Cyperinus rotundus and Parthenium are types of :

Option 1 -> Diseases are abnormal conditions affecting organisms, not plant species themselves.

Option 2 -> Pathogens are disease-causing microorganisms like bacteria or fungi, not these plant species.

Option 3 -> Both Cyperus rotundus (purple nutsedge) and Parthenium (carrot grass) are invasive weeds that compete with crops.

Option 4 -> Pesticides are chemicals used to control pests, not unwanted plants themselves.

Hence, Option 3: Weeds -> Cyperus rotundus and Parthenium hysterophorus are both notorious invasive weeds that reduce agricultural productivity by competing with crops for nutrients, water, and sunlight -> correct