There is one reported attempt, and even there the evidence is dubious as there isnt any record of it actually being done - just considered. Further, if it was carried out, it didnt work in that circumstance.
but yeah, lets attribute all the indian deaths due to diseases, including influenza, typhus, and cholera to a couple smallpox blankets. LMAO!!!
Lets also just conveniently ignore the early american governments attempts to vaccinate indians from smallpox too (which largely proved successful in the early 1800s) so that we can distort history and claim genocide.