Vine Weevils

Learning to live in harmony with nature is not always easy. Hours spent tending to your garden, ensuring your plants are healthy and well cared for, feeding and watering them, pruning when necessary, deadheading regularly, lifting, dividing, covering them, treating them for whatever pests are hounding them, giving them the best possible life, and then you wake up one morning and your favourite Fuchsia or hardy Heuchera is dead. And it’s not like a few leaves have turned brown, the entire thing is way past saving. It may have started to wilt recently, prompting a call for extra feed, extra water, extra attention, but none of it made a difference, and now there’s a huge void in your garden to fill; without knowing what killed your cherished plant, however, there’s always a risk of it happening again. And it could, if it’s an infestation of vine weevils.

Adult vine weevils alone are not the problem. They munch on the leaves of a variety of plants, and the tell-tale signs are irregular bite marks on the edges of leaves. Other insects could be equally responsible, but as vine weevils are only capable of munching on the leaf edges, ignoring the unsightly but seemingly innocuous sight in favour of providing for nature, would be inadvisable because it is the larvae of vine weevils that cause the fatal damage, and better to check early and be wrong than investigate later when it’s too late. Adult females have no need of males to reproduce and can lay more than 1000 eggs, so a single weevil is not as harmless as it might seem.

      

From late June to October, you’ll maybe stumble across a few adults in the garden during the day, but venture out at night, torch in-hand, and you’ll witness the family feast! Although the damage may be unsightly, it’s not devastating; that’s the work of the young, and the trouble starts from late summer to early autumn. Two weeks after the eggs are laid in the soil, the larvae hatch, and from that time until early spring – sometimes longer – they’ll devour the roots of the host plant, pupating in late spring and emerging as adults in summer to start the cycle again. Whilst it may be difficult to tell the weevils apart from other species, the damage could be just as destructive, so it’s worth treating them in the same way; bear in mind, also, that the times these pests can potentially cause problems is not limited to the months mentioned, so be vigilant all year round.

At less than 1mm, vine weevil eggs are difficult to see in the soil or compost, but the larvae grow to around 9-10mm. They look similar to maggots, are creamy-white with brown heads and plump, curled into a C shape and legless, but because they’ll be buried in the soil, munching on roots, you won’t see them unless you dig down. They’re often found in pots and planters, so if your infestation is contained, spotting the larvae may be easier, but only if you’re looking for it; waiting until your plants wilt is too late as they may have already lost their roots to larvae and the infestation may be well established.

  

Adult weevils are – in theory – easier to see, but as they feed predominantly at night, you could still miss them; it would be prudent to carry out the occasional evening inspection, particularly if you’ve spotted the damage to leaves of your plants. But what are you looking for? Adults are around 9mm long, dirty black in colour, with small, dark yellow markings (see below), and you’ll need to work by torchlight to avoid the feasting beasts bolting.

Although vine weevils feed on a wide range of plants, they have a particular liking for Bergenia, Camellia, Epimedium, Euonymus, Hydrangea, Primula, Rhododendron and strawberry; their larvae prefer Bergenias, Cyclamen, Fuchsia, Heuchera, Polyanthus, Primula, Saxifrage, Sedum, strawberries, succulents and young yew plants. Pots and planters are potentially more at risk, but that doesn’t mean border plants are safe, and it doesn’t mean your greenhouse is either; in fact, the warmth of a greenhouse could see vine weevil activity all year round, and it’s possible to spot them hiding under your post during the day. Consider planting one or two of these favourites around your outdoor space – preferably in pots – to alert you to the presence of these destructive bugs. If you notice damage to leaves, try gently tugging the plant; damaged roots will allow it to be pulled out easily.

What do you do if you find vine weevils? Wherever possible, non-pesticide solutions are recommended because the chemicals necessary are likely to harm natural predators and could inadvertently exacerbate the problem; there’s also the threat to bees and other pollinators, and that’s never a good idea. There are several options available, but some of them may also affect other wildlife, so be cautious.

Removal of the adult weevils is the safest option for your garden. On a dry evening, you can pick individual bugs off your plants or, if there are too many, you can shake the plant over newspaper, a large box or an upturned umbrella, and as brutal as it sounds, squash them. You can also check your compost and remove larvae before they get a chance to feast on your garden’s delights.

If removal by hand is not for you, encourage more wildlife into your garden. Both the adults and the larvae provide food for birds, frogs, hedgehogs, shrew and toads and some other insects, and whilst it may not be the best option for a major infestation, it will certainly help to prevent one.

Non-drying Insect glue can be effective if applied to parcel tape and the tape wrapped around pots and planters. Whilst it can work well in trapping adults – particularly females before they lay eggs – it’s a hazard to other insects and is difficult to keep debris-free.

Once the warmer weather arrives and the soil temperature is likely to remain around 14°C for around two weeks after application – July and August, potentially – pathogenic nematodes can be used, but once again, they can impact on other wildlife, so should only be used with care and for significant infestations. Nematode traps are a better option, and if placed under affected plants will encourage adults to enter when seeking somewhere to hide during the day.

Pesticides – including organic ones – can be rather detrimental to natural predators, other visiting wildlife and the quality of your soil, so they should really be a last resort. Choose one that can be found in-store, rather than randomly online, as they will have been approved for use – homemade pesticides will be untested and possibly more harmful than regulated ones. Be sure to follow the instructions and avoid using on edible plants unless the particular brand you’re using states otherwise. If your plants are flowering, you will need to remove the flowers for up to two months after using a pesticide to prevent harm to bees and other pollinators.

Vine weevils can devastate your garden if left unchecked, but vigilance and early detection can save you a lot of frustration and money. As always, we have experts in-store that can offer the best advice when needed, and if vine weevils decide to pay you a visit, it will most certainly be needed.