How do you get rid of black spot on roses?


We all love roses, They not only brighten up the garden, but they are given as a sign of affection, love or they can even be part of one of the biggest days of your life. Roses are one of those flowers that gardeners always want to grow and find a space for.

How do you get rid of black spot on roses? Black spot on roses can be a nuisance for any gardener. Caused by a fungus known as Diplocarpon rosae, this disease spreads blackspot spores which can greatly weaken the rose plant and reduce its vigor. There are a few treatments to rid you of this issue, so check out this post to learn more.

In this post, I will walk you through the possible options to get rid of black spot on roses so you can enjoy these beautiful flowers without the risk to your plants from the black spot. Well, read on to find out.

What is black spot?

Black spot is a fungus called Diplocarpon rosae. It is spread by the fungal spores being splashed up on to the lower leaves of roses, The spores are also airborne and typically start during early spring. If left untreated this rose disease can seriously affect the health of your rose plants.

It does this by spreading, Initially it will look like little black or dark brown spots around 15mm in diameter. This affects the lower leaves and will spread to the rest of the plant including the stems in worst-case scenarios. Really badly affected plants will not look like small spots but large blotches as they join together.

Ways to get rid of back spot on roses

Many gardeners, often than not, focus on treatment and forget addressing the conditions for the thriving of the black spot spores. While prevention tactics cannot completely eliminate the risk of black spot, they are your best line of defense to counter the issue. In fact, the preventative approach is easier than curing.

Here is a list of some of the best ways to prevent black spots on your roses:

  • Ensure the rose plant is properly watered
  • Water roses first thing in the morning
  • Observe proper spacing
  • Do not plant roses under too much shade
  • Prune your roses and clean up your garden
  • Clean your pruners with alcohol
  • Apply a thick layer of mulch
  • Grow natural disease-resistant varieties of roses

We will look more in-depth into each of these as we continue in this article. I would love to draw your attention tot he video below that will teach you everything else about roses. I would suggest if you are going to grow roses that this video would be of great help to you. Just click the video to view

Ensuring the rose plant is properly watered

Gardeners usually use automated watering methods such as sprinklers, or spray curtains that will wet the foliage, encouraging and spreading the disease to other leaves and plants.

The correct way is to water the roses is at ground level. It’s true that you can’t prevent rainwater from splashing on the leaves, but getting water directly to the roots means you reduce the amount of time that leaves stay wet.

Consider using drip tape or drip pipe to water, this will allow small droplets of water at the root zones and will keep the leaves above dry. This prevents the spores from splashing up.

Water roses first thing in the morning

If you’ve been watering your roses in the evening hours, then you’ve been doing it wrong and this could be the reason you’re always dealing with black spot. What! I hear you cry. It’s true. Watering in the evening means that the roses are wet all night right through until the sun dries them off the next day.

It’s time you switched to watering in the morning. Experts highly recommend this because it allows foliage to dry off before the black spot spores start to grow. Otherwise, the spores can easily sprout when continuously exposed to a lot of moisture for at least seven hours.

Observe proper spacing

Roses thrive in a planting site with good ventilation. It’s, therefore, essential that you leave enough space between your rose plants to promote good air circulation.

When air circulates freely, the leaves dry a lot faster and reduce the risk of fungus growth. Also, if one plant becomes infected, it will not easily infect its neighbours. Densley planted roses will quickly spread the black spot disease amongst the whole planting area.

On spacing and circulation, pruning is important too, You may have heard about pruning a goblet shape when it comes to roses. This simply means to thin out the middle of the plant. This will not only prevent black spot but also powdery mildew

Do not plant roses under too much shade

While roses can still grow under partial shades, they become more prone to developing the black spot problem. The leaves will not dry quickly after rain or watering, and this provides good environmental conditions for fungus growth.

Warm humid conditions are perfect for the black spot spores to quickly grow. As such, you’ll want to grow your roses on a site where they receive plenty of sunlight.

Prune your roses and clean up your garden

Make sure you snip off any infected leaves as soon as possible to prevent any potential spread to the rest of the bush. After that, you should also dispose of the dropped leaves immediately and properly. Some gardeners use the leaves for mulching. Unfortunately, the black spot spores can survive in the mulch and be spread back to the plant through splashing water and wind.

Pruning out the old, weak, or crowded canes in late winter is another excellent way to ensure proper air circulation in individual rose bushes. If some of the canes are infected, make sure you prune about 6-8 inches below the area showing signs of infection. Generally, it’s recommended to prune on a sunny day.

Clean your pruners with alcohol

Husbandry is very important when dealing with black spot. Always make sure to clean the pruning tools using either alcohol or a 10% bleach solution before you can use them on another plant.

These cleaning solutions can kill mould and fungi, thus preventing the possible spread of infection through plant wounds during pruning. You can use a clean rag to rub the solution on the pruners. Remember to clean them after their last use as black spot spores will lay dormant until you next use the pruners.

Apply a thick layer of mulch

Mulch in your garden will not only keep moisture in the soil to reduce your watering frequency but also prevent splashes of water up the plant reducing the risk of spreading spores. A 3-inch depth of mulch around the roses is enough. However, the layer of mulch should not touch the canes.

Another thing worth mentioning is that you need to replace the mulch with a new layer, preferably after every year at the start of the spring. You can use woodchip or my favourite is leaf mould. Leaf mould is ideal as it feeds the soil as it breaks down. If you want to learn how to make leaf mould watch the video below. It is known as gardeners gold for a reason.

Grow natural disease-resistant varieties of roses

Some roses are less susceptible to fungal diseases, including black spot or powdery mildew. Excellent types of roses in this category include Grandiflora roses, Meilland hybrids, drift roses, floribunda roses, and shrub roses.

Treatment solutions to get rid of black spot on roses

You can do everything right to prevent black spot but still, your rose plants can be infected with the disease. There is only so much we can do as a gardener, but we cannot control the weather like wind and rain. Both of these can carry spore to our rose plants.

Well, it happens sometimes. The good news, though; this disease can be cured using commercial and homemade solutions. Without further ado, let’s check out the most effective solutions below.

Homemade, DIY solutions for black spot

1. Baking soda

Baking soda works by creating an alkaline chemical condition on the leaves, which makes it hard for the black spot spores to sprout. It is because the fungus thrives in more acidic PH conditions. This solution is more effective when you apply it as soon as you see the first signs of the disease.

Preparing baking soda spray

  • Dissolve 2 teaspoons of baking soda in 1 gallon of warm water
  • Add 2 teaspoons of liquid soap (Castile soap not dishwashing soap which is a detergent and not a soap) to help the main ingredient adhere to the leaves

Apply the solution on the leaves thoroughly. Please note the solution can be washed off by the rain. So, it’s a good idea to spray the leaves frequently as necessary for better results. Spraying once a week is okay. Also, remember baking soda contains salts and applying high concentration can easily ruin your leaves.

2. White vinegar remedy for black spot

You can combine the ordinary white vinegar with baking soda for a more effective spray to get rid of the black spot disease.

How to use white vinegar remedy

  • Mix a tablespoon of white vinegar with a tablespoon of baking soda in one gallon of water
  • Add a tablespoon of canola or horticultural oil
  • Stir and shake the mixture before you transfer it to a spray bottle

Make sure you remove as many infected leaves as possible before you start spraying the mixture. Apply it weekly and after rain. When applying this mixture, however, make sure the temperatures are below 80 degrees Fahrenheit.

3. Milk solution

Milk mixed with water in a 1:1 ratio can be a good natural solution for black spot. If applied weekly, this DIY solution can control the disease just like a fungicide. However, nobody knows yet why milk works against black spot.

Its effectiveness is largely linked to the lactoferrin in milk, which helps fight diseases in people. It’s not any kind of milk that’s used for black spot, though. You need to use cow’s milk. Soy milk and almond milk, for example, will have no noticeable effect on the roses.

Unfortunately, the milk remedy can make other microorganisms to thrive on the leaves. Their presence may be aesthetically unappealing.

Commercial black spot solutions

1. Copper fungicides

If you are dealing with recurrent black spot problems, you can use copper fungicides to keep the infection under control. Demildex and Bordeaux mix are considered good examples of effective copper fungicides. They work by interfering with the spores and mycelium enzyme cycle, causing permanent damage. Make sure you follow the manufacturer guidelines on how to use the copper fungicides, as applying excessive of the product can burn the leaves.

2. Neem oil

Neem oil is an excellent natural product for a wide range of pests and fungal diseases, including black spot and powdery mildew. Another amazing advantage of using neem oil is that it gets absorbed into the plant system. So, there’s no need for reapplying after rain but, of course, you shouldn’t apply it on a potentially rainy day. And in line with that, we must say that proper application is essential to avoid injuring your roses.

Well, here are a few precautions to keep in mind.

  • Do not apply the oil when temperatures are above 90 degrees Fahrenheit or below the freezing point
  • Do not apply the oil when there is high humidity (above 90% )
  • Do not apply the oil within 30 days of using the sulfur-containing products

There are other products like neem oil which are not only good for black spot and powdery mildew but good to be used for aphids and whiteflies too I speak about 5 in this video that may be of interest to you.

3. Sulfur

Sulfur can kill any fungus spores on roses. And it works pretty quickly. While this product is available in a fine powder that can be used on its own, you can also opt for the type that can be mixed with water. Such sulfur products will be labelled as wettable.

4. Insecticidal soap spray

Insecticidal soap sprays are cable of destroying the cells of microorganisms. For better results, you will want to use insecticidal soaps formulated with organic fungicides like sulfur. The soaps help ensure the leaves are well coated with the fungicide.

If you prefer chemical fungicides, you can use products like captan, mancozeb, propiconazole, thiophanate-methyl, chlorothalonil, trifloxystrobin, and triforine. Be sure to follow the instructions on the product labels to avoid the risk of serious effects on your plants.

Related Questions

Can garlic kill black spot on roses?

Yes, Garlic can kill black spot. The reason for this is garlic omits sulfur from its chemical make-up and sulfur will kill black spot. To use garlic simply blend 2 garlic cloves to a litre of water and use this as a spray on the foliage. Be sure to spray both the top and bottom of leaves. Repeat this every fortnight throughout spring.

Will my rose bush die if it gets black spot?

Although black spot can seriously damage your rose plants, If treated there is no reason that any rose plant should die. However, if left untreated rose bushes will be greatly weakened by black spot and could then die. It is important to avoid this situation at all costs. All it takes is some intervention and good husbandry in the garden to ensure this fungus does not become an issue.

What should I do with infected rose leaves with black spot?

infected leaves should be taken off the plant as soon as they have been spotted. These should be placed into a bag along with all the fallen debris on the floor. This should then be disposed of in the green waste bin or burnt. Be mindful when collecting leaves not to infect additional plants.

Is it safe to add leaves with black spot to my green waste bin?

A lot of people think that if these leaves are added to the green waste bin that the black spot will survive the process when the green waste is collected. They worry this could reinfect others properties.

The black spot spores simply cannot survive the recycling process that green waste is subjected too. The heat generated will destroy all spores, so it is totally safe to add them to the green waste.

Can I add roses infected with black spot to my compost?

No. You should never try to compost material affected with black spot. The reason for this is that homemade compost simply cannot generate the heat required to kill the black spot fungal spores. This is a sure-fire way to reinfect your entire garden.

Conclusion

Roses are beautiful and after reading this post you could think they are not worth the effort. But following some basic principles, you can have beautiful plants with no black spot in sight.

I hope you enjoyed this blog post about black spot on roses. I trust it answered your question fully. If this was of interest to you, why not consider checking out some of my other blog posts and subscribing to the blog so you don’t miss future content.

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And remember folks, You Reap What You Sow!

Tony O'Neill

I am Tony O'Neill, A full-time firefighter and long term gardener. I have spent most of my life gardening. From the age of 7 until the present day at 45. My goal is to use my love and knowledge of gardening to support you and to simplify the gardening process so you are more productive

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