The Ultimate Guide: Houseplant Diseases
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WHY PLANTS GET SICK
Introduction: Understanding Houseplant Diseases
Owning houseplants is a complete joy; they're beautiful to look at, they help us to be more in touch with nature, and they've been scientifically proven to relax us when we're caring for them. It can often feel like a personal failure when our beloved plants get sick, however, it isn't always a reflection of our plant care routines. Sometimes, plants get diseases for reasons totally out of our control. The most recognisable houseplant disease is root rot, with most indoor gardeners being aware of how severely it can impact houseplants. We'll dive into root rot in more detail later on.
Whether you're a seasoned plant parent with a bulging collection, or you're just starting your indoor garden, understanding the reasons that plants get diseased is a crucial step in understanding and managing plant care. We believe that the best tool in your houseplant tool box is knowledge itself. When we understand why things happen, it can be easier to prevent them from reoccurring, and diseases are no exception. By understanding houseplant diseases, we can more effectively manage and prevent future issues.
Why Do Houseplants Get Diseases?
Diseases can strike for various reasons, including contamination, environmental stress, improper care, and exposure to pathogens. Overwatering or underwatering can stress plants, making them more susceptible to diseases like root rot and fungal infections. Poor air circulation creates a humid environment where fungal and bacterial diseases thrive, while low humidity weakens plants, making them more vulnerable to pests and diseases. Contaminated soil, infected plants, and lack of proper sanitation can also introduce pathogens to your collection. Additionally, nutrient deficiencies, temperature stress, and improper lighting can weaken plants, leading to increased susceptibility to diseases. Furthermore, an often overlooked carrier of disease are houseplant pests, like aphids, spider mites, and scale insects, which can transmit diseases as they feed on houseplants.
By identifying these factors and implementing proper care techniques, you can prevent many common houseplant diseases and ensure your plants thrive. In this houseplant disease guide, we will delve deeper into the most prevalent houseplant diseases, how they develop, and effective strategies to prevent and treat them. Let's have a closer look at how you can keep your indoor garden healthy and flourishing.
How To Identify Houseplant Diseases
Identifying houseplant diseases can be tricky, but being observant and knowing what to look for can help you catch issues early. Some symptoms that appear to be disease can actually be caused by common pests. To help you identify each houseplant disease, we've included images of what each different issue looks like, and we've written about the causes and treatments. Here are some common signs and symptoms of houseplant disease to watch out for, and how to fix them:
Yellow Leaves
Symptoms: Leaves turning yellow.
Caused By: Often a sign of overwatering, underwatering, or nutrient deficiencies.
How To Treat: Adjust your watering schedule and ensure your plant is receiving the right amount of nutrients. Check for signs of pests or for other symptoms of disease.
Brown or Black Spots
Symptoms: Brown or black spots on leaves.
Caused By: Can indicate fungal or bacterial infections.
How To Treat: Remove affected leaves and improve air circulation around the plant. Use a fungicide if necessary.
Pale or Bleached Leaves
Symptoms: Leaves appear pale or bleached, or even crispy when caused by sunlight.
Caused By: Might suggest pests like spider mites. If combined with crispy tips, it may be too much light.
How To Treat: Move the plant to a location with indirect light. Check for and treat any pests.
Yellowing and Wilting Combined
Symptoms: Leaves turning yellow and wilting.
Caused By: Could indicate vascular wilts, where the plant's vascular system is blocked by a fungus.
How To Treat: Remove affected parts, improve growing conditions, and use fungicides if necessary.
Wilting
Symptoms: Leaves or stems appear limp and droopy.
Caused By: Often caused by overwatering, root rot, or poor drainage.
How To Treat: Allow the soil to dry out and ensure the pot has proper drainage. Repot if necessary to improve soil conditions.
Fuzzy White Patches
Symptoms: Patches of fuzzy white material on leaves or stems.
Caused By: Typically signs of mealy bugs.
How To Treat: Treat the plant with insecticidal soap or neem oil. Remove visible bugs with a cotton swab dipped in alcohol.
Edema: Blister-Like Swelling
Symptoms: Blister-like swellings on leaves.
Caused By: Water management issues, often when roots absorb water faster than it can be transpired, or from water sitting on leaves.
How To Treat: Adjust watering habits, improve air circulation, and control humidity levels. We've found popping the blister helps it to heal faster.
Leaf Drop
Symptoms: It's normal for plants to drop the odd older leaf, but several dropped at once is an issue.
Caused By: Reaction to environmental stress, pests, or disease.
How To Treat: Identify and address the source of stress, whether it's temperature, too much light, pests, or one of the other diseases listed here.
Sticky Residue or Sooty Mould
Symptoms: Sticky substance on leaves, often accompanied by black sooty mould.
Caused By: Typically indicates a pest issue, such as aphids or scale insects.
How To Treat: Treat the pests with appropriate insecticides or natural remedies. Clean the leaves to remove the sticky residue and mould.
Root Problems
Symptoms: Roots are brown, mushy, or have a foul smell. Visible difference in healthy vs sick roots.
Caused By: Often caused by root rot.
How To Treat: Cut the affected roots back to the last healthy growth, then dip in rooting hormone, and repot in fresh, well-draining soil. Adjust watering practices and ensure adequate drainage.
Stunted or Unusual Growth
Symptoms: Plants not growing as they should. Galls or abnormal growths on leaves and stems.
Caused By: Root problems, lack of nutrients, or being infected by pests or diseases. Growths can be a sign of bacterial or viral infections.
How To Treat: Check root health, pests, & fertilize. Remove growths, and keep good hygiene.
Yellowing Leaf Tips
Symptoms: Yellowing tips on leaves, often accompanied by general yellowing or browning.
Caused By: Can be caused by overwatering, underwatering, nutrient deficiencies, or root issues.
How To Treat: Ensure soil dries out between watering, and feed regularly.
Bacterial Leaf Spot
Symptoms: Black spots, often with a yellow halo.
Caused By: Bacteria spread through water splashes, foliage, or contaminated tools.
How To Treat: Prune and dispose of infected leaves, cleaning all tools after use. Improve air circulation, avoid wetting leaves, and reduce humidity. Use a copper-based bactericide.
Did You Know:
Adding perlite to houseplant soil can help to reduce the chances of root rot.
Studies have shown that perlite's porous structure improves drainage and aeration, which helps to prevent the anaerobic conditions that promote root rot.
Root Rot: Causes, Symptoms, Prevention, & Treatment
Root rot is one of the most common and challenging diseases faced by houseplants indoors. This fungal disease can swiftly turn a vibrant plant into a wilted, lifeless one. We always say that the key to good plant care is knowledge, so let's explore root rot in houseplants:
What Is Root Rot?
Root rot is a condition caused by various fungi, including Pythium, Phytophthora, Rhizoctonia, and Fusarium, which thrive in overly wet soil. When plants are overwatered or grown in poorly draining soil, their roots can become waterlogged and oxygen-starved. This creates an ideal environment for fungal spores to infect the roots.
Causes Of Root Rot In Houseplants
Overwatering: The most common cause of root rot is excessive watering. When soil remains saturated, it deprives roots of oxygen, weakening them and making them susceptible to fungal infection. We really can't emphasise enough how important it is to allow the soil to dry out between watering to prevent root rot.
Poor Drainage: Using pots without drainage holes or soil mixes that retain too much water can lead to waterlogged conditions, encouraging fungal growth. Use a size 4-6 wood drill bit to create extra holes in plastic pots. Studies have shown that perlite's porous structure helps to improve drainage and aeration, which helps to prevent the anaerobic conditions that promote root rot.
Contaminated Soil or Tools: Using unsterilized soil or gardening tools can introduce fungal spores to your plants.
Environmental Stress: Sudden changes in temperature, humidity, or light levels can stress plants, making them more prone to diseases.
Symptoms Of Root Rot In Houseplants
Wilting and Yellowing Leaves: Despite adequate watering, leaves may wilt, turn yellow, and eventually drop off. Repeated watering offers no improvement.
Stunted Growth: Affected plants often show little to no new growth and may remain stunted.
Yellowing Leaves: When roots are compromised, the plant struggles to get the nutrients it needs, causing leaves to turn yellow.
Leaf Drop: The stress from root rot can cause leaves to wilt and eventually fall off as the plant tries to conserve energy. One leaf dropping is normal for plants as they grow, but several dropping off the plant at once is an indication that there's an issue.
Mushy Roots: When examining the roots, you'll find they are brown, black, mushy, and have a foul smell, instead of being white and firm.
How To Prevent Root Rot In Houseplants
Proper Watering: Water your plants only when the top inch of soil is dry. Ensure you’re providing the right amount of water for each specific plant species.
Use Well-Draining Soil: Choose soil mixes designed for houseplants that drain well and allow excess water to escape. Use the correct soil recipe for each species; our general houseplant soil recipe is suitable for most houseplants, and lists amendments for each different species. For cacti and succulents, use our cactus soil recipe. For Aroids and jungle houseplants, use our Aroid soil recipe, which is chunky, airy, and offers good drainage.
Appropriate Pots: Use pots with drainage holes to prevent water from pooling at the bottom. If necessary, add a layer of gravel or stones at the bottom for extra drainage. With plastic pots, use a size 4-6 wood drill bit to drill additional holes into the bottom of the pot. For fussy species, we recommend drilling a few around the side too.
Sterilize Tools and Soil: Always use sterilized soil and clean gardening tools to avoid introducing pathogens. We recommend wiping blades between each cut.
Good Air Circulation: Ensure your plants have good air circulation by spacing them adequately and using fans if needed.
Use Positive Stress: Healthy roots are less likely to get root rot, and positive stress can lead to increased root growth, which helps roots fight off disease. Studies have shown that positive stress can not only enhance root growth but also lead to thicker stems and shorter internodal growth, making plants more robust and better able to withstand environmental challenges, including root rot. Positive stress, such as directing a fan's breeze towards a plant, stimulates a process called thigmomorphogenesis, where growth changes in response to mechanical stimuli. By using fans to create a gentle breeze, we mimic natural wind conditions, promoting stronger and healthier plants. This method is particularly beneficial for indoor plants that don't usually experience wind stress in their environment. We use these exact fans at our nursery to promote stronger growth by providing positive stress. We like this particular model as the unit can be mounted on a wall, the head pivots to allow adjustability, and the 7m blast radius provides a stronger breeze to help move foliage and provide plosive stress.
Mycorrhizal Fungi: Studies have shown that this natural additive can help to prevent root rot. Mycorrhizal fungi form a symbiotic relationship with plant roots, extending their reach and enhancing water and nutrient absorption. This relationship also provides a natural barrier against soil-borne pathogens, including those that cause root rot. By improving nutrient uptake and overall plant health, mycorrhizal fungi can make plants more resilient to diseases and environmental stressors, including root rot.
Use Perlite In Soil Mixes: Studies have shown that support the use of perlite in reducing the chances of root rot. Perlite's porous structure improves soil drainage and aeration, which helps prevent the anaerobic conditions that promote root rot. Additionally, its ability to retain moisture while allowing excess water to drain away helps maintain the optimal moisture balance for healthy root growth. These properties make perlite a valuable amendment for preventing root rot in various horticultural applications
Treating Root Rot In Houseplants
If you suspect root rot, it's important to act as quickly as possible to save your plant. Understanding how to treat root rot is the key to successful disease management when symptoms have already taken hold. Often, when symptoms are visible above the soil, the disease may have progressed beyond treatment beneath the soil, and cuttings may be the only option to save the plant. Here's our go-to method to treat root rot in houseplants, and what to do when root rot is too advanced to treat:
Remove the Plant: Carefully remove the plant from its pot and inspect the roots. Rotten roots usually smell bad, and are slimy, wet, and dark-coloured.
Trim Affected Roots: Use sterilized scissors to trim away all the affected roots, leaving only healthy, white roots.
Dip The Roots: We recommend rooting hormone powder to promote new healthy root growth, and mycorrhizal fungi to help prevent root rot reoccurrence. Mix the powder together at a ratio of 50-50, then dip the roots, ensuring that all the roots are covered on all sides. Both of these products only work when the powder directly touches the roots, so ensure that they are well coated before planting.
Select The Correct Soil For Each Species: Using the correct soil recipe for each species helps to prevent root rot from reoccurring; our houseplant soil recipe is suitable for most plants, however, it's important to use a dedicated mix for cacti, succulents, and for Aroids as they can be picky about their soil properties. We like to add leca balls to the soil of sensitive plants to help add extra aeration. We find that this can help to provide better drainage and allows the roots to breathe, by providing pockets of air.
Repot: Repot the plant in fresh, well-draining soil and a clean pot with drainage holes. Avoid watering the plant immediately after repotting; wait until the soil is slightly dry.
Monitor and Adjust Care: Adjust your watering routine and ensure proper care to prevent recurrence of root rot. Consider adding a moisture meter for watering accuracy.
Take Cuttings: If your houseplant hasn't got enough roots left after trimming, or they're too rotted to save, a more drastic tactic may be needed. When large amounts of roots are removed from an already stressed plant, issues may occur. The pruned root ball may not be able to support the same amount of foliage as before, so taking cuttings can actually improve your chances of survival for the parent plant, as well as the cutting. Although it can be tempting to throw the plant into the bin after taking cuttings, we recommend trying to save it. For a complete guide on how to take cuttings, check our houseplant propagation guide. For a quick guide: cut a healthy stem from the plant, remove the lower leaves, place the cutting in water and wait a few weeks until roots develop, then repot into a soil mix suitable for the houseplant species' individual needs.
Fungal Diseases: Causes, Symptoms, Prevention, & Treatment
Fungal diseases are often hard to diagnose in houseplants without proper laboratory testing, as they can present with similar symptoms. Fleshy leaf plants like Hoya can be very susceptible to black spots on their leaves, without any obvious cause. Understanding how to treat these fungal diseases is the key to success when dealing with sick houseplants. Let's explore the different types of fungal infections, and how to treat them:
What Fungal Diseases Do Houseplants Get?
Fungal Leaf Spot: This disease causes spots on leaves that can be yellow, brown, black, red, or tan. Overwatering and wet foliage create ideal conditions for this fungus.
Powdery Mildew: This fungal disease appears as a white, powdery coating on leaves and stems, usually seen in humid conditions.
Anthracnose: A soil-borne fungal disease that causes yellowing leaf tips, which darken and die. It spreads easily in wet conditions.
Botrytis Blight (Gray Mould): This fungus thrives in cool, humid conditions and causes gray mould on plant parts, often leading to rot.
Sooty Mold: This black, sticky fungus grows on honeydew excreted by pests like scale insects and mealy bugs. It blocks sunlight and weakens the plant.
White Mould: This fungus appears as a white, fluffy growth on plant surfaces and can cause rot.
Root Rot: Caused by overwatering or poor drainage, rot occurs when roots become waterlogged, blocking the plant's oxygen supply and causing the roots to decay. We've listed root rot treatments separately, as they're a little more complicated and require some more specialised treatments.
Causes Of Fungal Disease In Houseplants
Overwatering: Excess moisture creates an ideal environment for fungi to thrive. Waterlogged soil can lead to root rot and other fungal infections.
Poor Drainage: Using pots without drainage holes or heavy, compacted soil can retain water, promoting fungal growth. Use a size 4-6 wood drill bit to create extra holes.
High Humidity: Humid conditions, especially in poorly ventilated spaces, can foster the development of fungal spores.
Contaminated Soil or Tools: Using unsterilized soil, pots, or gardening tools can introduce fungal spores to your plants.
Lack of Air Circulation: Crowded plants or poor airflow can trap moisture, leading to fungal problems like powdery mildew and mould.
Infected New Plants: Bringing home infected plants from the nursery can spread fungi to your other houseplants.
Overhead Watering: Watering from above and wetting the foliage can encourage fungal diseases on leaves and stems. Use n techniques.
How To Prevent Fungal Disease In Houseplants
Proper Watering: Water your plants only when necessary. Allow the top inch of soil to dry out between watering to prevent overwatering, which can lead to fungal growth.
Well-Draining Soil: Use a well-draining potting mix to ensure excess water doesn't linger in the soil. Additives like perlite or sand can help improve drainage.
Adequate Pot Drainage: Use pots with drainage holes to allow excess water to escape. Avoid using pots without proper drainage, as they can retain water and create conditions favourable for fungi.
Balanced Humidity: Maintain balanced humidity levels. If humidity is too high, it can promote fungal growth. Use a dehumidifier or increase air circulation if needed.
Good Air Circulation: Ensure good airflow around your plants by spacing them appropriately and using fans if necessary. Good air circulation helps to reduce humidity and prevent fungal spores from settling on plants.
Avoid Overhead Watering: Water the soil directly rather than wetting the foliage. This helps prevent fungal diseases that thrive on wet leaves.
Clean Tools & Pots: Always use sterilized tools and clean pots when repotting or pruning your plants. This helps prevent the introduction and spread of fungal spores.
Inspect New Plants: Before introducing new plants to your collection, inspect them for any signs of disease. Quarantine new plants for a few weeks to ensure they are healthy.
Remove Dead Plant Material: Regularly remove dead or decaying leaves and flowers from your plants to prevent fungal growth.
Use Fungicides: If necessary, use fungicides as a preventive measure, especially if you have had issues with fungal diseases in the past. Follow the product instructions carefully.
Treating Fungal Disease In Houseplants
Treating fungal diseases in houseplants involves a combination of removing infected parts, improving growing conditions, and, if necessary, using fungicides. Here's a step-by-step guide to help you treat fungal diseases in your houseplants:
Remove Infected Parts: Using sterilized scissors or pruning shears, carefully prune and dispose of infected foliage to prevent the spread of the fungus.
Clean & Sterilize: Clean and sterilize all gardening tools and pots to prevent the reintroduction of fungal spores. When repotting, use unused high-quality fresh soil to reduce the risk of contamination. If there's fungus on the leaves, clean with a damp, soft cloth to remove spores.
Improve Growing Conditions: Increase airflow around your plants by spacing them adequately and using fans if necessary.
Avoid Water Touching The Leaves: Water the soil directly and avoid wetting the foliage. Allow the top inch of soil to dry out between watering.
Reduce Humidity: Reduce humidity levels if they are too high. Use a dehumidifier or improve ventilation.
Use Fungicides: If the infection is severe, use a fungicide. Follow the product instructions carefully. For larger collections, consider buying a concentrated formula. For a milder approach, consider using natural remedies like neem oil, baking soda, or a mixture of water and horticultural soap.
Monitor & Prevent: Regularly inspect your houseplants for any signs of fungal disease and address issues promptly. Implement preventative measures such as proper watering, good air circulation, and using well-draining soil to reduce the risk of future fungal infections.
Bacterial Diseases: Causes, Symptoms, Prevention, & Treatment
Bacterial diseases can be tough to deal with in houseplants, due to the wide array of bacteria that cause indoor plants issues. Let's explore what causes these bacterial related issues in houseplants, how to treat them, and how to prevent them:
What Bacterial Diseases Do Houseplants Get?
Bacterial Leaf Spot (pictured): Caused by various bacteria, this disease results in black, water-soaked lesions on leaves, often surrounded by a yellow halo.
Bacterial Wilt: Symptoms include sudden wilting and die-off without yellowing, and stems that appear water-soaked and collapse easily. Caused by bacteria such as Ralstonia solanacearum.
Bacterial Blight: This disease causes dark, water-soaked spots on leaves, stems, and flowers that eventually turn black and necrotic. Various bacterial pathogens cause it.
Crown Gall: Characterized by swollen, tumourlike growths (galls) at the base of the stem or roots, caused by Agrobacterium tumefaciens.
Soft Rot (pictured): Symptoms include soft, mushy decay of stems, leaves, or roots, often accompanied by a foul odour. Caused by bacteria such as Erwinia and Pectobacterium.
Causes Of Bacterial Disease In Houseplants
Contaminated Soil: Using unsterilized soil that contains harmful bacteria can introduce infections to your plants.
Infected New Plants: Bringing home plants that already have bacterial infections can spread the disease to your other houseplants.
Water Splash: Water splashing on leaves can spread bacteria from infected plants to healthy ones, especially during overhead watering.
Poor Air Circulation: Lack of airflow can create a humid environment that promotes bacterial growth.
Overwatering: Excess moisture in the soil can create conditions conducive to bacterial infections.
Injuries to Plants: Cuts or wounds on plants, often caused by pruning or pests, can provide entry points for bacteria.
Dirty Tools and Pots: Using unsterilized gardening tools or contaminated pots can spread bacteria.
High Humidity: Elevated humidity levels can facilitate the growth and spread of bacterial pathogens.
How To Prevent Bacterial Disease In Houseplants
Use Sterilized Tools and Pots: Always use sterilized gardening tools to avoid introducing bacteria to your plants. Use high-quality, new soil for planting and repotting.
Inspect New Plants: Before adding new plants to your collection, quarantine them for a few weeks to ensure they are disease-free.
Avoid Overhead Watering: Avoid wetting the foliage, which can spread bacterial pathogens. Water from the bottom to avoid splashes, or gently pour directly onto soil.
Ensure Good Drainage: Use pots with drainage holes to prevent water from accumulating in the soil. Use a size 4-6 wood drill bit to create extra holes in plastic pots.
Improve Air Circulation: Ensure plants are spaced out to allow for good air circulation, reducing humidity and discouraging bacterial growth. Use fans to improve airflow.
Avoid Injuries: Avoid injuries during handling, as wounds provide entry points for bacteria. Keep an eye on pests, as they can cause injuries that become infection sites.
Reduce Humidity: Keep humidity levels in check using a dehumidifier or improving ventilation, especially in enclosed spaces.
Remove Dead Plant Material: Regularly remove dead or decaying leaves and flowers, which can harbour bacterial pathogens.
Avoid Contaminated Water: Use clean, treated water for watering your plants to avoid introducing bacteria from contaminated sources.
Monitor and Inspect Regularly: Inspect your plants frequently for early signs of bacterial diseases and address any issues promptly.
Treating Bacterial Disease In Houseplants
Treating fungal diseases in houseplants involves a combination of removing infected parts, improving growing conditions, and, if necessary, using fungicides. Here's a step-by-step guide to help you treat fungal diseases in your houseplants:
Remove Infected Parts: Use sterilized scissors or pruning shears to carefully prune and dispose of infected foliage. This helps prevent the spread of bacteria.
Improve Growing Conditions: Increase airflow around your plants by spacing them adequately and using fans if necessary.
Avoid Water Touching The Leaves: Water the soil directly and avoid wetting the foliage to prevent bacterial spread.
Clean & Sterilize: Clean and sterilize all tools and pots to avoid reintroducing bacteria. Use fresh, high-quality soil when repotting.
Clean Leaves: If there's visible bacterial infection on leaves, gently clean them with a damp, soft cloth.
Reduce Humidity: Reduce humidity levels if they are too high. Use a dehumidifier or improve ventilation.
Use Bactericides: For severe infections, use a copper-based bactericide or another appropriate treatment. Follow the product instructions carefully. For a milder approach, consider using natural treatments like neem oil, or a mixture of water and horticultural soap.
Monitor & Prevent: Regularly inspect your plants for any signs of bacterial disease and address issues promptly. Implement good watering practices, ensure proper air circulation, and use well-draining soil to reduce the risk of future infections.
Houseplant Viruses: Causes, Symptoms, Prevention, & Treatment
Although it may seem farfetched, plants also suffer from viral infections, just like us. Houseplants can catch a virus, which can make them ill, or they can carry it without symptoms and pass it onto other plants in your collection. Let's explore the different viruses that they can catch, how they impact houseplants, and how to treat them:
What Viruses Do Houseplants Catch?
Mosaic Virus: Causes mottled or mosaic patterns on leaves, often accompanied by yellowing and stunted growth. Typically spread by insects like aphids or through contaminated tools and hands.
Cucumber Mosaic Virus (CMV): Similar to mosaic virus, it causes yellow spots, streaks, and distorted leaves. Spread by aphids and through mechanical transmission (e.g., pruning tools).
Tobacco Mosaic Virus (TMV): Causes mottling and distortion of leaves, typically with a yellow-green appearance. Spread through contaminated hands, tools, and even tobacco products.
Impatiens Necrotic Spot Virus (INSV): Causes necrotic (dead) spots on leaves, often leading to leaf drop and stunted growth. Spread by thrips and through mechanical transmission.
Tomato Spotted Wilt Virus (TSWV): Causes spots on leaves, stems, and flowers, often leading to wilting and stunted growth. Spread by thrips and through mechanical transmission.
How Houseplants Catch Viruses
Insect Vectors: Insects such as aphids, thrips, and whiteflies can carry and transmit viruses. They are often the primary means of virus spread in houseplants.
Contaminated Tools and Hands: Using unsterilized tools or handling plants with contaminated hands can transmit viruses. This is common with Tobacco Mosaic Virus.
Infected Plants: Buying new plants that are already infected with viruses can spread the diseases to other plants in your home, even if the symptoms are not yet visible.
Propagation from Infected Plants: Taking cuttings or grafting from infected plants can spread the virus to new plants.
Seed Transmission: Some viruses can be transmitted through seeds, meaning that seedlings can already be infected when they germinate.
Environmental Stress: Poor growing conditions, such as improper watering, nutrient deficiencies, or extreme temperatures may cause plants to be vulnerable to viruses.
How To Prevent Houseplant Viruses
Inspect New Plants: Always inspect new plants for any signs of viral infection before introducing them to your collection.
Control Insect Pests: Manage pest populations through regular inspection and appropriate control measures.
Sanitize Tools: Regularly sterilize gardening tools and wash hands before and after handling plants.
Quarantine New Plants: Keep new plants isolated for a few weeks to monitor for any signs of disease.
Use Healthy Plant Material: Only use cuttings and seeds from healthy, virus-free plants.
Treating Houseplant Viruses
Unfortunately, there is no cure for viral infections in houseplants. Once a plant is infected with a virus, the best course of action is to manage the disease to prevent it from spreading to other plants. Here are some steps you can take to manage and prevent the spread of viral diseases in your houseplants:
Isolate Infected Plants: Immediately isolate any plant showing signs of viral infection to prevent the virus from spreading to healthy plants.
Remove Infected Parts: Use sterilized scissors or pruning shears to carefully remove and dispose of infected foliage. Make sure to disinfect your tools after each cut.
Control Insect Vectors: Manage pests such as aphids, thrips, and whiteflies. Use natural treatments like neem oil, or a mixture of water and horticultural soap.
Improve Plant Health: Ensure proper watering, adequate light, and good nutrition. Healthy plants are better able to withstand and recover from infections.
Sanitize Tools and Hands: Regularly sterilize tools and wash your hands before and after handling plants to prevent transmission of viruses. Only use new, unused soil.
Dispose of Severely Infected Plants: If a plant is severely infected, it may be best to dispose of the plant to prevent the virus from spreading to other plants.
Monitoring and Prevention: Implement good watering practices, ensure proper air circulation, control pests, monitor, and use clean tools to reduce the risk of viruses.
The Role of Biofertilizers in Preventing Diseases in Houseplants
Biofertilizers are an eco-friendly and sustainable alternative to chemical fertilizers, containing beneficial microorganisms that enhance soil health and promote plant growth. By improving nutrient availability and supporting plant immune responses, biofertilizers play a significant role in preventing diseases in houseplants. Here are some detailed ways in which biofertilizers contribute to plant health and disease prevention:
Enhancing Nutrient Uptake
Biofertilizers, such as Rhizobium and Azotobacter, are known for their ability to fix atmospheric nitrogen, converting it into a form that plants can readily absorb. This process not only enriches the soil with essential nutrients but also promotes vigorous plant growth. Enhanced nutrition strengthens plants, making them more resilient to diseases. The symbiotic relationship between these microorganisms and plant roots facilitates efficient nutrient absorption, leading to healthier and more robust plants.
Improving Soil Health
Biofertilizers improve soil structure and fertility by increasing organic matter content and promoting beneficial microbial activity. They stimulate the growth of soil microorganisms that decompose organic matter, releasing nutrients that plants can use. A healthy, well-structured soil environment supports robust plant growth and reduces the likelihood of disease outbreaks. Additionally, biofertilizers help maintain soil pH and enhance water retention, creating optimal growing conditions for houseplants.
Inducing Systemic Resistance
Certain biofertilizers can induce systemic resistance in plants, effectively “priming” them to defend against pathogen attacks. For example, mycorrhizal fungi form symbiotic relationships with plant roots, enhancing nutrient absorption and providing a protective barrier against soil-borne pathogens. This symbiotic association not only improves plant health but also enhances their ability to resist infections. The induced systemic resistance mechanism involves the activation of the plant's defence pathways, enabling them to respond more effectively to pathogenic threats.
Reducing Pathogen Load
Beneficial microorganisms in biofertilizers can outcompete and suppress harmful pathogens in the soil. By colonizing the root zone and establishing beneficial microbial populations, biofertilizers reduce the pathogen load and lower the risk of infection. These microorganisms produce antimicrobial compounds that inhibit the growth of harmful bacteria and fungi, creating a healthier soil microbiome. The competitive exclusion of pathogens ensures that plants have a reduced likelihood of encountering disease-causing organisms.
Eco-Friendly and Sustainable
Biofertilizers are environmentally friendly alternatives to chemical fertilizers. They reduce the reliance on synthetic inputs, promoting sustainable gardening practices and minimizing environmental impact. Unlike chemical fertilizers, biofertilizers do not lead to soil degradation or water pollution. Their use supports the preservation of natural ecosystems and enhances biodiversity within the soil.
Scientific Studies
The study “Role of Biofertilizers in Plant Growth and Soil Health” from IntechOpen discusses the importance of biofertilizers, also known as bioinoculants. These natural stimulants contain living microorganisms that significantly enhance plant growth and improve soil health by increasing nutrient availability and promoting beneficial microbial activity. The study found that biofertilizers help plants in the following ways:
Enhanced Nutrient Availability: Biofertilizers increase the availability of essential nutrients such as nitrogen and phosphorus through natural processes like nitrogen fixation and phosphorus solubilization. Nitrogen-fixing bacteria, such as Rhizobium and Azotobacter, convert atmospheric nitrogen into ammonia, which plants can readily absorb. Similarly, phosphorus-solubilizing bacteria, like Pseudomonas and Bacillus, release phosphorus from insoluble compounds, making it available to plants. These processes enrich the soil with essential nutrients, promoting vigorous plant growth and enhancing overall plant health.
Improved Soil Health: The application of biofertilizers enhances soil structure and fertility by increasing organic matter and promoting microbial activity. Healthy soil supports robust plant growth and reduces the likelihood of disease outbreaks. The microorganisms in biofertilizers help decompose organic matter, releasing nutrients that plants can absorb. They also produce substances that improve soil aggregation, leading to better water infiltration and retention. This creates a more stable environment for plant roots to grow and function, improving overall plant vigor and resilience against environmental stresses.
Plant Growth Promotion: Biofertilizers produce plant growth regulators such as auxins, gibberellins, and cytokinins, which directly promote plant growth. Auxins stimulate root elongation and branching, gibberellins promote stem elongation and seed germination, while cytokinins encourage cell division and growth. These hormones play a crucial role in various plant developmental processes, leading to enhanced root and shoot growth, increased biomass, and improved yield. By modulating the plant's hormonal balance, biofertilizers can enhance the plant's ability to absorb nutrients and water, withstand stress, and resist pathogens.
Incorporating Biofertilizers into Houseplant Care
To effectively incorporate biofertilizers into your houseplant care routine, consider the following steps:
Choose the Right Biofertilizer: Select biofertilizers that are specifically formulated for indoor plants and tailored to the needs of your particular houseplant species. At our houseplant nursery, we prefer to use seaweed extract, as we've found that it helps to prevent stress when pruning, repotting, or when propagating. Studies have shown that seaweed helps plants to develop resilience to stress, and we've seen the results first hand for ourselves here at the nursery. We've seen the positive effects of using seaweed to prevent stress on both young plants that we grow commercially, and on the older mother plants that we propagate to create our stock. We also use mycorrhizal fungi when we take cuttings, or repot plants as a matter of course, and we highly recommend that you do the same. Furthermore, we've seen good success with using trichoderma, but it's not cost-effective for the average consumer. We've compiled a list of the best biofertilizers for houseplants, and where you can buy them on our fertilizer page.
Application: Follow the manufacturer's instructions for application rates and methods. Biofertilizers can be applied during planting, repotting, or as a soil drench. We prefer to apply it using a watering can, as it can leave brown watermarks on the leaves that can permanently stain some species. We've found some plants to be terrible at getting stained when sprayed with seaweed, most notably Epipremnum Cebu Blue, Philodendron Silver Sword, Tradescantia Yellow Hill, and any paler leaf Aglaonema species, like Aqua Green. With the benefit of our professional experience, we highly recommend using a watering can, but you can use it as a foliar spray if you wish, but be warned, it may stain your plants.
Consistency: Regularly apply biofertilizers as part of your plant care regimen to maintain beneficial microbial populations and ensure continuous nutrient availability. You can apply seaweed as often as once a week with most manufacturers, but check the label for more information.
Monitor Plant Health: Observe your plants for signs of improved growth and reduced disease incidence, and adjust your plant care routine as needed. By incorporating biofertilizers into your houseplant care routine, you can significantly reduce the incidence of diseases.
The Science Of Houseplant Diseases
For those of you with a scientific mind, let's delve deeper into the science of indoor plant disease. Houseplants, like all plants, are susceptible to a variety of diseases caused by microorganisms including fungi, bacteria, and viruses. The study of these plant pathogens and their interactions with houseplants is a crucial aspect of plant pathology, which aims to understand the mechanisms of infection, spread, and control.
Fungal Diseases
Fungi are ubiquitous organisms that can cause significant damage to houseplants under favourable conditions. These pathogens often thrive in environments with high humidity and inadequate air circulation. For instance, Powdery Mildew is caused by a group of fungal species that produce a white, powdery growth on plant surfaces. This disease disrupts photosynthesis and weakens the plant. Root Rot, typically caused by fungi such as Phytophthora and Pythium, results from prolonged soil saturation, leading to oxygen deprivation and root decay. Fungi reproduce through spores, which can be disseminated by wind, water, insects, or contaminated tools. Effective management of fungal diseases involves improving environmental conditions, such as enhancing air circulation and optimizing watering practices, and employing fungicidal treatments when necessary.
Bacterial Diseases
Bacterial pathogens infect houseplants through natural openings or wounds, often caused by pruning or pest activity. Bacterial Leaf Spot, caused by species like Xanthomonas and Pseudomonas, manifests as water-soaked lesions that can coalesce into larger necrotic areas. Bacterial wilt, caused by Ralstonia solanacearum, obstructs the plant's vascular system, leading to sudden wilting without prior yellowing. Bacteria are primarily spread through water splashes, contaminated tools, and insect vectors. Control strategies include proper sanitation, avoiding overhead watering, and using bactericidal agents. Quarantine of new plants and regular inspections are critical to preventing bacterial outbreaks.
Viral Diseases
Viruses are obligate intracellular parasites that cause systemic infections in houseplants. They are notorious for their persistence and lack of curative treatments. Mosaic Viruses, such as the Cucumber Mosaic Virus (CMV) and Tobacco Mosaic Virus (TMV), cause characteristic mottling and distortion of leaves. These viruses are transmitted by insect vectors like aphids and thrips, as well as through mechanical means such as contaminated tools and hands. The management of viral diseases focuses on preventive measures, including pest control, sterilization of tools, and isolation of new plants. Once a plant is infected, it is often necessary to remove and destroy it to prevent the virus from spreading.
Prevention & Treatment
The effective management of houseplant diseases relies on an integrated approach that combines cultural, biological, and chemical control methods. Cultural practices include optimizing watering regimes, ensuring proper drainage, and improving air circulation to create conditions unfavourable for pathogens. Biological controls involve the use of beneficial microorganisms that antagonize plant pathogens. Chemical controls, such as fungicides and bactericides, are used as a last resort to manage severe infections. Regular monitoring and early detection are vital to managing plant diseases effectively. Understanding the science behind these pathogens and their interactions with houseplants enables gardeners to implement informed and effective disease management strategies, ensuring the health and vitality of their indoor gardens.
Summary Of Houseplant Diseases
Houseplant disease can usually be avoided with proper care, as most diseases are caused by overwatering, improper plant care, or harsh growing environments. By understanding the causes of plant diseases, we can effectively manage plant care to promote healthy plants that are resilient to disease. Over this article, we've looked at what houseplant diseases are, and why indoor plants get sick. We've looked at images of diseased houseplants, and learned what causes each issue, and how to treat it.
Next, we explored how to manage and prevent root rot, before then moving on to fungal diseases in houseplants, and how to effectively diagnose and treat them. We then discussed how to diagnose bacterial diseases, and their treatments, before finishing up our disease management section with viruses. Next, we've explored the role of biofertilizers in the disease prevention of houseplants, and how seaweed can help houseplants to better manage stress.
Disease is best managed by offering the correct houseplant care, so for further reference for each indoor plant species, check our A-Z of houseplants and see what the individual requirements are for your plant. Providing optimal care is fundamental in preventing and combating plant diseases. Most pathogens only successfully infect plants when they are already experiencing stress, whether from environmental factors, nutrient deficiencies, or physical damage. Ensuring proper plant care bolsters the plant's innate immune responses, reducing susceptibility to infections. This comprehensive care prevents diseases that might otherwise remain dormant or go unnoticed from taking hold.
Key aspects of optimal plant care include:
Adequate Nutrient Supply: Providing balanced nutrition supports vigorous growth and enhances the plant's natural defence mechanisms.
Proper Watering Regimes: Avoiding overwatering or underwatering minimizes stress and maintains healthy root systems. If the soil doesn't dry out quickly enough, or stays dry for too long, repot with one of our soil recipes that is appropriate for your houseplant. We have a multipurpose mix, a cactus mix, and an Aroid mix.
Optimal Light Conditions: Ensure that plants receive the appropriate light levels for their specific species, and consider using artificial light where needed to promote photosynthesis, growth, and overall vitality.
Good Air Circulation: Reducing humidity and improving airflow prevents fungal and bacterial growth. Remove dead or damaged leaves and regularly prune to encourage air flow, and to reduce decaying organic matter.
Regular Monitoring: Early detection and prompt intervention help manage stress and potential disease and pest outbreaks. Manage temperature levels and ensure that plants aren't subjected to extremes.
Edited & Fact Checked By: The Houseplant Shop
Article Published: 7th January 2025
About The Houseplant Shop:
Independent Houseplant Nursery
Horticultural Specialists
Managing Over 250 Houseplant Species Onsite
Over 15 Years Of Experience With Horticulture
As head of horticulture, Sarah manages the care and propagation of over 250 plant species at a commercial houseplant nursery. With over 15 years of experience in horticulture, specializing in houseplants, Sarah has extensive expertise in plant biology, soil science, and integrated pest management. She continually reviews and integrates the latest research into her plant care guides. Dedicated to educating others, Sarah has spent years diagnosing houseplant care issues and sharing her real-world experience. Her commitment to scientific accuracy and helping people diagnose plant health issues has established her as a trusted authority and expert in the field.
The Houseplant Shop is a dedicated houseplant nursery, growing all of their own stock from their botanical library of over 250 houseplant species. The nursery staff are horticultural experts who have dedicated their lives to cultivating and nurturing over 250 different species of houseplants, focusing on Aroids, tropical plants, and NOID collectables. All their plants are grown in house in Britain to be more environmentally friendly. The nursery is proud to have been featured by the Royal Horticultural Society (RHS) as a 100% peat free nursery.
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People also looked at: Pests, Watering, Humidity, Feeding, Temperature, Artificial Lighting, and Pruning.
How We Reviewed This Article:
Our horticultural experts continually monitor the houseplant space, and we update our articles when new information becomes available. We are committed to providing current and reliable information. If you have some information that you think would be helpful in this article, we'd love to hear from you. Our team works hard to revise articles for factual accuracy, and we regularly update our pages with new information, techniques, tips, images, trade secrets, and real world experience from the team here at the houseplant nursery. You can find a list of the article updates below.
Written By: Sarah Brooks, Head of Horticulture
Article Received: 4th January 2025
Copyright: The Houseplant Shop (https://thehouseplant.shop)
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Author: Sarah Brooks
Head of Horticulture at The Houseplant Shop