Occurring mostly in mild, moist conditions, rust affects many different kinds of plants. Circular to oval yellow spots appear first on the upper leaves that turn into the familiar reddish to orange bumpy-looking pustules.
Left untreated, you may notice yellowing of leaves and eventual leaf drop . Affected plants include hollyhocks, cactus, roses, monstera, beans, and tomatoes.
Chemical sprays are available to control rust plant disease. However, for organic gardeners, there are many home remedies and natural ways to treat the problem.
Here’s how to treat rust on plants organically.
1. Baking Soda
This is a readily available domestic product that can be effective against rusty plant disease. A fungicide spray can be made up and applied to the leaves at weekly intervals until the disease is under control.
A basic solution is 1 tsp. of baking soda to a quart of water and a little liquid organic soap. However, experts suggest 4 tsp. of baking soda to 1 oz. of horticultural oil and a gallon of water.
You can also add a little white vinegar. Mix well and use as a foliar spray to help get rid of rust fungus on plants.
2. Neem Oil
This is an old tried and tested gardener’s aid that is a natural fungicide that is great for treating rust on plants.
Neem oil sprays are commercially available online and at the garden store. Alternatively, make a homemade spray for rust on plants by combining one teaspoon of neem oil with half a teaspoon of mild liquid soap and a liter of water.
Spray affected plants, particularly the leaves, once per week to eliminate rust on leaves. You can also use the treatment fortnightly thereafter to avoid a recurrence of the fungus.
Neem has the added benefit of eliminating insect pests that deposit honeydew, a sticky substance that encourages fungal growth.
3. Prune Infected Leaves and Branches
Rust fungi can spread across other plants of the same genus. Therefore, pruning back infected leaves and stems will help stop the spread and encourage new healthy growth.
After pruning, clear any rusted leaves and debris from around the base of plants. Next, give the healthy plants a protective fungicidal spray.
Also, cut back any overhanging tree branches to let in light and air. Dark, damp, and humid conditions will only encourage fungi to grow.
Pruning is the recommended control method for white pine blister rust.
4. Bonide Liquid Copper Fungicide
In insufficient quantities, copper can kill plant cells. But, Bonide is a well-tolerated product that controls rust in garden and other fungal diseases on trees, ornamentals, and crops.
This ready-for-use copper soap spray kills rust on plants and is safe to use in your organic garden. Use it according to the packaging instructions.
Spray under and the upper surfaces of leaves plus the stems. Repeat every 7-10 days or so, depending on the degree of infection. This product works well for cedar apple rust and coffee rust.
5. Bonide Sulfur Plant Fungicide
This commercial product is formulated to prevent fungal spores from developing.
The sulfur fungicide comes in a powdered form, so you can dust it onto all areas of plants vulnerable to rust or mildew. Alternatively, mix it with water to make a solution that is best applied with a pressure sprayer in line with the product label guidance.
Bonide Sulfur is generally non-toxic to pets and wildlife. However, it is toxic to some aquatic creatures so avoid using it in areas near ponds/water features.
Applied with care, this product can prevent spores of rust fungi from germinating and ruining crops.
6. Clean Up Plant Leaves and Debris
This is another important practice to prevent rust spots on leaves from developing and spreading. The fungus can overwinter so clear away all debris from under and around plants.
Also, remove badly infected plants entirely and dispose of them away from the garden and not on the compost heap.
7. Avoid Overhead Sprinklers
Watering plants correctly can help in keeping the garden free of leaf rust. Overhead watering is likely to create the sort of moist environment that encourages spores of rust fungi to germinate.
Overhead watering also causes splashing. Consequently, the rust can be spread through droplets of water that splash off.
The solution is to water around the roots using a watering can or install a drip irrigation system.
8. Mulch Soil After Clean-Up
Using a thick layer of mulch will prevent the spores from splashing back on the leaves.
Additionally, mulch protects the base of the plant and keeps the soil moist, avoiding the need to water frequently. It will also keep weeds down.
9. Space Plants Properly
An abundance of flowers growing in the garden is a joy to behold. However, overplanting can provide a breeding ground for pests and diseases.
Plants will thrive with space between to absorb adequate water and nutrients and light and air to develop correctly.
Fungal problems like rust can appear in dark and damp closely packed areas where water droplets or and/or wind can spread spores easily.
As a result, resisting the temptation to fill every space will pay off in the long run.
10. Remove Weeds That Host Rust
Certain weeds and wildflowers can harbor rust. Wild mallow will host hollyhock rust and willow herb is well known as a host to fuchsia rust.
Thoroughly root out the infected weeds and dispose of them. Additionally, some rust fungi spores can overwinter and germinate in the spring.
Therefore, clear away all discarded debris with rust fungus from the garden. You can also toss them onto the bonfire.
There are many different rust diseases but fortunately, most respond to natural control treatments. Applying these organic methods can help to eliminate rusty mildew effectively and long term.
See also: eliminating powdery mildew naturally.