| Weed Resistance (1 Feb 2006) |
 Chart courtesy of Ian Heap, www.weedscience.org |
| The chart above shows the annual number of weed species that are
developing resistance in response to various herbicide modes of
action. While it is notable that the glycine herbicides
(Roundup etc) have the lowest rate of resistance development of the
classes listed, we cannot take that as an excuse to throw away
caution. The introduction of many Glyphosate tolerant corn
lines this year will compound concern by being included with a
rotation of glyphosate tolerant soybeans in many fields. In
fields where glyphosate is used two or more years in a row, the
opportunities for resistance to develop will increase exponentially. Since glyphosate is an extremely useful and inexpensive weed control tool we encourage growers to use good stewardship to forestall resistance development. Those practices may include the following. 1. Do not plant glyphosate tolerant crops in the same field in consecutive years. 2. Use at least a half rate of a pre emergence herbicide ahead of glyphosate. 3. When using only glyphosate use the full labeled rate. 4. Scout your fields. If you note any weeds that you think should have been killed but were not, make a note of it and develop a strategy to eliminate them as best as you can. (before they take over your fields). 5. Consider tank mixing herbicides where appropriate.
Dr. D Pike
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