lj field lab site1.jpg (2)

Leatherjacket control: A surprising result

A suprise result!

After treating half a field with a garlic solution, David Michie has returned this month for a leatherjacket re-count. And this time he got an even more unexpected result!


I am running a field lab that is looking at controlling leatherjackets, and we have tried out an unusual spray treatment. This February I went back to resample the field that we’ve used in the field lab.

Drum roll…

The numbers went from an estimated (pre-spray) 1.6 million leatherjackets per hectare… to zero!  Although to be fair, this is an estimate.  In the half of the field that we had not sprayed there was also a decrease in leatherjacket numbers: from about 2 million to just 0.7 million per hectare – which was pretty big considering we didn’t treat it.  Predation, disease and wet soil might have done this.

To be honest I was pretty sure that the results wouldn’t say very much at all – that there would be a few less leatherjackets, but not by much – and that it would be difficult to say if the spray had made a difference.  I was absolutely amazed that there was such a dramatic reduction.  It could be a fluke – but I followed all the correct sampling procedures, so I hope not!

soil sampling

I would love to try this out on more places around the country, to see if we can confidently say that it really does make a difference. It’s important for us to be aware that whilst these results are exciting, we need to consider that there could be sampling error, and there could be ‘variable factors’ that we were lucky with e.g. spray timing (hitting the leatherjackets when they’re most vulnerable – we might have got lucky with this!)

I also think weather may have been important – the field is in an area that is milder and wetter, and didn’t get much frost – this might have made the spray work better.  In a colder place we might not have got the same result.  It’s also worth thinking ahead as the climate changes – warmer weather with periods of heavy rainfall might make the spray more effective, but it might also mean an increase in leatherjacket problems in the first place.  One thing is for sure, farming is getting more unpredictable, and we need to respond to these challenges.

Get involved…

I’m really looking forward to seeing how this trial will work in other regions as we support farmers across Scotland facing similar problems. We’d love you to get in touch if you’re interested in trialling this treatment on your farm, or if you’ve had any experience with using garlic spray to control leatherjackets. It would be great to add to our growing knowledge of dealing with this problem, now that Dursban has been banned. This is a great project to demonstrate how cooperation and communication across a large area can really help to solve a common farming problem.