It is evident from the abstract that there has been a wrong usage of word. It was not actually bio-'degradation', but bio-'remediation'.
Interpreting from the abstract, they have synthesized AgNPs with biomolecules as the capping agents. These capping agents with adhesive functional groups can agglomerate with the pesticides in the water and accelerate their sedimentation rate. The pesticides get settled along with the bio-molecule coated AgNPs and the water is free of pesticide contamination.
However, this is possible in the lab scale. On the field, it is not feasible to prepare such a huge quantity of NPs.