TThe first sign of blackvine weevils is Otiorhynchus sulcatusThis is when your favorite pot plant dies in spring. The larvae, which are small white, sickle-shaped, grub-like insects, eat the roots of the plants and then the base of stems until the plant dies. In nurseries with many plants in containers, the grubs can be a major pest. They attack ornamentals of many kinds, including camellias and rhododendrons, as well as crops like strawberries. Although they are not usually fatal, they can cause damage to the plants.
They are only 10mm long when the adult beetles emerge in March and are nocturnal. Adults cannot fly but they can run fast, climb trees and eat leaves at night. To avoid being eaten by predators such as birds, toads and hedgehogs, they hide under soil debris during the day. In autumn they lay eggs in soil and the larvae munch away unobserved all winter.
Gardeners are advised to avoid pesticides which will kill the beetles’ predators. This is a refreshing change from the previous advice. Instead, gardeners should use torches to hunt down the weevils or buy biological parasite controls to eat the larvae.