Vine weevils are particularly dangerous due to their two-pronged attack: the adults eat the leaves and the grubs eat the roots. Many gardeners are afraid of this root-eating plant-insect, and it’s not surprising because suddenly, otherwise healthy-looking plants collapse and die at the feat of this garden pest.
The vine weevil used to have a more discerning palate, but nowadays they love a wide range of ornamental plants and fruits, especially those grown in containers.
Adults feed mainly at night on the foliage of many herbaceous plants and shrubs. Watch out especially for your camellias, rhododendron, hydrangea, bergenia and fuchsias.
How to spot vine weevil
Vine weevil larvae are creamy-white with light brown heads and no legs, these pests can measure up to 10mm long. Usually, you can find them curled up in a ‘C’ shape among the roots. Often, the first signs of damage from the grubs can only be spotted once a plant completely wilts and die during autumn to spring.
Although adult vine weevils can’t fly, they are able to climb easily. You’ll spot their unsightly, although not fatal, damage by semi-circular notches eaten into the edges of leaves. If you spot holes in the middle of leaves, they are more likely to have been made by slugs and snails.
If you spot adult vine weevils, put a tray down below the plant and they will fall to the ground if slightly disturbed. However, it is important to note that the real damage from vine weevils are done by the grubs which feed on the roots.
How to treat vine weevil
Vine weevils are difficult to control once established because of their nocturnal behaviour.
For more of a natural remedy for vine weevils, try to encourage natural predators such as birds, frogs, toads, shrews, hedgehogs, and predatory ground beetles.
If you don’t want to use pesticides in your garden, use a biological control based on parasitic nematodes. These microscopic creatures enter the bodies of the grubs and release bacteria that will poison them. They then multiply and go on to attack other grubs.
Apply during August and early September when the soil temperature is warm enough for the nematodes to be effective (5-20 degrees C) and before the vine weevils have grown large enough to cause serious damage. After applying the biological control, keep the soil moist for a fortnight after applying.
Finally, keep looking for vine weevils once you think they have been eradicated, as you don’t want to let the number of pests build up again.