Mick Lavelle is senior lecturer in horticulture at Writtle University College*

As the growing season reaches its peak during the long summer days, it is not only plants that find conditions to their liking. Among your treasured flowers and produce is an army of pests, seemingly hell bent on devouring your prize specimens. There are a few of these that stay hidden from view, and arguably the worst is a small black beetle known as the vine weevil.

Vine weevils – adults and larvae – feed on a wide range of ornamental plants and fruits, especially those grown in containers. Plants growing in the open ground are less likely to be damaged, although it is still possible that this will occur on strawberries, primulas, sedums and heucheras.

Adult weevils eat leaves and are rarely a serious problem; whereas the grubs eat roots and can be very damaging.

The ‘C-shaped’ larvae have light brown heads, are up to 10mm long and are active from late summer through the winter. They can only be detected by looking in the soil or compost. Adult weevils are 9mm long, dull black and chew irregular-shaped notches on leaf edges. They are around from spring to late summer but are only active at night. All adults are female, and each can lay several hundred eggs during the summer, so you need to control them now.

Fortunately, there is help at hand. The most effective – and environmentally safe – control is attained by using microscopic nematodes. The most effective of these is a species called Steinernema kraussei, which kills the larvae. They are easy to use and can be bought online or in garden centres.