A population of common waterhemp has developed resistance to postemergent application of HPPD-inhibiting herbicides(e.g., Callisto, Laudis and Impact). This resistance occurred in a seed-cornproduction system where these HPPD-inhibiting herbicides were repeatedly used over the last five years.

The good news is that the resistance was identified at only one location. The bad news is that this can easily happen in other fields, as HPPD-inhibiting herbicides are commonly used in Nebraska and the Midwest.

Resistance is a phenomenon that usually results from the repeated use of the same chemical. This can occur with herbicides and many other pesticides. In addition to the weeds already found in Nebraska to be resistant to glyphosate – marestail, giant ragweed, kochia – a new type of weed resistance has developed in the state.

Repeated use of the same herbicide can easily result in the evolution of weed resistance, regardless of the type of herbicide used. We have forgotten the time of atrazine and ALS resistance (15-30 years ago) and with the recent developments of glyphosate resistance, Mother Nature is reminding us that weeds can develop resistance to any type of chemical we develop.