Sasha CampbellRust diseases affect many kinds of plants. However, each rust fungus usually infects only certain host plants. Some rust fungi need two different plant types to complete their life cycle.
Rust often grows well during mild, humid weather, especially when leaves stay wet for several hours. Commonly affected plants include hollyhocks, roses, beans, snapdragons, daylilies, apples, pears, and some houseplants.
If the disease becomes severe, leaves may turn yellow or brown and fall off [1]. The plant may also become weak or produce fewer flowers and fruits.
Chemical sprays are available to help control plant rust. However, organic gardeners can also use natural products and good gardening practices to manage the disease.
How to Treat Rust on Plants Organically
Rust often causes raised, powdery bumps called pustules. These bumps usually develop on the undersides of leaves. They may be orange, yellow, brown, red, or black.
Other plant diseases can cause similar spots. Therefore, identify the problem before applying any treatment.
Rust-damaged leaves will not turn green again. The goal is to remove infected material, protect healthy growth, and prevent the disease from spreading.
1. Choose Rust-Resistant Plants
Growing resistant plants is one of the best ways to prevent rust.
When buying seeds or young plants, check the label or plant description. Look for varieties described as rust-resistant.
Resistance does not always mean that a plant can never become infected. However, resistant plants are less likely to develop a serious disease.
This method is especially helpful for beans, snapdragons, daylilies, roses, and hollyhocks.
2. Use Neem Oil Carefully
Some neem oil products are labeled for controlling certain fungal diseases. However, neem oil will not control every type of rust.
Check the product label to make sure your plant and its disease are listed. Follow the mixing and application instructions carefully.
Spray a small part of the plant first. Wait at least 24 hours and check for leaf damage before spraying the whole plant.
Do not apply neem oil during hot weather or when strong sunlight is shining on the leaves. Spray early in the morning or late in the evening.
Neem oil may also help control certain insect pests that add stress to plants.
Neem oil is an oil-based product. Do not use it close to a sulfur treatment. Follow the waiting period listed on the sulfur product’s label.
3. Prune Infected Leaves and Branches
Remove infected leaves and stems as soon as you notice rust. Early pruning may reduce the number of spores that can spread to healthy growth.
Use clean, sharp pruning tools. Place infected material in a bag or container instead of dropping it on the ground.
Do not remove too many leaves at one time. A plant needs healthy leaves to make food and recover.
Clean pruning tools after working on an infected plant. You can wipe the blades with 70% rubbing alcohol. Keep the alcohol away from flames, and let the tools dry before using them again.
Some rust diseases require special pruning methods. For example, you may manage white pine blister rust by removing an infected branch before the disease reaches the trunk. If the trunk is infected, ask a local tree expert or Extension office for advice.
4. Apply a Labeled Copper Fungicide
Bonide Liquid Copper Fungicide is labeled for certain rust diseases and other plant problems.
Copper fungicides mainly protect healthy plant tissue from new infections. They do not repair leaves that are already damaged.
Some copper products are approved for organic gardening. However, this does not mean that they are harmless. Copper may burn sensitive leaves, and repeated use can cause copper to build up in the soil.
Use the product only if your plant and its disease appear on the label. Follow the label for mixing, timing, protective clothing, harvest waiting periods, and the number of treatments allowed.
Cover the upper and lower surfaces of the leaves. Do not assume that one spraying schedule is right for every plant.
5. Use Sulfur Fungicide Carefully
Bonide Sulfur Plant Fungicide is labeled for rust on certain fruits, vegetables, roses, and ornamental plants.
Sulfur works best as a protective treatment. It can help stop rust spores from infecting healthy plant tissue, but it will not restore damaged leaves.
Apply the product as a dust or mix it with water, depending on the label. Cover the plant evenly without using more than directed.
Do not apply sulfur during very hot weather. Sulfur may also harm certain plant varieties, so read the label carefully and test it on a small area first.
Never apply sulfur within two weeks of neem oil, horticultural oil, or another oil spray. Some plants may require a longer waiting period [2].
Avoid breathing sulfur dust or allowing it to enter your eyes. Keep it away from ponds and other bodies of water.
6. Clean Up Fallen Leaves and Debris
Many rust fungi can survive in infected leaves, stems, or other plant material. Spores may become active again when suitable weather returns.
Remove fallen leaves and infected debris from under and around affected plants. Clean the area at the end of the growing season, too.
Do not place infected material in a home compost pile unless the pile becomes hot enough to destroy plant diseases. It is usually safer to bag the debris or dispose of it according to local yard-waste rules.
Good garden cleanup will not remove every windblown spore. However, it can reduce the number of spores close to your plants.
7. Avoid Wetting the Leaves
Water plants near the soil instead of pouring water over their leaves. A watering can, soaker hose, or drip irrigation system can help keep the foliage dry.
Wet leaves may give some rust spores the moisture they need to infect plants. Splashing water may also move spores to nearby leaves.
If you must use an overhead sprinkler, water early in the morning. This gives the leaves time to dry during the day.
Do not water late in the evening if the leaves will remain wet overnight.
8. Add Mulch After Cleaning the Area
After removing infected debris, place a moderate layer of clean mulch around the plants if mulch is suitable for them.
Mulch may reduce soil and water from splashing onto the lower leaves. However, it will not stop rust spores carried by the wind.
Mulch can also help keep the soil moist, protect plant roots, and control weeds. This may reduce how often you need to water.
Do not pile mulch against stems or tree trunks. Leave a small open space around the base of each plant. Mulch that is too thick or too close to stems can trap excess moisture and encourage other diseases.
9. Space Plants Properly
Crowded plants stay damp longer because air cannot move easily between their leaves.
Follow the spacing directions on seed packets or plant labels. Thin seedlings when necessary, and prune crowded growth without removing too much foliage.
You can also cut back nearby plants or overhanging branches if they are blocking too much light and air.
Better spacing helps leaves dry faster after rain or watering. It also makes plants easier to check for early signs of rust.
10. Remove Infected Weeds That Host Rust
Some rust fungi use weeds or wild plants as hosts.
For example, wild mallow can host hollyhock rust. Willowherb can host fuchsia rust. Cedar-apple rust uses junipers and plants in the apple family to complete its life cycle.
Identify the rust before removing nearby plants. Pulling every weed or wildflower will not control all rust diseases. Many rust spores can travel long distances in the wind.
Remove confirmed host weeds that show signs of infection. Place them in a bag and dispose of them according to local yard-waste rules.
Wash your hands and clean your tools after handling infected material.
How to Help Prevent Rust
Check your plants regularly, especially during mild, damp weather. Check both sides of the leaves to catch early infections.
Keep plants healthy by giving them the right amount of sunlight, water, and nutrients. Avoid using too much high-nitrogen fertilizer. It can produce soft, leafy growth that may be more open to some diseases.
Do not save seeds or cuttings from badly infected plants. If a small annual plant is covered with rust, removing the whole plant may be the best choice.
When adding new plants to your garden, inspect their leaves and stems first. Keep infected plants away from healthy ones until you know what is causing the spots.
Takeaway
Rust diseases cannot always be cured after they appear. However, early action can slow their spread and protect healthy growth.
Remove infected material, keep the leaves dry, improve airflow, and clean up fallen debris. When needed, use a copper, sulfur, or neem product that is labeled for the plant and disease.
Always follow the product label. Even natural and organic treatments can damage plants, people, helpful insects, or the environment when used incorrectly.
See also: How to Get Rid of Powdery Mildew Naturally.
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