Raspberry beetle

The grubs of raspberry beetle damage the fruits of raspberry, blackberry and other cane fruits and is the most serious pest of these plants.

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 causes damage in its grub stage, which 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 (about1/4in)  long, may be found inside the fruits

Control

Chemical control

  • Pyrethrum (e.g. Py Spray Garden Insect Killer, Bug Clear Gun for Fruit & Veg,) can be used to control raspberry beetle. A minimum one day interval  is required between spraying and picking the fruit
  • A better level of control may be achieved with deltamethrin (e.g. Bayer Sprayday Greenfly Killer), which has a seven-day harvest interval on most cane fruits or lambda-cyhalothrin (e.g. Westland Resolva Bug Killer) which has a 28 day harvest interval on raspberry. For both these pesticides check and follow the manufacturer’s instructions for these food plants
  • 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

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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