You may need to resort to a one-time soil application of Imidicloprid to knock them out, dirtslinger. They will spread to the rest of your plants if you can't get rid of them, and then you're really going to have your hands full. Here's some information on how to control scale.

Patty S.

Here is a link that might be useful: UC IPM: Scale Maangement Guidelines

Also make sure you are controlling ants. Many people skip this step and it is a mistake especially when you're likely overwintering the pots indoors. The scale infestation flares up when the pots are indoors and the ants take notice and will defend the scale and farm them all winter. When you take the pots outside for the growing season the ants will fight off the natural predators. Often the ants setup shop in pots as well.

Use boric acid baits (Terro makes one) - if you have quite a few pots you can buy your own bait stations (or re-use disposable ones you buy) and make your own bait with boric acid + sugar syrup.

Some of the disposable bait stations need to be tipped forward to refill from a reservoir in the back - make sure you do that regularly and keep the station full until the ants stop eating it.

Also remember that if you use the imidacloprid you need to water very carefully to prevent leeching for about a week for it to be effective and depending on the size of your tree it can take some time for it to be effective. Also be sure to pinch any flower buds for 1-2 flushes to try to protect the bees. For someone who overwinters indoors the best time to use imidacloprid is right before you bring them indoors - it reduces the risk to the bees as they will likely be in for 4-5 months and that's when you need the most protection from scale anyway - there will be few if any natural predators.

Very good point, redshirtcat. I meant to mention that, but forgot. The boric acid bait traps work very well. Place several at the base of the tree. Also, it helps to put a barrier up on the trunk if your tree is big enough. You can wrap the trunk with trunk wrap or use a strip of landscaping cloth. Then, apply Tanglefoot to the wrap/fabric.

Patty S.

Be sure to research the timing of any systemic pesticide application so that you aren't causing harm to pollinators AND so that there is less chance that you will be harvesting fruit laced with the chemical. Make sure that if you do go with such a pesticide, that it is labeled not only for container use, but for the indoors.

It is also helpful to know what species of scale you have. The systemic (Imidacloprid) mentioned is not effective on all kinds.

So, do you have any pictures?

Rhizo is correct on this, redshirtcat. Read through the article I provided, as it does state which types of scale are not treated with Imidicloprid, and I would only use this after blossoms are done, so as to reduce the impact on pollinators.

Patty S.