I will like someone to advice me on how to get a private funding opportunities to run a PHD course in the study of insects pest of field crops.

Good question.

Basically, what you need to do is ask the question, then wait a little while....if no-one knows, ask the same question again.

The Scottish Crop Research Insititue might, they sometimes have PhDs. There is nothing up at the momenet though. Here is the website anyway:
http://www.scri.sari.ac.uk/research/index.htm
http://www.scri.sari.ac.uk/HR/Jobs.htm

Also forgot theses guys:
http://www.rothamsted.bbsrc.ac.uk/careers/vacancies/Studentships.html

They sometimes have PhDs for international students.