i dunno about neem oil. you should replace the top inch or two of soil from the pots, its got the eggs in. i used nicotine solution made from soaking some nicorette inhalator cartridges in a pint of warm soapy water - i used 6 which was about 60mg - thats about a pack of cigarettes. i then sprayed every three/four days for a couple of weeks. the idea is to stop em breeding cos they don't live long and its the young uns that do most damage to the plant.