2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38
White spot, or septoria, affects not only raspberries (both cultural and wild varieties), but also blackberries. As a rule, the first signs of a harmful misfortune can be seen on the leaves by mid-May, and the peak of the development of white spot usually occurs at the stage of berry ripening. To a large extent, the development of this ailment is facilitated by moderate temperatures in combination with abundant rainfall (mainly spring). White spot especially affects old raspberry leaves
A few words about the disease
On the raspberry leaves attacked by white spot, the formation of rounded specks, painted in light brown tones, begins. Their average diameter is about 3 mm. Gradually, as the disease develops, the spots turn white, and brown edges appear along their edges. Often specks merge with each other. And with the onset of July, the formation of tiny black dots is noted in their middle. The center of the leaves begins to slowly collapse and gradually crumbles.
If there are a lot of spots on the leaves, and the disease, in addition to everything, has been neglected, then most of the leaves die off. Most often, infection begins on the undersides of the leaves.
By the way, white spot does not bypass raspberry stalks, which are gradually covered with black dots - this is the appearance of the fruiting bodies of the pathogen fungus. Often, in infected areas, peeling of the bark and a huge number of multidirectional cracks can be noticed. Weakened berry bushes freeze quite a bit in winter. And, of course, such bushes give much less yield compared to healthy ones.
A harmful fungus causes white spot. It is preserved mainly on overwintered shoots with leaves, and its spores are carried by air currents. In addition, the spread of infection can occur through infected planting material. Fallen leaves and diseased stems are considered to be the main source of infection.
How to fight
To avoid possible white spot infestations, only healthy vegetation should be used for planting. Before planting raspberry seedlings, their stems must be disinfected in a suspension of copper oxychloride (0.5%). In this case, it is important to ensure that the suspension does not accidentally fall on the roots - in no case can they be disinfected.
Periodically, in order to improve air circulation, planting fragrant berries should be thinned out. If, when inspecting the berry bushes, infected shoots are found, then they must be disposed of in a timely manner, and the diseased leaves must be collected and promptly destroyed.
With the onset of early spring, raspberry plantings are completely sprayed with a solution of "Nitrafen" (2%). And during the growth period, it will be advisable to use one percent Bordeaux liquid, the first treatment of which is carried out before the start of flowering, and the second - when the collection of fragrant berries is completed.
Processing can be carried out according to the following scheme. As soon as the tiny buds begin to bloom, the raspberries are sprayed with a 1% suspension of colloidal sulfur, copper oxychloride (0.3%) or 1% Bordeaux liquid. The second treatment is carried out just before flowering, the third - immediately after its completion, and the last, fourth - when the crop is harvested.
In the fall, at the end of leaf fall, it is recommended to carry out the so-called eradicating spraying. For this purpose, copper oxychloride (0.4%) or Bordeaux liquid (3-4%) is perfect. It is allowed to use a two percent solution of potassium salt for processing.
Also, in late autumn (or, alternatively, in early spring), it is recommended to dig the soil under raspberry bushes, embedding high-quality phosphorus-potassium fertilizers in it.
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