Roses - diseases

Table of contents

Roses are wonderfully flowering shrubs, very willingly grown in gardens. The most common are bedding and large-flowered roses, which are mainly threatened by two diseases - powdery mildew and black spot of rose leaves. But the list of diseases that attack roses is much longer. See how to recognize rose diseases and how to cure ailing plants. Here are proven ways to make he althy roses!


Rose diseases - leaf chlorosis

Rose diseasescan be divided into infectious diseases, caused by a specific pathogen, and non-infectious diseases related to improper cultivation conditions or inadequate fertilization.We can prevent diseases by providing plants with the right cultivation position and proper care. Neglected plants are much more susceptible to disease, as well as to pest attacks. We will reduce the risk of infection with many diseases by removing weeds and fallen leaves from under the bushes, by watering the plants directly on the soil below them, so as not to wet the leaves and shoots. It is also important to cut the roses properly and to ensure that the bushes do not get too thick. For planting in gardens, it is also worth choosing the most durable roses - varieties not very susceptible to disease and pests.

Roses - non-infectious diseases

A common non-infectious disease of roses is the sudden blackening of shoots that were previously green and he althy, noticed in early spring. The reasons for this phenomenon are spring, drying winds, still frozen ground and the inability to replenish the water transpired by the shoots. This can be referred to asfrost damage The occurrence of such damage is prevented by making mounds of soil or mulch at the foot of the shrubs, and by wrapping the shoots with insulating material intended for covering the plants (agrotextile, jute, straw). If we notice frost damage to rose shoots in spring, cut blackened fragments of the shoots and then spray the bushes with one of the fungicides, e.g. Topsin M 500 SC, which will prevent possible penetration of pathogens through the cutting wounds.
Numerous symptoms of the disease may also indicate a deficiency of nutrients. Deficiencies can occur as a result of inadequate fertilization or incorrect soil pH, at which plants are unable to take up nutrients from the soil.


Red or purple color of rose leaves may indicate nutrient deficiency

How to recognize nutrient deficiencies?
Lack of nitrogen is manifested by the bright color of the leaves, sometimes reddish spots and inhibition of the growth of shrubs.In the case of phosphorus deficiency, the leaves are smaller and purple in color. Due to the lack of potassium, the leaves are reddish with brown edges, they appear burnt. A light green or yellowish tinge in the leaves may indicate a lack of iron or magnesium. We are talking then about leaf chlorosis. In the case of chlorosis, the discoloration is quite characteristic, because it affects the tissues between the leaf veins, while the innervation itself remains dark green. Nutrient deficiencies can be prevented by using an appropriate fertilizer for roses, containing not only the basic composition of NPK (nitrogen, phosphorus, potassium), but all the macro and microelements necessary for roses to develop and grow. In the event of symptoms of nutrient deficiencies, the soil pH should also be checked, which can be done using any pH meter purchased in the store. The appropriate soil pH for roses should be 6-7.


Rose diseases - powdery mildew

Roses - fungal diseases

During the growing season, young rose leaves may develop a white, powdery coating, indicating that the bushes have been attackedpowdery mildewIt is a disease commonly found on many different plants garden. Infected leaves deform and the edges of the rose leaves slightly curl, usually after a dozen or so days the bloom changes from white to gray. There are also symptoms in the form of spots on shoots, peduncles and flower petals.


Rose diseases - powdery mildew

Powdery mildew is caused by the fungus Sphaerotheca pannosa var. rosae, infection is favored by excessive wetting of plants during watering. In order to limit the spread of this disease, in the fall, we rake the fallen leaves from under the roses, which may be the source of infection in the next year. During the growing season, we regularly control weeds, because they help to keep more humidity under the bushes, cut out heavily infested rose shoots, and spray the plants 2 to 3 times at 10-day intervals with fungicides: Baymat Ultra 0.015 AE, Discus 500 WG, Domark 100 EC, Score 250 EC.In order to limit the use of chemicals in the garden, they can be used alternately with biopreparations such as Biochikol, Biosept Active, Bioczos BR.
Another common rose disease isblack spot of rose leavesWhen shrubs are infected with this disease in the spring, the leaves show numerous light brown spots, oval or round in shape. Around the spots, the tissue turns yellow, on the surface of the dead tissues you can see black spots that are clusters of fungus sporulation. Leaves are falling down massively.


Rose disease - black leaf spot

This disease is caused by the fungus Diplocarpon rosae, which hibernates on fallen leaves, and its spores are transferred during rainfall. Fighting black spot consists in avoiding wetting the plants during watering (water directly on the ground), removing fallen leaves, and cutting out heavily infested shoots. After finding symptoms, the bushes should be sprayed 3 or 4 times, at 10-day intervals, alternately using fungicides, such as: Baymat Ultra 0.015 AE, Discus 500 WG, Dithane NeoTec 75 WG, Score 250 EC, these preparations should be used alternately with biopreparations , such as: Biosept Active, Biochikol, Bioczos BR.


Rose disease - black leaf spot

Rose bush leaves may also featurerose rustIn case of rust infection, one can observe round or oval yellow patches up to a few millimeters in diameter. These spots appear on the upper side of the leaves. On the underside, orange and brown clusters of fungal spores are visible at the spots. Infected leaves deform, dry and fall off.
Rust can be caused by fungi of the genus Phragmidium, hibernating on shoots and fallen leaves. Their development is favored by frequent rainfall and plant wetting during watering. Fighting rust: avoid soaking leaves during watering, collect and remove fallen leaves, cut out infected shoots. After noticing the symptoms of rust, spray the plants several times at 10-day intervals with fungicides, such as Discus 500 WG, Dithane NeoTec 75 WG, Score 250 EC. They can be used alternately with the above-mentioned biopreparations.

Roses can also be attacked by gray mold. When infected with this disease, the petals of roses show watery, numerous, rapidly enlarging spots. With time, the whole flowers rot and become soft, covered with a profuse, gray, dusty coating. Necrosis passes from infected flowers to shoots and causes their death.
Rose mold is caused by the fungus Botrytis cinerea, the development of the pathogen is favored by high air humidity. Fighting gray mold is primarily cutting and removing infected shoots. It is also necessary to remove bleeding inflorescences, which are very susceptible to infection. Spraying preparations such as Kaptan 50 WP, Teldor 500 SC will help. You can also try the biological method of spraying with Polyversum WP. This preparation contains a fungus harmless to plants, which parasitizes pathogenic fungi. It is very effective against gray mold on e.g. strawberries.


Rose diseases - shoot dieback

The same fungus Botrytis cinerea can also cause another disease -dieback of rose shootsThe causes of this disease can also be Coniothyrium fuckelii or fungi of the genus Alternaria spp., Nectria spp. Symptoms of shoot dieback are browning, drying up and dieback as well as light brown shoot necrosis. Necrosis often develops at the cut site and moves downward, causing the entire shoot to die over time or may end up on a branch.
To prevent the disease from occurring, remove the remnants of the shoots on which the fungus can winter and develop further, try not to injure the shoots during the care works. After noticing the symptoms of the disease, cut the affected shoots a centimeter below the necrosis, above the strong side bud and smear the cutting wounds with Funaben 03 PA paste or emulsion paint with the addition of a fungicide, e.g. Topsin M 500 SC.
If the rose shoots turn brown and die from tops, and the whole shrub grows slower, the cause may bewerticyliosis The leaves turn yellow and fall off, the youngest leaves wilt in hot weather, and then return to a better shape after cooler nights. The bush can be sick for several years and then dies.
Verticillium disease is caused by fungi of the genus Verticillium, found in soil and plants. It attacks many other plant species grown in gardens and greenhouses. The spread of the disease is prevented by removing fallen and infected leaves, cutting and removing infected shoots, keeping clean and disinfecting shrub cutting tools. After diagnosing the symptoms of the disease, the diseased bushes must be dug up and removed (it is also worth removing the soil directly from under the infected bush), and the plants growing in the neighborhood should be watered with Topsin M 500 SC as a preventive measure.

Note!
According to the current regulations, smoking leaves and branches, even if they come from sick plants, is forbidden. From gardens and plots, we should dispose of them in accordance with the principles of segregation and return of green waste in force in our commune.

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