the other ants will try to carry on.
In general, brewing up your own homemade pest control is not a great idea. For more details on this subject, I found this article Myth-busting Homemade Pesticides that is was compiled by Virginia State University.
Salt for Weed Control?
Similarly to using salt to control insect pests, the ‘net is full of suggestions to use salt to control weeds. Will applying rock salt to weeds kill them? Yes. Is it a good idea? NO!!
For the same reason that salt is not a good choice for pest control, it is not a good idea for weed control. It will kill your desirable plants just as fast as it kills weeds, and you can create a salinity problem in your soil that is hard to fix. Just don’t do it.
Final Thoughts
Whatever you decide to put on your yard or garden to deter insect pests, consider that you also might be affecting desirable insects such as honey bees, ladybugs, native moths, earthworms and more.
Featured Photo by Erik Karits.
