Now is the time for all good gardeners to get down and dirty. The days have lengthened, birds are nesting and buds are budding. I’ve been doing a huge clearing out session in the garden, pulling decayed foliage from last autumn, pruning the lavender and the hyssop. I’ve dispatched weed seedlings, dug over the beds and started to think about spring sowing. I know that many of you have already sown your seeds. I am late this year. But every year I leave the sowing just a bit later and every year I find my crops come into fruit/leaf/bud at exactly the same time. Perhaps that’s a lesson for the over enthusiastic early planter. Later sown seeds need less cosseting.
Leaving plant debris in the garden over winter is the ‘correct’ organic approach. It leaves lots of nesting places for beneficial insects to over-winter. However it also provides fodder for not so beneficial insects. The problem is, to be able to tell the difference between the benign and the pesty.
I’ve found ladybirds on the wing and their larvae already this year. So far there are no aphids to be seen, but I shall leave them as food for the ladybirds. I’ve notices quite a few spiders going about their business and a few flies, out on patrol. There are a few slugs also, and I’m planning to spray against them later this month. But so far the dry spring seems to have kept them at bay.
I was beginning to feel quite happy with my eco-system as I turned over some deliciously rich soil in one of the pots. Then I saw one. Then I saw another. Then a third creamy bug appeared, armoured and curled like an ammonite, with a brown face. It was a vine weevil larva. The adults eat leaves, not too much of a problem, but the larvae eat roots. That can be a major problem with perennials, destroying the entire root ball in a few days.
Whilst I sorted through pots from last year, digging out the soil and preparing for a new seasons planting, I seemed to see them everywhere. If I’ve got an infestation, then you can bet that other people have as well, so I went to my library to discover solutions. At least I can share my research. I’m somewhat heartened that the number of column inches devoted to vine weevils, are rather limited. Does that mean they don’t do so much damage in the end? Does their maggot like looks make them seem more of a pest than they really are?
Last year was the first time I’d ever seen adult weevils. They are about 12mm long, slow and fat, with a grey/back carapace, spindly legs and wiggly feelers. I’d seen a few larvae before. And if I found just one in any pot on the rooftopvegplot, I’d dispose of the entire pot of soil. But finding the odd one all over the place, was a new experience. I can’t change all the soil in the rooftop beds.
They cannot fly. They are all female and they all lay tiny brown eggs, that hatch into the disgusting bugs. In the autumn I ordered some vine weevil nematode and soaked the soil.
But it clearly has not worked. Or, to be more precise, it has not worked enough.
My gardening books were relatively helpful, but a few minutes on twitter were even more helpful. @Pixelpusher83, a veg growing eco-warrior from the North East, gave me tons of useful advice. Have others had this problem too I wondered. I searched through images and came up with this this horror movie from Barbara Seagall, @gardenbarbara who had suffered a far worse infestation than mine has been.
I can hardly bare to look at the image. It seems that she merely left the grubs as a feast for the birds. Meg Roper (my fellow partner in crime over at @SetinModern, @Meg_e_r) also told me that her friendly garden Robin enjoys the grubs.
The problem is that we don’t have little birds round here. I know that I could not rely on something sweet like a thrush, robin or blackbird swooping down to much them up, though I’m hoping the pigeons might have a try.
Linden Hawthorne, @Haggewoods, suggested dealing with the problem pot by pot. She advised replacing the soil and cleaning the roots of anything precious before re-potting. I shall certainly plant my new grapevine in fresh soil. (I’m assuming a ‘vine’ weevil will like a grapevine.) But if you have a lot of pots, the cure could be less bearable than the pest.
@JeffryeJones suggested a Bayer insecticide, but that would be a step too far for my organic principles. In any case, the chemical stays in the soil and is toxic. It may be okay to use it in a flower garden, but you can’t even compost the sprayed soil if you plan to use it for veg.
@suebeesley, who owns a beautiful cottage garden, at Bluebell Cottage and runs a nursery, calls herself ‘green-leaning’. She recommended the nematode soak that I used last autumn. I went straight to the internet and ordered two more batches. Pixelpusher83 advises that you have to really soak the soil with the nematode mix. Perhaps I’d spread the stuff too thinly last autumn?
Lastly the lack of winter has again caused problems for me. Nothing has died down. That is marvellous for my late carrot crop, for the spinach beet that is still sprouting, for the Osteospermum that never stopped flowering all winter. But it’s also far too cosy for bugs.
So for the record here is a list of treatments for vine weevil:
- Spray the soil with vine weevil nematodes in spring and autumn.
- Hand-pick and kill all larvae and beetles that you find.
- Dispose of the soil, clean off roots and re-pot your specimen into new soil.
- Dig over the soil to loosen the bugs and let the birds pick them off. (If you can rely on birds, that is.)
- Water the effected patch of soil with boiling water. It will kill everything else around, but at least it will also kill the larvae.
- To prevent the adults laying eggs, place a 5cm layer of sharp grit over all the soil.
- Place specimen plants in water trays. The blighters can neither swim nor fly.
- Place a sticky band around the rims of pots to deter their climbing in.
But as I cleared the soil in the raised beds preparing for next year’s crops, I noticed that where rampant legumes and climbing courgette had been growing there was still a massive amount of roots left in the soil, so tangled, that it was hard to break it up. I mused that perhaps a few vine weevils here, to eat the tangled mass of last year’s roots, might not be such a bad thing.
That’s the problem with nature; you never know what is beneficial and what is not. I see my role as a moderator, only stepping in where something reaches plague proportions. Two swallows don't make a summer, we all know that. But do ten vine weevils make an infestation? That is a harder sum to resolve.
