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Insect of the month may, strawberry blossom weevil

The strawberry blossom weevil can cause enormous damage in strawberry fruit cultivation.
30-04-2020

The strawberry blossom weevil (Anthonomus rubi) and the strawberry bud weevil are often confused with each other. The blossom weevil is slightly smaller, but a bigger difference is in the feelers. The bud weevil does not have curved feelers, but the blossom weevil does.

Strawberry blossom weevil

The strawberry blossom weevil is a beetle in the weevil family. It is about 2 to 4 mm long and becomes active when the temperature reaches 18 ° C. It is a species that is found all over Europe, from North Africa to the very tip of Scandinavia and to China in the east. Adult beetles occur all year round, they become active from March or April and quickly become numerous. The peak is somewhere between late May and early June, but beetles can be found until September.

Living area’s

Typical habitats can include rugged grassland, wasteland, wooded banks and hedges. They develop on various woody and herbaceous crops of the Rosaceae family, a large family with 3 to 4,000 species. Think of Geum, Potentilla, Fragaria, Rosa, Rubus, Cotoneaster and more. Newly hatched beetles first feed on leaves before going to the flowers. Eggs are laid in April with the female making a small hole in an unopened flower bud and laying a single slightly translucent egg.

Aardbeibloesemsteker-Anthonomus.rubi

Fertilisation could play a role in the attractiveness of the plant

The larvea

Of course, there have already been several studies into the behavior of the beetle. From these studies we know that the damage was greatest near a forest edge. The intensity decreased the further away from the forest edge. The damage was also greater in older plantations than in younger ones and additionally, variety differences have been observed.

What can be done?

How does the beetle find its way to the plant? Beetles have ‘receiver’ neurons on the feelers. This allows them to absorb odors emitted by the plant. These connections are normally quite common and probably part of the natural communication between plant and insect. These compounds are influenced by abiotic factors (climate, weather, temperature, etc.) and by biotic factors (for example, when fed, the plant releases substances that attract natural enemies).

In the specific case of the strawberry blossom weevil, various compounds have been discovered which are released by the plant and received by the receptors of the beetle. Where the beetle eats, a change in the substances is observed, but also larger quantities are emitted. It is not yet clear exactly what this means. On the one hand it is thought that it is an invitation to a meeting (read sex), on the other hand it could be a warning to avoid the bud because it has already been punctured.

What could be a critical factor

Fertilization could play a role in the attractiveness of the plant, as any insect has specific nutritional needs. It may be that through fertilization we provide what the beetle is looking for and what nature provides less of. Nitrogen and phosphorus in particular are important building blocks in addition to amino acids for building up the insect’s body.

In the above we have also seen that scent plays a role in the communication between plant and insect. Perhaps masking the smell by spraying could contribute to masking the compounds emitted by the plant.

More information? Please feel free to contact us.

See the illustration for the simplified life cycle diagram of Anthonomus rubi.

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