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Did you know ash trees can get a rust infection at all? I didn’t, but I was doing some head-scratching at a client’s grove of ash trees that’ve been treated since the ash-bomb went off, here at ground zero in the Detroit area. He’s said in the last 10-ish years he’s had a decent amount of late spring, early summer leaf drop. The fallen leaves have a peculiar ‘kink’ in their leaves. I’d brushed it off a few times as wet-spring foliar shenanigans like anthracnose or something common like that. It never seemed to defoliate too severely, and the trees carried on through their seasons unbothered. To flex a little, the above photo I took was the first leaf I looked at. Having seen some of the less common rusts in my area before like buckthorn rust and spruce cushion rust, the little spent pustules on the underside of this ash leaf immediately screamed ‘rust’ to me. A fun little rabbit-hole for me to read about: Puccinia fraxinata. Like all rusts, it requires two separate species to complete its life cycle. In the case of ash rust, its alternate host is a type of shoreline marshgrass or cord grass. Which totally aligns with this ash grove’s location on Grosse Ile, an island in the Detroit River. In places where these marshgrasses and ash trees coexist, the ash rust can appear. Where they don’t coexist, you won’t see the ash trees affected by this disease. Not a huge concern for their wellbeing, a minor nuisance. A nice little discovery amidst the fatigue of summer. Something interesting, something encouraging.
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