Yellow Jackets On Our Linden Trees - October 2020

 For the past two years, I've noticed that some sort of bee¹ has been finding a home on our espalier'd Linden trees.  There has been A LOT of them.  Swarming around the tree, climbing on the leaves, etc.  I If you look closely at the photo, you can see some of them.  Each tree has dozens of them.

I figured that they had a nest close or something.  But, I wanted to find out more.  First, I wanted to figure out what they were.  This handy chart from Rescue.com shows difference between wasps and yellow jackets.  Based on that, I'm pretty sure these are Yellow Jackets.  They're short and fat. 

So, I went out onto the Web to try to figure out why our Lindens are covered in these things.  And, sure enough, there are a series of posts on Extension.org.  Including this one that was answered by Robert Cox from CSU that tells me that the Yellow Jackets aren't there because they love the Linden. They're there because the tree has aphids is what he suspects.

Yellowjacket wasps are attracted to sticky-sugary "honeydew" excreted by aphids on the linden leaves. Aphids are very common on linden tree leaves. Look to see if any linden leaves look shiny wet and sticky; these have had aphid honeydew dripped onto them by aphids on leaves above.

Now, that makes sense.  When I look at some of the leaves of the tree, they are tattered.  Eaten through like lace.  

Aphids it seems.  We're this/close to a hard frost in our zone this year, so I'm thinking that the problem will go away naturally.  But, now I know I have to try to stay on top of them next year. Off I go to read up on the Linden aphid, Eucallipterus tiliae.

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^{1. [I say "bee" because that's what I call all flying, stinging, yellow and black insects, generally.]↩}