V against n
The 'insure' group
These verbs are concerned with taking precautions against possible harm. The person or thing that is being protected is not explicitly mentioned. We include here the verb guard, which is used to indicate that someone avoids doing something or letting something happen.
While many insure against death, far fewer take precautions against long-term or permanent loss of income because of sickness.
In your part of the country it is exactly the right time to spray against the potato blight fungus.
In the case of guard, the preposition against is sometimes followed by an '-ing' clause.
ensure guard hedge insure protect spray
He warned the jury to guard against returning a tough verdict out of sympathy with relatives.