As soon as I saw the title of the post I said to myself "aphids", and where there are aphids you usually find plenty of ants... I'm happy to say we've been spared this year, we have a birch in the front sideyard and it has had severe haircuts over the past couple of years and is finally coming out in September, it has started to lft the driveway. That birch was our major source of aphids, it would blacken the concrete driveway and make the car's paint sticky and then some, it was a bugger to remove. I believe you'll find aphids predominantly in deciduous trees and if that's the predominant type around your yard, there's your answer.

Pieter

Yes, I knew when I saw it. It's Aphids. I have aphids in my pecan trees. I've tolerated it for a long time. I have to clean up the "mold" every fall. Everything is sticky. I have lots of ants, too. I think it's time for them to move. I'm going to change the immediate environment. I can't spray the tree. It's too big. So, I'm going after the ants. They are symbiotic. If the aphids have no protector, might they go away? (On the other hand, what will take it's place?)

bk

Don't know if it's still available but you may want to look for a product called Tanglefoot. Ants will not make it across a band of TF circling the main trunk of the tree.

Big trees are difficult. But aphids are easily defeated with water. There is a product called a Bug Blaster. You can attach it to the end of a wand attached to a hose, and adjust the spray to blow off the aphids with a very fine firm spray. Once they/their eggs hit the ground they are rendered harmless. I use this thing (little attachment) on my fine leaved jap. maples and their tender foliage in spring here and it works. Just plain old water. About every 3 days, 3 times does it for me.

-Babka

Ammonia (10% to 25% dilution of household strength ammonia) will kill aphids and ants and fertilize with nitrogen as well. I also thought of horticultural soap or plain old Ivory liquid in water. Either ammonia solution, hort. soap or Ivory will also help clean off the poo goo.

Jon

Great information

arcy, hard to argue with your methods when you have such gorgeous results.

Last year I over-pruned a stand of young sassafras trees that shaded one of my earlier hosta beds. They got sickly and rained that black goo all over that bed. It still hasn't worn off the hosta labels. Glad to know what it was.

Kathy

zkathy, if you took a sponge out with you I bet the markers would clean easily. This gunk is all over--patio furniture, decking,cars..it comes off very easily if you WIPE it. Rinsing doesn't seem to budge it but wiping does. I am not sure why I had less luck on living things i.e. leaves...but for all the work it looks like it would be to remove from everywhere else..it is not.