i've grown in las vegas and tucson outdoors and have never had a mold problem of any kind and some of the strains produced those extra fat and thick beercan buds too. just keep the sprinkler off the tops when you water up to 3x's/day in the summer and they should be fine. it's just too damn dry outside and the wind will also help keep them dry. i always water by flood irrigation anyway (3x's/day during the heat of summer) and once every week or so give them a light shower after sunset to wash off the dust.

good luck fellow desert rat...