Agents that spread plant diseases — UPSC Prelims PYQ 2018

Consider the following:

Birds: Birds can carry disease-causing pathogens on their feathers, feet, or beaks as they move from one plant to another. This can result in the transmission of pathogens to healthy plants.
Dust blowing: Wind-blown dust can carry spores of fungi or bacteria, spreading diseases across fields or even long distances.
Rain: Raindrops can splash pathogens from infected plant surfaces to healthy ones, facilitating the spread of disease, especially for diseases like blights and rusts.
Wind blowing: Wind can carry fungal spores and other pathogens over great distances, aiding in the transmission of airborne plant diseases.

Plant diseases are commonly spread through natural carriers such as birds, wind, rain, and dust. Since UPSC is asking from a broader perspective, eliminating any option becomes difficult because each factor can potentially carry pathogens. When all given agents are plausible spreaders, it is safer to go with all options rather than trying to negate one.