Its native here. Even if it was alternating, it would be hard to tell, because the years are either very dark and rainy or temperate and warm. And even then, it's not an abundant producer. Both pisocarp and gymnocarpa seem to gravitate more towards being a niche forest rose, where they can survive for long lengths in low-light, crowded situations, and repeated maulings by elk and similar. You often see them near native huckleberries, or in depressions with water where other short plants are less competitive for space. Every once in a while, you will find one in a ditch or edging toward a body of water.

They're great at surviving and letting animals spread their seed! Rather poor at anything ornamental.

They can get powdery mildew, depending on the scenario, but I have never seen downy on one. Which struck me as interesting, because the short native species (californica's kin) in california can be very prone to downy. As for blackspot, its hard to tell, because they're often in moisture dense areas, and its often dark, so it's hard to see where its bs, anthracnose, or cercospora, which tend to look alike in certain weather and unalike in other weather. I imagine their bs resistance is simply average, if I had to guess.

I don't see moss balls on them, like I do naturalized canina. I don't see raspberry cane pests or aphids on them, either. Not that they couldn't be targeted. I have just never seen it. I think it's because other hosts are better targets, like woodsii and himalayan blackberry.

edit: I forgot to add: They all rust. All of the natives from Oregon to B.C. rust. Gymnocarpa, Woodsii, Acicularis, Pisocarpa. All of them rust. Acicularis being the worst. They will put acicularis in Wal-Mart parking lots (don't ask me why... probably conservation rules), and you will see orange streaks where the rust tends to ball up in one section of the plant. It's amusing, but a little weird.