This example of how a seemingly well-designed herbicide program can be all wrong is very enlightening. I'm the first to admit I need some improvelemt in my weed control planning. Bob Hartzler gives an illustration of how a two-pass program doesn't really kill waterhemp like you'd think it should.
http://www.weeds.iastate.edu/mgmt/2012/resistsheet.pdf
Conclusions
Herbicides are valuable resources that need to be conserved since it has been more than 20 years since a new site of action has been discovered. Managing herbicides efficiently is the first step in reducing herbicide resistance problems, but this approach alone will fail in the long run. An increase in the use of cultural strategies that enhance the competitiveness of the crop with weeds and the wise use of mechanical practices will become increasingly important in the future.
