by Kate and Len Lucas
This is the first of a series of articles dealing with nature’s non-stop attempts to undo all our good work. Almost all of them can be found in anybody’s garden no matter how experienced. And in common with all living things, the warmer it gets, the more there are of them. In addition, they will arrive without permission and almost without warning.
Vine weevil is a beetle. The adults are very dark in colour, about half an inch long, with what looks like a long nose. Both adults and grubs cause damage, but the grubs do the most which can be fatal to the plant.
These adults are slow moving and cannot fly, and even though they are nocturnal, you can catch them quite easily in broad daylight even on the walls in your kitchen. The adults feed on the leaves making very characteristic small U-shaped notches at the leaf edges and whilst not fatal they disfigure the plant. The C-shaped grubs are another thing. They live under the ground and eat the roots of plants, and often you are not aware of their presence until the plant suddenly collapses and dies. These grubs are unmistakable. Cream to ivory white, they have no legs and have a distinct dark coloured head.
Believe it or not, all vine weevils are female and no males are needed for reproduction. This might seem odd to us but is common enough in the insect world. This pest will have arrived in your garden either by literally walking in from somebody else’s garden, or from a plant you bought and planted it yourself.
The adult beetles emerge around May, feed, and begin laying eggs in the soil. Those eggs hatch and the grubs feed very rapidly until late summer when they pupate in the soil where they remain dormant over the winter to emerge as adults next year.
This is a common and serious pest but some plants are more susceptible than others. Particularly affected are strawberries, Cyclamen, Begonia, Primula, Polyanthus, Sedum and Heuchera and very likely many others. We have had a serious and fatal problem with chocolate Cosmos grown in a container.
So what are we supposed to do about it? First of all, the biggest problem we have had with it is when growing plants in containers, especially those in the list above. So for any plants newly bought, take them out of the pot and check the roots for grubs no matter what the time of year. For plants you already have in containers check for leaf damage of the kind described above or wilting when the plant is not dry then vine weevil is very likely in there.
Here are some possible courses of action:
There are biological control methods available which use nematodes as a natural parasite. You can buy them online, but we are not sure if you can buy them off the shelf as they have specific storage requirements because they are living organisms.
There are chemical remedies specifically for this pest and they will name vine weevil on the box. Usually supplied as a concentrate for diluting down and watering onto affected plants. You may find it is worth having a look on the Royal Horticultural Society’s Website for suggestions about other insecticides that you could use.
We have read gardening books that advise going out at night with a torch and catching the nocturnal adults. We don’t know about you, but opening a bottle of french red is much more attractive on a warm summer evening. It is our experience that this pest attacks individual plants and is difficult to predict when you will get it. Which means that treating plants before you think you will get an attack is not only expensive but often a complete waste of time.
Therefore if you check the plants you have just bought and be aware of the tell tale signs, then you will be better prepared to avoid the disappointment of losing a plant and you don’t know why.
We are not alone.
Nevertheless we wish you all a happy New Year.