Resistant Weeds

Glyphosate is the most widely used herbicide in the United States. Glyphosate, or trade name Round up, was marketed in 1973 by Monsanto. 1996, Monsanto started genetically engineering crops to be resistant to the popular herbicide, which were called Roundup Ready crops (RR). This allowed farmers to apply glyphosate as a post emergence herbicide against broadleaf and cereal weeds without affecting the crop. This was a significant breakthrough in the Agricultural Industry. Unfortunately several weed species started to become resistant to glyphosate, known as super weeds. This has become a problem because these weeds are developing into a nuisance.

The problem first started with the over use of glyphosate. Throughout the years farmers where only using one form of management to control their weed problems, which was spraying glyphosate. It’s cheap, easy to use, and effective. Even though the total number of glyphosate resistant weed species is low, the number of species is increasing at an alarming rate. The important thing is that there is still time to reverse this problem. Yes there will still be weeds resistant to glyphosate, but with a good management practice, we can limit the selection of additional glyphosate resistant weeds, and extend the benefits of glyphosate and Roundup Ready crop technology.

Interning as a scout this last summer in Wheaton Minnesota, I learned a lot about resistant weeds. The one I had most problems with was Waterhemp. This nasty weed has infested most of the mid-west, covering millions of corn and soybean acres. Waterhemp like other weeds needs to be controlled with multiple herbicides mixed together. The consequences of spraying multiple herbicides increase cost and the chances of crop injury.

There are many things we can do to limit the number of resistant weeds. First of all we need to become educated. Understanding what rates to apply and how weeds work, makes it easier for control. There are also four types of control that farmers should practice when maintaining their farm, biological, mechanical, cultural, and chemical. Using all four of these methods will help reduce the amount of resistant’s on a field. Using a biological control is using predatory insects to control other insects that are feeding on the crop. This helps to limit insects to build a resistance to insecticides. Mechanical control is the use of farm equipment to till up fields. By digging up the fields in the spring this disrupts the growth of weeds and insects. Cultural is one of the more important controls. Having a crop rotation prevents disease, insects, and weeds. Last but not least, Chemical control. This is where the over use of glyphosate has come into effect. Farmers need to start practicing all these types of controls to not only limit the resistant on weeds, but the resistant on insects and diseases also.

As of now there are no new herbicide ready crops, but as a future Agronomist, I also have to take in consideration of these problems. It will someday be my job to make sure farmers are using the proper techniques to limit the resistance.