Raspberry beetle

The grubs of raspberry beetle can damage the fruits of raspberry, blackberry and other cane fruits.

Raspberry beetle (Byturus tomentosus) on Loganberry (Rubus hybrid). Credit: RHS/Entomology.

Raspberry beetle (Byturus tomentosus) on Loganberry (Rubus hybrid). Credit: RHS/Entomology.

Quick facts

Common name: Raspberry beetle
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?

Raspberry beetle affects fruit in the larval stage. 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.

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

Control

Non-pesticide control

A host plant odour (karimone) water trap is available from Agralan, Ken Muir, Harrod Horticultural and some other suppliers. This will trap both male and female beetles which may help reduce infestation levels.  

Pesticide control

  • Ideally 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
  • Organic contact insecticides containing natural pyrethrins (e.g. Bug Clear Gun for Fruit & Veg, Ecofective Bug Killer). Several application of these short persistence products may be necessary to give good control. A minimum one day interval is required between spraying and picking the fruit
  • More persistent contact insecticides include the synthetic pyrethroids lambda-cyhalothrin (e.g. Westland Resolva Pest Killer), deltamethrin (e.g. Provanto Ultimate Fruit & Vegetable Bug Killer) and cypermethrin (e.g. Py Bug Killer). These may give a better level of control.   with deltamethrin has a seven-day harvest interval on most cane fruits,  lambda-cyhalothrin has a 28 day harvest interval on raspberry. For both these pesticides check and follow the label instructions for these food plants
  • Inclusion of a pesticide product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener

Download

Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)

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


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