For me neem concentrate in higher ratios was worthless.
I don't know what it does but it did make my plants look greener after application but the mites turned them yellow eventually.
I started spraying neem at first every other day as suggested on the instructions.
Then 1 time a week...
Spraying my plants down with water worked as well.
I think I tried everything in the book to kill the spider and broad mites.
Birds were dropping out of the sky if they flew over my pots.
I tried everything over 4 seasons to get rid of them.
Sufur seems to be the only thing that works if you use it right.
Find a fugacide that is sulfur and oil.3in1 was what worked but Sulfur works best=so far.
http://www.natureslawn.com/liquid-sulfur.php
I spray my plants down with my pump sprayer.
I don't measure the sulfur,I just add a couple shots to my 2 gal. sprayer.Maybe 4 oz. +/-.
Shipping sucks,costs more than the ga.
Mites are worse though.
I used to use this stuff but can't find it anymore.
http://www.amazon.com/Soil-Sul-Liquid-Sulfur-Gallon/dp/B000FPX25K
When I order it they say it's out of stock...
Beth at Peppermania told me about it years ago.