Add one and a half tablespoons of baking soda plus one tablespoon of dish soap and one tablespoon of vegetable oil (or any other cooking oil). Stir this mixture into one gallon of water, and spray it on your roses' foliage. Reapply every seven to ten days, or after a rainstorm.
Apply the spray one time each week on a cloudy or overcast day to avoid plant burning. Spot-treat a few leaves as a test before widespread use. Another preventative option is a spray made with four teaspoons of baking soda in one gallon of water. Apply regularly to prevent disease onset.
Baking Soda.
Dilute 1 teaspoon to 1 quart of warm, soapy water and spray on your roses' leaves. The baking soda will treat and prevent diseases like black spot, while the soap helps it stick, and is also mildly effective at smothering many insects pests.
A Cornell University researcher demonstrated that a mixture developed for powdery mildew—1 tablespoon of baking soda mixed in a gallon of water, with a bit of horticultural oil or liquid soap added to help it cling to the leaves—is also effective for reducing the spread of black spot.
Spray your rose with a strong spray of water from the hose in the morning now and then to wash off any fungus spores that have not yet embedded themselves into the leaves. Reapply powdery mildew treatments often, every two or three weeks, throughout the growing season.
By treating every seven to 14 days, or until conditions no longer favor the disease, unfurling new leaves are protected right from the start. If black spot is already active on your roses, move quickly to control and stop its advance.
To keep the fungi from developing a resistance to your homemade spray, it is recommended that you alternate remedies each week. Use baking soda one week and milk the next. Whether spraying with water or a home remedy, do it early in the day so the leaves can have a chance to dry before evening.
Organic growers have used milk and baking soda with success. Simply mix half a litre of milk with two tablespoons of baking soda in five litres of water and spray liberally over foliage and stems. This formula can be applied at any time of the year.
Rose sprays with tau-fluvalinate and myclobutanil as the active ingredients (like in Yates Rose Gun, and Yates Rose Shield), will be effective in the control of black spot and insects such as thrips and aphids.
Using vinegar in flower water can help you keep your cut flowers looking fresh and vibrant for several days longer than they would without it. Adding vinegar to flower water helps to prevent bacterial growth, which is often the culprit behind wilting flowers.
Mix one tablespoon of vinegar with one cup of water. Add one and a half tablespoons of baking soda plus one tablespoon of dish soap and one tablespoon of vegetable oil (or any other cooking oil). Stir this mixture into one gallon of water, and spray it on your roses' foliage.
Baking soda contains sodium and sodium is toxic to plants. So yes, if you dump enough sodium onto a plant, it will die. However, sodium is very soluble in water. So when it rains, the sodium is washed into the rest of the soil, where it might kill plants that are not weeds.
Insecticidal soap and horticultural oil are also effective against rose slugs. Other insecticidal sprays that are labeled for homeowner use include acephate, bifenthrin, cyfluthrin, lambda cyhalothrin, permethrin, or spinosad. Sprays should thoroughly cover both upper and lower leaf surfaces.
Use baking soda to not only get rid of aphids but also mites and whiteflies. Make a solution at home by adding 1/3 teaspoon of baking soda to 500ml of warm water. Also, add half a teaspoon of vegetable oil and mix well. You can also add 7-8 drops of liquid soap to make the solution even more effective.
To use baking soda on roses, mix 1 tablespoon of baking soda with 1 gallon of water. Add ¼ to ½ teaspoon of insecticidal or liquid soap to the mixture once the baking soda dissolves completely. Shake it well and spray it weekly on the roses to treat powdery mildew and black spots.
Baking soda helps the plants become less acidic and prevents fungal growth.
Black spot is a fungal disease (Diplocarpon rosae) that affects roses.1 The fungus develops as black spots on the leaves, which eventually causes the leaves to turn yellow and drop off. Besides looking unsightly, it can seriously weaken the rose plant. Black spot on roses thrives during cool, moist weather.
Nutrient Deficiencies
If your leaves are turning yellow and have brown or black spots, it is likely that your roses are suffering from a nutrient deficiency. The most common deficiencies include nitrogen, iron, magnesium, and a soil pH that is high.
Mix fat-free milk with water in a 1:1 ratio and apply it using a spray bottle. Spray the solution directly onto the clean leaves of your roses. The milk-and-water solution coats the leaves and leads to the growth of an invisible fungus that frightens off black spot!
Give each rose a teaspoon of Epsom salts. In a fortnight, new growth will form, minus blackspot on the leaves. To control diseases, roses must be sprayed each fortnight with fungicide.
Baking soda solution: Mix 1 tablespoon baking soda and ½ teaspoon liquid soap such as Castile soap (not detergent) in 1 gallon of water. Spray liberally, getting top and bottom leaf surfaces and any affected areas.
Powdery Mildew Rose Treatment
If you're seeing just a light case of powdery mildew, you can try spraying it off with water on a warm, dry day. However, it's good to keep an eye on it, because it's more than likely to return. Perhaps the best way to stop the fungus in its tracks is to treat your roses with neem oil.
Baking soda is pure sodium bicarbonate, a fine white powder that has many uses. You may wonder about bicarbonate of soda vs. baking soda, but they are simply alternate terms for the same ingredient. If your recipe calls for bicarbonate of soda, it is simply referring to baking soda.
Milk works best as a preventative measure rather than as a cure. This means you ideally should apply it at the start of warm, humid weather before powdery mildew has appeared on your plants.
The good news is that powdery mildew infections are typically mild. Otherwise healthy plants will often recover on their own after changes in the weather, and with proper care to improve airflow. Treatment is often unnecessary.