Hi DL, I am making some assumptions here but
, I think I can see a couple of problems with your moth garden catching.
Firstly when you say you are running your trap for a couple of hours, once the light goes out the moths will escape, it needs to be on all night, many moths come out in the middle of the night, or certainly a few hours after what we think of as dark. I know i tried this for a while, put it on a timer that will go out after dawn. I get up early fill in the trap hole and go back to bed!! otherwise you have to contend with the birds!!! that's another story.
You really must use MV in a garden (actually fullstop, its the wavelength of light that attracts the moths et al to the trap, black bulbs have a 70-80% catch rate it doesn't attract all spp, the same with actinic etc, MV are the way to go!!) the reason i say this is, experience again, gardens have hedges, walls, fences etc which restrict the light therefore you need a very bright light, i have found, that lights upwards to the sky. In the open countryside the light travels so much further, I put up baffles of plywood to shield my neighbours upstairs windows, you can see the shadow and know where to place the baffle to cast the shadow!!
To combat the weather i place a pyrex glass shallow round baking tray type thing which sits upside down over my bulb to stop water hitting the bulb, (expensive but chepaer in the long run than MV bulbs, heat resistant and wont break easily) my home made trap has veins in an x shape looking from above to direct in the moths, before i fitted this the moths would bounce off the bulbs into the undergrowth and stay there hiding from the light, so it's worth looking around the trap in the morning amongst all foliage for the moths after trapping. The very expensive robinson trap has a weather shield i believe too.
Also plant as many wildlife friendly spp as possible, im sure you do, uncut grass areas, you know the drill im sure
Finally my advice would be to not trap too often from my experiences at a couple sites i know people trap every night and numbers have crashed.
I hope my experiences help you.
