How to control or prevent Aphlds (oily dots under leaves and fungal disease in lime and lemon plants.

We have recently received an inquiry from a fellow farmer in India regarding the fungal disease in lime and lemon plants. The inquiry goes as follows:

"Please provide practical know-how on -How to effectively control/prevent aphids, 'tilla'(local name for oily dots under leaves) and fungal disease on lime and lemon plants ( lime raised with tissue culture I believe), without using commonplace insecticides and fungicides."