The fuchsias should be looking at their best in the summer, but look a little closer and you may want to know what’s eating the scalloped patterns in the edges of the leaves. And while the larvae of this particular bug eat the roots of a range of plants, the adults have altogether different tastes. So what is the culprit. Why it’s the vine weevil!
Late spring and summer (particularly mid summer) is the time when such chomping symptoms of the adults are seen. But the insects themselves aren’t usually seen by day. To catch a glimpse of them you’ll need to go on an evening safari by torchlight. Check the leaves of the damaged plants and warm walls close by. By contrast their grubs are hidden below the soil or compost surface and only emerge in waterlogged conditions. The only way you are likely to see them is by digging up plants that show signs of sudden collapse. They’re most likely to be found in mid summer through autumn and winter and on into spring.
What do vine weevils look like
The vine weevil grubs are cream in colour and grow to around 9-10mm long at their largest. Their curved bodies are corrugated and they have a distinctive brownish head and, in this stage of their lifecycle, no legs. They hatch from brown eggs, no more than 1mm in size, laid close to the soil surface by the adults.
Feeding on the underground roots and corms of plants, they are able to grow rapidly, undetected. They then pupate inside a hard case, to emerge as adults in mid to late spring.
The adult weevils are black with cream-yellow mottling on their backs, and have a distinctive pear shaped body. They have a pair of antennae on their heads held in a V-shaped formation. At 9mm they are a little shorter in overall length than the grubs. They are flightless, but able to walk actively and climb.
Can vine weevils survive the winter
The eggs and larvae of vine weevils are able to survive the winter months by being underground where they are insulated from the cold. Adults may survive in very sheltered places in mild conditions, and occasionally indoors if they have a food source. Most adult vine weevils die in cold weather, particularly during periods of sustained frost.
Mild winters favour their survival. Hard, penetrating frosts and wet winters may kill larvae in the soil, as well as the adults. In our changing climate, vine weevil are likely to spread further north and into upland areas where they were previously unable to thrive.
Which plants do vine weevil eat
The grubs (larvae) are regularly found on the soft roots of heucheras, primulas and sedums, as well as both the roots and corms of cyclamen and begonias. They also eat into the roots and basal tissues of cacti and succulents, and are also able to munch off the protective surface on the roots of woody plants.
Meanwhile the adult weevils are partial to the leaves of epimedium, hydrangea, rhododendrons, bergenia, strawberry plants, primulas and, to my particular annoyance, fuchsias. Their tastes seem to be widening, although their diet seems to vary from year to year and in specific locations.
How to get rid of vine weevil
Birds, amphibians, hedgehogs, shrews and some types of beetles have a taste for the vine weevil eggs, grubs and adults. Lightly cultivating the soil and compost may expose eggs and grubs. Encouraging beneficial wildlife by creating habitat for them and by feeding is hugely useful at keeping down the numbers.
Weevils are particularly problematic in light soils and in compost. Standing pots in a bucket of water for a day will often force the grubs to come up the surface where they can be picked off. Checking compost by knocking plants from their pots also allows the grubs to be removed by hand.
In summer check on damaged plants and their surroundings for the adult weevils. Do this in the evening and remove by hand.
There are effective biological controls for vine weevil, consisting of microscopic worms (nematodes) which parasitise the grubs. The nematodes need to be applied in warm soil conditions to be effective.
There are other types of weevil that cause damage to plants, most notably the pea and bean weevil, the leaf damage of which is distinctively similar to that caused by adult vine weevils.