Lime tree infected

[Gardenhelp]

Hi,

My lime tree has been infected. There are big black insects on the tree and the leaves are curled. I used Yates Natures Way  Citrus spray but  I am unable to control the insects. Please let me know if I could do anything to save this tree or do I need to have up rooted? My neighbours have very tall Lily Pilly trees on their side and it could be that there may  not be  much sunlight for the citrus plant? 

Thank you

Regards

Garden help