Didimella (purple spotting) is common in all areas of raspberry cultivation, both in our country and abroad. It causes especially great harm in the humid zones – Forest-Steppe and Polesie. How to recognize a disease? How to deal with didimella? Read about it in our material.
Why Does Didimella Occur?
The causative agent of didimella parasitizes on cultivated and wild raspberries, blackberries, infecting the aboveground organs and rhizome. Mushroom viability is surprisingly high. Depending on the atmospheric humidity, the first signs of purple spotting appear on young shoots in early or mid-June. First, at the base of the roots, at the points of attachment of leaf petioles, small (up to 1 cm in diameter) violet-brown spots form. Over time, the disease progresses, spreading up the stem, the spots merge, completely ringing the shoot.
Why Is Didymella Dangerous?
If no protective equipment is used on the site, then by the fall (September-October), under optimal climatic conditions for the development of the disease, all shoots will be affected. At the same time, dark brown spots with a white center appear on the affected stems, and then longitudinal cracks that lead to the breaking of the shoots.
The affected kidneys are inhibited, they do not develop, large brown spots appear on the leaves with a wide, blurry yellow border. + Next year, the tops of the strongly affected shoots fade, many cracks form on the surface of the cortex, black dots are visible – sporulation of the fungus (the primary source of the disease).
Can Didimella Go to Other Plants?
Spores of the pathogen of purple spotting spread to other plants by wind, water, insects, through the soil and planting material. The mushroom hibernates in the bark in the form of fruiting bodies and mycelium. It develops in late autumn and winter at a moderate temperature (up to 20 ° C) and high humidity (up to 100%). The disease progresses in the spring and in the first half of summer in warm and humid weather.
What Factors Contribute to the Development of Didimella?
In addition to abiotic (weather) factors, didimella development is promoted by:
- Plant thickening and crop cultivation on soils with high nitrogen content, heavy in mechanical composition, with a high occurrence of groundwater.
- The infection of raspberry shoots occurs when the integrity of the bark is violated, for example, under the influence of low temperature in severe winters and with sharp fluctuations in the temperature-humidity regime.
- Damage to the shoots is also caused by the shoot gall midge, a pest that develops in galls under the bark of plants.
In epiphytotic years, more than 85% of shoots are affected by purple spotting.