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Roses are an “eternal” trend in landscape design. However, they are susceptible to diseases that adversely affect the decorativeness of the bushes. One of the common symptoms is blackened rose branches. In this case, it is necessary to be able to correctly identify the disease by “associated” signs and know what to do in each case. Naturally, preventing a disease is easier than fighting it, so the gardener needs to pay attention to preventive measures.
What do blackened branches of roses look like?
When the stems and other parts of the rose turn black, it can look different. And often this is not the only symptom that indicates the disease.
Blackness on stems of roses can be “solid” and “spotted”. The affected areas themselves are dry or “weeping”, as if slimy to the touch. Fabrics that turn black, in some cases, are greatly softened, while in others, on the contrary, they unnaturally “harden” and crack.
However, in garden and domestic roses, when their trunk turned black, one can also reveal some similarities, in addition to the fact that their decorative effect suffers greatly:
- The disease does not stop on one stem, it first spreads to the entire already infected bush, then “spreads” to neighboring roses.
- Plants “refuse” to form buds, their development practically “freezes”, the tone decreases literally before our eyes.
- Already existing buds on bushes, in which the stems turn black, dry and fall off without opening, or are severely deformed.
- The stems of roses themselves, when they turn black (even from above), cannot be used for propagation (cuttings do not give roots).
In order to correctly “diagnose”, it is necessary to evaluate in a complex, taking into account all the negative changes
Why does a rose turn black trunk
Often, the gardener himself is “to blame” for the fact that the stems of the rose turn black. Diseases are much more likely to “catch” bushes whose immunity is weakened due to serious errors in care or the wrong choice of landing site.
Basically, the stems of roses turn black for the following reasons:
- Excessive “crowding” in the flower bed. A thick planting prevents normal air circulation and light access to the inside of the bush. Pathogenic microflora such a “stale” atmosphere is very suitable.
- Too much watering. High humidity and “swamp” in the flower bed contributes to the activation of many pathogenic fungi.
- excess nitrogen in the soil. “Overfeeding” with nitrogen fertilizers greatly “undermines” the immunity of roses. They become more susceptible to diseases, including those that turn the stems black. A calcium deficiency has a similar effect.
Improper watering is the cause of many bush problems.
Bacterial cancer (burn)
When the stems of roses turn black due to bacterial cancer (aka bacterial burn), “depressed” black-brown small spots of a fairly regular round shape appear on them along their entire length. Gradually, they grow, the tissues affected by the bacteria dry out and die, as a result of which the spots turn into “ulcers”. The shoots dry, the aerial part of the bush dies, it dies.
If nothing is done, not only the stems, but also the leaves turn black in roses. “Wet” rounded black spots appear on them. When tissues die, holes remain in this place. As a result, the leaves fall off.
From bacterial cancer, the stems of old roses often turn black, the shoots and roots of which are prone to cracking.
Activation of bacteria contributes to:
- temperature in the range of 25-30 °C;
- alkaline substrate (pH 6.0-9.0);
- heavy clay soil;
- excess nitrogen in the soil.
However, despite the relatively high favorable temperature, the stems of roses turn black from bacterial cancer quite early, even before flowering. The pathogen “seizes the moment” and begins to actively progress when the bushes have not yet recovered from the “stress” in the form of wintering.
Gray mold
When gray rot develops on roses, they not only blacken the stems. First of all, the buds suffer: “clots” of dark mucus appear in the core and at the base, the petals soften and turn brown.
Then similar damage in the form of “weeping” dark spots are noted on the leaves and stems. Gradually, they are covered with a layer of “fluffy” gray plaque with small black “grains” (accumulations of fungal spores). The last pathogen infects the root system, the stems of roses turn black completely, the leaves fall off, the plant dies.
Young roses are most susceptible to gray rot; the disease manifests itself quite late, at the end of summer
Favorable for the development of gray rot are the following factors:
- cool weather (about 20 °C), high air and soil humidity caused by frequent rains and fogs;
- excessive “crowding” in the flower bed;
- mechanical damage to the stems of roses.
Black spot
It is also sometimes found under the name “marsonina” (from the name of the disease-causing fungus). The stems of roses in this case are affected and blacken much less frequently than the leaves, only if the process of the development of the disease is “started” to the state of a “severe case”.
Rose leaves are the first to suffer from black spot. Purple “blurred” spots appear on the front side. They quickly turn black and become covered with a “scab” of accumulations of fungal spores.
The process goes from the bottom up, most often the rose fungus is “picked up” from the ground. If nothing is done, the leaves turn brown, curl up and fall off. Then the disease “spreads” on the stems of roses, they turn black.
In the bushes affected by black spotting, not only decorative effect suffers. They become more susceptible to other pathogens, their cold resistance is greatly reduced.
The fungus overwinters, from which the leaves and stems of roses turn black, in plant debris. In the spring, he waits long enough for favorable weather, so the symptoms appear closer to the middle of summer.
From diseased bushes to healthy spores are carried by wind, raindrops, dew; the gardener himself can “contribute” to this
Mučnistaâ rosa
An extremely common disease in which mainly young stems turn black in roses, and subsequently leaves. At first, it looks quite “harmless”: like a grayish powdery coating on the shoots.
Gradually it thickens and darkens. The tissues on the stems under it turn black, depending on the humidity of the air, they dry out or rot and die. The shoots themselves are deformed.
Then the fungus “moves” to the leaves. They also gradually turn black, curl and fall off. Powdery mildew rarely captures rose buds, only in the most severe cases – they dry without opening, the outer petals of already blooming flowers curl and die.
The fact that the bushes turn black stems, “damage” is not limited. Immunity suffers greatly, the bushes lose their ability to normally tolerate temperature fluctuations. They probably won’t survive the winter.
Roses are especially susceptible to powdery mildew with an excess of nitrogen in the soil and calcium deficiency.
What to do if the stem of a rose has turned black
There is no cure for bacterial cancer: if the stems of roses turn black because of it, the bush can only be dug up and burned to prevent the spread of the pathogen. “Therapies” are only amenable to fungal diseases, and it is worth starting as soon as possible after the symptoms are detected.
What to do when you see that the stem of the rose has turned black and identify the pathogen:
- With a sharp, disinfected knife or pruner, cut off all parts of the plant that show symptoms, even slightly. All “wounds” are immediately disinfected, sprinkled with sifted wood ash, crushed chalk, and activated charcoal.
- Burn plant waste as soon as possible. Adding it to compost is a very bad idea.
- Spray the roses themselves, in which the stems turn black, and the soil in the flower bed with a solution of any fungicide. It is not advisable to use folk remedies in this case, it will just be a waste of time. All processing is carried out in strict accordance with the manufacturer’s instructions. This is especially true for the concentration of the solution and the frequency of procedures.
- Provide the highest quality aeration. In climbing varieties and hybrids, the stems are removed from the support and laid out in a fan so that they do not touch each other. In ground cover creeping shoots, they raise the shoots above the ground, laying them on the “horns”, completely changing the mulch layer. Others carry out pruning, as much as possible “opening” the middle of the rose.
- 2-3 weeks after the condition of the bushes improves and their stems stop turning black, it is advisable to carry out foliar feeding with any biostimulant.
When pruning, it is desirable to capture some healthy-looking tissues – most likely, the pathogen managed to spread there as well
It is impossible to spray rose bushes, in which the stems turn black, with fungicides to infinity. If after 3-4 treatments their condition has not improved, you can not continue further. Plants are dug up and burned.
preventive measures
Preventing roses from becoming infected with diseases that turn their stems black is much easier than dealing with them later. Preventive measures are simple, they will not take much time and effort from gardeners:
- regular inspection of plantings for suspicious symptoms;
- weeding flower beds;
- cleaning the soil at the end of autumn from plant and other debris, deep loosening, updating the mulch layer;
- competent care of landings during the season;
- timely and high-quality shelter for the winter;
- choosing a place for a seedling according to the “requirements” of the culture;
- planting in accordance with the scheme recommended for this variety or hybrid in order to avoid “crampedness” in the flower bed;
- targeted pest control.
It is impossible to neglect the examination of even absolutely healthy roses – this is what will allow you to notice the development of the disease in time
Conclusion
If the branches of the rose have turned black, this indicates that the bush has been infected with a dangerous disease. The gardener is required to determine as quickly as possible what exactly he is dealing with, otherwise it will not be possible to “prescribe” the correct “treatment”.
