The delicious and healthy raspberries (Rubus idaeus) are threatened by various raspberry diseases, especially infections caused by fungi, and pests. These sometimes reduce the yield considerably, and with some pathogens the entire stock is at risk. In particular, fungal diseases often prove to be difficult to combat, especially since the use of chemical pesticides is not only viewed critically in self-sufficient gardens.
The chemical club – not always the first choice
Rapid action is extremely important, especially in the case of fungal diseases, in order to prevent the uncontrolled spread of the pathogen and the death of the stock. The pathogen should always be precisely determined in order to adapt the necessary treatment as precisely as possible – the better the countermeasures work.
In order not to disturb the natural balance in your garden, chemical pesticides such as fungicides or insecticides are always the last resort when nothing else helps. Everything you do in the garden has an impact not only on the raspberries you treat, but on the entire “garden” ecosystem. Insecticides also kill useful insects that are important for pollination of crops, for example, or poison songbirds that feed on pests.
Proper prevention of diseases
With many raspberry diseases and a pest infestation, a vigorous pruning of the diseased parts of the plant and treatment with biological or household remedies are the better choice anyway. There is also a lot you can do to keep your raspberries healthy from the start:
- Choosing a sunny and airy location
- optimal growing conditions: loose, well-drained soil
- drain soil if necessary
- a balanced supply of nutrients and water
- Hygiene in care and cutting measures
For example, pruning tools should be thoroughly disinfected before and after each use to avoid spreading pathogens from one plant to another. Clippings, on the other hand, should be removed, as they are a source of infection, especially during the winter months: fungal spores and pests like to overwinter here and spread to the plants again from the leaves lying on the ground in the following spring.
Deficiency symptoms in raspberries
If the raspberries make a sick impression, pathogens or pests are not always behind it. Yellow leaves, for example, can also be an indication of a lack of nutrients or water, which in turn can be managed with better care:
- Fertilize twice a year with organic fertilizers
- stable manure, compost and horn shavings are suitable
- self-made nettle manure mixed with rock dust is an excellent fertilizer
- this also repels many pathogens and pests
- first fertilization in early spring in the course of budding
- second fertilization after harvest
Avoid fertilizing summer and autumn raspberries before harvest, as this will negatively affect the aroma of the fruit. Strong, healthy plants are less likely to be attacked by raspberry diseases than already weak ones: Strengthen your plants and the harvest will be all the better.
Raspberry Diseases from AZ
The red fruits are particularly plagued by fungal raspberry diseases, the fungal spores of which can withstand even the most adverse environmental conditions and, after years of dormancy (e.g. in the ground), can cause renewed infection if the weather is suitable. There are also a number of bacterial and viral culprits, which in turn can spread very quickly. In general, quick action is required for all raspberry diseases in order to keep the damage as low as possible.
1. Botrytis fruit rot (Botrytis cinerea)
If the raspberries are covered with a greyish, dusty coating, it is probably Botrytis fruit rot. Infection with the causative fungus Botrytis cinerea occurs through a pronounced rainy or wet period during the flowering period.
The moldy fruits are no longer edible and should be collected and disposed of with household waste. Never throw them in the compost, as the fungal spores overwinter there and can cause reinfection the following year. In autumn, the rods must be cut back vigorously – the fungal spores also overwinter here. As a natural fungicide, you can use field horsetail decoction that you have made yourself and spray the raspberries with it several times at intervals of a few days.
The best prevention is a sunny and airy location where the raspberry leaves can dry off quickly after a downpour. In addition, the canes should be regularly and vigorously thinned and the fruits should be harvested in good time and completely.
2. Raspberry mosaic (various pathogens)
This is basically not a single clinical picture, but raspberry diseases caused by different viruses. However, all pathogens have in common that an infection results in a high yield loss.
There are three different types of raspberry mosaic:
- Mosaic of spots : broad, yellowish to light green spots on the leaves
- Vein Banding : Areas along veins are blotched with yellowish, leaf-tip curling
- Vein chlorosis : Leaf veins are distinctly lighter in color than the rest of the leaf
The discolouration is easily confused with what is known as chlorosis, a deficiency symptom. The damage picture of the raspberry leaf gall mite looks very similar. Typically, however, a raspberry mosaic develops significantly fewer and smaller fruits, which also have a bad taste.
Since the viruses are transmitted via aphids, any aphid infestation should be eliminated as soon as possible. A strong pruning helps as the first control measure, whereby the highly contagious clippings should definitely be disposed of with the household waste.
Once the stock is infected, you can hardly get the viruses out. Therefore, when planting a new plant, you should preferably plant aphid-resistant and virus-tolerant raspberry varieties.
3. Raspberry cane disease (various pathogens)
Various fungi as well as the raspberry rod gall midge are responsible for raspberry rod disease. This common disease appears in early spring and must be treated immediately, otherwise there is a risk of severe yield losses.
The raspberry cane disease shows itself in the course of the spring shoots, when the fresh canes have reached a height of around 20 to 40 centimeters. Buds and leaf bases turn purple and spread very quickly. The bark shows a silver-grey discoloration and dies off quickly. The causative fungi are spread by rain and wind, and they prefer to colonize injured rods.
Biological fungicides that are gentle on beneficial insects quickly remedy the situation. In the event of an infection later in the growing season, severe pruning can also help.
Prevent these raspberry diseases by planting the shrubs in an airy and sunny spot and by observing the recommended planting distance. Remove weeds regularly and also regularly thin out raspberry branches that are too close together. Injured tails must be removed immediately, as they are a gateway for the disease.
4. Himbeerrost (Phragmidium rubi-idaei)
One of the most common raspberry diseases is raspberry rust, which overwinters on fallen leaves and from there infects the fresh foliage in spring. The plants are particularly at risk when the weather is damp.
The infection shows through
- yellow spots and dots on the top of the raspberry leaves
- orange spots on the underside of the leaf
- Spots quickly turn dark brown to black
- infected foliage is shed and represents a new source of infection
Check the raspberry bushes regularly for infection. This can often only be recognized late, since the spots and dots can be very small. Infected canes and leaves should be cut off and disposed of with household waste. Also treat the plants with a fungicide that is gentle on beneficial insects and as biological as possible, whereby the treatment should be carried out several times in a row.
Be sure to keep the recommended planting distances or separate bushes that are too close together: the raspberry rust prefers to settle where the plants are under stress due to lack of space. Weeds should be weeded regularly and fallen leaves should always be removed.
5. Mildew (various pathogens)
Powdery mildew can affect almost all types of plants, including raspberries, of course. Basically, there are two raspberry diseases, as a distinction is made between powdery mildew, also known as fair-weather mildew, and downy mildew. The former occurs mainly in dry and warm weather, the latter in warm and humid.
If the upper sides of the leaves are covered with a white to grayish, wipeable fungus lawn, then it is an infection with a powdery mildew pathogen. The spores are mainly transmitted by wind and insects. Downy mildew, on the other hand, is indicated by a gray layer of fungus on the underside of the leaves. Brownish to violet leaf spots can also appear.
Cut back the affected shoots and dispose of them with household waste. Spraying with home remedies that you have prepared yourself, such as horsetail or a mixture of whole milk and water (ratio 1:10) helps very well with powdery mildew. Garlic broth also often has a good effect. The treatment should be repeated several times at intervals of about two weeks.
Plant raspberries in a sunny, airy spot with well-drained or well-drained soil. Water from time to time with field horsetail broth to strengthen the plants against the pathogen.
6. Phytophthora-Wurzelfäule (Phytophthora sp.)
This is one of the raspberry diseases that endanger entire stocks within a very short time. A typical trigger is wet, compacted soil in which waterlogging has formed.
Since the roots rot in this disease, they can no longer supply the above-ground parts of the plant with water and nutrients. As a result, the whole plant dies off within a very short time, which is reflected in various symptoms:
- Leaf discoloration
- general signs of wilting
- a dark brown colored and soft rod base
- not or hardly developed fruit shoots, which also die off soon
It is not possible to combat it, you can only tear out the affected plants and dispose of them. However, never plant raspberries again in the same spot, as the pathogen survives in the soil and can also infect other plant species. Replacing the soil can help.
The most important prevention is to always plant raspberries in well-aerated, drained and loose soil and to ensure that waterlogging does not occur in the first place.
7. Degenerative disease (Rubus stunt)
This disease is also known as Rubus disease and mainly affects the flowers. As a result, no or inedible fruits are formed, so that the yield fails. In addition to raspberries, blackberries are also affected.
The whole plant typically looks stocky, is significantly lower than normal and also develops a conspicuous number of non-fruit-bearing annual shoots. The flowers are deformed and show, for example, elongated sepals. The disease inevitably leads to the death of plants.
Unfortunately, effective control is not possible. Affected plants should be dug up and discarded.
The dwarfism disease is transmitted by the cicada species Macropsis fuscula and Macropsis scotti, which is why you should always combat an infestation by these animals with a suitable insecticide.