what the local laws were on responsibility and liability are with the farmer working in the gov't R?W. I was surprised to learn in my last visit to England that the hedges that are planted to close to the roads to prevent erosion by farmers are considered by the gov't there to be the responsibility of the farmer. That means when the county calls the English farmer up to trim his roadside hedges, he only has 30 days or will be fined, and so on. The antithesis of your statement that the Iowa law doesn't allow farmers to mow the R/W until June whatever, would seem to infer the farmer has an obligation to do so, but is limited for environmental reasons. In Florida, many cases were lost for people hydroplaning off the roadway because of a failure to mow which held water up on the road and thereby didn't meet the Federal requirements. I participated in gathering and analyzing data on highway maintenance issues which led to development and approval of Florida's standards. All states have to adopt either the Federal Standards or individual State Standards that are approved by the Feds or they don't get back any of the Federal Tax money they collect from the State. I know the average statewide annual rainfall in Iowa is about 34 inches which is about half Florida's but its really not about how much rain hits the pavement but rather the rate of precipitation versus cross slope of the roadway, how many lanes, the posted speed and contributing area.
I'm for saving the butterflies but I would think the approach Iowa has taken must require an elaborate management scheme. In Florida the best thing they could do is mow more frequently to discourage them from being next to the roadway. More butterflies are killed by vehicles than anything I know. But it is an interesting attempt even though I wouldn't think it has merit except when located along low speed facilities.