What to Watch for This Month

Welcome to September. Short and golden blaze the final days of summer. The atmosphere stirs. Chickadees, nuthatches, creepers and kinglets gather into acrobatic groups. Blackberries are again enemies.

Most flowers are long gone, but if you are lucky, you may witness something I first saw last fall. Climbing through a clearcut at dusk, a little jumpy thanks to a deer, I sensed a ghostly presence in the wood line before me, like a girl in a white dress in a horror movie. It was a dogwood tree in full bloom. They are known to do this, bloom a second time in fall. No one knows why.

On September 26, Jupiter is in opposition, meaning it is directly opposite the sun, fully illuminated and as close to Earth as it gets. Look for it in the constellation Pisces. A telescope should reveal its clouds. Binoculars might pick up its four largest moons.

Of course, the great event this month will be the rain that breaks summer’s drought. I think this should be a yearly celebration on par with the first hot spring weekend, with everyone out and about, drinking coffee together in parking lots, splashing through parks, letting our skin luxuriate in the long-lost free dampness. It’s just as grand as that first heady dose of sunshine.

Then again, I’m a mossback. Not everyone perks up in the rain like me.

Calling All Crawdads

Did you know that crayfish live on the Key Peninsula?

That’s still a thrill to me. They are not common, so when a friend of a friend texts photos of a crayfish crossing a quiet road, where a tiny creek goes through a culvert, I itch to get out there and see.

A single species is native to Washington. Called the signal crayfish for white patches like semaphores at the joints of its claws, it lives in lakes and streams with a preference for rocky bottoms. Two invasive species are present in Washington and could be on the Key Peninsula.

The signal crayfish grows slowly and can live almost a decade. In Europe it is an invasive species. Originally taken there to supplement native crayfish that had been decimated by a fungal plague, it instead spread the plague and outcompeted the natives. Sweden in particular has a commercial crayfish fishery (a crayfishery?) that has had to wrestle with our humble local crayfish.

It is strange when a species you know and love for being native is running amok in another part of the world, like Douglas fir in New Zealand. One result is that the signal crayfish is better studied in Europe than here at home.

I’d like to know: Where exactly are they? How do they get around? What streams and lakes do they prefer? Why? If you have tips or insights, I’m all ears at nature@keypennews.org.

Powdery Mildew on Bigleaf Maple

Have you noticed bigleaf maples with white powder dusting every leaf, giving them a look of leprosy in the late summer forest? This is powdery mildew, a fungus.

Powdery mildews feed on leaf tissue, and many of the over 800 described species are specific to their hosts. They reproduce fast, jump around a lot, and cause some of the most significant agricultural damage of any fungus, on crops from wheat to roses. They do not typically kill the hosts but nibble away at their productivity. Importantly for roses and other ornamental plants, they also look ugly as sin.

It can be prevalent on our native bigleaf maple. The “snowiest” maples I have seen this year are south of Longbranch. Is this a new phenomenon? Spreading? It is hard for researchers to tell. It is patchy and varies year to year and no one has tracked powdery mildew on bigleaf maple over decades, long enough to confirm or reject the feeling among many residents that the last five years have seen unprecedented infections.

Still, researchers at the University of Washington have unearthed some intriguing new knowledge. For the past decade attention has been paid to dieback in bigleaf maple. Much like the dieback in western redcedar, bigleaf maples seem to be experiencing higher than normal death rates across Western Washington. No smoking gun has been found — unlike in the annihilation of ash trees across the Eastern United States thanks to the emerald ash borer (which made its first appearance in the Pacific Northwest this summer) or the death of 90% of our Western white pines in the early 1900s due to the alien white pine blister rust. There seem to be correlations with hotter, drier summers and human development, but it is not yet an epidemic. Far more data is needed.

The UW researchers wondered if there might be a correlation with recent outbreaks of powdery mildew. Conventional wisdom says that powdery mildew on shade trees is not worth worrying about, as it disappears when leaves drop in fall and may or may not return the next year. Conducting experiments in the summer of 2018, when 518 of the 519 bigleaf maples on UW’s Seattle campus had severe infections, the researchers used genetic sequencing to identify the exact species of powdery mildew and trace it to a likely European origin — though it is not exactly new here, as they found a museum specimen from British Columbia in the 1930s that was infected with it.

In greenhouse tests, bigleaf maple was the most susceptible maple species. But the powdery mildew did not decrease its photosynthesis or growth.

So, who knows? It’s good research. It demands more, offering a portrait of a genetically variable, continent-hopping fungus with an unclear past and, honestly, an unclear present and future. Has a more virulent strain recently emerged or been introduced? Is this an epidemic in the making? Do bigleaf maples care? 

The great thing is that the data most needed — patterns of dieback, hotspots of powdery mildew, yearly and decadal changes — can be provided by anyone who cares to pay attention.

Contact me at nature@keypennews.org if you’d like to trade ideas on how.