Napalm works on slender spikerush - sometimes. Otherwise, it is one of the toughest aquatic plant species I've ever encountered - and extremely difficult to control.
I've had limited success with tank-mix treatments of 2,4-D and carfentrazone - but not consistently enough to encourage their use due to the tricky application technique.
I think slender spikerush enjoys dining on the standard aquatic herbicides for dessert (diquat, endothall, fluridone, copper).
This is one of those situations where a grapple on a long rope, combined with a lot of sweat, might be the best recipe.
PS: I haven't yet tried CLIPPER or CLEARCAST on slender spikerush. Based on past experiences with other products, I'm not overly optimistic; but who knows.....
