Gesundheit für Mensch, Tier & Pflanze

Strawberry blossom weevil

Anthonomus rubi

Profile

The strawberry blossom beetle occurs on strawberries in spring and its feeding activity causes the flower-bearing stems to snap off. Especially in young plants, the beetle can cause great damage.

Appearance

The strawberry blossom weevil is a black-gray colored weevil about 3-4 mm in size.

The legless larvae are yellowish-white in color with a brown head and grow up to 4 mm in size.

Biology

Strawberry flower beetles appear in spring from soil temperatures of 10-14 °C. The beetles feed on petals of strawberry and various ruderal plants.

The females bore a hole in the flower bud with their proboscis, in which they lay one or more eggs, depending on the flower size. The beetles then gnaw the bud stalk, the upper part of which folds over and dries up, causing the bud to fall to the ground. After six to eight days, the beetle larvae hatch, develop further in the bud, and pupate after ten to 14 days. The pupal stage lasts about one week. In June/July, the young beetle appears, causing insignificant feeding damage to the leaves, and moves into winter hiding in the soil or under plant debris in August. The strawberry blossom weevil produces only one generation per year.

Damage symptoms

Individual flower stems are gnawed and snapped off or bitten through. The flower buds above the damaged area dry out and fall to the ground (determined by visual inspection).

If entire inflorescence stems are damaged, it is the strawberry stem borer(Coenorhinus germanicus).

The damage pattern could also be caused by the Union quarantine pests Anthonomus bisignifer (Japanese strawberry blossom engraver) and Anthonomus signatus, which have not yet appeared in Europe.

Host plants

The strawberry blossom borer occurs on strawberry, raspberry, blackberry, blueberry, roses, and dwarf medlars(Cotoneaster), as well as on herbaceous plants such as lady's mantle (Alchemilla), carnationwort (Geum), or foxglove(Potentiella).

Distribution

The strawberry blossom borer occurs throughout the Palaearctic region (Europe, North Africa to the southern edge of the Sahara and Asia) on its host plants.

Propagation and transmission

The strawberry blossom borer often occurs in nests, but is capable of flight and can migrate to strawberry plants from surrounding vegetation with appropriate host plants.

Economic importance

The strawberry blossom blight occurs on strawberries in spring from the end of April and can cause major damage in nests, especially in young plants. Depending on the strawberry variety, yield losses of up to 80% are possible.

Prevention and control

  • Treatment of the plants with plant protection products approved for this purpose (see list of plant protection products approved in Austria).
  • immediately after reaching the damage threshold. The damage threshold for treatment measures is the first appearance of bent flower stems or 1 adult beetle/100m².
  • In the hobby garden, flower buds lying on the ground or destroyed can be collected and destroyed as a direct measure

Specialized information

Lethmayer, C., Hausdorf, H., Blümel, S., 2004. The first field experiences with sex aggregation pheromones of the strawberry blossom weevil, Anthonomus rubi, in Austria. IOBC/WPRS Bulletin, 27(4), 133-141.

Blümel, S., 1989. the strawberry blossom weevil - interesting facts about biology and control. Better Fruit, 34(5), 127-129.

Last updated: 18.11.2021

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