Wednesday, May 4, 2016

The Galling Occurrence of a Fun Guy

Spring rains have brought on the "blooming" of the cedar-apple rust galls.  I know I've previously described this fascinating disease, but since it is... well... fascinating, it bears repeating.  This gelatinous ball of orange horns adorning cedar branches -- and they are ALL OVER right now, as though they have been decorated for Christmas by a strange alien -- is one part of the life cycle of a fungus that affects both the cedars and apple trees.  Its lifecycle requires two hosts living in proximity (and by proximity, I mean within the few-mile radius of each other that spored can blow in the wind).

These orange protrusions, called telia, emerge from tight brown galls on cedar trees during spring rains.  Over the course of April and May(ish), they can swell and dry up many times as wet weather comes through.  When they do, the horns emit spores into the air.  These blow in the wind until they find their other host -- an apple or crabapple tree at the vulnerable point in their own lifecycle when they're flowering and leaves are new.  (Also hawthorns and quinces can be infected).  Soon, splotches of discoloration appear on the leaves, yellow, turning orange/rusty, then black as well.  Crabapples are very common around here, and hawthorns as well.  I've been looking for symptoms on them, but, notably, haven't found any.  While the infection spreads within hours, it takes about a week, I think, for the spots to appear, so I'll keep looking.  At any rate... In late summer, these rusty splotches release spores, which, born upon the winds, find... you guessed it!  Cedar trees!

When spores land on cedar trees, it takes much longer for symptoms to develop than it does on the apple.  At first it's a hard, small, brown gall.  In fact, the fungus overwinters this way.  The telia don't actually swell to their gelatinous, alien-like arms until their second year of cedar infection!  (And after that, they're done.)  Most of the time, what you'll see on cedars is just brown, woody protuberances that pretty well blend in.  Upon inspection, they do have little pock-like marks that are where the individual telia will come out.  

The cedar-apple rust fungus can be pretty devastating for apple crops, so it's generally viewed as a negative, but... come on, those crazy things are pretty cool looking, right? 

Another notable spring development -- oak trees (bur oak shown here) have tiny, translucent leaves... perfect, 1-inch miniature versions of their future selves...

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