Take a look at the pictures above and below and please excuse the poor quality. This was taken today and it shows one of a number of complete and utter bastards I found in a pot today. This particular little bugger is vine weevil grub – study it closely and take heed – note its curly little white body and its dirty brown mouth and if you see one SQUASH THE LITTLE BLIGHTER IMMEDIATELY.
I knew something was up when I saw that my old reliable French Marguerite (Argyranthemum frutescens) was looking not just poorly, but utterly defeated. On touching it, it just came away in my hands and I immediately knew what was up. A quick investigation in the soil in the pot revealed a gang of the white wriggly grubs close to the top of the soil and confirmed that I had a serious vine weevil problem,
Vine weevils are dreadful pests, really, really annoying and tend to pick on favourite plants. Container plants are particularly susceptible. Though the adults are troublesome; they chew tell-tale semi-circular bites of out of leaves, it is their grubs that cause the catastrophic damage by eating the roots of plants, sneakily under the soil surface, so it is only when the damage becomes apparent and the plant dies that you notice their presence. By this time it usually too late to save the plant.
Adult vine weevils are curious creatures their Latin name is Otiorhynchus sulcatus – the sulcatus means grooved and you will notice the leathery backs of the vine weevils are indeed grooved. They look like beetles but there are matte and leathery rather than shiny and have little snouts. All of them are female. They reproduce by parthenogenesis –which means virgin creation in Greek, but anything less virgin-like and innocent you would be hard pressed to find. Each female fan produce offspring from unfertilized eggs.
Naturally weevils have no taste for dandelions, common daisies, thistle, bind weed or other pesky plants, instead they prefer ornamental plants and fruits, especially precious container grown specimens. From now – late spring until midsummer the little fat grubs will be feasting, growing fatter and greedier by the day until the time comes for them to sleep and metamorphose into adults and the adults will be busy laying more eggs – each one will lay hundreds in a lifetime, and remember, she doesn’t have to hang around waiting for a Mr vine weevil to mate with.
So how do you control these little creeps? The best way is obviously to stamp on, squash, and crush and give no quarter at all to any live adult weevils or their grubs. Sometimes the odd adult, brazen hussies that they are, will waltz across the floor of the house. You must immediately kill the beast and dispose of the body. When you find an infestation in a pot you must throw away the soil – every bit of it. If you think the plant has a chance of survival wash the roots thoroughly, take off every bit of soil and examine it to make sure there are no grubs (or adults) left on the plant, repot in clean, sterile soil and give it a good water and feed.
As I do with slugs, the best way to find the weevils is to get out in the evenings and hunt them down. If you suspect and infestation or see the tell-tale chunks bitten out of the leaf margins of plants like bergenia or rhododendron, lay some newspaper underneath the plants and give them a good shake to see if you can knock any weevils that might be hiding off their perches. Regularly check pot plants for signs of weakening, look underneath them and dig your fingers into the soil to see if you can spot any white grubs.
The best control for vine weevils is by encouraging gardener friendly wildlife into the garden such as hedgehogs, frogs and birds who will eat the grubs. A biological control is readily available, a nematode worm. The nematode is a tiny little creature which loves to feast on the baby grubs. When you buy the nematodes they come in a packet and you mix what looks like dry powder into water and pour it onto your plants. The down side to nematodes is that they only work in warmer weather.
If you are non-organic and have just had enough you can go for the scorched earth solution and try acetamiprid – a chemical insecticide. You can’t use this on any edible plants and you also run the risk of killing bugs that really don’t cause any harm at all.