Last updated on April 1st, 2022
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You’re doing your usual morning stroll through your garden, admiring all of your beautiful flowers. You make a stop to enjoy your roses and their fragrant scents. Unfortunately, something is amiss. There are black spots on the leaves and upon a closer inspection, you realise that several of your roses are infected with black spot fungus.
You can’t let your precious roses go down without a fight. So you set out on a mission to find the best fungicide, to not only control and treat black spot but also prevent and protect the roses from further attack.
Well, we are way ahead of your dilemma and have listed four of the best fungicides for black spot, most of which are available as ready to use sprays or concentrates, so you can mix a larger batch. Most will also treat mildew and rust and our top recommended pick is also a systemic pesticide and will also help control aphids. Here, we have compiled a list of factors you should consider before purchasing and we went one step further into reviewing (in-depth) the top fungicides for black spot on roses and other plants.
It’s also worth considering how to help prevent black spot in the first place, by providing the ideal growing conditions and keeping the area clear from fallen debris that will harbour spores.
Let’s get started.
Fungicide Buyer’s Guide – What to Consider Before Purchase
Yes, there are limitless fungicides available on the market today. Unfortunately, the chasm between the performance of established brands and conventional sprays has no Venn diagram with a bit of an overlap. Therefore, forget the price and brand, and instead, focus on crucial information and features, as outlined below.
Fungicides are made of a mixture of ingredients, in which case active ingredients are sourced from different fungicide classes. For instance, you can have ingredients from the Triazole fungicide class that function to inhibit enzymes crucial in fungi sterol-production; combined with those from the strobilurin class that are locally systematic and hurts fungal respiration.
While premixes can widen the disease and bug control spectrum. It’s vital to understand what is contained in the product you are purchasing, its purpose, the percentage of active ingredients and knowing the effectiveness of the product in treating the targeted disease. This is especially vital with the rise in repackaged products.
So, be sure to always check the label information to see whether the targeted disease you are looking to treat is listed.
And when it comes to treating black spot, Penconazole, Myclobutanil, Protectant Mancozeb or Sulphur are your go-to active ingredients.
Curative vs Preventive fungicides
As the name suggests, curative fungicides will work on present fungal diseases, while preventive fungicides are functional before the onset of a disease.
The truth is, that all fungicides can play preventive roles. They form a barrier on the plant which stops fungal spores from germinating. Nevertheless, fungicides specially designed to prevent the occurrence of the disease will do better.
Curative fungicides work best in cases of an early disease diagnosis. Say a day or two after infection. In other cases, curative fungicides are unlikely to cure or eliminate disease spots and lesions already present, however, they can slow or stop the targeted disease.
Note, some have more curative properties than others so choose carefully.
Always settle for a fungicide that matches your specific needs. And when applying, follow the instructed procedure and follow all the laid out precautions. Obviously, don’t go spraying fungicides near streams or ponds, unless it’s labelled for such use.
Also, consider the prevailing weather condition. For instance, there is no use in selecting washable/contact fungicides if you are spraying your plants just before it starts raining, check the weather forecast that there is no rain due for at least 24 hours, but check the packaging as this should give guidance.
Target area (size)
The size of the area to be sprayed with a fungicide dictates the amount of fungicide required.
Therefore, settle for concentrated products if you have lots of roses to spray and mix your own. It will be much more affordable and go further in terms of the litres of spray you have available. You can check the manufacturer’s directions with regard to product dilution to gauge whether the package you are planning to purchase will be adequate.
There are other formulations such as solutions, wettable powders, granules, and dust; so, select accordingly. Personally, we recommend using liquid concentrates that you simply mix with water.
Note, you should buy only the quantity you intend to use right away because stored fungicides tend to lose their effectiveness over time. This is also where concentrates are better because you can just mix what you need rather than buying a ready to use spray, where you might have too little or too much.
This refers to the duration the fungicide is effective. Some offer a short protection period (weeks) while others provide a longer period of control (over 3 months). Therefore, select what best suits your circumstances.
For instance, when spraying to prevent a fungal attack, it would be wise to settle for fungicides offering long-term protection. This will eliminate the need for multiple fungicide applications throughout the season.
However, when dealing with the need to stop or slow down a fungal infection; you’re better off settling for a fungicide with more curative properties regardless of its protection period. That’s following the short application interval that overrides the need for long-term protection.
Top 4 Fungicides for black spot on roses
In this day and age, nothing gives black spot on roses and other plants’ cold feet like the following 4 fungicides.
1. RoseClear Ultra Fungicide Concentrate with 3 in 1 action
The RoseClear Ultra Concentrate is an excellent choice for gardeners growing roses, flowering plants, and other ornamental plants in areas (and weather conditions) that make them highly susceptible to rust, powdery mildew, and of course black spot; as well as aphids, which is pretty much every garden for those little pests. Being a dual systemic insecticide and fungicide enables it to slow down the spread of the aforementioned diseases whilst preventing further outbreaks.
This fungicide kills on contact and systematically which means you can see instant results (usually within 24 hours when controlling aphids) whilst still enjoying plant protection of up to 3 weeks. Being a systematic fungal killer means it is easily absorbed by the leaves and moves to protect all parts of the plant (the stem, leaves and buds included). Therefore, a dose is enough for the entire plant. In addition, because it is absorbed into the plant system, it cannot be washed away by rain or irrigation, which can be an issue with fungicides in powder form.
The Rose Clear Ultra is a concentrate, in which case a 200ml bottle can make up to 10 litres of fungicide, enabling you to spray large areas at an affordable price. For the best results, it’s advisable to spray the fungicide at first signs to target the disease, then spray subsequent applications as per the recommended interval periods, usually around every 14 days or 21 days if black spot is already established. Most importantly, observe all the safety precautions outlined by the manufacturer’s label.
- This fungicide does everything. Protects against rust, black spot, mildew, etc; as well as aphids such as greenfly and blackfly.
- 3 In one action means it kills aphids, controls fungus and then prevents further attacks.
- Systematic control means it’s taken into the leaves and spreads to all parts of the plant.
- Suitable for other types of plants so can be used around your whole garden when needed, not just on roses.
- Protects for up to three weeks.
Overall, we would nearly advise using RoseClear every time, but because it is an insecticide as well you need to be careful not to kill beneficial insects such as ladybirds and bees. We recommend buying the concreate version and a small hand sprayer, however, you have the option to purchase a ready to use 1-litre sprayer if you only have one or two roses to treat.
2. FungusClear Ultra 225ml
The FungusClear Ultra 225ml is best suited for controlling fungal infections on roses, although it’s also perfect for treating shrubs and most ornamental plants. It can even be used on plants inside the home, conservatory, and greenhouse.
It provides systemic control of rust, powdery mildew, and black spot on roses and may slow down the spread of other diseases such as conifer leaf blight and Anthracnose on ornamental plants. It’s also effective in protecting roses (and its new growth) from further attack from any diseases, which is something we look for in a good fungicide. This can be attributed to its systemic killing properties because once in the plant system, the plant is safe from weather elements – the very reason it can protect plants for over 3 months. This is why we try to recommend systemic products because we do tend to get our fair share of rainy days in the UK.
The recommended dosage is 15ml per litre of water, making up 15 litres per package which means it offers an excellent value for money in comparison to buying the ready use sprays, where for a similar amount of money you would get 1 litre.
Be sure to follow the outlined instructions from the manufacturer to the letter, including how and when to use the fungicide. For instance, if it’s recommended for use between March and September; or whether it needs to be applied using a clean garden pressure sprayer.
- Great at fighting established diseases like black spot, powdery mildew and rust, and preventing further attacks.
- Provides long-lasting protection to plants (over 3 months).
- A small portion (15ml) of the concentrate makes up to 15 litres of solution, so it provides excellent value for money.
If you have had previous problems with black spot we recommend spraying the leaves as soon as the buds start shoot in spring. This way all your new foliage will be protected from the start.
3. Provanto Fungus Fighter Plus Ready to Use 1 Litre Sprayer
This Provanto Fungus Fighter Plus Ready to Use 1 Litre is good at controlling common rose and ornamental plant diseases, including black spot, rust and mildew. We like that it also kills powdery mildew on greenhouse crops such as squash, cucumber, and courgette so you may get more use out of this spray.
The fungicide employs a smart mechanism – Fungus Fighter Plus – in controlling diseases for three weeks. For effective results, as with all fungicides, we recommend applying Provanto at the first signs of disease (either in the late evening or early morning) and try to avoid spraying on sunny days. Follow the stipulated guidelines to the letter when spraying both edibles and ornamental plants, and don’t forget to read the outlined precautions on the label before use and act accordingly.
- Although very good for roses, especially black spot, it’s also one of the best to use on edible plants if you are growing veg or fruit.
- Fast results within just 24 hours.
- Protects for up to three weeks.
- With contact and systematic action for best results.
- Ready to use, no mixing required.
- Can be used both indoors and outdoors.
If you need to treat roses but also have a need to spray vegetables, then this ready to use fungicide is well worth trying rather than trying to buy a separate veg-friendly fungicide.
4. Bayer Garden Concentrated Fungus Fighter
This fungicide works well for both ornamental garden plants and houseplants. Following its systemic fungal killing characteristic, this Bayer Garden Concentrated Fungus Fighter can kill rust, black spot and mildew on roses as well as hollyhocks, asters, and snapdragons; whilst preventing the plants from being further attacked by the aforementioned plants for around 3 weeks. Its active ingredients can also kill fungi upon contact, which leads to faster results whether used indoors or outdoors.
Additionally, the fungicide comes equipped with a dose bottle but this is what lets it down, it is, what you might call, very awkward. This makes mixing and dosing not as easy as it should be. Note, during reading other reviews we read complaints from a dozen people with regards to the dose bottle usage so be sure to check the bottle again to know how to properly use it. The product seems to work fine it’s just let down by the measuring system. You can also buy it ready to use, so that might be something worth considering if you don’t have many plants to spray.
- Controls a wide range of diseases that affect ornamental plants and roses including black spot, mildew, rust and box blight.
- Effective active ingredients give contact action to immediately fight fungus and systemic action for up to 3 weeks of ongoing protection.
Black Spot FAQs
How do you treat black spot fungus on roses?
The treatment of black spot on roses follows 4 easy to complete steps. These are…
This involves paying close attention to your roses during your morning and evening strolls through the garden. Once you identify the first signs of the black spot it’s time to apply the treatment.
Treatment can either be organic or non-organic (use of chemicals).
The latter involves the use of chemicals containing active ingredients (such as sulphur, protectant Mancozeb Myclobutanil, and Penconazole) that are known to help prevent and fight black spot on roses.
Organic treatment on its end includes non-chemical measures in controlling black spot such as the removal of infected stems and leaves and promptly burning them; hard pruning shoots and burning them; and use of organically acceptable sulphur.
Prevention includes measures taken to minimise the chances of disease occurrence. Such include:
- Choosing resistant cultivars
- Allowing for air circulation
- Watering in the morning, being keen to avoid the foliage
- Keeping the garden clean
- Applying preventive treatment
- Regular inspection
- Discarding fallen leaves instead of waiting for them to compost
How do you get rid of black spot on roses naturally?
Through the removal of infected stems and leaves and promptly burning them; hard pruning shoots and burning them; and use of organically acceptable sulphur. In addition, the following mixes have been found to be effective.
- Baking soda and vinegar – a mixture of 1.5 tablespoons of baking soda, 1.5 tablespoons of hand soap, 2 tablespoons of vegetable oil, 1 tablespoon of vinegar, and 1 gallon of water can kill the fungus on roses by altering its pH.
- Baking soda and oil – a mixture of 3 tablespoons of baking soda, 1 gallon of water, and 1 tablespoon of canola oil can cure black spot by changing its pH.
- Neem oil – oil extracted from Neem tree that prevents the formation of the fungus spores, ultimately controlling its spread.
- Milk and water – milk helps to alter the pH level of the fungus, eventually killing it.
How do you treat black spot on plants?
Treatment of black spot on flowering and ornamental plants is not that different from that on roses. Just be sure to follow the manufacturer’s (of whatever product you’re using) instructions carefully.
Can black spot on roses spread to other plants?
The black spot fungus spores produced during humid conditions can be spread by wind, water, tools, hands, or clothing to other plants. The spores on fallen leaves can be passed to other plants too, which is something to be aware of if the leaves collected are used as part of compost manure.
Why do the leaves on roses turn yellow with black spots?
The yellowing of rose leaves infected by black spots can be attributed to the enlarging and merging of dark-brown spots that first appear on the upper side of the leaf. The more the dark spots the more dead plant cells there are, which make it hard for the leaves to access water, capture sunlight, or resist heat stress. The plant then pulls its chlorophyll out resulting in yellow leaves.
Can black spot kill roses?
Though a rarity, a heavy untreated infection of black spot can kill roses.
Note, the resulting yellow leaves eventually drop because they are unable to access the necessary nutrients to continue living. This defoliation if in large scale will weaken the plant following the lack of means for the plant to access energy. Leaves are responsible for photosynthesising the energy and food required by a crop to keep growing, so if they are non-existent, the plant will weaken and eventually die.
You love your roses and other plants in the garden, who doesn’t?! That’s why you cannot let that black spot disease damage what you have worked so hard to grow. Therefore, armour yourself with the list of features to consider before purchasing fungicides or better yet, select one of the top 4 fungicides for black spot for roses and other plants (that we have reviewed above) and show that shameless disease the hell it deserves.
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