Wednesday, June 24, 2009

Are You Doing Everything Possible to Prevent Glyphosate And Other Herbicide Resistance In Your Weed Crop?

I thought this was a good read for everyone to be aware of. We all need to be concerned with the possibility of weeds becoming harder to control with herbicides. Good practices help overcome this.

Slowly they change. Ever so slowly. Year by year. Field by field. Weed by weed. Until suddenly your herbicide is nothing more than a warm summer mist that refreshes the weeds you wanted to kill. You’ve read magazine article about weeds becoming resistant to one or more herbicides, and now you have found it to be true on your farm. Short of sharpening Dad’s weed hook, what should be done?

Whether weed resistance is reality or a cold sweat nightmare for you, there is a variety of Best Management Practices (BMP) that can be adopted to delay the inevitable or totally avert the possibility of your farm being the talk of the neighborhood. Those BMP’s were identified by ag economists George Frisvold of the University of Arizona, Terrance Hurley of the University of Minnesota, and Paul Mitchell of the University of Wisconsin, who looked at corn, soybean, and cotton production practices that might provide a key to successful weed control. Their research involved a survey of 1,205 producers, who used a total of 10 different weed control practices.

Those practices were:
1. Scouting fields before herbicide applications
2. Scouting fields after herbicide applications
3. Start with a clean field, using either a burndown herbicide application or tillage
4. Controlling weeds early when they are relatively small
5. Controlling weed escapes and preventing weeds from setting seeds
6. Cleaning equipment before moving from field to field to minimize spread of weed seed
7. Using new commercial seed as free from weed seed as possible
8. Using multiple herbicides with different modes of action
9. Using tillage to supplement herbicide applications
10. Using the recommended application rate from the herbicide label

This list should be nothing new to most farmers, who have used most or all of the practices at various times. The critical issue is the fact that over 80% of corn and cotton acres and over 90% of soybean acres are planted to varieties that are resistant to glyphosate, and the evolution of weeds that are also resistant to glyphosate are threatening the sustainability of the transgenic technology. Farmers are urged to adopt a variety of practices to prevent resistance, but what is really happening?

To determine common practices, four hundred growers of each of the three commodities were surveyed, and questions were asked of those with more than 250 acres of the specific crop. The researchers found that 6 of the BMP’s were always practiced by at least 71% of farmers, but three were never practiced by a significant number of farmers. Those three were 1) cleaning equipment between fields, 2) rotating herbicide mode of action, and 3) using supplemental tillage. It should be noted that 49% of corn growers used multiple herbicides with different modes of action either often or always.

At least 90% of producers adopted five or more of the various practices. The economists also found that the number of BMP’s that were adopted:
• increased with a grower’s level of education
• increased for growers with expected yields greater than the county average yield
• was lower in counties with more variable yields
• was lower in crop reporting districts reporting more resistance problems.

The economists suggest, “These results suggest that yield risk is an important factor discouraging BMP adoption and that there may be some form of “good manager” effect at work, where growers with higher yields (or at least higher expected yields) than their neighbors tend to adopt more BMPs more frequently.”

The growth in the number of weed species and population groups that are becoming resistant to one or more herbicides is a function of the weed control practices that are used by corn, soybean, and cotton farmers who plant 80% to 90% of their crops with varieties that are glyphosate resistant. However, among 10 clearly defined weed management practices, six of them have been thoroughly adopted by more than 70% of farmers, yet three of the practices have very minimal rates of adoption. Those with lower rates of adoption could be promoted by educators to increase the number of practices that are used to slow the growing weed resistance to various herbicides.
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