Black Vine Weevil

Otiorhynchus sulcatus

Black Vine Weevil, Snout Beetle , Vine Weevil

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A close up of a black vine weevil
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A Vine Weevil is a beetle that feeds off of a broad range of plants, both indoors and out; but these beetles have the biggest impact on container plants. Adult beetles are most active in spring and summer eating leaves at night. The grubs are most active during autumn and winter, where they feed invasively on the plant roots. If root infestations are particularly heavy, the plant will quickly lose vigour. Young plants in containers are most likely to die from a Vine Weevil infestation.
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Traits

Grubs eat plant roots resulting in wilting plant death.
Vine weevil eggs are a source of food for soil-dwelling insects.

Appearance

Adults: The adult weevil is a dark black, matte colour and have fused wing covers so are unable to fly. They have six legs and two long antennas on their head. They're nocturnal, so they come out at night to feed on the outer parts of leaves. They have elongate heads, with a 'snout'. Larvae: Small, slightly curved and are creamy-white with light brown heads that measure around 10mm in length. They are located on the roots. Pupae: Currently unavailable. Eggs: The eggs are so tiny you need a hand lens to see them.

Symptoms

You may see irregular notches in your leaf margins during the summer months. Small, black beetles on leaves at night. Sudden wilting of plants in autumn and winter. Numerous creamy-white grubs around the roots of plants.

Activity

Nocturnal

Personality

Order

Coleoptera

Family

Curculionidae

Metamorphosis

Complete

Distribution

Central Europe, including the UK

Biological treatment

Unfortunately, few treatments can eliminate this pest because they burrow within the roots of host plants. It's important to note that Weevils are nocturnal, so you're not going to catch them in the daytime. If you find irregular notches in the leaf margins, you may want to attempt a few evening torch checks. Check on and under the leaves and fruits of plants. It's thought that good housekeeping, such as practising: mulching, re-hilling, field sanitation, crop rotation and using clean planting material, can significantly reduce the severity of an infestation. Pheromone traps can be used to monitor pest populations in the garden. Sticky barriers can also be effective around the base of ornamental plants and shrubs. Likewise, diatomaceous earth dusted over leaves and around the bases of plants can kill Weevils. Be careful during application, as this stuff is nasty if inhaled and can be extremely irritable when in contact with the eyes. Nematodes can be used and introduced to the soils of your plants, and you can buy these from some garden centres or online. You can use them in both containers or open ground. By using nematodes such as Steinernema kraussei, you can help to reduce any grubs that are in the soil. These should be applied from August to early September for the best results, as larvae will be smaller in size and not have caused too much damage already. Always read instructions before application.

Chemical treatment

Currently unavailable Throughout 2019 and during the start of 2020 the European Commission placed new restrictions on neonicotinoids. Neonicotinoids are active, toxic molecules found in some of the products we treat our plants with. Not all products contain neonicotinoids, but it’s our responsibility to always check for banned active ingredients before applying products to our plants. It is recommended to check your pesticides yearly in regards to their authorisation of use. If you possess an excess of a banned EU product, it’s suggested to contact your local authority for further guidance. Currently, imidacloprid, thiamethoxam and clothianidin are banned for outdoor use in the EU because of the threat they pose to pollinating insects. Thiacloprid will be banned for outdoor use in the EU in April 2020. Currently, acetamiprid is still regulated for outdoor use in the EU. It’s thought these products are most effective against aphids and the Colorado Potato Beetle. In the meantime, there are an array of contact insecticides available for use on the market that is more environmentally friendly than the above products (e.g. Natural pyrethrum/pyrethrins and insecticidal soaps). Again, more persistent products include synthetic insecticides with a contact mode of action (e.g. cypermethrin, phenothrin, lambda-cyhalothrin and deltamethrin). These can still be toxic to some wildlife and a pollutant to water bodies, so please take care to research products and read instructions carefully before using them. Please see our ‘Biological Treatments’ for alternative solutions to plant problems.

Attracts

Ornamental plants and fruit plants, in particular vines, Primula, Rhododendron, Heuchera, Cyclamen and strawberries.

Repels

Place any grubs found on perches for garden birds to feast.
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