Needle loss, color change, on evergreen trees

November 17, 2010

As usually happens in the fall, I’ve been getting calls from people concerned about the yellowing or dropping of needles from their evergreen trees (another call this morning). In most cases this is normal – the older needles drop off in fall. The tree doesn’t need that full canopy for photosynthesis in the winter, and the reduction in surface area could benefit the tree by decreasing water loss and lessening potential for storm damage. It seems like the phenomenon is more apparent than usual this year; Penn State has been getting a lot of calls too. Here’s the news alert they recently sent out: My evergreen is turning brown! But there ARE some needle diseases that might deserve a closer look. In particular, I’m going to re-examine some of the Colorado blue spruces I’ve seen this fall to make sure that they’re not infected with Weirii rust. That’s a new disease in our area, and it has the potential to be more problematic than some of the other fungus diseases because it doesn’t require an alternate host species for reproduction. It’s hard to identify now, but in the spring, the “rusty” looking spores will give it away! (I’ll show you some pictures tomorrow)

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