I had a severe case of scale on my orange tree. Once I understood the relationship between the ants and the scale, I went on a mission to kill the ants. I used a product called Green Light Many Purpose Powder. You use a very small amount. I'm an organic gardener, but I don't think it is something I can accomplish 100% of the time.

Here is a link with directions for making an ant trap using boric acid and sugar dissolved in water.

ant trap

Don't use the Tanglefoot directly on the tree bark, it can damage it. Best to tape a strip of heavy paper (tape only on the paper) around the trunk and then spread the Tanglefoot on that. It works well to keep the ants off as long as you make sure none of the branches are touching somewhere else like the ground or a fence where the ants could bypass the Tanglefoot to get onto the tree.

Neem oil or hort. oil like the posters above said works well on the scale. Don't cut off too many leaves if the tree is small, it needs them.

And I second CaptainJack's Dead Bug Brew. It's an Organic pesticide that works really well. The main ingredient is Spinosad.

The boric acid bait does a good job too.

Use the garden sprayer set to "jet"...blasts off most of the scale to give relief to the plant. The only way to totally get rid of ants is to cut off their food supply. Tanglefoot,Petroleum Jelly...like that. Doing both should be hard on the ants.

My experience with Tanglefoot - and the like - is that the ants just built a bridge across it. I imagine they'll do the same to Petroleum Jelly, but I will give it a try. I will try the 'jet set' spray too.

And, thank you to everyone for your ideas. I'm trying not to spray anything since the tree is full of buds and I don't want to do anything that would harm even one bee. Smear - and squish - I will try.

If you spray the Spinosad (Cap.Jacks) in the late evening when the bees go home, it will be dry by morning. An insect has to ingest part of the leaf for the Spinosad to work. The bees won't do that and it does no damage to then to walk on it when dry. It's a really safe spray for the bees and environment.

Spinosad is good, unfortunately it does work on cotton cushiony scale.

I have fought with all kinds of pests on my citrus trees. This year I bought a systemic.

Tim, you plan to use a systemic, do you plan to eat the fruit?

The systemic will be long gone before it fruits.

keep in mind nurseries use a systemic.

Thanks Tim

I had some powdered Diatomaceous Earth and I coated the ground around the base of the tree and so far haven't seen any ants or new scale on the tree. I seem to remember reading that the stuff gets in their joints and they can't walk and die. I'll keep you all posted on this non-poisonous experiment.