Dear Jerico Echo ,

Some metal nanoparticles can be employed as nano-pesticides, and citric extracts can be used to prepare some of those nanoparticles following green synthesis routes. You can check this article and references therein:

Article Green Synthesis of Gold and Silver Nanoparticles from Plant ...

Citrus plant extracts contain vit c or Ascorbic acid, flavonoids, limonoids and polyphenols which are antioxidants which are bioactive compounds and are useful in reducing metal nanoparticles like Ag & Au from their salts. It can be of use as pesticide.

This is a good researchable topic, and good studies must be taken up on these.

@ Jose-Miguel Garcia-Martin's

@ Shrikaant Kulkarni

useful comments.