How to Submit a Weed Sample and Shipping Guidelines for Herbicide Resistance Diagnostics Assays


  1. First and most important is to only collect from treated herbicide areas. In order to properly assess if a weed species is herbicides resistance one must collected for an area that has been treated with the herbicide of interest.  Treatment with a herbicide allows for the selection of plants that are resistance and removal of weeds that are not resistant.  The application of a herbicide creates the classic segregating population where susceptible plants are killed and any resistance plants are selected.  If you do not collect from a treated area then plants collected could be a mixture of susceptible or resistant and any diagnostic test will yield spurious, often inconclusive results.
  2. Wrap grass and sedge whole plant roots in a wet paper towel prior to shipment. Grasses and sedges can easily survive for 48 hours after collection if roots remain moist.
  3. Place plants in a plastic bag, but to not complete seal the bag to allow for gas exchange. Sealing the bag can kill live plants if shipment is delayed.
  4. Collect and ship on Monday or Tuesday. Do not ship over the weekend.  Packages are only delivered on Monday through Friday to the Herbicide Resistance Diagnostic Lab.  Make sure that plants will arrive to the diagnostic lab by Friday (or earlier if a holiday is occurring).
  5. The vast majority of broadleaf species cannot be shipped and survive as whole plants. Please contact Dr. Scott McElroy if broadleaf weeds are suspected resistant.  Often plants must be collected and directly potted in the field or seed must be collected from mature plants.
  6. Different plant numbers are required depending on the herbicide bioassay. The follow number of plants are required for each individual assay.  DNA sequencing: 1 to 2 plants; ACCase and ALS herbicides:  10 to 15 plants (as longs plants are tillering); Preemergence herbicides:  10 to 15 for grass and sedges (multiple tillers per plant); Photosystem I, glufosinate, and protox inhibitors:  20 to 40 plants (less if plants are tillering).  Traditional Screening Bioassay: 40 to 60 individual plants.  While not ideal, diagnostic assays can be conducted with as few as one surviving plant.  Please contact the diagnostic lab to discuss your specific situation and we will accommodate you as best we can.