Plant pest or biological control

[Michael Gochfeld]

There is clearly a distinction between a plant pest (presumably 
something that attacks desirable plants) and a biologic control (the 
same kind of creature attacking an undesirable plant).  Since Milkweeds 
are desirable in butterfly gardens but not on lawns, where does that 
leave the Monarch.  But are there any places where Monarchs are 
sufficiently numerous to actually impact a milkweed clone  (or for that 
matter a single milkweed plant)----not in my New Jersey yard at least. 

M. Gochfeld