Raspberry diseases: identification & remedies

If present, raspberry diseases can ruin their precious crop and, in some cases, lead to the eventual demise of the plant. Read on to learn more about how to identify the most common raspberry diseases and how to prevent and treat them.

Raspberries (Rubus idaeus) are easy to grow and are ideal for growing at home. However, even the hardy raspberry is not spared from the odd disease and pest, which if not controlled can lead to reduced harvests and widespread failures. Identifying raspberry diseases is key to their management, we’ll show you how to recognise, prevent and treat those most prevalent here in the UK.

The most common raspberry diseases

Buying raspberry canes from a reputable supplier and planting them correctly can go a long way to reducing the chance of raspberry diseases. However, even the healthiest raspberry plants can succumb to the following diseases:

• Raspberry rust (Phragmidium rubi-idaei)
• Raspberry blight (Paraconiothyrium fuckelii)
• Raspberry root rot (Phytophthora)
• Raspberry grey mould (Botrytis cinerea)
• Verticillium wilt (Verticillium dahliae and albow-atrum)

Rust on raspberries

Raspberry rust is caused by Phragmidium rubi-idaei pathogens and is one the more common fungal diseases here in the UK. However, although unsightly, rust on raspberries rarely hinders yields significantly. It is identifiable in early summer by yellow, orange or red pustules on the upper and lower surfaces of the foliage, which turn black as the growing season progresses.

Severe cases may cause the leaves to drop prematurely and no chemical controls are currently available for home growers, which makes prevention all the more important. Raspberry rust occurs when the leaves are wet or damp and is most common during the UK’s wet summers. Ensuring good air circulation between plants and planting canes at the recommended spacing can help guard against rust.

If you spot pustules on a few leaves in spring, removing the affected foliage may help prevent the rust from spreading. To further reduce the risk, any prematurely fallen leaves along with those that drop naturally should be cleared away, as the spores can over winter only to reinfect the plants the following year.

Raspberry blight

Raspberry cane blight is caused by the Paraconiothyrium fuckelii fungus which enters the canes through a wounded area. Symptoms of cane blight include the foliage of older canes shrivelling and dying and the canes darkening in colour at soil level and becoming brittle.

As with the other diseases, there are no chemical applications approved for raspberry blight for the domestic gardener. Preventative measures include promoting good ventilation around plants and avoiding stress caused by dry conditions, which mulching and regular watering will help ward off. If cane blight is detected, you should remove any affected canes cutting just below the soil level and disinfect any tools after use. Replanting raspberries or strawberries (Fragaria) in the same site is not recommended unless the soil is renewed as the fungi can survive on old wood in the soil for many years.

Raspberries can also fall prey to another disease called spur blight, which is another fungal disease caused by the Xenodidymella applanata fungus. In contrast to cane blight, raspberry spur blight can be identified by purple areas that develop around the cane’s buds in late summer, which eventually turn grey and cause poor growth and yields the following year. If purple patches appear, you should cut down the affected canes and dispose of them carefully. To help prevent spur blight, raspberry varieties with more resistance against this disease can be chosen, along with not planting too densely.

Raspberry root rot

Caused by Phytophthora pathogens, root rot is a destructive soil-borne disease that can affect raspberry plants. Most commonly present on waterlogged or compacted soils, root rot targets the plants’ root system eventually leading to its decay and inability to support the plant. The first signs of root rot are often the wilting and discolouration of the foliage in early summer, which is followed by the canes darkening and dying from ground level upwards. When established, on lifting the canes the roots can be visibly seen to have rotted away.

With no treatment available to home growers, prevention is key. Along with growing more resistant cultivars, avoiding water-logged or heavy soils can help prevent raspberry root rot from occurring. However, if root rot is identified, you should remove all the infected plant material and avoid growing non-resistant plants on the site for several years.

Grey mould on raspberries

Grey mould is a common fungal disease that affects soft fruit and ornamentals and is caused by Botrytis cinerea fungi. Although capable of developing all year round, grey mould is most common in humid conditions and is easily identifiable by its furry brown-grey mould, which develops on raspberry flowers and fruits. Grey mould on raspberries tends to affect damaged or stressed plants, but can also impact healthy and robust plants.

No fungicidal controls are available and being easily spreadable, you should remove and dispose of any infected material, including any fallen leaves or fruit and not add it to any home compost systems. Since stress or damaged plants are most susceptible, careful pruning and the correct growing conditions can help prevent grey mould from occurring. To ensure plants are as healthy and strong as possible, you can fertilise your raspberries with a feed such as our Plantura Tomato Food, which contains phosphorus and potassium required to support their growth and fruiting.

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Verticillium wilt on raspberries

Often affecting strawberries, verticillium wilt can also be identified on raspberries and other cane fruit. Caused by the Verticillium dahliae and albow-atrum fungi, verticillium wilt is a serious soil-borne disease that leads to wilting and leaf drop from the bottom up and can have devastating effects. Minimal infections may only reduce crop yields; however, severe infections may cause the total loss of all plants.

Sadly, if suspected, you should remove the infected plants including their root system and destroy them. As a soil-borne fungus, contamination is easy and disinfecting any tools used is highly recommended. Due to its capacity to live in the soil for many years, and with no chemical measures available, affected sites should be grassed over or planted with a resistant crop.

Prevention of verticillium wilt on raspberries is only possible through the growing of disease-free plants on uncontaminated soil, which makes using reputable suppliers and a fresh growing site all the more important.

Some raspberry diseases can cause the leaves to discolour, however, there can be other reasons as well. You can read more about what can cause raspberry foliage to turn yellow in our separate specialist article.