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Following the Path of Least Resistance in 2016

University of Minnesota Extension, Stearns County News
February 24, 2016        
Source:  Dan Martens, Extension Educator
University of Minnesota Extension
Stearns, Benton & Morrison Counties

Following the Path of Least Resistance in 2016
By Dan Martens, University of Minnesota Extension

FOLEY, Minn. (02/24/16) — One of the key themes at crop meetings this winter is managing resistance of pests to pest control products. For crops, pests primarily include weeds, insects, diseases, and rodents as in the case of pocket gophers. Resistance means that a herbicide, insecticide or fungicide that used to work well, isn’t working well anymore because the pest population has selectively adapted to survive the treatment.

At one meeting a speaker noted that “The most expensive pesticide application is the one that doesn’t work well.” Getting it as right as we can counts for a lot of reasons. This includes producing a good crop, the economics of making a living, and taking care of the natural resources we depend on.

Resistance is not new. Pursuit and atrazine are a couple of herbicides that were used widely years ago for the control of some important weeds, and fell out of favor because of weeds that became resistant to them. About the same time, glyphosate herbicide (originally known as Roundup) came on the scene as an herbicide that would kill a wide range of weeds – fairly easily and fairly economically. 

Now there are some troublesome weeds that have developed resistance to glyphosate; so farmers are going back to using more different kinds of products to control a variety of weeds. This is more expensive. Waterhemp, giant ragweed, and common ragweed are three that we see in our area. One of the primary keys to dealing with resistance issues, or to reduce the risk of developing resistance, is to rotate the use of products with different Sites of Action (SOA’s).

The SOA refers to the specific process in a plant that is interrupted by the product to kill it. Products are labeled with a number that represents the SOA. Glyphosate is SOA-9. It interrupts an enzyme that is the key to making a particular amino acid that the plant needs. Dicamba and 2,4-D are SOA-4, growth regulators. The choices get more limited based on whether the herbicide is safe for specific crops, and effective for specific weeds. Insecticides and fungicides are also labeled with an SOA number that gives farmers and farm advisors some help in selecting different products from crop to crop and year to year to minimize resistance issues. There are about 19 SOA’s for herbicides, and much less for insecticides and fungicides.

Other crop production practices are significant in managing pests such as crop rotations, tillage, cultivation, natural predators, biological controls, and following researched based thresholds for insect treatment decisions. All of this together is called “Integrated Pest Management” – thinking strategically based on observations in the field, understanding a variety of management practices, and making use of credible field and lab research, past experience…and a healthy dose of common sense.

National FFA Week – February 21-27 – Learning, Doing, Earning, Living, Serving.

Private Pesticide Applicator Renewal Workshops - Foley, Thursday, Feb. 25, 12:30 to 4 p.m. at Henry’s Catering.

Parlors or Robots Dairy Workshop – Pierz, Friday, Feb. 26, 10:30 to 3 p.m. at the Brickyard Bar, 214 Main Street South. Call Extension Educator Emily Wilmes at 320-255-6169 to help with meal count.

Nitrogen Smart Workshop –  8 half-day workshops in Minnesota, no registration fee, no meal. Consider products, timing, rates, placement that makes sense for your crops. Details can be found at Contact Brad Carlson,, 507-389-6745; or in Stearns, Benton and Morrison Counties – Dan Martens at 320-986-5077.  Nearby sites include:
Willmar, Thursday, March 3 at MinnWest Tech. Campus LSI Building Auditorium, 1 p.m. to 4 p.m.
St. Cloud, Friday, March 4 at the River’s Edge Convention Center, 9 a.m. to noon. 

Farm Business Succession and Estate Planning Workshop – St. Cloud Tech and Community College, Wednesday March 9th from 9:30 to 2:30. The workshop is free with an RSVP and lunch is provided. Contact Cindy Kantor at St. Cloud Tech to RSVP by March 4, 320-308-6641 or More information can be obtained from St. Cloud Farm Business Management Instructors Ken Thiesen 320-309-3293 or Jim Molenaar 320-309-3571.


Daniel Martens
Extension Educator, Ag Production Systems
(320) 968-5077
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