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When brown spots appear on rose petals, there can be a variety of reasons. In many cases, it is important to act quickly in order to prevent life-threatening damage. But the cause must be known exactly in order to act correctly. The plant expert describes possible causes and remedies in detail.
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Brown spots on rose petals - what's wrong with my roses?
The rose is one of the most popular types of flowers for gardens and homes. The noble overall picture is often disturbed by brown spots on the rose petals, which can often mean the beginning of dying. Therefore, quick action is essential, which only makes sense if the cause is known. Find out below what could be behind the brown spots on rose petals and how you can remedy them.
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When brown-colored spots have developed on one or more leaves, this is usually a serious sign that something is wrong with the rose. Usually it is a fungal disease or a pest infestation. However, treatment of the rose is necessary in any case, as healthy leaves are vital for the rose. It stimulates the metabolism by means of photosynthesis and secures the plant's energy supply. The brown spots on rose petals either indicate a malfunction that hampers the natural process, or ultimately lead to dysfunction because photosynthesis cannot take place properly via the damaged leaves. Sooner or later the rose will die here, because it cannot survive without intact, healthy leaves.
mushrooms
mildew
Downy mildew (Peronospora sparsa)
Although many types of roses are considered to be quite robust, most specimens are not resistant to the so-called "downy mildew". This is a fungal infection that roses are afflicted with from time to time. Above all, cooler temperatures and high humidity favor this type of fungal infection on roses. The fungal disease is mainly observed from spring to autumn. But downy mildew can also spread in winter when roses are cool and damp. The fungal spores survive the cold season without any major problems.
Recognize
- Leaf spots between yellow-brown and violet-brown
- Spots only on the upper side of the leaf
- Underside of leaf covered with white-grey, slightly sticky mushroom carpet
- increased leaf drop
- in the advanced stage, shoots are affected
- Buds remain closed and dry up
- without treatment, the rose will eventually die
Blackspot (Marssonina rosea)
Stubborn and difficult to identify or to recognize an infestation is the so-called black spot, which likes to tamper with roses as a fungus. All types of roses can be affected, with shrub roses being predominantly infected by the fungal species.
It will be moving into German gardens as early as the end of May, but it takes a long time with visual characteristics. It is not uncommon for an infestation to be noticed only in mid- or late summer, when the Marssonina rosea has spread throughout the rose beds and the roses are now visibly losing strength and power. The sac fungus, as it is also called, triggers the black spot disease, which occurs more often than any hobby gardener would like, especially in roses.
Recognize
- large black-brown spots on the upper and lower sides of the leaves
- Spots start from the stem and extend to the leaf edges
- often only older leaves near the ground are affected
- then yellow leaves form
- Leaves fall off in large numbers
- Shoots are affected, no longer mature and dry up
- Reduced frost hardness with possible frost damage
rose rust
Rose Rust (Phragmidium mucronatum)
A very common rose disease is the so-called rose rust, which develops from the fungus Phragmidium mucronatum. It is long-winded because it survives the winter with ease and can haunt and damage roses in the home garden or balcony for many years if not recognized and treated. It loves damp summers and prefers loamy, compacted soil.
Recognize
- initially yellowish and reddish spots on the upper side of the leaf
- rust-brown, small punctiform spots on the underside of the leaf
- these turn black-brown in winter (winter storage of the spores)
ring spot disease
Ring spot disease is one of the typical fungal diseases of roses and is caused by the harmful fungus Sphaceloma rosarum. Especially in the rainy summer months, it attacks the plants. Due to its striking optical properties, this type of mushroom is easy to identify.
Recognize
- initially red-brownish spots
- later fill up with gray dots in the middle
- first distributed individually
- later the spots cluster into one or more large spots
- affected leaves fall off
- bud growth stops
- Flowers wither quickly
First aid
If possible, contact with roses and other plants affected by a fungus should be avoided and kept dry. A generous pruning is usually unavoidable in the event of a larger infestation. But at least all infected rose petals must be cut off immediately and disposed of in the household waste or burned.
treatment
As a rule, fungi penetrate deep into the leaf tissue and shoots, damaging the rose from the inside out. Therefore, a quick and above all effective fight is always recommended to avoid bad things. There are various options to choose from, from home remedy recipes to organic antifungal agents and chemical fungicides.
fungicides
Fungal spores are usually very stubborn because they penetrate deep into the interior of the plant and can cause life-threatening damage to the plant structure from within. If there are already numerous brown spots on the leaves, it can be assumed that the fungal infection is far advanced. Here you can usually only achieve a quick stop of fungus with chemical products. Bayer, for example, offers Baymat Rosen-fungusfrei and Ortiva Special is available fungi-free from CAMPO. Organic products are usually only suitable if only older leaves are affected and the infection has not yet spread that far.
home remedies
In practical tests, the self-prepared onion broth has shown itself to be optimal against fungal infections in roses.
The preparation is quite simple:
- Cut 150 grams of onions in quarters - cut off the ends beforehand
- Pull apart the onions and place them in a saucepan along with the skins and ends
- boil two liters of water
- Pour the boiled water over the onions and cover the pot
- Let the brew steep for about 30 minutes
- then sift onions out of the broth
- Let the soup cool down
- Dilute the broth with water in a ratio of 1:5
- pour into a spray bottle
- Spraying soil and rose petals morning and evening for four days
- From the fifth day spray only once a day
- After about eight days, the fungal infection should have subsided
- preventively spray roses every 14 days
parasites
spider mites
Spider mites (Tetranychae)
A common condition with brown spots on a rose leaf is spider mites, which sneak into gardens and homes as annoying parasites. They can be seen with the naked eye if you look closely. They threaten almost all types of roses, especially between autumn and spring. They feed on the pulp of the leaves and prefer dry and warm places.
Recognize
- small white animals up to a millimeter in size
- brown spots form around the sucking sites, mostly on the underside of the leaf
- white, sticky webs form all over the leaf
- after the brown spots, the rose petal usually turns yellow
- after that it falls off
- the spider mites escape down to the shoots
- form their webs there
- wooden parts die off and the rose dies
Rose sawfly (Cladius difformis)
Cladius difformis is a parasite. Once the rose has been attacked by this pest, it spreads rapidly and leaves fall off within a very short time. Typical identification features are the signs listed below.
- brown spots on leaf surfaces
- Leaf damage with central holes or marginal bays
thrips
Thrips (Thysanoptera)
Thrips are particularly attracted to the plants in winter when the heating air is dry, although roses are usually attacked less frequently. But even in midsummer, they get their food from the green leaves and leave behind damage that, if left unchecked, will cause the leaves and ultimately the roses to die off.
Recognize
- one to three millimeters long, multi-legged, elongated animals
- colored dark brown to brown-black
- Larvae colored yellowish to white-yellow
- are usually on the underside of the leaf
- leave yellow and brown spots
- the brown spots often have a small hole in the middle
- dark brown to black spots on the leaf due to faecal excretion
First aid
In order to avoid the spread of parasites in the house or in the plant bed, it is essential to isolate affected roses. In the case of bed roses, planting out is recommended if other roses or other plants have not yet shown any typical symptoms, but are close to the affected specimen.
treatment
Parasites on roses are usually quite easy to control once they have been identified as such. The dangerous thing about them is that they can spread extremely far if left unchecked. This means that the worst case scenario does not occur when your rose dies, but when the rose pests have spread throughout your floral landscape.
insecticides
Toxic insecticides are offered specifically for parasites on roses. They mainly contain substances that affect the central nervous system and thus cause the parasites to die off. In most cases, they are not very environmentally friendly and their own health often does not react positively to the use of chemical insecticides. For example, they can cause skin irritation or aggravate asthma. It is therefore advisable to only use chemical insecticides if large rose beds are infested with pests and rapid control is required.
For smaller infestations, the use of biodegradable products is recommended, which "work" just as effectively but may take effect a little later. The manufacturers Neuendorff and BAYER have such products in their range, for example based on neem oil.
TIP: Neem oil is also a great way to prevent spider mites. From May, simply spray on the roses every 14 days when they have sprouted at least five centimeters.
home remedies
A little slower in action, but no less effective are some home remedies that you can easily prepare yourself into sprayable solutions. There are numerous home remedies for pest control on the Internet. However, the garlic brew is one of the most effective against the rose pests mentioned here.
- Provide one liter of water with a pH below 6.0
- crush three cloves of garlic
- Pour the garlic mixture into the water and stir
- Leave the brew at room temperature for 24 hours
- stir vigorously again
- Sieve the garlic out of the water
- Pour the juice into a spray bottle
- Spray infested roses generously every day
- after about a week, the pests such as spider mites & Co. should be gone
TIP: Putting a clove of garlic in the ground near the root of the rose provides protection and keeps almost all parasites at bay.
Conclusion
Brown spots on the leaves of your roses should not be taken lightly, as they can be life-threatening not only for your roses. If you can at least roughly distinguish whether it is a fungal disease or a pest, you can quickly help roses with the control measures mentioned here and let them bloom again with the usual elegance.