Consider the following:

1. Birds — Birds can act as mechanical carriers of plant pathogens and also spread seeds of parasitic plants/weeds. Correct.

2. Dust blowing — Dust particles can carry fungal spores, bacteria and other inoculum from infected fields to healthy plants. Correct.

3. Rain — Rain splash is a major agent for spreading many plant diseases, especially fungal and bacterial infections. Correct.

4. Wind blowing — Wind widely disperses spores, pollen-borne pathogens and other disease-causing agents over short and long distances. Correct.

Hence, all four can spread plant diseases.