I am thinking about ways of hopefully reducing the large swarms of St Marks fly (aka Hawthorn fly) that I get round the end of April. The adults are harmless enough and supposedly good plant pollinators, but walking through a swarm of these slow moving ugly jet-black beasties is not pleasant.
Their larva apparently eat grass roots and rotting plant matter (how do they know that
![Huh? ???](https://www.accidentalsmallholder.net/forum/Smileys/default/huh.gif)
), but are they also nibbling at my other plant roots I wonder !? Anyway, I haven't noticed birds taking the adults as prey and if the larva are part of a mole or field vole diet, then I could do with a few less of them too. Therefore, I don't feel bad about trying to reduce the fly numbers.
So, has anyone tried a neem oil soil drench solution to control ground larva of one species or another and were there any signs that it worked ?