Easiest and cheapest way to get rid of aphids on my lemon tree?

Wow, I am not that far out of LA but have been lucky enough to not have aphids on my citrus and I do not use any chemicals either. How big is your tree?

I would find the ant sources and start there - flour alone will suffocate them.

To treat the aphids you can flour those too, though I was not as successful with that method on my roses. If you are willing to use a bit of Dawn blue original, mix with water and if you have a pump sprayer use that.

I have had the most success treating at dusk, letting sit over night then a good wash with the hose at first light in the morning.

Hope this helps at least a little!

Spray the tree down with horticultral soap.With that purchase a systemic organic fruit tree granular treatment

Seems like you need to get rid of the ants. Down here we feed them dry grits it works. There's also a product called diatomaceous earth (this is a natural product) that will kill the ants. Just follow the package directions . I'm growing lemons from seeds and they're growing so fast! I haven't seen any aphids yet but then I haven't invited them to my tea party either. Good luck. TeresaC

Mix red pepper flakes with water and shake and spray. Just wash your fruit before you eat it.

We use soapy water to spray on plants to eliminate aphids. This should be safe for your fruit