Source: University of Illinois
A waterhemp population in a central Illinois seed corn production field has been found resistant to several commercially available HPPD-inhibitor herbicides. Last year, the field contained waterhemp populations that were not controlled by foliar-applied HPPD-inhibitor herbicides.
Initial greenhouse experiments conducted at the University of Illinois confirmed anecdotal reports from the field. Plants grown from field-collected seed and treated with tembotrione, topramezone or mesotrione survived, whereas treated plants from two known sensitive populations (used for comparison) were completely controlled. Tank-mixing atrazine with each HPPD inhibitor improved control of the resistant population over that provided by each HPPD herbicide alone, but survival was still much greater than with the sensitive controls.