In addition to fungal diseases, roses can be sick with cancer. There is bacterial root cancer and stem cancer or bacterial burn.
Bacterial root cancer
The first disease is caused by the bacterium Agrobacterium tumefaciens. In this disease on the roots and at the base of the stalks are formed growths that harden, and eventually rot. As a result, the rose bush dries out. Infection occurs through the wounds of the roots received during planting or transplanting. It occurs more often on heavy clay soils with alkaline reaction of the medium and with an excess of nitrogen. The disease disrupts the supply of the rose bush with water, nutrients.
It is necessary to fight the disease in the early stages of pruning small growths, followed by treatment of the roots with 1% solution of copper sulfate for 2-3 minutes. Then rinse the roots with clean water. If the plant is severely affected by this sore, then it must certainly be burned. Also, plants that have growths formed at the root collar, must also be destroyed.
The cause of the second disease is the bacterium Pseudomonas syrindae van Hall, which spreads in the rain, is carried by the wind, by insects and is transmitted from the diseased plant with the help of the tools used for pruning. Park roses are most prone to this disease. It has a chronic and transient form, characteristic of roses. The symptoms of the disease are: the leaves on the shoots suddenly wither, curl and dry up, but do not fall off. Toxins secreted by bacteria, contribute to the fact that the bark on the shoots and wood in places of defeat begins to grow brown and dies.
Bacterial burn appears on the stems in the early spring period (after release from the shelter). Before withering away, the spots of brown become grayish-brown with a wide purple border. Gradually they ring the branches and they dry up. The cancer pathogen overwinters in the affected plant tissues. Most of all, stem cancer is manifested in poorly overwintered and weakened roses. The disease will develop with an excess of moisture in the soil and bark damage.
To combat this type of cancer should be circumcision and burning of the affected stems. Cut diseased branches should be 10 cm below the affected leaf with the capture of healthy tissue. Also, be sure to remember to disinfect the instrument you are using. Spraying of bushes in the phase of kidney swelling with 3% zinc sulfate (300 g, zinc per 10 l., Water) helps. This procedure is recommended to spend 2-3 years in a row to complete cure of the disease.
Before blooming buds, it is also possible to spray the plants with a solution of copper sulphate or Bordeaux mixture (200 g, 10 l., Water). Spraying with 1% Bordeaux liquid (100 g, 10 liters, water), 0.4% copper oxide (40 g, 10 liters, water), or 0.2% Topsin-M (20 G., 10 liters., water). It would be good, at the end of the summer to feed roses with potash fertilizers (30-40 g., Per 10 l., Water) for better aging of the shoots. Before sheltering roses for the winter, remove the leaves, not matured shoots. And sprinkle 2% Bordeaux liquid (200 g, 10 liters., Water).