Need help with my myer lemon tree!

I purchased a myer lemon tree in July 2013, it is an area that gets a lot of light and temperature stays stable. Recently we noticed black dots on the bottom of the leaves and on top of the leaves are brown bumps that look like little clumps of dirt. Some of these brown bumps are on some of the branches now too. The tree has also been dropping sap for about 3 months now, which I am not sure is normal or not. I am really hoping we can save my tree, it's my first tree and I have been loving it and looking forward to seeing new lemons.
Please help!

 

Welcome. The tree has an infestation of scale. The sticky substance is honeydew that has been excreted by the pest.

 

So how do I get rid of it?

 

Insecticidal soap is one option but it has to be applied multiple times for it to be effective. The adult scale, the ones that you can see, must be physically removed before applying the spray. An old, soft toothbrush dipped in the soap solution can be used to gently remove them. Spray all plant surfaces, stems included, making sure to cover both sides of the leaves. Repeat after 10 days or so until there is no sign of the pest. Remember that sticky honeydew is the first telltale sign of an infestation, even before you see any adult scale.

Horticultural oil is another product that can be used but one which I have not used before. It is reputedly more effective than insecticidal soap.

 

Thank you so much for your help! Still a little nervous about losing my lemon tree. Hopefully I can find the soap or oil where I live and get this taken care of ASAP.
Do you know what causes scale? And is there ways of preventing it in the future?

 

If your other plants are not infected then it's likely the scale got onto the tree while it was outdoors at sometime. I believe only the males are mobile so once eradicated you'll likely not have any more problems if the tree stays indoors.

 

Insecticidal soap is easy to get. Try any big box store. Just watch what the directions say about dilution -- if it's meant to be diluted don't use it full strength!

I have used Q tips to get scale off leaves and stems as I find them gentler than a toothbrush. Gentle is good, but if you need to rub a LITTLE to get the scales unstuck, you can.
keke