Does herpes causes scabs on the scalp.

Not as only symptom. Scabs alone, without prior blisters, sores, etc, almost certainly are not due to herpes of any type. Of the 3 main herpes infections, herpes zoster (shingles) would be the most likely and would start with painful lesions then scabs, on only one side of the scalp. Herpes simplex virus types 1 or 2, the causes of oral and most genital herpes respectively, would almost never involve the scalp.