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How to treat powdery mildew on succulents

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How to treat Powdery Mildew on succulents

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Succulents are the rebels of the plant world, tough and resilient, thriving in conditions that would spell disaster for many other species. They're perfectly content in poor, dry soil, requiring minimal water and care routine. 

We all know that, if there's one thing that can dampen the spirits of succulents, it's high humidity. While succulents can withstand periods of drought and dry conditions, excessive humidity can spell trouble. It creates a breeding ground for many overwatering and fungal problems. A lot of succulent lovers keep their plants away from high humidity and think that their succulents are safe from fungal diseases. Unfortunately, this is not entirely accurate.

Powdery mildew on Succulents
Photo via LaprasLily

One fungal disease, powdery mildew, does not require a humid environment to grow. In fact, it thrives in warm, dry conditions, making it a common issue in indoor settings and during dry spells. Therefore, even in arid climates, succulents are not immune to the threat of powdery mildew. As powdery mildew can weaken the plant, hinder photosynthesis, and stunt growth or lead to death if left untreated, it's crucial to know how to address this disease effectively.

What is Powdery Mildew?

Powdery Mildew on succulents
White to grayish powdery patches on the surfaces succulents
Photo via Pinterest

Powdery mildew is a fungal disease that can affect a wide variety of plants, from vegetables and ornamentals to fruit trees and succulents. It manifests as white to grayish powdery patches on the surfaces of leaves, stems, buds, flowers, and fruit. Despite its name, powdery mildew is not related to soil moisture; instead, it thrives in warm, dry climates with high humidity levels.

This fungal disease is caused by different species of fungi, each with its own host specificity. Powdery mildew fungi do not require water on leaf surfaces for infection to occur; instead, they rely on high humidity levels for spore germination. Once established, powdery mildew fungi send haustoria, which are root-like structures, into the epidermal cells of the plant to extract nutrients.

How To Spot Powdery Mildew In Succulents?

Powedery Mildew in Succulents
White patches on the leaves and stems that can quickly transition to a yellow-brown and then darkening to black
Photo via Pinterest

Spotting powdery mildew in succulents is relatively easy once you know what to look for. When powdery mildew infects a succulent, it typically manifests as a distinctive white or grayish powdery coating, resembling a layer of dust. Initially, circular white patches appear on the leaves and stems. Over time, these patches may transition to a yellow-brown hue, eventually darkening to black. Initially, these patches may appear small and inconspicuous, but they have the potential to spread rapidly if not addressed promptly.

Beyond the visual cues, powdery mildew can also manifest in other ways. Infected leaves may exhibit distortion, curling, or puckering, accompanied by discoloration such as yellowing or browning around the affected areas. This deterioration in leaf health can lead to stunted growth in succulents, hindering their overall development and vitality.

One distinctive characteristic of powdery mildew is its powdery residue, which can be felt upon touch. This residue, often left on fingers or hands after handling infected plants, serves as a tangible indicator of the presence of the fungal disease.

Moreover, it's crucial to monitor new growth for signs of powdery mildew, as the fungus tends to target these areas first.

How Do Succulents Become Infested By Powdery Mildew?

Succulents can become infested with powdery mildew through various means, including these methods: 

Spore Transmission

Powdery mildew fungi produce airborne spores that can be carried by wind currents, insects, or other means to nearby succulent plants. These spores can land on the surfaces of succulent leaves, stems, or other plant parts, initiating infection.

Environmental Conditions

Powdery mildew thrives in warm, dry conditions with high humidity levels. Succulents grown in environments with poor air circulation or excessive humidity are more susceptible to powdery mildew infestations. Additionally, crowded plantings and dense foliage can create microclimates conducive to fungal growth.

Contaminated Tools or Equipment: Tools, pots, or other gardening equipment that come into contact with infected succulents can serve as vectors for spreading powdery mildew to healthy plants. It's essential to practice good sanitation by disinfecting tools and equipment regularly to prevent the spread of fungal diseases.

Introduction of Infected Plants

Bringing in new succulent plants from nurseries, garden centers, or other sources without proper inspection and quarantine measures can introduce powdery mildew or other fungal pathogens to your collection. It's crucial to carefully inspect new plants for signs of disease before introducing them to your garden or indoor space.

Natural Spread

Once established in a succulent population, powdery mildew can spread from plant to plant through direct contact or by dispersal of fungal spores. Infected plant parts, such as leaves or stems, can shed spores, which can then land on neighboring plants and initiate new infections.

Powdery Mildew vs Other Fungal Diseases

Powdery Mildew on succulents
Powdery mildew thrives in warm, dry conditions with high humidity levels
Photo by Kat McCarthy

Powdery mildew typically produces distinctive white to grayish powdery patches on the surfaces of plant parts, making it relatively easy to recognizecompared to some other fungal diseases. This characteristic facilitates early detection and intervention, allowing growers to implement control measures promptly. Moreover, powdery mildew infections primarily occur on the surface of plant tissues, forming a superficial layer of fungal growth. As a result, powdery mildew does not typically penetrate deep into plant tissues or cause extensive internal damage. This surface-level infection may make powdery mildew easier to manage compared to fungal diseases that invade deeper into plant structures.

However, when it comes to spreading rate, powdery mildew can spread rapidly under favorable environmental conditions, including warm temperatures, high humidity, and poor air circulation. It spreads faster and more easily than other fungal diseases do. This rapid spread can pose challenges for containment and control, particularly in densely planted areas or during periods of conducive weather. In terms of aesthetic damage, while powdery mildew infections may not typically cause severe damage or plant death, they can affect your succulents’ visual appeal. The presence of powdery patches on leaves, stems, or flowers may indeed reduce the ornamental value of the most striking succulents. 

Morever, powdery mildew is one of the most difficult diseases to get rid of.  This fungal infection can recur frequently, especially when our indoor environments are usually dry and warm. 

How To Treat Powdery Mildew

1. Isolation and Quarantine 

First thing first, as with any other diseases in succulents, we need to isolate the affected plant right awayAs soon as you notice signs of powdery mildew on any of your succulent plants, promptly isolate the infected plants from healthy ones. This isolation helps prevent the fungal spores from spreading to neighboring plants and causing further infections. Move the infected succulents to a separate location, preferably away from other plants, to minimize the risk of transmission.

If you purchase new succulent plants or suspect that a plant may be infected with powdery mildew, implement quarantine procedures to prevent the potential spread of the disease. Place the newly acquired or potentially infected plants in quarantine away from your existing plant collection. Quarantine areas can include separate rooms, shelves, or designated spaces where the plants can be kept isolated. During the quarantine period, closely observe the quarantined succulents for any signs of powdery mildew or other diseases. Monitor the plants regularly, paying attention to changes in appearance, such as the development of white powdery growth on the leaves and stems. If any symptoms of powdery mildew are observed, take immediate action to treat the infected plants and prevent the spread of the disease.

2. Natural Remedies

To treat powdery mildew, it is recommended to combine many methods to avoid recurring. Natural remedies are effective, affordable, and easy to apply. Please note that when using natural remedies to manage powdery mildew in succulents, it's important to apply the solutions during mild weather conditions and avoid spraying during periods of high humidity or intense sunlight. While these remedies may not completely eradicate powdery mildew, they can help suppress fungal growth and reduce disease severity. We recommend that you try these natural remedies: 

  • Baking Soda Solution: Mix one to two teaspoons of baking soda (sodium bicarbonate) with one quart of water to create a solution. Add a few drops of mild liquid soap to help the solution adhere to the plant's foliage. Spray the affected succulents thoroughly with the baking soda solution, ensuring full coverage of the infected areas. Repeat the application every one to two weeks as needed.
  • Horticultural Oil: Dilute horticultural oil according to the manufacturer's instructions. Typically, horticultural oil is mixed with water at a specified ratio and applied as a foliar spray. Spray the diluted horticultural oil onto the affected succulents, covering all surfaces of the leaves and stems. Apply the oil during mild weather conditions when temperatures are below 90°F (32°C) and avoid spraying during periods of high humidity or intense sunlight.
  • Milk Solution: Mix one part milk with two to three parts water to create a milk solution. The exact ratio may vary depending on the severity of the powdery mildew infection. Spray the milk solution onto the infected succulents, ensuring thorough coverage of the affected areas. Repeat the application every one to two weeks to suppress fungal growth and reduce disease severity.
  • Garlic Extract: Prepare a garlic extract by crushing or finely chopping fresh garlic cloves and soaking them in water for several hours or overnight. Strain the garlic-infused water to remove any solid particles, leaving behind a concentrated garlic extract. Dilute the garlic extract with water at a ratio of one part extract to five to ten parts water. Spray the diluted garlic extract onto the affected succulents, focusing on the areas with powdery mildew. Repeat the application every one to two weeks for optimal results.

3. Fungicidal Products

Fungicidal treatments are an effective method for managing powdery mildew on infected succulents. To begin, carefully select fungicidal sprays or treatments labeled specifically for controlling powdery mildew. These products often contain active ingredients like sulfur, neem oil, potassium bicarbonate, or fungicides formulated for powdery mildew control. Before application, read and follow the instructions provided on the label of the selected fungicidal product. Dilute concentrated fungicides with water as directed and ensure thorough mixing. Transfer the prepared solution to a clean spray bottle or garden sprayer for application. Apply the fungicidal spray evenly to all parts of the infected succulent plants, including the leaves, stems, and affected areas. Ensure thorough coverage, including the undersides of leaves where powdery mildew spores often accumulate.

Don’t forget to follow the recommended timing for application specified on the product label. Depending on the severity of the infestation, multiple applications may be necessary. Adhere to the suggested application schedule provided by the manufacturer for optimal results. 

It is important to take appropriate safety precautions when handling and applying fungicidal treatments. Wear protective clothing, gloves, and eyewear to prevent skin contact and inhalation. Avoid spraying on windy days to minimize drift, and keep pets and children away from treated areas until the spray has dried completely.

After application, monitor the infected succulents closely for signs of improvement and disease progression. Repeat the fungicide applications as needed, following the recommended intervals and dosage rates. 

Powdery Mildew Prevention

When it comes to prevention, pruning and sanitation are essential practices for managing powdery mildew on succulents. To prune, you can begin by inspecting the plants for any signs of infection, such as powdery white spots on the leaves and stems. Use clean, sterilized pruning shears or scissors to remove and discard any infected plant parts, including affected leaves, stems, and flowers. By removing these infected tissues promptly, you can prevent the spread of the fungus to healthy areas of the plant. When pruning infected succulents, be sure to make clean cuts and avoid leaving behind any jagged or torn edges, as these can serve as entry points for pathogens. Dispose of the pruned plant material carefully to prevent the spread of spores to other plants or areas of the garden.

Powdery Mildew on succulents
Use pruning shears or scissors to remove and discard any infected plant parts
Photo by Cori Sears

Moreover, improving air circulation around succulents is another effective strategy for preventing powdery mildew. Overcrowding and dense foliage can create conditions conducive to fungal growth by trapping moisture and reducing airflow. To enhance air circulation, space succulent plants apart when planting them in containers or garden beds. This allows for better airflow between plants and helps reduce humidity levels, making the environment less favorable for powdery mildew development. In addition to spacing plants apart, consider pruning back any overgrown or dense foliage that may impede airflow. Remove any dead or decaying plant material from around the base of the succulents to further improve air circulation and reduce the risk of fungal infections.

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