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Mildew on a dying leaf
7 MIN 16 Apr
Last update: 13 Apr 2023

Fighting mildew in your garden: how to recognise and tackle it!

Mildew is a serious threat to the health of your plants and lawn. Find out how to identify it and tackle the problem before it spreads.

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Do you sometimes see little powdery white spots on your plant’s leaves? Maybe you see it spread across your greenhouse, or perhaps you see it develop over individual plants in your veg patch? Either way, you’re spotting mildew.

Table of contents:
Show all
  • What is mildew?
  • Powdery Mildew
  • Downy mildew
  • How does mildew occur?
  • How harmful is powdery mildew?
  • Which plants are susceptible to mildew?
  • How to prevent or get rid of mildew
  • How to fight mildew
  • How to remove fungal infections from plants
  • FAQs
  • Fighting mildew in your garden

Mildew is a fungal disease that can seriously damage your plants. You’ll spot it by the grey or white spots that spread across the leaves, stems, and flowers — sometimes even causing your plant to die. 

This article is about identifying this particular mould that negatively impacts your plants and the measures you can take to prevent and combat this powdery mould. 

Ready? Let’s get started.

What is mildew?

Mildew is a fungus that appears on plants’ leaves, stems, and flowers. You’ll recognise it as small, irregular, powdery spots that spread across the entire plant and can jump from one plant to another. 

Two principal types of mildew affect veg patches and ornamental gardens: powdery and downy. 

And this is how to recognise them:

Powdery Mildew

Powdery mildew on a leaf
Powdery mildew

This fungus is a problem for many plants, including annuals, perennials, fruits, herbs, and vegetables. It spreads quickly and seriously damages the vitality of your plants if you fail to address the problem. 

While you probably associate mould around the house with damp, powdery mildew mainly occurs during dry and hot weather. Microscopic air-borne spores spread during the growing season, landing and establishing on your plants’ surfaces, producing a powdery growth. 

If you don’t tackle powdery mildew in time, the fungus darkens, causing the leaf to curl up and wither. 

Unlike other fungal infections, it spreads across dry leaves — it’s not caused by extended periods of leaf wetness, making this a particular problem during dry summers. 

How to recognise powdery mildew

It appears as:

  • White or grey spots
  • Circular patches
  • Powdery in texture

The condition can cause:

  • Leaf yellowing
  • Stunted growth
  • Flower death

So, if you spot these symptoms, take action before it’s too late. Read on to discover how to tackle powdery mildew on your plants.

Downy mildew

Signs of downy mildew on a leaf
Downy mildew

This is a fungal disease that presents as bright yellow or orange spots on leaves, stems, and flowers. Indeed, it’s easy to overlook downy mould as a fungal condition because it doesn’t present as typical “fuzzy mould” — many gardeners misdiagnose the problem as pest-related. 

However:

Look a little closer, and you’ll spot the signs of classic fuzzy fungus on the underside of the leaf.

How to spot downy mildew

Your plants are infected with downy mould if they have:

  • Light green or yellow angular spots on the upper leaf surface
  • White fluffy growth on the underside of the leaf
  • Overtime, the lesions go brown and dry

You’ll see downy mildew on older leaves first, but it can quickly spread to younger, healthier leaves if left untreated. 

While powdery mildew thrives in dry weather, downy requires a moist environment. 

How does mildew occur?

Droplets of water sitting on green leaves
Wet leaves can cause mildew – Photo by Timothy Eberly on Unsplash

The fungus develops on or between plants — spread via spores carried on moisture droplets or through the wind, on animals and insects, and through water. 

Fungus prefers a temperature of between 20 and 25℃, with a humidity of between 80 and 90%. 

The problem is often exacerbated by poor air circulation between plants. So, if you’re packing your greenhouse or flowerbeds too tightly, you could create perfect conditions for this fungal infection to spread. 

How harmful is powdery mildew?

Mildew on a lawn
Mildew on a lawn

The fungus can cause severe damage if you don’t tackle it quickly enough. The white mould spreads quickly, covering large areas of the plant within days. 

And in some cases, the spots will cause the leaves to turn yellow, wither up, and die. And once the leaves have died, the rest of the plant is sure to follow. 

Incidentally, mould can also wreak havoc on your lawn — it’s one of the most common lawn diseases after red thread, fairy rings, and rust disease. If given free rein, it sucks the moisture out of the grass blades, causing them to die and go brown or yellow. 

So, tackle it quickly, even if it doesn’t appear serious at first. 

Lawn doctor Louis says:
Mildew isn’t harmful to humans, but the spores can irritate the airways of some pets, such as cats and dogs.

Which plants are susceptible to mildew?

A basket of fruit and veg harvested from a garden
Garden veg are particularly susceptible to mildew

Mildew funguses can affect a wide variety of garden plants, including annuals, perennials, fruits, herbs, and vegetables. 

In the ornamental garden, keep a close eye on:

  • Roses 
  • Bergamot
  • Begonias
  • Honeysuckle
  • Marigolds
  • Zinnias

In the edible garden, look out for:

  • Strawberries
  • Grapes
  • Cucumbers
  • Pumpkins
  • Tomatoes
  • Courgettes

However, you can also find the mould on fruit trees, especially apple and peach. So, if you spot powdery or downy mildew, act fast to combat the disease. 

How to prevent or get rid of mildew

While totally preventing the fungal infection is impossible, you can limit its impact. 

Air circulation

Firstly, ensure there’s plenty of space around your plants to aid air circulation. That applies to plants in your greenhouse, flowerbed, and veg patch. 

Always follow the growing guidance on seed packets (or the plant tag if you’re buying plants from a garden centre). This will tell you how much space you should leave between plants to help them thrive. 

You can also trim the leaves if the vegetation becomes too dense. 

Light and water

Make sure you give your plants enough light and water — this will help prevent fungal infections. 

Water plants around the base of the stem or trunk, avoiding wetting the leaves, as this can promote fungal growth. 

How to fight mildew

Act quick. The most common treatments are shop-bought fungicides, but there are several more natural approaches.

Natural ways to prevent plant damage from fungal growth

There are several natural ways to prevent plant damage from fungus, including:

  • Neem oil — a natural antifungal agent that you can buy in squirty bottles
  • Garlic — mix with water and spray it onto plant leaves and stems
  • Apple cider vinegar — mix ¼ tablespoon with water for a 1-litre spray bottle, and spray onto fungus-infected leaves. 
  • Baking soda — mix 1 tablespoon baking soda with a litre of water and add a few drops of gentle liquid soap to help the liquid stick to the leaves. 
  • Milk — a surprisingly effective remedy. Mix 4 parts milk with 6 parts water, and spray the affected leaves. Repeat until the fungus has completely disappeared. 

Fungicides

Fungicides are chemical solutions that kill fungal infections but use them cautiously as they can be toxic to animals and humans. 

We always recommend against chemical fungicides and pesticides as much as possible. This helps maintain your garden’s delicate ecosystem. It’s always better to go with a natural alternative if there is one.

How to remove fungal infections from plants

If you’ve spotted the first signs of mildew, gently remove it with a swab of cotton wool or a soft brush. However, ensure you don’t spread the spores, so a little moisture on the cotton wool will help collect the spores. 

Additionally, remove dead or dying leaves and stems to prevent the fungus from spreading to healthy parts of the plant. 

Lawn doctor Louis says:
Do not throw fungus-affected plants onto your compost heap; otherwise, it will spread throughout the compost and ruin the batch. Dispose of damaged plant limbs in your unrecyclable waste bin.

FAQs

Is mildew harmful?

A little mildew isn’t immediately harmful to your plants, but the white mould will penetrate the plant’s cells and absorb nutrients and moisture if left to its own devices. Prevent fungal spread by leaving plenty of space between your plants, and spray a natural remedy onto the leaves if you can. 

What can you do to tackle mildew?

Control fungal infections with chemical fungicides or use more natural remedies such as baking soda, milk, garlic, or neem oil. Mixed with water, these store-cupboard items can help tackle mildew and stop it from spreading. 

What causes mildew?

Powdery mildew develops in hot, humid weather, but it can equally occur when it’s hot and dry. It settles on and between plants via spores, which spread in the wind and within water droplets or get dispersed by animals and insects.

Fighting mildew in your garden

Remember, the most crucial thing with plant-based fungal infections is to act fast. It’s a very common problem for domestic gardeners, so use our tips to spot the first signs of fungus and tackle it.

I hope you’ve got all the information you need to help spot and combat mildew, but if you have questions, don’t hesitate to contact us. 

We love hearing from you and will reply as soon as we can. 

Thanks for reading, and happy gardening!  

Louis Hooft
Founder & Lawn expert
Introducing Louis Hooft, the founder of MOOWY and your reliable expert. With a profound love for stunning lawns and extensive experience in garden maintenance, Louis is here to assist garden enthusiasts in achieving a greener and livelier outdoors than ever before. Count on Louis for invaluable tips, clever tricks, and top-notch products to make your garden flourish!
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