Homemade Plant Pest Sprays

Whipping up DIY concoctions to get rid of plant pests or diseases to save money is not penny-wise, unless you’ve got the right ingredients. Listen up, frugal gardeners… Homemade plant pest sprays and fungicides aren’t the answer. The same can be said for those who want to avoid nasty chemicals in the garden. Don’t let the cure decrease your harvest, or worse, kill your plants.


It’s never a good idea to spray dish soap on plants you don’t want to injure. Do you know what’s in that stuff? Even if it is totally free of fragrances, there are other ingredients in that bottle your plants could really do without. Yes, soap is a sticker for applications like baking soda fungicide, but once it dries, it’s stuck on the leaves of your plant. Unless it rains a few hours after application, or you put the plant in the shower for an hour or so to flush the surfaces – the degreasers and skin moisturizers in dish soap can burn the foliage of the plant, even on house plants. On plants with really sensitive leaves, the burning could be catastrophic, because just as when the insects you were trying to kill are allowed to defoliate it too severely, it won’t be able to perform photosynthesis. In short, the plant will starve to death in the end.

Dish soap is also known to cause fruit and vegetable plants to produce less to no food at all. It is way less effective as an insecticide as insecticidal or horticultural soaps.

Insecticidal soaps are not just higher priced than dish soap – they’re completely different, and totally safe for most plants. These are effective pest management for hard-shelled insect larvae and caterpillars, as well as sap-sucking insects, and spider mites. They aren’t a true soap in terms of what you buy for household use, they’re called a soap because of the fatty acids they contain. You can buy them in concentrated or ready to use formulations. Ready to use sprayers are convenient, but you’re paying a lot for the container and shipping on water content. To save money, always buy the concentrate, and store it where it can’t freeze. It will still be effective, and safe to apply for 3-5 years, and you’ll be armed to battle a lot of garden pests right away by quickly diluting some with the right amount of water in a spray bottle or sprayer tank. Whether you grow organically, or not, insecticidal soap is a powerful grower’s tool. One that pests will not develop an immunity to.


Vegetable oil is for cooking – not gardening. It’s not an organic garden solution, nor is it a good way to cut costs. Cheap and efficient aren’t the same thing, just as corn oil or olive oil and motor oil are totally different. Just because it’s oil doesn’t mean it’s what you want to use. What you want is horticultural oil.

What is horticultural oil? Depending on the brand, it can be a petroleum-derivative, or a mineral oil, neem oil. Both are effective for controlling some plant pests and diseases, and it can also be a handy sticker in some homemade garden preparations. Like old-fashioned dormant oil used on fruit trees in the past, it kills over wintering pests, but it won’t harm plants during the growing season like dormant oil would. And they are also effective at eradicating plant diseases, both fungal and viral – like leaf blights, black spot, and powdery mildew.

As with insecticidal soaps, you’ll be saving money by buying horticultural oils in undiluted concentrates. As long as the container is stored in a cool place sheltered from freezing and temperatures above 100 degrees, it too has a shelf life of 5 years.

And, in case you were wondering, neem oil is not the same as horticultural oil. It is more toxic than both insecticidal soaps and horticultural oils, though it is a valuable for controlling many plant pests and diseases when you want to avoid chemicals that are both toxic to the environment, and cause immunity to the cure to develop.


First off, like anything else in gardening, there is a right time to get a disease or insect issue under control, and if you wait too long, it might be too late anyway. Which is why it’s never smart to let a garden go without inspection for long, if you detect the problem in an early stage, it will be much easier to correct. Sometimes it’s the time of year the possibility for an eruption is likely, or knowing current weather could bring it on. Other times, especially in the indoor garden, checking conditions every day clues you in as to when to pull out the artillery.

Insecticidal soaps kills eggs and soft-bodied insects by dissolving the natural coating of their bodies, and disrupting it’s cell membranes. It’s highly effective on troublesome garden pests: aphids, whiteflies, spider mites, scale, and more.  Horticultural oils work by suffocating both plant pests and their eggs, with the added benefit of protecting plants from fungal issues, and pest-borne diseases.

Whenever you see a recipe for mixing a homemade fungicide or insecticide that calls for oil or soap – be sure to use the appropriate horticultural product as a substitute. Not only is is better for your plants, it will give you a far more effective measure of controlling pests and diseases. Both are safe for the environment, pollinators, and birds. They are not a preventative, having no residual effect, but you don’t need a hazmat suit for spraying, though making sure you have a mineral oil-based horticultural oil makes more sense than using one made from petroleum oils.

Always spray horticultural soaps and oils early morning or in the evening, so they dry before direct sunlight hits the plants. You also need to make sure that the application goes on between 40-90 degrees Fahrenheit. A cool, cloudy day when there is no wind is highly suggested for the outdoor garden, while indoor gardeners can create the right environment for spraying when it’s needed.


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Tammy Clayton

Contributing Writer at Garden Culture Magazine

Tammy has been immersed in the world of plants and growing since her first job as an assistant weeder at the tender age of 8. Heavily influenced by a former life as a landscape designer and nursery owner, she swears good looking plants follow her home.