The winter frost isn't the only thing affecting our nation's crops, according to the Purdue University Weed Science team. The team is working hard to educate food growers on a major culprit: herbicide-resistant weeds to be exact. Food growers across the country are finding it increasingly difficult to kill "super weeds" as they become resistant to the most popular herbicides. After years of constant exposure to these herbicides, certain invasive plants have also developed a resistance, leading farmers to use more of the chemical. In some cases, the weeds have grown completely tolerant to these chemicals, allowing them to grow as high as eight feet tall.