Nematodes – My army of 30 million soldiers


A couple of weeks ago I mentioned that I am having a terrible time this year with slugs and snails devouring the garden in a very messy fashion, leaving almost nothing untouched. I am not alone of course. It has widely been reported that following last year’s wet summer and warm winter we were likely to see an explosion in garden molluscs. In fact, conservation charity BugLife Chief Executive Matt Shardlow heralded a summer of super-sized, sleepless slugs devastating veg and flower patches around the country.

Well, today is the summer solstice and it looks like it is also going to be the longest day of rain! It is tipping down, I got drenched walking the dog and I am watching slugs and snails slide across the patio with abandon (e.g. first photo).

However, it is not all gloom and doom, because after trying various solutions to combat the slimy devils, I did indeed splash out and purchase a large packet of Nemaslugs, nematodes for slugs. It was enough to cover 100m² of ground. I applied it to all of the raised beds in the vegetable patch last Sunday and over the last week I’ve gradually planted out all my dwarf beans, climbing beans and courgettes …. and as of this morning, with one exception, they were all still there.


Whereas, back on the patio, I’ve watched sunflower after sunflower suffer decapitation and the spare climbing beans (waiting outside the greenhouse in case of loses) have all  been stripped and truncated.

Maybe there is hope after all!

According to the blurb, the nematodes start being effective between 4 and 21 days after application and should continue to work for roughly 6 weeks. With any luck, by then, the plants should be large and tough enough to take a little damage.


Since using a biological control was a new approach for me and not many people that I have spoken to have tried it, I thought that I would point out some useful bits of information about using a nematode army. I’d also like to thank Kate at the Barnhouse Garden for her pointers on using nematodes, because when the packet arrived, all sealed in its nicely illustrated sleeve, I would probably have put it to one side for a day or two before I did anything with it, but Kate’s comments had alerted me to the fact that I needed to refrigerate the container immediately. I know it says that on the cover (see above photo), but you can easily miss such a detail until you get round to reading the instructions properly when you are doing the actual job. So,

  1. The packet contains ‘living material’. It needs to be refrigerated immediately upon receipt.

This sealed packet contained 30 million Phasmarhabditis hermaphrodita, microscopic round worms, that are lethal parasites of various slug species

There is a ‘Use by’ date on the packet and mine was only 5 days from the arrival day. I assume that this is never a long period, since the worms are alive, so make sure that you check this immediately too. Note that once the packet is opened the mixture must all be used up at the same time. The stock solution can’t be stored. Hence,

2. Check the ‘Use by’ date immediately.

3. Be prepared to use the entire packet at one time.

The Phasmarhabditis hermaphrodita nematodes are approximately 1mm in size and are formulated onto clays or gels as infective juveniles, which can then be added to water for application. The powdery mixture looks like this, i.e. a bit like wholemeal flour:



Clay and nematode mix

This powdered mixture is added to water (as per instructions) to make a ‘stock’ solution, i.e. a concentrated mixture, which will then be transferred to a watering can in fixed amounts for dilution to the final ratio, ready for application. To make up the stock solution a bucket or container is required, preferably with volume markings clearly visible. Therefore,

4. You will need a bucket, a watering can and a smaller measure to transfer the stock solution from bucket to watering can.

I used a plastic bottle, marked up to show 1/2l, which was the amount to add to each watering can.


You are suppose to stir the stock solution vigorously. This is to make the mixture as homogenous as possible. After making up the second watering can I noticed that the solution I was taking looked more transparent. This was because the clay particles (and nematodes) were sinking to the bottom. So it is important to stir the stock solution vigorously before transferring the measure to the watering can EVERY TIME.

5. Before taking the measure out for the water can stir the mixture, every time.

You will notice that the clay particles are not all small, some are more clumpy and some look more like fibres. It is therefore necessary that the rose on your watering can has large enough holes for the particles to pass through, otherwise you will end up straining out the nematodes! Luckily for me the rose I had was OK, but this is something to watch.

6. Use a coarse rose on the watering can.

There are plenty more recommendations and bits of advice on the inside of the sleeve. For instance, the solution is ideally applied during rain! However, the only other thing that I will point out here is that there is a temperature restriction on when you can treat slugs with nematodes and that is at temperatures above 5°C.

5°C is the temperature when slugs become inactive and last winter the average temperature was roughly 7°C and that is what has lead to these ‘sleepless’ monsters that we are now dealing with this summer.

Happy slug fighting!



About Frogend_dweller

Living in the damp middle of nowhere
This entry was posted in Nature, The home garden, Vegetables and tagged , , , , . Bookmark the permalink.

12 Responses to Nematodes – My army of 30 million soldiers

  1. inesephoto says:

    Sounds like a good solution for the problem.

  2. Great post, Alison, full of lots of very useful tips. I hope your secret army win the war. Thanks for the kind mention, too.

  3. This is so interesting, thanks for posting. There’s not much to like about slugs and snails, unless you’re a bird.

    • For some reason I never find snails as disgusting. It is the number around this year that is hard to deal with. I am painnfully aware that I’ve treated a tiny area in the middle of a mollusc ocean!

  4. Chloris says:

    What a useful post, thank you. I have never tried nematodes but this year is such a bad year for these pests that I think I will give it a go.

  5. Eliza Waters says:

    Very helpful step-by-step … thanks, Allison!

    • Thanks … I was fortunate to have the right stuff to deal with the nematodes two or three days after receiving them, but it would have been easy to have not had a suitable rose or put them in the fridge etc.

  6. FlowerAlley says:

    I have never heard of this. Fascinating.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s