Although raspberries are generally easy-to-grow and care for plants, there are quite a few pests and diseases that may affect your raspberry plants. Here are the most common ones to be aware of.
1. Raspberry sawfly
Sawfly damage can be identified by the look of the plant or by finding the culprit. The leaves will appear like skeletons, sparsely covered in small veins that look like lace. The large veins of the leaf are usually left intact.
The small, green larvae can be picked off by hand or sprayed regularly with a horticultural soap, this won’t harm the plant or the environment.
2. Raspberry beetles
Raspberry beetles are harmless to the plant. They do however produce grubs that will devour any fruits before you can get to them. Raspberry beetles are tiny brown, hairy beetles that usually live in the soil.
You can buy water traps that are effective at controlling raspberry beetles or try an organic insecticide. You can also try encouraging natural predators; birds and ground beetles.
3. Cane midges
Cane midges are tiny flies that usually live in the soil. The female fly will lay eggs on emerging canes. The grubs then damage the cane. You might notice brown spots on your raspberry canes when cane midge is present.
Cane midges alone don’t do much damage but they do create wounds that can get infected by fungus. Cane midge is usually grouped together with spur blight and cane blight for this very reason.
There is no control for the cane-midge but you can take steps to remove infected canes from your raspberry plants (see below).
Weevils are tiny insects that feed on the leaves and roots of your raspberry plant. Damage to the plant is usually noted first and can be identified by large notches chewed into the leaves. Damaged roots will cause plant growth to slow and it will look sickly.
To control weevils, try introducing entomopathogenic nematodes. These are tiny roundworms that occur naturally in soil and will reduce the number of weevil larvae.
5. Fire blight
Fire blight is a bacterial infection that affects the tips of canes. The tips will usually turn black and fold over like a hook. You might notice the affected cane oozing a cream coloured liquid if conditions are very humid.
There is no cure for fire blight, remove any affected canes and destroy them, taking care to disinfect garden tools after use.
6. Raspberry bushy dwarf virus
This viral infection causes the raspberry plant to become dwarfed. The cane height will be reduced, leaves will have a yellowish appearance and fruits become quite brittle.
The only way to control this virus is to plant resistant cultivars.
7. Leaf curl virus
Leaf curl causes the leaves to remain small and curl inwards. If a cane is affected by this disease, the new shoots will grow back shorter the next year and appear stiff and yellow in colour. They are also quite brittle.
To treat this virus, remove and double bag any affected plants, helping to prevent spread to nearby plants.
8. Raspberry ringspot virus
Raspberry ringspot is characterised by delayed leaf development. Once the leaves do develop, they have yellow veins and yellow rings on them. The fruit will also be poorly formed and the canes may have a yellow colouration.
This virus is transmitted by nematodes and by seed. It can be treated by adding nematicides to the soil. Try to keep your raspberry patch as weed-free as possible as weeds can act as hosts for many viruses.
9. Raspberry mosaic disease
Raspberry mosaic disease causes the canes to grow back shorter and more brittle. The leaves will also be affected, curling upwards. Green blisters can be seen on the leaves along with yellow mottling.
Unfortunately, there is no cure for this disease, affected plants need to be removed and destroyed.
10. Cane blight
Cane blight can be identified by looking for brown cane midge wounds that have developed purple cankerous growths. These cankers enlarge and circle the cane which causes wilting and death of lateral shoots.
Cut and dispose of any affected canes, disinfecting tools after use.
11. Spur blight
Spur blight can be identified by looking for purple-brown lesions under leaves or buds. These lesions are usually found near the ground since cane midges can’t fly. This fungus usually takes advantage of wounds caused by cane midges.
Remove and dispose of any affected canes, taking care to disinfect tools after use.
12. Grey mould
Grey mould is caused by the fungus Botrytis cinera. It causes browning and drying of blossoms. It also affects the fruit leaving light brown spots that grow rapidly until the fruit is covered by a grey powdery substance.
Try to plant resistant cultivars to reduce the likelihood of grey mould developing. If it does, remove damaged fruit and harvest ripe fruits as quickly as possible.
13. Yellow rust
This fungus forms yellow-orange pustules on the underside of leaves. It also weakens the plant which leads to premature leaf loss and increased cold-weather damage.
If just a few leaves are affected, they can be picked off and disposed of to help slow the spread of the disease. Try to make sure canes aren’t overcrowded to keep air circulating freely.
14. Raspberry leaf spot
Raspberry leaf spots usually appear as dark green spots on new leaves. As the disease progresses, the spots will turn lighter until they eventually fall out, leaving a hole in the leaf. These leaves might also fall off prematurely.
Improving air circulation is one of the best ways to help prevent this disease. Thin out and prune crowded canes to help.
15. Root rot
Root rot is easily recognised by looking at the leaves of your plant as well as inspecting the soil. Leaves will usually have scorched edges, take on a yellowish-orange colour and begin to fall off. The soil will be smelly and very moist. The whole plant will appear sickly and the roots will have a brick-red colouration when the outer surface is scraped away.
You can try treating root rot by lifting the plant, rinsing the roots in water and carefully cutting away the affected roots. If the plant is severely affected, dispose of the plant. Plant resistant cultivars if you can.