WSJM September 7, 2005 Herbicide resistant weeds
This is Al Gaus the Berrien County Extension Educator for fruit and ornamentals reporting from the MSU Extension office in Berrien County.
As many agricultural producers look over their fields, vineyards, and orchards, some are seeing some weeds that should have been controlled by their herbicide treatment. It is possible those weeds are herbicide resistant weeds. Steven Gower, of the Diagnostic Services lab at MSU indicates that there are several weed species that have developed resistance to popular herbicides used in Michigan. In fact, he states there are at least 15 weed biotypes resistant to one or more herbicides in the state. These herbicide-resistant weed species have been documented in field, vegetable, and fruit crops, as well as tree plantations and nurseries throughout Michigan.
Once growers identify and confirm a herbicide-resistant weed, they can then implement appropriate management strategies to prevent or limit weed seed spread. If you suspect resistance in any weed species and would like to confirm this, seedheads can be collected upon maturity and submitted to MSU Diagnostic Services for a herbicide resistance screen.
The next several weeks are perfect for collecting mature, viable weed seed. Select plants that were definitely sprayed (not along field edges or sprayer skips).
Fees associated with herbicide-resistant weed testing are generally $50 per herbicide mode of action (a sample could include multiple plants of the same species from one field). Two exceptions to this fee are marestail (Conyza canadensis) and common lambsquarters (Chenopodium album) from Michigan soybean fields. These two weeds will be screened for resistance and costs will be covered by check-off dollars through the Michigan Soybean Promotion Committee.
Samples should be sent to the Diagnostic Services lab on the MSU campus in East Lansing. It will take several weeks for the results to be known. Please contact our office at 269-944-4126 for details on sample submission.
That is all for today. This is Al Gaus for Michigan State University Extension in Berrien County.