Raspberry beetle
The grubs of raspberry beetle can damage the fruits of raspberry, blackberry and other cane fruits.
Quick facts
Scientific name: Byturus tomentosus
Plants affected: Raspberry, blackberry, tayberry, loganberry
Main symptoms: Fruits have dried up patches; may contain beetle grubs
Most active: June to August
What is raspberry beetle?
It is the larvae of raspberry beetle that affects fruit. The larva feeds at the stalk end of the fruits. It is mainly a problem on summer-fruiting raspberries. Early fruits on autumn raspberries may be damaged, but those ripening after late August are less likely to be affected.
Raspberry beetle adults are small 4mm long pale brown beetles in the family Byturidae. There are only two species of beetle in this family found in Britain. The other species B. ochraceus looks similar to the raspberry beetle but is associated with Geum urbanum (wood avens) and does not affect garden plants. UK beetles information on Byturidae.
Symptoms
- Damaged ripe berries have greyish-brown dried up patches at the stalk end
- A brownish-white grub, up to 8mm (about 1/4in) long, may be found inside the fruits
Management
If raspberry beetle has been a problem in previous seasons consider control actions before the crop develops. Check susceptible cane fruits frequently as fruit develops so action can be taken before a damaging population has developed. When choosing control options you can minimise harm to non-target animals by using the methods in the non-pesticide section below. Pesticide treatments are likely to kill natural enemies and are only likely to be successful if the entire plant can be reached.
Non-pesticide
- Where possible tolerate some beetle damage, often only a small proportion of the crop is affected. Later ripening berries tend to be less affected
- Encourage predators and other natural enemies in the garden such as birds, hedgehogs and ground beetles
- A host plant odour (karimone) water trap is available from Agralan, Harrod Horticultural and some other suppliers. This will trap both male and female beetles which may help reduce infestation levels
Pesticides
The RHS recommends that you don't use pesticides. Most pesticides (including organic types) reduce biodiversity, including natural enemies, impact soil health and have wider adverse environmental effects.Where you cannot tolerate raspberry beetle, manage them using the information above as your first course of action.
Pesticide treatments are likely to kill natural enemies and so reduce the likelihood of natural control and can lead to resurgence of the target animal.
If you do decide to use pesticides, the shorter persistence products (that are usually certified for organic growing) are likely to be less damaging to non-target wildlife.
The pesticides listed are legally available in the UK. This information is provided to avoid misuse of legal products and the use of unauthorised and untested products, which potentially has more serious consequences for the environment and wildlife than when products are used legally.
Always follow the instructions on the products. For edible plants, make sure the food plant is listed on the label and follow instructions on maximum number of applications, spray interval and harvest interval.
Homemade products are not recommended as they are unregulated and usually untested.
Be aware that products such as Neem oil are not registered for use in the UK and we cannot advise on their use.
In the past it has been advised that best control will be achieved by spraying raspberries when the first pink fruits are seen, with a second application two weeks later, however, plants should not be sprayed when in flower due to the danger to pollinating insects and so spraying is ill-advised.
- Organic contact insecticides containing natural pyrethrum (e.g. Bug Clear Ultra 2, Neudorff Bug Free Bug and Larvae Killer) have a largely physical mode of action. These are broad spectrum so will kill a wide range of insects. Several applications of these short persistence products may be necessary to give good control. Plant oil and fatty acid products are less likely to affect larger insects
- Further information about the use of pesticides available for management of raspberry beetle is available on the pesticides for gardeners leaflet
Download
Pesticides for gardeners (pdf document)
Biology
- The 4mm (about 1/8in) long adult beetles are pale brown and they lay eggs on the flowers in May to mid-July
- The young larvae feed at the stalk end of the developing fruit, but later move inside to feed on the central plug
- In late summer, the fully-fed larvae move into the soil where they overwinter as pupae
Get involved
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