[arobwk]

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  ), 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 ?