there is enough studies to support that the best time to spray fungicide is at 90% tassel.   with that being said, here's the problem, you don't want to use any adjuvants from v5 to brown silk.  we have had enough trials and oops locally to support this.  with that in mind you'd be quite a salesman to get a plane guy to spray the gals per acre that they spray without adjuvants, helicopter guys will run alittle more gpa but i'm not sure it's enough.

so you're kinda limited to highboys to get the gpa that is needed to get the fungicide applied good enough without adjuvants.   another factor in the reluctance to leave adjuvants out is that I suspect that they are a fairly high margin product.

we have been spraying at 90% tassel for several years with a hagie at 15-20 gal acre and have seen good response.  but to be fair we don't spray all of our corn fields.

the closer you you get to brown silk the less of response there is.