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Raspberry didymella is a dangerous disease caused by the fungus Didymella applanata Sacc. Penetrating into large and small cracks on the branches and roots of raspberries, purple spot (another name for didimella) very quickly affects all vegetative parts of the plant, causing a deterioration in its general condition.
Raspberry didimella spoils the appearance of the plant
Symptoms of Purple Spot
With the onset of warm weather, fungal spores that have overwintered in the raspberry bark or under a layer of fallen leaves wake up and, moving onto the bushes, begin their destructive activities. First, didimella symptoms appear on the stems of the plant, and then on its leaves.
On the stems
The presence of didimella can be determined by changes in the appearance of raspberry shoots:
- small bluish spots form at the base of the stem, which, quickly increasing in size, after some time cover its entire surface;
- there is a total defeat of the branches, which are covered along the entire length with a bluish coating;
- in places where spores multiply, small cracks appear on the bark, gradually increasing in size;
- Past shoots dry out and die prematurely.
Didimella-infected stems change color
On the leaves
Having moved to the raspberry foliage, didimella manifests itself by the appearance of small white-brown specks. As they grow, they merge into large and small spots - brown or crimson in the middle and rusty at the edges. Leaves affected by the fungus gradually dry out and die.
It is difficult not to notice leaves affected by didimella
Causes of the disease
The cause of infection of raspberries with didimella fungus can be:
- increased air humidity combined with a decrease in air temperature below +20 ° C;
- dense plantings;
- excess nitrogen in the soil;
- the presence of growths formed by gall midges;
- close location of groundwater;
- stagnation of moisture on the soil surface during the rainy season or as a result of improper watering.
Close planting makes it difficult for oxygen to reach plants
Why is didimella dangerous?
A fungal infection spreading at high speed quickly covers the entire plant, which causes disruption of vegetative processes and sometimes the death of raspberry bushes.
As a result of didimella development:
- the plant becomes weak and vulnerable to other infections;
- slows down, and after a while the formation of new shoots stops;
- the root system is damaged, as a result of which the raspberry does not receive enough nutrition and dies;
- The berries dry out at the ovary stage.
Didimella is especially dangerous in combination with the activity of the gall midge (raspberry mosquito), a harmful insect that climbs into cracks on raspberry branches formed as a result of the disease and lays eggs there.
After some time, thickenings are formed in such places, filled with larvae, which are called “gall midges”. Simultaneous exposure to didimella and the raspberry mosquito can most likely lead to the death of the bush.
The presence of gall midges can be diagnosed by the characteristic bumps on the stem
Can it move to other bushes?
During sporulation, the infection quickly spreads throughout the raspberry tree, and if emergency measures are not taken, Didimella will infect other bushes, affecting an increasingly larger area.
Didimella spores can travel:
- through the air with the wind;
- with water when watering;
- on the legs of insects during pollination
Bees can become carriers of infection
Treatment of purple spot on raspberries
There is no cure for purple spot, but you can stop its spread.
To do this, first of all, remove all infected shoots and leaves, and then burn them away from the raspberry tree. You need to carefully ensure that not a single diseased branch remains.Otherwise, the effectiveness of treatment will be zero.
You should also not use trimmed parts of raspberries to make compost. The fungal spores will thrive in the moist environment of the compost pit, and it is likely that in the spring, with a portion of organic fertilizer, they will again end up in the raspberry field.
To prevent infection of other plants, experts recommend spraying raspberries against purple spot with one of the chemicals.
Urea
Raspberries are sprayed with an aqueous solution of urea twice with an interval of 15 days. For the first treatment, 700 g of dry preparation is poured into 10 liters of clean water and thoroughly mixed until the urea is completely dissolved.
It is better to spray shoots in dry, windless weather.
After the buds open, the raspberries are sprayed with a solution prepared at the rate of 50 g of urea per 10 liters of water.
Bordeaux mixture
The drug can be bought ready-made in a store or made by dissolving 100 g of copper sulfate and the same amount of quicklime in 10 liters of water.
For preventive purposes, raspberries are treated with 1% Bordeaux mixture three times a year: at the stage of leaf formation, during budding, and also after picking the berries.
Bordeaux mixture is a non-toxic and harmless product
Cuproxat
To prepare a working solution, 50 ml of the drug is diluted in a bucket of clean water. Raspberries are processed with the prepared mixture in two steps.
The recommended period of time between spraying with Kuproxat is two weeks.
Topaz
This solution, prepared at the rate of 15 g of the drug per 10 liters of water, is used to treat raspberries immediately after sanitary pruning. It is recommended to repeat the procedure two weeks after the first spraying.
Topaz should not be used during fruiting
Fundazol
20 g of the drug is dissolved in a bucket of water and the plants are sprayed with it after sanitary pruning. Next time the treatment is carried out after 15 days.
Timely treatment of didimella with Fundazol will help save the harvest.
Raspberry varieties resistant to purple spot
Unfortunately, breeders have not yet developed raspberries that are absolutely resistant to didimella. However, there are many varieties that offer good purple spot resistance.
You can reduce the likelihood of bushes being damaged by didimella fungus by planting the following varieties of raspberries on your plot:
- Bryansk;
- Brigantine;
- Newburgh;
- September;
- Julia;
- Shy;
- Mikolaychuk news;
- Balm;
- Glen Moe;
- Companion;
- Kuzmin News;
- Chief;
- Latham;
- Molling Leo.
Raspberry Sputnitsa practically does not suffer from didimella
Preventive measures
Any disease, including raspberry didimella, is easier to prevent than to treat. Given the high viability of the spores of this fungus, one should take the utmost responsibility in preventing the disease.
The following will help prevent the development of purple spotting on raspberry branches and leaves:
- Growing varieties that are immune to this disease.
- Use of high-quality planting material. Healthy seedlings are strong and flexible, they cannot have cracks or stains.
- Choosing a suitable site for growing raspberries. Acidic soil combined with dampness and shade are ideal conditions for the development of didimella.
- Organizing proper watering - raspberries equally dislike both a lack of water and its excess.In the first case, the bushes will lose vitality and dry out, and in the second, there is a high probability of developing fungal diseases, including didimella.
- Regular fertilizing - a deficiency of nutrients in the soil leads to weakened immunity in raspberries, as a result of which the risk of didimella infection increases.
- Regular thinning of plantings to ensure normal ventilation of the bushes. High humidity with closely spaced shoots is an excellent environment for fungal growth.
- Growing raspberries on trellises helps provide oxygen to all parts of the plant and reduces the likelihood of disease development.
- Loosening the top layer of soil in spring and autumn. This helps to destroy most of the pathogenic microorganisms overwintering in it.
The ideal irrigation option is drip
Conclusion
Raspberry didimella is a serious disease that can destroy an entire plantation in one season. Only through competent prevention, as well as timely detection of signs of disease and treatment, can you grow healthy bushes and get a good harvest of ripe, juicy berries.
