Saturday, 4 May 2013

Weapons of precise destruction

Vine weevils. Just hearing the words makes me shudder. Small yucky white grubs in the soil and adult grey-black beetles that eats unsightly marks on the leaves on many types of garden plants. Have you had any in your garden? Do you even know if you have any? You might have some, without it representing an infestation.

Last summer I had a particularly bad attach of vine weevils it seems, although all I saw was the result of the adult beetles munching away on my plants. Well, that in itself is not devastating harm to a plant, but on evergreen plants it is rather unsightly, my rhododendrons have still got the same leaves with the same notches and holes. I have tried to remove some of the worst leaves the last few months, hoping the evergreens will produce some new leaves when they discover the missing ones. I can’t remove all the ones with damage, that would be too stressful for the plants I think.

The leaf damage is just part of the vine weevil problem and to be fair, is more of a cosmetic problem, what goes on underground is much more devastating. Each female beetle lays 1.500 eggs every summer, which all becomes larva and those are the real threat to the plants. They stay between the roots of the plants, eating away the whole root system of a whole range of plants, especially plants in containers and pots , but also plants in open ground. With an infection big enough, a gentle tug at the crown of the plant will usually pull it away from the soil surface, as there is no root system left. Sometimes the first clue that something is wrong is when the plant blows across the garden like a ball of tumbleweed with all roots having been munched through. An exploratory dig around the planting area usually reveals the larvae about 2-5cm down, in what was left of the plant roots.

Here comes a solution - hence the title of this post! “Nematodes are naturally occurring microscopic worms, already present in our soil in the UK. Beneficial nematodes attack and kill targeted garden pests. They are environmentally friendly, safe for children, pets and wildlife. Research scientists have isolated the nematodes that kill specific garden pests including slugs, vine weevils, chafer grubs, leatherjackets, caterpillars, codling moth and various others. Millions of nematodes are bred to be easily applied by gardeners. When nematodes can no longer find prey they will die back to their original numbers. The nematodes in the Nemasys Range are naturally occurring so you are only boosting existing populations and not adding anything new to the environment.  They are effective in controlling pests without the restrictions associated with chemical controls.” (info from the nemasysinfo.co.uk)

I bought my nematodes on Amazon, but you can get them from many places including garden centres. If you live outside UK I am sure there are similar products in your country. Nematodes is a live product and have an expiry date of around 3 weeks from purchase and they need to be kept in the fridge until the day you want to use them. I carefully read information about this product before making my order, and one of the most important thing is that the soil need to be above 5 degrees for this particular product to work (some need even higher), or the nematodes will die. So when is the soil above 5 degrees C then? And does it need to be above 5 degrees both day and night? With the weather we have had this spring I have waited and waited and waited – normally this product is applied in March, but we were in the middle of deep arctic winter in March! And in April we were still having frost nights. Finally, last week of April I sent off an email to the company and asked some questions. Basically what they said was: "Generally air temperature during the day needs to be twice that of soil, so above 10 degrees C air temp applications should be fine and it needs to be that for the duration of the application period, 10-14 days. This particular type of nematode is a cold tolerant nematode and should not be affected by any light night frosts, provided well watered in."

So two days ago I went ahead with it. According to the instructions, the pack I have bought should be more than enough for my garden, covering up to 100 sqm, but the dilution method seemed a bit tricky: divide the batch of nematodes in 8 portions, mix each portions with 8 litres of water in a watering can. To me that sounded very difficult - to manage to spread this solution all over my garden and on every pot using only 8 watering cans. It would not be much on each plant, just a quick pass by, how would I ensure every plant actually got some of the solution around the base of the plant? The website said: drench pots or infected soil with nematodes. Drench? I have around 200 pots and containers from the smallest to the largest, in addition to my whole garden – how can I drench with only 8 watering cans? I asked about that too in my email, their answer was to dilute it more, they said: “Mix pack with 5 litre of water. Mix 500 ml to 10 litre of water.” 

Since my watering can only took 7 litre I used 350 ml of solution and mixed with 7 litre of water. That became around 15 watering cans of the standard 7 litres. So to recap:
One 100 sqm pack of nematodes in a bucket of 5 litres of water, then 350 ml of that solution into each full 7 litre watering can of water until all solution is used up. I am glad I asked them, I think I would have struggled to spread only 8 watering cans evenly on my whole garden, even though I don’t have a full 100 sqm garden as the pack was intended for.

The first thing to do was to give the garden a really good watering, even though we are in the spring, it hasn’t rained much and the nematodes need a moist ground to move so to be sure it was wet enough I gave the whole garden and all the pots a good soak. Here is what the nematodes looked like out of the box. I must admit I was fully protected with gloves when I opened it, not really knowing if the nematodes were going to spring out in the air once I removed the plastic film – but I needed have worried, they all stayed together. When I tipped it out in to the water it looked like a piece of old cheese someone had long forgotten about at the back of the fridge (not that I have ever had that kind of things on my fridge, no!) The block of nematodes just floated around on the top of the water so...

...after a good stir it looked like this. I had to keep stirring it throughout the process, as the product kept separating, so in the end I just left the stick there and gave it a good stir every time I filled up a new watering can. This solution seems very opaque, but mixed again with the right amount of water it simply looks like water. You could not see at all that there was anything added to the water, and crucially, the day after, there was no residue on any of the plants either, as some pesticides and fertilisers leave, very annoying when you come out the next day and find greyish blotches on all the leaves. There was no sign of any residue at all here, could not tell at all that I had added anything.

So here is what I needed in order to treat my whole garden: A bucket and a bamboo stick, a small measuring jug, a 7 litre watering can with a rose, access to water and a stool to sit on when filling the watering can (optional).  In hindsight there is one more thing I would have liked to have had; someone young, tall and strong who could have carried all those 15 watering cans for me, it became a struggle in the end, but I did finish it – the whole thing took me just over an hour. And what is an hour’s work if it can save my garden this summer from those pesky things?! After I had treated the whole garden I gave the garden another good splash of water, just to make sure the solution was going to get down in the ground and that all areas were thoroughly wet.

Now, this is an experiment, I hope it will be successful, but only time will show. However, the treatment I have done now is only half of it, to ensure to minimise the population I will have to repeat this treatment in the autumn, before soil temperature goes below 5 degrees, and possibly again next spring too. And as my garden is not in a sterile glass bubble, nothing is stopping vine weevils from next doors gardens from making a visit to my garden for breakfast, lunch and dinner. Future treatments might be necessary.

Have you used vine weevil nematodes before? I would love to hear what success you had with them, if any. And have you used any other beneficial nematodes in your garden? Please share with us! I am not sure when I will be able to share my success rate with you all, I suppose it depends whether I’ll get any attacks or not this summer. Last year the first attack happened in May, but with everything being so late this year, many insects have hardly woken up yet. I will get back on this topic at some point I suppose.

And finally, slightly off topic, but staying with the issue of insects just woken up. I found this one in my garden yesterday and I don’t think I have ever seen it before. Not sure though, because I don’t tend to study the creepy crawlies in my garden too closely, and anything that flies I tend to duck for or wave away, depending on what it is. But this one was just sitting there on a leaf, completely still. I went inside to get my camera, assuming it would be gone by the time I was back but it wasn’t – still there. Getting a photo means identification is so much easier. I found it on Google, after a bit of searching. It’s nothing unusual, but like me you might never have heard about it before? It is a bee-fly, a fly that mimics a bee, this particular one is called Bombylius major, since it is a ‘large bee-fly’. It is a parasitic fly, the eggs are flicked by the adult female toward the entrance of the underground nests of solitary bees and wasps. After hatching, the larvae find their way into the nests to feed on the grubs. Hmm, the world of insects is so cruel. On the other hand, this Bombylius is also a pollinator, along with all other bees, so it has its rightful place there, however, the larvae limit the population of other pollinators. Cruel world indeed.

OK, enough about creepy crawlies and flying things. It’s May Bank Holiday in Britain, usually a wash-out and although it rained for a few hours today, tomorrow seems much better and Monday we might get as much as 22 degrees and full sun here in London. When did we last have a May Bank Holiday Monday when it didn’t rain?? Must be many years ago, I can’t even remember. This one is very welcome! Until next time, take care.

34 comments:

  1. I have never had to deal with vine weavils, fortunately. Good luck!

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    1. Thanks, I didn't know about them until a few years ago.

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  2. I don't think we have vine weavils, but I have heard of using nematodes for numerous things. I have often wondered about them, so I read your post with great interest. I do think this is the wave of the future, and will be interested to know if you feel it's successful for you.

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    1. It will be an interesting experiment, I have read about nematodes for slugs and snails too, perhaps more successful in a green house than outside, but might be something to consider in our slug filled country!

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    2. Ooooo, vine weavils, a nuisance. We had them a long time ago in our pots with Fuchsias, i am not sure how we got rid of them, i think we used one or another pesticide. Wish you good luck with the experiment of using nematodes.

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  3. Simply beautiful colours...lovely!

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    1. I hate it when people leave comments without even reading the post, clearly you haven’t!

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  4. We have had vine weevil grubs in containers but do have trouble with pea and bean weevils on the plot that munch notches in the plant leaves.

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    1. I have seen vine weevil grubs both in pots and out in the garden here, but has yet only had root damage to plants in pots. Four of my fuchsias in pots died over winter, there were no roots left, whilst all the fuchsias in the ground are fine. I have treated everything so I hope to reduce the grub population, but I wish I could treat the neighbour's gardens too!

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  5. I have heard about nematodes and good thing is it is completely organic. However, I have also heard that nematodes attack some vegetable plants. So, those growing vegetables/fruits have to be careful about the types of nematodes, etc. I hope they work for your garden :-).

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    1. You have to get the right nematode for the pest you are getting rid of, the nematodes you buy are specifically picked for that pest and would not be interested in any of your plants, or other pests.

      There are foliar nematodes too, among the around 28.000 species of nematodes that so far has been described – and there are possibly 1 million different on the planet, but foliar nematodes is of course not something you would deliberately introduce in a garden, not even sure if you can buy it. All nematodes have adapted to their own environment, have their own diet and won’t stray to other menus. Nematodes for vine weevil for example is completely safe for plants, animals and humans, the nematodes are only interested in one thing, the vine weevil grubs.

      Yes, I hope they work too, but realise it is more of a long term program so will make some follow up post when I have something to report :-)

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  6. Once we had vine weevils, a long time ago in our pots with Fuchsias. I don't remember how we managed to get rid of them, I think we used a pesticide in that time. Hope you will have success with nematodes, for these weevils are a real nuisance.

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  7. Good luck with your war on VW Helene. They can be a pest, which is why it is also important to encourage all wildlife into the garden. I've read/heard mixed results with Nematodes and haven't tried it yet.

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    1. Thanks Angie, I have heard mixed reviews too, but I think it is important for success to follow up with twice yearly applications, doing it once won't solve the problem so I am prepared for doing that.

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  8. Hi Helene
    Best of luck with the nematodes. I feel bad that you have these rotten weevils and I especially feel bad that you had to lug that watering can around so much. But if the method works, that's fantastic! Fingers crossed!!

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    1. Thanks Astrid, fingers crossed it will work, I had the first attack in May last year so I suppose I will soon see if it has worked - although things might be a bit later this year, including the vine weevils!

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  9. Touch wood I have never had trouble with vine weevil I know they can kill plants off pretty quickly. Hope your precautions work.

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  10. Don't talk to me about vine weevils, Helene. As I mentioned in a previous post of mine, they've munched their way through a few raised beds of my strawberries over winter. Luckily, they don't seem to be a problem in the actual garden. I'll be interested to see how it goes with the nematodes. I'm holding off from using them as they're quite pricey and I have such a large area to treat.

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    1. I remember from your post, like you I have not had much damage by grubs in the garden, only in pots and containers. But I have so many evergreens and I hope by treating the whole garden I will reduce the leaf damage from adult beetles from now on.

      The nematodes I bought was for a 100 m2 garden, which is just over 1.000 ft2, I paid £23.50. You could just treat the worst affected areas, there is one smaller pack covering 12 m2, around 160 pots for £7. (All prices from Amazon today)

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  11. We've been dealing with all kinds of new bugs coming in from other countries and into our gardens in the last few years. Like you, I'd rather use something natural to get rid of them. I'll keep my fingers crossed for you that the nematodes work. Sounds like you have some wonderful weather coming up, enjoy!

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    1. Thanks Rosemary, time will show!
      We have had some wonderful weather, but it didn't last long, we have some pretty stormy weather coming up!

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  12. Nasty little things. I find the grubs with alarming frequency in containers and raised beds in other people's gardens... not yet in mine, but I suspect that it's only a matter of time! I always squish the grubs, but I like to use nematodes as a control. You're very wise to keep treating them - the problem is that if the vine weevils appear to have gone and you stop treating them/looking out for them, their numbers may very well increase. Here's hoping your soil is the right temperature and all goes to plan!

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    1. I inted to keep up the treatment, wish it was a bit cheaper though, could get many nice plants for £23!

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  13. I haven't experienced vine weevils, either. I'm finding that the compost harbors a lot of beneficial insects--so that's probably great for the soil and plants. When I have slugs and earwigs, I put shallow tubs of beer in the garden and they flock to it and drown. Hopefully they die happy. ;-) Good luck with the nematodes!

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    1. I haven't yet tried the beer treatment for slugs, but I have heard about it. Since I don't drink beer myself I never have beer in the house. I suppose I could buy it and keep it in the fridge for when needed - just as I bought nematodes and kept them in the fridge :-)

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  14. Helene, you have me thinking now because I have seen some slug damage in my garden in very strange places and you now have me thinking I have vine weevils.

    I used the Nemaslug system against my slugs and also found it difficult to apply but I have a tiny garden so I managed. It would have been good to have had that info you provided from the manufacturer. I also lost one pack to the expiry date as I ordered it in March and it was far too cold to apply it. They have a very short shelf life.

    I haven't actually seen any slugs since applying it which is great but I have been wondering why so many holes in leaves...it seems there is another enemy!

    Have you sold many of your cards yet?

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    1. Great to hear you have had some success with Nemaslug, I have been wondering whether to introduce that too, but I use slug pellets and don't really feel that slugs are a huge problem anymore and I hardly ever see a snail at all so they are almost gone.

      It is definitely possible that you have vine weevil damage in your garden, May is the typical month where you start to see the damage on the leaves. You could do a one-off treatment with a pesticide like Bug Clear Ultra, if you want to use that, just make sure to use it late in the evening, after the bees have stopped flying. That will only kill the beetles, you will then need to use for example nematodes to take care of any grubs in pots and soil. However, you can’t stop beetles coming over from your neighbour’s gardens so you can still have leaf damage right after killing off all the bugs in your garden. Hopeless at times, isn’t it?!

      As for my cards, well, I haven’t sold one single card….I guess it takes a bit more advertising than just me writing about it on my blog! I have bought a few myself and I am very happy with the print quality, and P&P is very reasonable if you buy more than 5 cards. I suppose I could have done a lot more out of it, bought a lot of cards and sold them off E-bay, but I don’t have the energy, time nor the money to do all that. I was kind of hoping that this was something that could run on its own accord. I think it can, if only more people knew about my cards – all down to advertising :-)

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    2. I haven't sold anything through FAA either - I was going to buy some cards and a piece of wall art but the postage put me off and I bought from MyDoodle instead as postage is free and the card arrives the next day. A bit longer for wall art though. I know you don't like their website but I've sold things from that site - not much but more than FAA

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  15. Helene,
    poor your rhododendrons!
    I had a weevil the apple tree last summer.
    I did not know that it was necessary to struggle against its larvae in the ground. Thank you, now I'm going to look a similar treatment here.

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    1. Nadezda, if you can find someone producing nematodes it would of course be the best and most ecological way to treat for vine weevils, but it is a long term treatment so if you already have an infestation like I, expect further damage to your leaves while the treatment works. I might not see a drop in the beetle population until next year.

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  16. Helene, this is such an interesting post. years ago I had trouble with weevils on rhodos too and heard about using nematodes. I never did try it myself so I'm quite curious how this will work out for you.

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    1. I am prepared for this being something that takes a long time, possibly a year rather than a quick fix like a pesticide would do. I guess it depends on how many grubs that has become adult beetles by now, with me being so late applying the nematodes, however, I could not do it earlier because the soil was too cold. I think whatever happens the next couple of weeks, only next year will be a test of the nematodes. I will post when I have an update :-)

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