Translation of "insidiously" into French

It sets in insidiously, often without any significant associated weakness.

Elle s’installe insidieusement, souvent sans que la faiblesse associée soit importante.

By insidiously introducing, under the agricultural guideline, expenses until now non-compulsory, you cloud the distinction between the two types of expenditure.

Ainsi, en introduisant sournoisement, sous la ligne directrice agricole, des dépenses jusque là non obligatoires, on brouille la distinction entre les deux types de dépenses.