Vine weevils and their grubs can wreak havoc upon carefully crafted container displays, but August is a good month to gain the upper hand.
Vine weevils are the stuff of gardeners’ nightmares. Show any gardener the images on this page and you’ll likely be greeted with shudders. The adults, dark-brown-and-black with a long snout, eat irregular notches around the edges of leaves – the damage they cause is unsightly but plants usually survive it.
The worst damage, which is often fatal, is caused by their larvae, which hatch from eggs laid by the adults in the soil and feast on plant roots – they can be particularly troublesome in containers. If plants such as heuchera suddenly wilt, or rosettes of echeveria come away in your hand – two of their absolute favourites – vine weevil grubs decimating the roots are the likely culprits.
Unfortunately, because the larvae (C-shaped and cream with an orange head) live below ground, you don’t usually notice you have them until the damage has been done. Keep an eye out for the adults and the damage they cause, because if there are adults, there are bound to be grubs somewhere nearby.
Luckily, there is a biological control – a parasitic nematode called Steinernema kraussei, available from Nemasys – that can be very effective when applied to container compost in August or September, just after the grubs hatch but before they are large enough to cause much damage. The benefit of using nematodes is that they cause none of the environmental concerns of the soil-drench neonicotinoid pesticides that are also available to treat these insects.
Meanwhile, control the adults by inspecting plants after dark with a torch, when they come out of hiding to feed. With an element of surprise, you can pick them off and squash them before they go on to mate.
You might also like:
- How to stay in control of greenhouse pests
- 10 ways to win the battle against slugs
- A guide to some of the more common garden pests and what to do about them
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