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The bright red raspberries (Rubus idaeus) are threatened by pests and various diseases, especially fungal infections. Aesthetics suffer when blotched or yellow leaves appear and stems turn an unhealthy color, as does yield.
Fungal infections are difficult to combat and effective fungicides are harmful to the environment and human health. In addition to a few biologically effective measures, "it's better to be safe than sorry" because proper care prevents infection.
Diseases
The diseases - the usual suspects
A wealth of different types of fungus makes it difficult for the layperson to identify the respective species. The most common are cane blight, raspberry rust and root rot, but botrytis fruit rot is not uncommon either. A curiosity, however, are white spots on the raspberries, which only appear in a sun-exposed location.
Fast and decisive action is essential for all fungal infections, otherwise the pathogens will spread uncontrollably and decimate the population.
mushrooms
The mushrooms have struck - now what?
Raspberries are exposed to fungal attack in all parts of the plant. Symptoms vary: discolouration, spots and yellow leaves are the most common. Regardless of the type, first aid is needed quickly before the disease spreads.
Infected plant parts must be removed quickly. Tails are cut down to the ground, leaves are snapped off in the branches and fallen leaves are removed. But all components must not end up on the compost! - the household waste is the right place.
Fungal spores survive extreme environmental factors, so the temperature development on the compost is not sufficient to kill them. A later re-infection through compost fertilization is possible in such cases.
Note:
- Always remove infected plant parts
- dispose of with household waste, never use for composting
- Clean scissors with alcohol
How does the infection come about?
Fungal spores are everywhere in the air. However, they only settle in parts of plants when they are given access. This is done with the help of animal pests such as the raspberry rod gall midge (Resseliella theobaldi) or by mechanical damage to the plant parts.
Cracks in leaves and stems are caused by wind and crop and maintenance damage, which the fungus then invades. Therefore, great caution is advised when working. Too close stocking, extreme locations or high weeds increase the risk of infection due to persistent moisture. The roots are threatened by waterlogging. But voles and strong winds also cause injuries.
Note:
- Avoid extreme locations
- Wind hurts the delicate plants
- prevent waterlogging
- control animal pests
- low stocking without weeds
tail disease
Cane disease - high crop failures are the rule
Large violet spots on the tails, yellow leaves, black spots and dying plant parts are unmistakable signs of tail disease. The different pathogens attack different parts of the plant. Predominantly only bearing canes are affected, the exception being Elsinoe veneta, which primarily affects young canes. Didymella applanata and Leptosphaeria coniothyrium are more common.
While Didymella applanata invades the cell walls, especially in the upper part of the tail at the level of fruit development, Leptosphaeria coniothyrium infects its host at ground level and produces the characteristic purple spots. Other causative agents of tail disease with a different clinical picture such as grey-black spots are Botrytis cinerea and Fusarium avenaceum with brown tail lesions.
Note:
- Cane disease is often characterized by purple patches and yellow leaves
- bearing rods are affected
- high yield losses
- Note the differentiation from root rot
Diagnosis of rod disease - what now?
In conventional cultivation, fungicides and copper are used for treatment. Both methods that the nature-loving hobby gardener does not want to use in his garden. However, treatment with biological agents is difficult and is mainly limited to the removal of affected parts of the plant and preventive measures.
Remove infested rods as soon as possible, as they support the growth of the fungus and do not produce any yield anyway. In addition, it is advised to combat animal vectors such as the raspberry rod gall midge (Resseliella theobaldi). This pierces the rods to suck the sugary plant secretion. Fungal spores attached to the mosquito penetrate the raspberries.
Note:
- remove affected rods
- combat animal vectors
Prevention - so that rod disease does not break out
The most effective way is to fight the causes and create suitable growth conditions. Sufficient space between the plants, a reduction in the support rods to a maximum of eight and a minimization of the new rods allow light and air to reach the stems: Less breakage and faster drying take away the basis for the mushrooms. Mulching prevents spores lying on the ground from finding their way onto healthy rods.
In addition, a biological decoction made from field horsetail can control or prevent an incipient infestation.
The recipe:
Leave one kilogram of fresh or dried, chopped cabbage to ferment in ten liters of water for three days. Then boil for about 30 minutes and spray regularly on all parts of the plant when cooled and diluted (1:5). The silicic acid supports the natural cell healing of the plant and forms a film on which fungi have difficulty gaining a foothold.
Note:
- horsetail brew
- mulching
- Reduction of carrying rods
- Always remove old rods to the ground
One tip: There are resistant varieties in which the rod disease rarely occurs. All autumn raspberries are also hardly affected by this disease.
root rot
Root rot - the culprit is hidden
In contrast to cane disease, root rot affects both young and carrying canes. Yellow leaves, leaf necrosis and stunted growth are signs of root rot. It occurs primarily on wet soils that do not have adequate drainage. Treatment is not possible: the root rot leads to the death of the plant.
As with cane disease, there are more resistant varieties. But even these are powerless against waterlogging.
Note:
- no waterlogging
- resort to resistant varieties on loamy, moist soils
- no curative means
raspberry rust
The raspberry rust - gone with pretty leafy green
Raspberry rust is caused by a rust fungus (Phragmidium rubi-idaei). It causes characteristic rust-red spots on the leaves. In the early stages, these can only be seen on the leaf surface, whereas in the final stage, the underside is also covered with red spore clusters.
Extreme infestations can cause yellow leaves and lead to premature leaf drop. A decline in earnings is to be expected as a result.
In addition to removing affected parts of the plant, a reduction in the nitrogen supply has a particularly positive effect. A light stock, which contributes to reducing moisture, is also advisable and can counteract raspberry rust in the future.
Note:
- remove affected plant parts
- reduced nitrogen supply
- Reduce leaf moisture
Gray and white spots
Gray and White Spots on Raspberries - Botrytis Fruit Rot or Sunburn?
Wet weather, little sun and overripe fruit provide a good basis for botrytis fruit rot (Botrytis cinerea). The fruits infected with the fungus are covered with white-grey down and are not edible. Without decisively destroying the affected fruit, the fungus overwinters as grey-black spots on the canes and leads to reinfection in the following year.
Biological treatment of fungal infections is only possible through plant strengthening and ideal growth conditions.
White spots on the fruit, which cannot be traced back to fungal infestation, appear in unshaded crops. The direct midday sun does not please the former inhabitants of the edge of the forest and leads to sunburn. These white spots are safe to eat.
Note:
- if there is no visible furry mold covering, the fruit is edible
- white patches are signs of harmless sunburn
- the plant suffers from the growing conditions: shade is necessary