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Raspberry beetle

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last updated Apr 19, 2011
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Raspberry beetle (Byturus tomentosus) on Loganberry (Rubus hybrid). Credit: RHS/Entomology.

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

What is raspberry beetle? Back to top

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 Back to top

  • 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 Back to top

Chemical control

  • Pyrethrum (Py Spray Garden Insect Killer, Bug Clear Gun for Fruit & Veg, Doff All in One Bug Spray) 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 is likely to be achieved with deltamethrin  (Bayer Sprayday Greenfly Killer), which has a seven-day harvest interval on cane fruits
  • Spray raspberries when the first pink fruits are seen, with a second application two weeks later
  • Treat hybrid berries at 80% petal fall and blackberries when the first flowers open
  • Apply insecticides in the evening when bees are not active on the flowers
  • Derris/rotenone is no longer available for use as a garden insecticide

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

Links

Chemicals: storing and disposing safely

Biology Back to top

  • 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

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

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