No, crane flies don't affect Irish moss, which isn't really a moss at all :-) In fact, unless you had a major invasion, crane flies don't really cause much of a problem with lawns here in the PNW. Since the grubs that do the damage like very moist conditions, just cutting back on the summer watering/allowing the lawn to go dormant (as it is naturally inclined to do) is usually all the control that is required.

Irish moss, Sagina subulata, needs moist soils but very good drainage. With the amount of rainfall we have received this winter and spring, I would check to make sure drainage is good and the soil not waterlogged. In our climate, full sun is fine but in hotter locations, some afternoon shade is desirable. Otherwise, Irish moss is not prone to much in the way of insect or disease problems.........most issues will be cultural in nature.