7 Best Fungicide for Dahlias 2023 [Top Picks & Reviews]

The fungus is the most persistent problem for Dahlias and you know; the fungicide is the ultimate solution. 

But there are hundreds of fungicides available in the market today. Definitely, all are not perfect fungicides to prevent or control the diseases of Dahlias.

Now the question- what is the ideal fungicide for Dahlia to treat fungus?

Briefly, any organic or synthetic fungicide that contains eco-friendly fungus-killing agents like neem extract, natural essential oils, copper substances, myclobutanil, tebuconazole, etc.

Good news- after thorough research, I have enlisted & reviewed the 7 best fungicides for your Dahlia that can protect all the fungal diseases of Dahlias including Powdery Mildew, Flower Blight, Tuber Rot, Cottony Stem Rot, Dahlia Smut, Leaf Spot, Southern Blight & Verticillium Wilt.

So, why don’t you give it a look?

Best Fungicide for Dahlia- Comparisons

FungicideActive IngredientSolutionTypePrice
Bonide Copper FungicideCopper Octanoate ConcentrationOrganic
Garden Safe Brand FungicideNeem oil Ready-To-UseOrganic
Southern Ag – Liquid Copper FungicideCopper Diammonia Diacetate Complex ConcentrationOrganic
Spectracide Immunox Multi-Purpose Fungicide MyclobutanilConcentrationSynthetic
Bayer Advanced Disease Control FungicideTebuconazoleConcentrationOrganic
Dr. Earth Disease Control FungicideRosemary oil, Clove oil & Peppermint oil Ready-To-UseOrganic
Daconil Fungicide ConcentrateChlorothalonilConcentrationSynthetic

Best Fungicide for Dahlia- Reviews

1.Bonide 811 Copper 4E Fungicide

Bonide 811 Copper 4E Fungicide

Are you shilly-shally about using fungicide on your Dahlia? Cast your hesitations aside as Bonide Copper fungicide can be your pick for its organic nature. Let’s see what else it has.

Active Ingredient

This OMRI-listed fungicide offers 10% Copper Octanoate (1.8% metallic copper) as the active ingredient which is a combination of soluble copper fertilizer & naturally occurring fatty acid.

It especially acts as a preventive measure for Dahlia. The copper ions kill the fungi or their spores by disrupting their cell membrane & internal cell metabolism.


Multiple fungal diseases can be checked by it. Its effectiveness against powdery & downy mildew, leaf spot & blight on ornamental shrubs, fruits & vegetables is proven. Seems promising, right?

Why for Dahlia

How to get rid of powdery mildew on dahlias?“- is one of the top FAQs about Dahlia.

Well, Bonide Copper Fungicide is widely used against powdery mildew. Let’s just say, powdery mildew fungus hates Copper.

Want bonus? This fungicide is profoundly effective against another two most common diseases of Dahlia- Dahlia flower Blight & Leaf Spot.

Applying Method

Mix 0.5 to 2.0 ounces of this concentrated fluid with 1 gallon of water. Spray over & under the Dahlia leaves thoroughly & repeat after every 10 days. Check the packet label for more details.

2. Garden Safe Brand Fungicide

Garden Safe Brand Fungicide3

Garden Safe has offered a combo for your Dahlia- A fungicide that also acts as an insecticide & miticide.

Moreover, it is approved for organic use by OMRI.

Now be honest, would you or would you not call it the best organic fungicide for your Dahlia? Let’s see further-

Active Ingredient

Surprisingly the fungicide uses 0.9% clarified hydrophobic extract of neem oil as the active ingredient. We know the efficacy of neem oil as a fungicide & pesticide, right? Additionally, its hydrophobic nature ensures minimal wash-off due to rain.

This ready-to-use fungicide can be used both for prevention & cure. It stops spreading fungal diseases on your Dahlia by barring fungal germination & suffocates insects by coating their outer body.


The multipurpose fungicide will chuck away lots of your tensions. Because-

  • It is highly recommended against fungal diseases like mildews, leaf spots, scabs, blights, etc.
  • Effectively kills Japanese beetles, whiteflies, mealybugs, aphids, mites & many more.

 Why for Dahlia

Have you ever seen white powder on Dahlia shoots? It is very common in Dahlias. This symptom marks either powdery mildew or a mealybug attack.

You know, aphid, whitefly, Leafhopper & mites- these four pests visit Dahlia frequently. Along with causing several diseases, additionally, they transmit fungus & viruses. And that further results in wilt, Leaf Spot, Dahlia flower blight, etc.

But good news-

This fungicide can relieve your Dahlia from all these problems shortly. So, Hurry!

Applying Method

You won’t have to make a solution as it is a ready-to-use Fungicide. Shake well & spray thoroughly. Repeat after 7-14 days.

3. Southern Ag – Liquid Copper Fungicide

Southern Ag Liquid Copper Fungicide

Here’s another Copper liquid Fungicide for your Dahlia. Don’t jumble it with the previous one. It has some specialties that you might want to know-

Active Ingredient

27.15% Copper Diammonia Diacetate Complex is the Active Ingredient of this fertilizer. It contains 8% metallic copper.

There are mainly 3 types of copper fungicide in the market. Among them, Copper Diammonia Diacetate Complex is the strongest because of its mixing capability & thin nature.

Also, it is a natural product to use on your Dahlia but sadly isn’t OMRI approved.


Its wide range of potency is enough to get you bedazzled. Want some proof? let’s see-

Firstly, it is marked to use against both fungi & Bacteria. And surprisingly it clears out algae from turfgrass too.

Care to know the most exclusive part? This copper fungicide is valid against nearly 100s of fungal diseases of fruits, vegetables & ornamental plants.

It covers more or less 50 Ornamental plants involving Bougainvillea, Dahlia, hibiscus & many more.

You can also use it for 11 fruit trees including apple, Avocado, Citrus, etc & 25 vegetables like Tomato, Potato, Eggplant, etc. A fair amount, isn’t it?

Why for Dahlia

The fungicide specifically covers 3 common fungal diseases of Dahlia. These are-

  1. Alternaria leaf spot
  2. Botrytis gray mold &
  3. Cercospora leaf spot

Applying Method

To get it done, spray thoroughly over your Dahlia foliages after every 7-14 days. Applying dose is 2 tablespoons of liquid copper fungicide per gallon of water.

4. Spectracide Immunox Multi-Purpose Fungicide Spray

Spectracide Immunox Multi-Purpose Fungicide Spray

Let me introduce you to one of the finest fungicides for your Dahlia. Once you finished with the review, I am sure you will find out why-

Active Ingredients

It is an inorganic Fungicide. But assuredly using one of the best killers of fungus as the active ingredient- Myclobutanil(1.55%).

Want to know how Myclobutanil works as a fungicide? Here is the answer-

Whenever you spray Immunox over your Dahlia, it Gets absorbed by dahlia plant tissues and moves upward or downward of the cells through the xylem & phloem (Fungus collects nutrients from xylem & Phloem).

Myclobutanil blocks the enzyme of fungi to produce Ergosterol (Ergosterol controls fungus cell membrane integrity) Break down of cell membrane & ultimate death occurs.

So the bottom line-

This superlative killer machine defends your Dahlia from the inside.


Its wide coverage makes it a multipurpose fungicide. It alone can cover your lawn, fruits, vegetables & ornamentals from the powdery mildew, brown patch, black spot, blight, rust, and other fungal diseases. You can use it for-

  •  Flowers- Rose, Dahlia, Calendula, Zinnia, Hydrangea & many more.
  •  Fruits- Apple, Apricot, Peach, Cherry, Strawberry, etc.
  • Vegetables- Asparagus, Cucurbits, Bean, Tomato, etc.

And lastly, once dried, Spectracide guarantees no “wash-away” by rain.

So basically it is a packet of brownies with some funfetti.

Why for Dahlia

The Immunox fungicide has declared its complete protection against Powdery Mildew of Dahlia.

Additionally, it is also effective to defend Dahlia flower blight & Leaf Spot.

Applying Method

For your Dahlia, mix 2 tablespoons of the concentration per gallon of water & spray thoroughly after every 7-10 days. 

5. Bayer Advanced Disease Control for Roses, Flowers, and Shrubs Garden Fungicide

Bayer Advanced Disease Control for Roses, Flowers, and Shrubs Garden Fungicide

Are you looking for an ideal fungicide of Dahlia which kills almost all the diseases alone? Then check it out-

Active Ingredient

2.90% Tebuconazole is the prominent component of the fungicide. Tebuconazole is best known for its mode of action. It inhibits fungal germination & spreading.

Tebuconazole works in a tripartite way. It-

  1. Destroys already infested fungi
  2. Builds a shielding barrier on the outside of the plant  &
  3. Gets absorbed into the plant to provide internal protection.

This systemic fungicide is waterproof as it works inside mainly. So, you won’t have to worry about washing away.


You already know, it is the terminal protection for your flower & ornamentals like Dahlias, Roses, Rhododendrons, Ground vines, houseplants & many more.

Want to know what diseases it covers? Well, it is actively functional against Black Spot, Powdery Mildew, Rust, Leaf Spot, Southern Blight, Anthracnose, Scab, Flower Blight, Boxwood Blight & Petal Blight.

So, the sum is- it controls almost all the fungal diseases that you may face in your garden.

Why for Dahlia

Your Dahlias will love you for it because it controls their 4 common diseases-

  1. Powdery Mildew
  2. Leaf Spot
  3. Southern Blight &
  4. Dahlia Flower Blight

Applying Method

Mix 1.5 tablespoons of concentration per 1 gallon of water and spray thoroughly after every 2 weeks.

6. Dr. Earth Ready to Use Disease Control Fungicide

Dr. Earth 8007 Ready to Use Disease Control Fungicide

It is a highly recommended organic fungicide for Dahlia. Care to know why? Just go through the review of this OMRI-listed product & you will know why.

Active Ingredient

3 natural essential oil extract works as the active ingredient in this fungicide. They are-

  1. Rosemary oil (0.06%)
  2. Clove oil (0.05%)
  3. Peppermint oil (0.05%)

You know, each of them is well known for their antifungal activity. And additionally, they repel harmful insects to keep your Dahlia safe. Quite a great deal!

This scientific formula grants supreme killing power against fungus.

Good news- it also provides minerals to your Dahlia to recover disease damages.

Now be honest with me, could that be any better? I don’t think so.


The disease control fungicide is ideal for trees & shrubs, Flowers & Lawns, Fruits & Vegetables.

It controls diseases like powdery mildew, Rust, Peach leaf curl, Leaf Spot, Leaf Blotch, Scab, Brown Rot, Botrytis, Fusarium Blight & many more.

And the best part? It provides year-round disease control.

Why for Dahlia

You know, Dahlia tubers often face fungal attacks because fungi tend to stay dormant inside them. It is best to spray fungicide to the tubers before planting. In that case, you might search for a fungicide for your Dahlia tubers.

Good news- Dr. Earth Organic Gardening Fungicide makes an excellent protective dormant spray.

Along with this, it is also very effective against Powdery mildew & Flower Blight of Dahlia.

Applying Method

As it is a ready-to-use Fungicide, just shake properly & spray thoroughly.

7.Daconil Fungicide Concentrate

Daconil Fungicide Concentrate

Daconil is manufactured by Gardentech. Its wide range of killing potential keeps your dahlias & other houseplants safe. Let’s know more about this-

Active Ingredient

The Active Ingredient is 29.6% Chlorothalonil. It is a broad-spectrum non-systemic fungicide. That means it shields your Dahlia from the outside.

Care to know how it works? Well, Chlorothalonil attacks the enzyme system of fungus, which eventually causes death.

Daconil is recognized because of its three-way control.  It kills the fungal spores, stops their spreading, and prevents their invasion beforehand.

And the best part? It is effective against over 75 plant diseases.


Daconil is an inorganic fungicide for flowers, vegetables & fruits.

It is a potential cure for diseases like Die-back, Flower Blight, Leaf Blotch, Scab, Anthracnose, Leaf Spot, Powdery Mildew, Rust, Botrytis, Alternaria Leaf Spots, Black Spot, Helminthosporium Leaf Spot, Botrytis Gray Mold, Phytophthora Blight, Ascochyta Blight and many more.

Good news- Gardentech guarantees its rainproof nature.

Why for Dahlia

Daconil Fungicide protects your Dahlia from some common diseases. For instance Powdery Mildew, Dahlia Flower Blight, Botrytis Gray Mold & Leaf Spot.

Applying Method

Spray thoroughly over the Dahlia foliages. The mixing ratio is 1 tablespoon of concentration per 1 gallon of water.

How often Apply Fungicide on Dahlia?

If you search for it, Most of the fungicides of Dahlia require to reapply after 14 days on average. It is because the fungicide remains effective for 14 days. Then it needs another dose. So, you can simply go for it.

But wait, there’s more. If you no longer see any symptoms & the environment is not favorable for fungal growth, you can take a pause.

When is The Best Time to Spray Fungicide on Dahlia?

Fungicide Treatment for Dahlia

“Timing” is the first requirement for effective fungicidal activity.

You know, prevention is better than cure, especially for fungal growth. Exactly why the best time to spray fungicide is before the fungus invades. The second best time is just after your Dahlia starts showing symptoms.

Now, while spraying, you must want to spray the fungicide early in the morning or at dawn. In these periods of the day, plants have to deal with environmental stress. It is necessary for a positive fungicidal effect & reduces the evaporation of fungicides.

 How to Apply Fungicide on Dahlia?

Applying Fungicide on Dahlia Plants

 Most of the fungicides of Dahlia are either Concentrated or Ready-to-Use. So it is easy to apply.

But before applying, make sure you are protected by wearing safety gadgets. Then follow the steps-

  1. For concentrated formula, make the solution accurately with clean water (as per packet label).
  2. Pour the solution into a clean Sprayer.
  3. Shake properly
  4. Spray over & under leaves thoroughly.

For Ready-to-use fungicide, start following from no 3.

 Homemade Fungicide for Dahlia?

Fungicide making with Fenugreek, Clove, Cinnamon

There are plenty of homemade fungicide recipes available for instance, Neem oil, Baking soda, Milk, Insecticidal soap, Bordeaux mixture & many more. All of them are super effective and easy to use.

But today I am sharing an organic fungicide formula with you. Give it a try. I bet you will thank me later. Let’s start-

Items Required-

  1. Clove 25 gm
  2. Fenugreek Seed 25 gm
  3. Cinnamon 25 gm
  4.  Water

Making Procedure-

  1. Put clove, fenugreek seed & Cinnamon in three different pots
  2. Add 200 ml water in every pot
  3. Mix them with water properly
  4. Let them soak for 24 hours
  5. Collect the water from 3 pots separately after 24 hours & preserve the items for further use. The collected water samples will be brown.
  6. Mix the water samples. Your fungicide is ready.
  7. Pour 50% water & 50% fungicide into the sprayer and shake properly.
  8. Spray over & under the Dahlia leaves properly.

This hand-made organic fungicide acts both as fungicide & insecticide. Interesting, right?

Frequently Asked Questions

 #Is Neem oil good for dahlias?

Proper application of Neem Oil is definitely good for Dahlias. Neem works as a fungicide, insecticide & Miticide. So what are you waiting for?

#How do you treat Dahlia rot?

Dahlia rot is not that easy to treat. If you find any symptoms of rot, immediately use a proper fungicide. But, the fungicide has to be systemic to stop further rotting.

The best Cure is prevention. Plant your dahlia in warm, well-drained soil & avoid overwatering.


Honestly speaking, it is hard to resist the beauty of Dahlia. Whenever you pass through a garden & there’s Dahlia, one sight is not enough. You have to look back twice or thrice.

That is why when fungus tries to invade over beautiful Dahlias, gardeners are like-Heck, no!

keeping that in mind, I did deep research for the ideal fungicides. Fungicides that cover all the fungal diseases of Dahlia. And finally, I have come up with the best fungicides For Dahlia.

Now it’s your turn to pick the right one. Pick wisely & protect your Dahlias.

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