How to deal with Vine Weevil in Hop Plants and Grape Vines

Potentially one of the most damaging pests a gardener will face off against is vine weevils. Evil is even in the name. Both as larvae and adults a small population can be incredibly destructive and even kill your plants. So it is important to deal with them early.

Spotting you have adult vine weevils is fairly easy. They will gorge themselves on foliage, though rather than finishing a meal hop between leaves creating a trail of destruction.   For plants in the ground this is unsightly though rarely deadly. Smaller potted plants may sustain enough damage to stop them producing the resource needed to survive. Fairly easy to pick out they are rather large black beetles with a slender head. The adults are most active in late spring and summer.

But it’s actually the larvae that pose a bigger risk. Young vine weevil start off as little white grubs in the soil. Rather than the leaf of a plant they like to snack on roots, and this is a huge danger for potted  plants. If they get a bit too peckish a group of vine weevil larvae can quickly kill a plant with only a small root system.  Yet it is hard to notice them till a plant is wilting. Digging a little under the surface will reveal them curled but you can’t do this every day. These are mostly active in autumn and spring. The former being when they are laid and latter when they start to emerge.

So what are our methods of dealing with them? Prevention is always the best solution, if we can kill them in their larvae state it greatly reduces the risk in the next cycle. For this we use nematodes. A roundworm that in nature can be a pest themselves, though we used specialised breeds that target pests. By applying them in spring and autumn we can reduce the number that’ll survive to adulthood. This is done by mixing the packet of nematodes with water and applying them to your plants. The nematodes will multiply in number and protect your plant for many months.

However what if you already have an infestation of adults? This can be a little trickier. Many insecticides can kill vine weevil. Finding which is right for you can take some time. Hop and Grape leaves are on the delicate so varieties used on ornamental plants likes roses are a safe bet. You may also not want to use inorganic pesticides on plants you intended to take a crop from. Organic alternatives do exist though they are usually weaker. Whatever you choose the plants suffering an infestation should be sprayed every couple of days to kill any new weevils emerging. After that every 1 or 2 weeks should prevent further problems.

There’s always the option to pick weevils off as you see them. A task made harder by them mainly coming out at night. So how about a little more help? Birds, frogs and other creatures find weevils super tasty. A healthy ecosystem keeps itself in check so you may find things are kept in better control if you encourage some new neighbours.

Dealing with vine weevils is a task without end. Once you find which solution works for you it becomes a mostly painless part of your routine.  Keeping a keen eye out for them will help you notice other potential threats and the methods we’ve suggested very often help prevent them too. Better yet you can use this vigilance to enjoy your garden.

For more info check out the RHS' page on Vine Weevil

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