Slugs and snails top pest chart but gardeners panic over spread of giant harlequin ladybird
THE COOL, wet summer of 2009 helped slugs and snails cling on to their title of worst garden pest. Figures released by the Royal Horticultural Society showed that munching molluscs were a menace last year, based on the number of enquiries the RHS Advisory Service received from Society members. In second place were harlequin ladybirds while third place went to the troublesome lily beetle. Vine weevil and chafer grubs took fourth and fifth place respectively (see panel).The biggest surprise was the high ranking of the non-native harlequin ladybird, especially as it is not a conventional plant pest. Since its arrival in the UK in 2004, it has become a nuisance, taking up residence in houses as it tries to hibernate in autumn. But harlequin ladybirds have gained a bad reputation for destroying gardeners’ friend the native ladybird, as well as other aphid predators. RHS principal entomologist Andrew Halstead appeared to defend the antics of the much-hated harlequin: Andrew said: “Adult harlequin ladybirds and their larvae feed mainly on greenfly and other aphids so are helpful to gardeners. They will eat other insects if aphids are in short supply but it remains to be seen whether the arrival and spread of the new ladybird will have an undesirable impact on other aphid predators.”
The RHS top 10 pest survey identified lawns as the source of the most pest enquiries. The main lawn problems are chafer grubs, moles, leatherjackets, ant nests and worm casts. Andrew added: “Chafer grubs can be a severe problem for lawns, especially on sandy or chalky soils. The beetle grubs sever the grass roots, allowing foxes, badgers and crows to rip up the loosened turf in autumn and winter. “The animals eat chafer grubs and so provide some control but the lawn can end up looking like a badly ploughed field,” Andrew added.
