Blooming Times – War On Weevils
by Flo Whitaker
When observing the activities of garden insects it pays to know your enemies and give a helping hand to your friends.
There is a pest for every season. My award for September’s ‘Pest of the Month’ goes to the Vine Weevil beetle. Adult beetles are 8-10mm long, greyish/black with dull yellow spotting. They are most active at dusk, munching irregular-shaped holes on foliage. The damage is annoying, but mostly cosmetic – a more serious problem is caused by the juvenile grubs. Throughout the summer, female beetles lay eggs just below the soil surface. As they hatch, the creamy-white larvae burrow deeper, feasting on plant roots before pupating into adults the following year. Out of sight and undetected, it could be months before the gardener becomes aware of the infestation. Come springtime, affected plants attempt to grow but the severe root damage ensures their rapid demise.
Established plants growing in open ground often survive an attack. Hedgehogs, birds and frogs predate on adults and larvae, but newly-planted specimens are highly vulnerable, as are any pot grown plants. Patio pot compost is lighter and drier than garden soil; the perfect environment for larvae to burrow and overwinter. Potted conifers, acers, primulas, hydrangeas, fuchsias, cyclamen, rhododendrons and azaleas are their favourite foods, so be vigilant. I seldom use garden chemicals, but do treat my patio pots against Vine Weevil every autumn, while the young grubs are active, but before they have a chance to do significant damage. I use a ‘drench’ method; diluting the chemical as directed, then drenching the soil with a watering can fitted with a fine rose.
The random bite marks of Vine Weevil vandals should not be confused with the activities of the admirable Leaf Cutter bee – they have far superior table manners. Leaf Cutters neatly snip near-perfect semicircles around leaf edges, (rose leaves are a particular favourite,) then, with heroic effort, carry the pieces off to a nest site. Each leaf portion is rolled into a cone shape and pushed inside a hollow stem or a crevice in rotting timber. A single egg is laid into each cone, and the end sealed with more leafy material. They are diligent parents; regularly checking their incubating offspring and making repairs to the nursery.
When clearing your borders this autumn, don’t be too tidy. Leave clumps of hollow-stemmed plants standing and tuck handfuls of dry leaves under a hedge or in the corner of a sheltered border. These hidey holes will give protection to many beneficial overwintering insects. Leaf Cutter bees are passive individuals who very rarely attack. In any case, their venom is 50% less powerful than a honey bee sting, so you can tell their hearts aren’t really in it. These charming creatures are some of the most important pollinators on earth. The very least we can do is to give them a helping hand.