Springrowth Garden Centre: Dealing with vine weevil in Derry

I didn’t mean to bombard readers with too many garden pest articles, but I think this one is important.

Most people won’t know what they are unless they’ve had the misfortune to meet them.

They are the most harmless insects, but they can cause the most damage to your plants because they attack above and below ground.

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Close up of black vine weevil, Otiorhynchus sulcatus sitting on a piece of wood

Adults are nocturnal and normally only come out to feed at night.

They can be spotted during the day if disturbed from their hiding places, which include the undersides of pots and the undersides of leaves and branches.

They have a dark gray body with pale yellow spots and are very slow moving.

They won’t move at all if they see you.

One of the telltale signs that you have vine weevil are eaten notches on the leaves from the outer edge of the leaf.

Other signs that you have these little terrorists are when your plants start to wilt and discolor and look unhealthy for no apparent reason. The reason for this is that the larvae are in the ground and they actually do more damage than the adults.

An adult can lay up to a thousand eggs, not all of them will hatch but a large percentage will survive. The larvae are about 10mm long and are a creamy white “C” shaped larva with a light brown head.

When they hatch they will begin to eat the fine root hairs of your plants and as they grow they will eat thicker roots and even strip the bark around the stem at ground level on some softer plants.

Cyril and Alison Quinn, owners of Springrowth Landscape and Garden Centre, Springtown Industrial Estate. DER2115GS-028

The vine weevil seems to have a preference for the nice soft fleshy roots of herbaceous plants such as Hosta, Astilbe, Polyanthus, Heucheras, but I have also seen them in pots of laurel and Leylandii hedges so they eat everything you need to survive.

There are several ways to control the vine weevil; Chemically – there are a few products available such as ‘Provado’ which kill the larvae.

Biologically – “nematodes” which are parasitic worms that enter the larva and feed on it until the larva dies.

Physically – if you think you have vine weevil larvae in your pots you can tell by the unhealthy plant or by pulling it and if it looks loose in the soil they may be there gnawing.

Take the plant out of the pots and shake the soil where it will be clearly visible. You cannot see the eggs because they are microscopic.

If you don’t have the heart to kill the larva or are disgusted, pick them up and put them on a feeder, the robins love them and will gobble it all up. Sometimes the plant can be saved if you catch it in time and there are still enough roots left to feed the rest of the plant, but I would use a product like Provado to make sure I kill the ones I could have missed too.

The adults also have natural enemies such as beetles or clockflies as they are known locally, so don’t be tempted to step on them as they are a beneficial insect to have in the garden and are carnivorous so as not to damage your plants.

You can make traps for adults, a simple trap is a toilet paper tube filled with screwed paper, leave a few around your greenhouse or garden and shake them out in the morning. Earwigs will hide there too!