Controlling Vine Weevil (Otiorhynchus sulcatus)
Vine weevil is one of the most widespread, common and devastating garden pests. The adult weevils eat plant leaves during spring and summer, but it is the grubs that cause the most damage to plants. Over the autumn and winter they feed on plant roots. This damage often results in wilting and plant death.
Plants growing in pots and containers, outdoors or under cover, are most likely to be severely damaged by vine weevil grubs. Plants growing in the open ground are less likely to be damaged.
Adult beetles feed on the foliage of many herbaceous plants and shrubs, especially Rhododendron, evergreen Euonymus, Hydrangea, Epimedium, Bergenia, Primula and strawberry.
Adults rarely cause enough damage to affect the vigour of plants.
Look out for these symptoms:
- Adult weevils are approximately 9mm (about 5/16in) long and dull black with dirty yellow mark on the wing cases.
- They cause irregular-shaped notches of leaf margins during the summer.
- They do not fly and are all females. They will generally feed and breed within a very small radius.
- The plump c-shaped white legless grubs are of more concern to gardeners.
- They have light brown heads and are up to 10mm (about 3/8in) long.
- They are likely to be found among the roots. Plants wilt and die during autumn to spring as a result of grubs devouring the roots
How we control Vine WeevilOn our nursery we have a strict practise in place to protect the plants that you purchase from us.
- We use sticky traps to monitor our crops for any adult beetle population that could enter the nursery. This enables us to react to a potential problem outside of our normal procedures.
- The entire plant stock on the nursery is treated with biological control nematodes in the early spring, as the soil temperatures start to rise and stabilize and again in late summer, this ensures that we break breading cycles.
- All our stock has a chemical treatment added to the compost which gives the plants root ball at least 12 months 100% protection, with a diluted rate of protection from then onwards.
- We actively encourage wild lives that are the natural enemies of Vine weevils. Birds, frogs, toads, shrews, hedgehogs and predatory ground and rove beetles all eat both Vine weevils and their grubs
- Good Husbandry of the growing environment with clean pots, tools and clean growing areas.
How to manage vine weevil at home
- Keep an eye out for notching of leaves, lift up pots etc. to see if adult beetles are hiding under the pots during the day time. Even go on a night patrol as this is the best time to find the adult beetles.
- If you find that you have Vine weevils, isolate the plant if possible & remove grubs that can be found & then for immediate protection use a treatment such as "Provado".
- Treat your containers with a nematode treatment such as "Nemasys" which can be purchased online or from most large Garden Centres.
- If extensively infected, you may decide to dispose of the plant, but you must also dispose of all the compost as the weevil eggs are not visible to the naked eye.
- Clean pots with a suitable disinfectant.
Commonly asked questions and mistakes.
- We use slow release fertilisers in our composts which are often mistaken for eggs. Vine weevil eggs are brown and less than 1mm (about 1/16in) in diameter, making them very difficult to see in soil. Larger yellowish-brown spherical objects seen in our potting composts are likely to be controlled-release fertiliser pellets.
When it freezes will it kill the Weevils? No, unfortunately they are resistant to extremely low temperatures even over several months of below freezing temperatures.