Vine weevils are very common on the Netherlands. The beetles and the larvae live in the soil. The adult beetles hide during the day and crawl out of their hiding places during the night to look for food. The beetles cannot fly and walk from place to place. The species causing most nuisance and damage in the Netherlands is the black vine weevil (Otiorhinchus sulcatus)
Vine weevils have a very characteristic appearance with a strikingly long snout ans bent knee-shaped antennas with a clear club at the end. Vine weevils are about 1 cm long and are black. The elytra is grooved with scattered specks consisting of greyish yellow hairs and is very hard.
The eggs of the vine weevils are laid in the soil. The females lay about 1000 eggs in July and August. In the fall, the eggs hatch and the larvae hibernate. The larvae feed with the roots of all kinds of plants. The adult beetles feed themselves with plants elements from above ground.
In the house, vine weevils can cause some damage because they eat from underground or above-ground elements of pot plants. Most damage is caused by the larvae, because they eat the roots, which weakens them and can even kill them. In large numbers, they can be a great nuisance.
Vine weevils often enter houses via open windows and doors. With the help of an insect screen, this can be prevented. The beetles can also be chased away. The best moment to do this is during dusk. In addition, replacing pot soil is another possibility to reduce the nuisance.
The use if chemical pesticides is not useful. Vine weevils are insensitive to most insecticides. When repotting plants, shake them well and collect the larvae that are released. Don’t punt the old pot soil with the compost heap, since unnoticed larvae can spread in your garden. You’ll have the least risk of damage if you also report the pruned plants before you bring them into the winter storage. A plant in which you discover larvae during repotting, should be placed in a bucket of water, not too cold. Rinsing in water aids in the release of hidden larvae. Pot the plant in a different pot and thoroughly clean the old pots (due to unhatched eggs in the soil residue). In particular in species with fleshy roots, check whether any larvae are hidden.
Pesticides against weevils and larvae may only be deployed by professional growers. The only way to eliminate nuisance by weevil larvae is to use an organic extermination method with parasitic nematodes – (Heterorhabditis sp.) The nematodes do their work in a soil temperature above 14 degrees C. The best time to administer these nematodes is therefore between late September, early October.