How To Treat Leaf Streak on Daylilies (Complete Guide)

Daylilies are beautiful and hardy perennials, but sometimes their foliage can develop issues. Leaf streak is common on daylilies and appears as yellow stripes on the leaves. It is caused by the fungus Aureobasidium microstictum, which thrives in wet conditions.

You can treat leaf streak on daylilies by removing and discarding damaged foliage, diving and replanting the daylilies, and applying a fungicide to the plants. Clean all the garden tools used to work on the daylilies to prevent the fungus spread and monitor the plants closely for signs of infection.

However, some advanced techniques can be used to treat leaf streak on daylilies. The rest of this article will discuss the basic and advanced techniques for treating leaf streak on daylilies so you can return to enjoying your beautiful plants.

1. Identify the Problem Accurately

The first step in treating leaf streak on daylilies is to confirm that the problem is indeed caused by the fungus Aureobasidium microstictum. Rust is a common daylily disease and can look similar to leaf streak, so it is essential to ensure you are treating the right problem.

Leaf streak will usually appear as wide and pale yellow stripes on the daylily foliage. If the yellow stripes are accompanied by orange, red, or brown spots, the problem will likely be rust. Additionally, if the stripes appear on new foliage and older leaves, it is more likely to be a leaf streak.

2. Get the Right Tools

Once you have confirmed the cause of the problem, you can get the right tools before starting treatment. You will need sharp scissors or pruning shears that have been disinfected. Additionally, you will need a fungicide specifically designed to combat Aureobasidium microstictum.

A fungicide containing the active ingredients mancozeb, chlorothalonil, or thiophanate-methyl effectively controls the fungus. You should also have some safety equipment, such as protective glasses, long sleeves, and gloves.

These products are available at most garden or hardware stores. Follow the products’ instructions carefully, and ensure you wear the safety equipment when applying them.

3. Remove the Affected Leaves

Now that you have the right tools, it is time to start treating the daylilies. The leaves of the daylily affected by leaf streak should be removed as they are the most visible symptom of the disease and can spread the fungus to other plants.

Cut away all the leaves that are heavily affected by leaf streak. To do this:

  1. Put on your safety equipment.
  2. Use sharp scissors or pruning shears to cut away affected leaves at their base. Cut well away from the main crown of the daylily, as you do not want to damage any of the healthy foliage.
  3. Place the leaves in a plastic bag.
  4. Repeat this process until you have removed all the affected leaves.

Now that you have removed the affected leaves, you are halfway to treating leaf streak on your daylilies. 

4. Discard the Leaves

While you have removed the infected leaves, they may still spread the fungus to other plants. To prevent this from happening, it is essential to discard the leaves responsibly.

The best way to dispose of the infected leaves is to burn them. Find a safe open space away from trees and bushes, away from any children or pets. Build a small fire and burn the leaves completely before disposing of the ashes in the trash. 

If this is not possible, you should place the leaves in a sealed plastic bag and dispose of them in a garbage bin. You can also bury them deep in the ground if you do not plan to use that area for other plants. Composting the leaves is not recommended as the fungus can still spread to other plants, even in the compost heap. 

5. Divide and Replant

After removing and discarding the infected leaves, you should divide the plants in your daylily bed into smaller clumps and replant them in a sunny area with good air circulation. This will help to reduce the spread of the fungus as it thrives in humid areas.

Separate the clumps of daylilies into smaller sections to reduce overcrowding. To divide the clumps:

  1. Use a shovel or spade to cut around the edge of the plants.
  2. Carefully lift out each section.
  3. Replant the sections in a sunny area with good air circulation.
  4. Place in a separate area.

To replant:

  1. Prepare the soil by tilling it to a depth of 10-12 inches (25.4-30.48 cm).
  2. Mix some compost into the soil to add nutrients.
  3. Dig holes for each section that are deep enough to cover the roots and crowns.
  4. Gently place the daylily into the hole. 
  5. Backfill the hole and pat down gently to secure the plant in place.
  6. Water thoroughly. 

Plant the daylilies in well-drained soil and keep the soil evenly moist to reduce the likelihood of leaf streak reappearing. The distance between plants should also be increased to provide better air circulation. Keeping a distance of at least 18 inches (45 cm) between plants is best. 

Daylilies should be fertilized once a month in spring and early summer, but don’t overdo it. Too much fertilizer can cause leaf streak to reappear. You can also add mulch around the daylilies to help retain moisture and prevent weeds from growing.

Replanting the clumps in this way should help to reduce the spread of the fungus and prevent it from affecting other plants. 

6. Apply Fungicides

Once you have replanted the daylily clumps, you can apply fungicides to help prevent leaf streak from returning. These chemicals are applied directly to the foliage and inhibit the fungus from growing. Many fungicides are available, so choosing one specifically designed for treating leaf streak on daylilies is important. 

Fungicides can be applied in several ways:

  • Spray application: This is the most effective way to apply fungicides, as it helps distribute the chemical across the foliage evenly. To do this, you should use a hand-held sprayer or an automated system to ensure even coverage. You should ensure that the fungicide reaches the underside of the leaves for maximum effect and should reapply every two weeks.
  • Soil application: This method creates a barrier in the soil that prevents the fungus from growing. It involves mixing the fungicide with water and applying it to the soil around the daylilies. You should apply the fungicide every four to six weeks and ensure it is distributed evenly throughout the soil. 
  • Drench application: This involves mixing the fungicide with water and pouring it directly onto the leaves. It effectively controls leaf streak, but you should be careful not to get the chemical on other plants as it may harm them. Ensure that the drench reaches all parts of the plant, including the undersides of the leaves. This method should be used sparingly, and you should reapply every two weeks. 

Use at least two active ingredients when applying fungicides to prevent the fungus from becoming resistant. Alternate between the two active ingredients every time you apply the fungicide for maximum effect.

Once you have applied the fungicide, keep an eye out for any signs of new growth and remove any infected leaves as soon as possible. This will help ensure that the fungicide is effective and stop the fungus spread. 

Ensure that you follow the product’s instructions when applying fungicides and take all necessary safety precautions. Apply the chemical at the correct rate and don’t overuse it, as this can damage the daylilies and make them more susceptible to infection. 

7. Clean All Gardening Tools

Cleaning gardening tools and equipment is essential to preventing the spread of leaf streak. The disease is spread by the fungus spores, which can be moved from one plant to another on gardening tools. Cleaning the tools will prevent the spread of the fungus to other plants in your garden and help to stop the spread of leaf streak on your daylilies.

  • Using a cloth or brush dipped in rubbing alcohol (isopropyl alcohol), clean the blades of the shears to remove any spores or infections that may be on them. When finished, rinse off with clear water.
  • You can also dip any other tools you used in a solution of one part bleach to nine parts water. This will help to disinfect them, as well as remove any remaining spores or infections. Rinse off the tools with clear water after dipping them in the bleach solution.

After cleaning your tools, let them dry completely before using them again. This will help to prevent any further spread of the fungus.

8. Monitor the Plants for Signs of Improvement and Treat Them as Necessary

Once the fungicide has been applied and the tools are clean, you should monitor your daylilies for signs of improvement. The fungus should die off, and the leaves should heal after a few weeks. 

Inspect your daylilies every few days, checking for any signs of new infections. Remove any infected leaves as soon as possible to prevent the fungus from spreading further and ensure that the plants heal properly.

If you notice that the leaves are still infected or not improving, you may need to increase the application rate or switch to a different fungicide. Several effective fungicides are available, so it is best to consult a professional before making any decisions. 

How To Prevent the Spread of Leaf Streak on Daylilies

Leaf streak can be a severe problem for daylilies, but they can be easily managed with the correct treatment and preventative measures. There are several steps you can take to help prevent the spread of leaf streak on your daylilies:

Choose Resistant Varieties

Some varieties of daylilies, such as ‘Ella Pettigrew’, Edna Spalding,’ ‘Nancy Hicks, and ‘Globe Trotter’, are relatively resistant to leaf streak. Choosing these varieties will help avoid introducing an infected plant into your garden. 

However, even resistant varieties may still be affected if exposed to an infected plant. The best practice is to purchase daylilies from a reputable nursery or other reliable sources, as they are more likely to be free of infection.

The environment in which the plant was grown can also play a role in resistance. Plants grown in shady, wet areas are more susceptible to infection than those grown in a warm, dry climate. So, choose plants that were grown in an environment similar to yours. 

Avoid Overcrowding

Daylilies should be planted in areas with plenty of air circulation and full sun. Avoid overcrowding plants, which can lead to increased humidity, promoting disease development. Reasonably spaced plants will also allow for better air circulation and sun exposure, helping reduce the risk of infection.

Avoid Overhead Watering

Overhead watering can spread the leaf streak fungus as it can splash the spores onto other plants. Instead, water your daylilies at the base of the plant using a watering can or hose with a nozzle to help keep the leaves dry and reduce the chances of the fungus spreading.

A sprinkler system is also discouraged as it can increase humidity and spread the fungus. Use a soaker drip or hose irrigation system to avoid splashing water onto the foliage and help keep the environment dry.

Avoid Watering at Night

When possible, avoid watering plants in the evening or at night. The leaves will remain wet for longer, making them more susceptible to infection. Opt for watering during the morning hours when temperatures are higher, and there is less humidity in the air. Your daylilies will have a chance to dry off before nightfall, discouraging fungal growth.

Water Your Daylilies Only When Necessary

Over-watering can also increase humidity and promote the spread of disease. Water your daylilies only when the soil is dry; this will help keep humidity levels low and discourage fungal growth. You can also use a mulch to help retain moisture in the soil, reducing the need for frequent watering and decreasing the chances of disease development.

Plant Your Daylilies in Well-Draining Soil

It’s important to plant your daylilies in well-draining soil, as this will help keep the environment dry and discourage fungal growth. The soil should be light and loose, with plenty of organic matter added to it. Avoid planting in heavy clay soils, as this can lead to water-logging and increase the risk of infection.

Daylilies also prefer acidic soils, as this inhibits the growth of fungi. If you have alkaline soil in your garden, you can amend it with peat moss or other organic amendments to help lower the pH and reduce the chances of infection.

Maintain Proper Hygiene 

You can also help prevent the spread of leaf streak by keeping the area around your daylilies clean and free of debris and avoiding contact with other infected plants. This includes removing fallen leaves or other plant matter, which can provide a breeding ground for the fungus. 

Prune off dead or infected leaves regularly, and dispose of them away from your garden to prevent the spread of the disease. Burn or bury the infected material away from other plants and sterilize pruners or other tools to avoid cross-contamination. 

Additionally, keep an eye out for signs of infection and immediately remove any infected plants from the garden. This will help prevent the spread of the fungus and keep your daylilies healthy and disease-free. It’s also a good idea to avoid planting daylilies in areas where the fungus is known to be present, as this can help prevent the disease from occurring in the first place.

Avoid Working in Wet Conditions

Avoid working in wet conditions, as this can increase the chances of spreading the leaf streak fungus. If the foliage of your daylilies is wet due to rain or dew, wait for it to dry before engaging in any gardening activities such as deadheading or pruning. This will help prevent the spread of infection, as the fungus is more likely to spread in moist conditions. 

Also, avoid working in the garden when it is damp, foggy, or humid outside. This will reduce the chances of infection and help keep your daylilies healthy and disease-free. 

Cut Back Daylilies in the Fall

Cutting back your daylilies in the fall can also help minimize the risk of infection. This is because removing the old foliage will reduce humidity levels and discourage the growth of fungi over the winter months. Additionally, cutting back the foliage will help reduce the amount of debris and plant matter in the garden, which can provide a breeding ground for the fungus.

Use Fungicide

As a last resort, fungicides can control leaf streak on daylilies. Once you have identified the disease, immediately apply a fungicide to the foliage and soil to stop the spread of infection. Several products are specifically designed to treat leaf streak, so follow the instructions on the product and reapply as necessary according to the manufacturer’s recommendations. 


Leaf streak is a common fungal disease that can cause significant damage to daylilies. However, following the above tips can help treat and prevent disease outbreaks. 

You can keep your daylilies healthy and disease-free by planting in well-draining soil, maintaining proper hygiene, paying attention to your watering practices, and avoiding working in wet conditions. If an infection does occur, applying an appropriate fungicide can help control the fungus and stop the spread of the disease.

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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