DIY Garden Fungal Sprays: Which Ones Actually Work?

Common fungal diseases like powdery mildew, black spot, root rot, and anthracnose are unwelcome visitors in our gardens. Hot summer conditions, humidity, and dry and wet fluctuations are the basic breeding grounds for developing spores. Cool, damp conditions of spring and fall also challenge prevention.

Fungal plant problems pop up and spread quickly. Signs include leaf spots, dieback, and discolored growth and patches. Early detection is the key to reducing fungal spread among plants. Grow disease-resistant selections in areas prone to high humidity or with a history of infection.

With early detection, the benefits of homemade fungal sprays become more effective. Commercial fungicides may contain harsh chemicals that aren’t ideal to use on indoor houseplants or in the home garden environment. Simple sprays that use household ingredients are nontoxic to people and pets and can be effective in preventing fungal outbreaks.

How To Use Homemade Fungicide Treatments

If you don’t want to use commercial fungicides, consider testing home remedies. Experiment with what works for your plants by testing a single leaf or small section with a treatment. Observe the response over two to three days before continuing the application.

Use ingredients and water dilutions in the appropriate amounts. Increasing active ingredients leads to adverse effects and plant damage. 

Avoid applying treatments in high heat and intense sun exposure. Morning is a good time for applications when conditions are mild before evaporation in the day’s heat. Water plants the day before treatment to ensure they have ample moisture and vigor.

Baking Soda

Baking soda is a common household ingredient we use in baking. Sodium bicarbonate also serves to disrupt the cell walls of fungal spores like powdery mildew. 

Baking soda applications are best as a preventative measure rather than treating severe infections. If your plant is already fungus-laden, skip this remedy and go to solutions like neem oil and sulfur commercial applications.

Make a simple spray using baking soda powder and water. Add a small amount of horticultural soap or castille soap to act as an adjuvant. The soap is optional, but it helps the baking soda and water adhere to leaf and stem surfaces. 

Avoid using dish detergent in lieu of castile or horticultural soaps. Dish detergent has ingredients that can burn leaves.

Use this mix fresh, as it doesn’t store well. Also, take care not to overuse or overapply baking soda. It accumulates in the soil, affecting salts and pH levels.

Milk

Milk has surprising antifungal qualities for plants. It’s one of those home gardener remedies passed along for generations, and now science is supporting the practice.

Milk has compounds that may be antiseptic against fungal spores. The compounds may prevent outbreaks and support plant resistance against diseases.

Research indicates that higher-fat milk is more effective against fungus than skim or whey products. For effectiveness, combine one part of milk with up to nine parts of water. Straight milk without water can have side effects.

Combine the milk and water and shake the mixture. Use it as a foliar spray and weekly preventative. A drawback to this easy spray may be a spoilt milk smell in summer’s high heat. Adjust applications accordingly.

Mouthwash

If spoilt milk is offensive, opt for a refreshing mouthwash spray. Just as it’s antiseptic as an oral rinse, its properties also hold against fungal spores.

Mist plants with diluted ethanol-based mouthwash to kill germs and spores. An experiment in the Horticulture Department at the University of Minnesota found that it reduces powdery mildew infections.

Use caution when applying the mouthwash mixture to new leaves and young plants. It may burn new growth.

Vinegar

Vinegar contains acetic acid, shown to be effective against powdery mildew and other plant fungi. For the most effectiveness, opt for apple cider vinegar with 5% acetic acid mixed with two to four tablespoons of water.

Apple cider vinegar has natural sanitizing qualities that prevent pathogenic fungi.  Apply this easy remedy as a spray treatment, but use caution. Vinegar is a natural herbicide in strong concentrations. High amounts burn leaves and stems and alter the composition of soil.

Hydrogen Peroxide

Hydrogen peroxide has many disinfecting, astringent, and oxidizing abilities. Diluted in water, it makes an efficient spray against powdery mildew and other fungal problems. It also repels pests and kills eggs and larvae.

For best control, use a 3% peroxide solution (commonly available). As with our other astringents, high concentrations can lead to plant burn and damage.

Cinnamon

A spice cabinet essential with potential healing qualities makes cinnamon a fine ingredient in the garden. Research indicates that cinnamon, with its essential oils and elements like calcium and manganese, may keep plant diseases at bay.

Cinnamon oils and extracts may offer protective alternatives to chemical treatments and preventative measures in garden fungicides. The substances may stave off bacterial and fungal growth, including botrytis and phytophthora.

Cinnamon is a natural pest deterrent. The compounds affect egg and larval health, and the aroma repels adults. Ants don’t like to walk across the powder (though it won’t affect their health). Cinnamon also serves as a natural rooting stimulant for cuttings and seedlings.

As with any treatment, avoid overapplying ground cinnamon. With natural herbicidal qualities, high concentrations damage leaves.

Treatments to Avoid

Not all commercial or homemade treatments will be effective against fungal diseases. Plant selection, type of disease, level of infection, and resistance to treatments play into spore spread. Sometimes, pulling the plagued plant or rotating crops is the best solution.

Treatments to avoid are those whose damage outweighs the benefits, whether for plant and soil health or environmental impacts. Avoid applying higher concentrations than recommended levels. Two common do-it-yourself applications to skip are dish detergents and blasting leaves with water.

Dish Detergent

Liquid soaps are often powerful cleansing agents with multiple compounds to remove grease and grime. These agents cause foliar burn and plant cell damage, even in water dilutions. 

Mild soaps have long uses as at-home insecticides and fungicides, but milk and commercial treatments like neem and horticultural soaps are more effective and have less risk of burn than many detergents. 

An unharmful exception is castille soap, which is effective in a water dilution as an insect deterrent. It also acts as a carrier and surfactant in household remedies using powders like baking soda.

Water Spray

Spraying leaves and stems with a strong stream of water is sometimes thought to rid plants of fungal growth. Unfortunately, it serves the opposite effect. Splashing water is one of the primary spreaders of fungal spores. Spraying them with a jet allows spores to travel between plants and soil surfaces.

Save the water blasts to rid plants of pests and knock them off stems and leaves. Do this spraying early in the day so leaves dry in the day’s sun.

Prevention

Prevention and early detection are the best ways to rid the garden of diseases. Home remedies and commercial treatments inhibit the spread when caught early.

Frequently Asked Questions