In addition to insect pests, there are a large number of fungal organisms that cause and contribute to the development of various diseases of roses. For the successful cultivation of healthy and beautiful plants, it is necessary to know the diseases of roses and their methods of treatment and be able to recognize diseases at an early stage.
Most pathogens of roses have the ability to remain on dead plant debris for a long time and therefore it is very important to collect absolutely all fallen leaves, cut shoots, removed weeds and burn them.
If the leaves are not removed from the bushes before the winter shelter of roses, then the eggs of pests and fungal spores remaining on them will perfectly endure the winter, and with the onset of spring they will hit the plant.
It is recommended for prophylactic purposes to treat the bushes in the spring with a solution of copper oxychloride (0.4%), and in the fall with ferrous sulfate (3%). It is very important to disinfect the cutting tools before starting pruning, and treat the cut points with garden pitch or clay mortar.
One of the most common diseases, rose rust is a fungal disease that is caused by a rust fungus.
As a rule, it occurs in a weakened plant in a cold spring after a harsh winter and completely affects the plant around the middle of summer. Symptoms of rose rust, which appear as early as early spring, are rusty spots on the upper side of the leaves and bright orange pads, which are clusters of spores, on the underside of the leaves, which turn black in the second half of summer. Infected leaves fall off, and young shoots turn red and shrivel.
Rose rust control methods:
- removal and destruction of the affected parts of the plant at the initial stage of the development of the disease;
- spraying the plant with a decoction of horsetail;
- dusting the bush with ground sulfur, or a mixture consisting of ground sulfur with slaked lime in a ratio of 5: 1;
- spraying and watering plants with tincture of wormwood consisting of 400-500 g of fresh leaves and 40-50 g of dried wormwood leaves filled with 10 liters of cold water and infused for 2-2.5 weeks until the start of fermentation. Before use, such an infusion must be diluted with water in a ratio of 1:10;
- in case of severe damage, it is necessary to treat the lower surface of the leaves with copper-containing preparations once every 2.5-3 weeks;
- as an extreme measure – spraying with a solution (1%) of Bordeaux liquid.
Rose diseases: black spot
The main threat to ground species is rose diseases such as black spot and powdery mildew. The causative agents of black spot are parasitic fungi that infect the plant with an excess of moisture or a lack of nutrients in late spring or early summer, but the disease appears only in August-September.
At the initial stage of the development of the disease, the upper surface of the leaves is covered with very rapidly increasing dark brown spots with yellowish edges. After 1.5-2 weeks, the leaves of the plant turn yellow and fall off, then the stems become stained, flowering stops, growth stops, the rose loses all foliage and the plant dies.
Black spot control methods:
- systematic destruction of the affected parts of the individual at the initial stage of the development of the disease;
- spraying with a decoction of horsetail;
- spraying with sulfur-containing preparations 1 time in 7-10 days with severe damage;
- spraying with copper-containing preparations, such as copper-soap emulsion and copper sulfate (5%);
- extreme measure of control – 1 time in 6-8 days with a solution (1%) of Bordeaux liquid, watering the soil around the bush and spraying the entire plant.
The most common disease of roses, powdery mildew, got its name because a white coating forms on the stems, leaves and young shoots. It is very similar to flour, and after the spores ripen, a liquid resembling dew drops begins to stand out.
Most often, this disease affects greenhouse and indoor varieties of roses , as well as actively growing young shoots and leaves. The disease is caused by a fungus and spreads very quickly throughout the plant and is transferred to neighboring bushes.
At first, powdery mildew spots are easily erased, and under them there are no noticeable damage to living tissues, but after 1.5-2 weeks they cover the entire bush, turning into a solid white coating. This leads to twisting and falling of leaves, curvature of stems, deformation of flowers and death of young shoots. As a result, the bush quickly withers and very often dies.
The infection develops very quickly under such favorable conditions as a hot, humid day and a cool, condensing night.
This disease is much easier to prevent than to fight it. In autumn, you need to remove all affected shoots from the plant, remove all leaves under the bush and burn. Add ashes under the bush and dig it up with the obligatory transshipment of the soil – this will make it difficult for oxygen to reach the pathogens. It is recommended for prevention in autumn and early spring to spray roses with a solution (3%) of copper sulphate.
Powdery mildew control measures:
- exclude fertilizing with nitrogen-containing fertilizers that stimulate the development of the fungus, giving preference to ash and potash fertilizers;
- at an early stage of the disease, organic preparations are effective – 1 kg of manure diluted in 10 liters of water and 200-300 g of wood ash, infused for 5-7 days. Then the infusion should be filtered and sprayed on the bush at intervals of 1 time in 4-5 days until the signs of the disease disappear completely;
- with an average degree of damage, a copper-soap solution is effective, consisting of 100 g of grated laundry soap dissolved in 10 liters of water, with the addition of 30-40 g of copper sulfate. With such a solution, you need to spray the bush at intervals of 1 time in 8-10 days;
- in case of severe damage, special means are used, such as topsin and benomyl. It is necessary to carry out treatment with such preparations in a row 3-4 times at intervals of 1.5-2 weeks. In the case of an advanced disease, the affected plant must be removed and destroyed to avoid damage to neighboring plants.
There are a number of main reasons why roses most often get sick:
- improper pruning, after which the cut point does not overgrow for a very long time;
- evening watering of plants;
- plants growing next to roses are already infected with bacterial diseases – most likely rose bushes will suffer the same fate;
- cool humid climate actively contributes to the development of fungal diseases;
- waterlogging or lack of moisture;
- lack of nutrients in the soil.
The method of treatment of roses depends on the disease:
- fungal diseases are treated by destroying infected leaves and pruning the plant;
- sulfur or Funginex is used to combat mold foci;
- in case of a bacterial disease, the infected stem must be removed and destroyed along with the ulcer;
- with sulfuric rot on branches and buds, the affected parts must be removed;
- in the event of a bacterial gall disease, it is necessary to remove the infected plant from the garden or flower bed as soon as possible, otherwise it will lead to the death of crops growing nearby.
The treatment of roses after wintering deserves special attention, since the plant has weakened and become very vulnerable over a long cold and damp period. The main diseases are stem blight, fusarium rot, and bacterial canker develop due to poor ventilation and excessive moisture during the dormant period. In this case, roses need to be fed with mineral and complex fertilizers. Carry out the necessary course of treatment of diseases with the help of drugs. In case of severe infection, the plant or its infected parts must be removed.
Protection of roses from pests
The main pests of roses are: rose cicadas , leafworms, sawfly, aphids, spider mites and scale insects. Protection of roses from pests is carried out using such means as: phytoverm, insecticide, actar, intavir, karbofos, as well as spraying with a water-soap solution, iron or copper sulfate, paraffin or mineral oil, nettle infusion and pyrethrin-containing preparations. With severe damage, the infected parts of the plant must be removed.