The green bottle causes flystrike as well.
These damn flys seem to be causing a lot of people problems this year. me included.
Have just taken a look at my bottles of purple spray DL. i think the one Anne uses is probably the Septi Clense by Nettex which is an antiseptic spray with violet, it has a bactericidial action. i use this on my ponies & guineapigs too. Ive also got the Gentian spray which I use to cover any red, but dont find this sticks as well as the Septi Clense. Still trying to clean it of my boy whos going to a show in a few days.
The maggots these flies lay are really, really tiny - OH spotted a couple on a hen we've got a problem with at the mo.