With that much rain and no fungicide, I'd expect Iceberg to have problems with black spot and cercospora spot.

Try looking at the newer Kordes landscape roses. They may have superior disease resistance for your rainy area. Northland Rosarium (Spokane), Chamblees, & Palatine sell them--see if there is some you like, then ask about those cultivars and see if anyone in your area has success with them. 'Iceberg' is stellar here, but we limp along on 12" a year (when we are lucky!), not 60".

Thank you. I did go to those sites, though not much info is provided on disease resistance. I do have two climbing Icebergs in another spot, only (now) second season. I wasn't terribly impressed with the first season, so I guess I should observe and then decide. Our climate is odd: huge rain, as mentioned, but reliably bone dry from July, Aug, Sept-- sometimes called a modified mediterranean climate.

Michael is right, Iceberg does suffer from what I think is cercospora spot here. Actually, between the pink freckling they show from botrytis blight in rainy conditions and thrip damage in the summer, white roses don't usually look the best for me. (I don't spray, though, if you do you may have better results.)

I've written here before that my exception for a good white rose has been Mrs Herbert Stevens--fragrant, disease free here, but I see her as more of a specimen rose than making a nice hedge.

I don't know how tall of a hedge you were thinking? My first thought was rosa rugosa alba, then you'll enjoy yellow fall foliage and big hips, too....

Or maybe some albas...Alba maxima? Alba semi plena? Madame Plantier? I don't have experience with the albas, but have seen beautiful rugosa albas around the neighborhood.

I think nice year round structure, beautiful disease free foliage is especially important for a hedge, moreso than the form/beauty of individual flowers.

Here is a link that might be useful: Rugosa Alba