Herbicide Resistance in Waterhemp: PPO inhibitor and Glyphosate Testing University of Illinois Plant Clinic 2016

What is your waterhemp doing ? Waterhemp glyphosate and PPO inhibitor resistance testing was offered by the Plant Clinic for the first time in 2015. Due to the strong demand for this testing, we are offering it again this year. We adapted protocols developed by Dr. Tranel’s lab in the Dept. of Crop Sciences to transition the molecular protocols for glyphosate and for PPO Inhibitor resistance from a research laboratory to a service lab offering. In 2015, we screened plants from 338 fields (approx. 1350 plants) in 5 states, including 240 fields from Illinois. To the best of our knowledge, we are the only Plant Clinic in the country offering this service.

The data  generated showed that the majority of the fields sampled contained waterhemp resistant to at least one of these two classes of herbicides. The Plant Clinic was sponsored by the Regional Crop Management Extension Conferences to purchase some of the necessary equipment for this endeavor.

2015 Counties with waterhemp samples testing positive for PPO inhibitor or glyphosate resistance, University of Illinois Plant Clinic.

2015 Counties with waterhemp samples testing positive for PPO inhibitor or glyphosate resistance, University of Illinois Plant Clinic.

To submit waterhemp samples for testing: After applying herbicide, select up to 5 waterhemp survivors. Remove the top inch or two from each plant (containing young, newly-emerged, healthy leaves. Older leaves and leaves that are damaged by herbicide will be more difficult for us to work with), and seal it in a sandwich-sized tip-top plastic bag. Use a separate bag for each plant. Place the bags in an envelope and send via overnight delivery to the University of Illinois Plant Clinic, along with a Waterhemp Testing sample submission form (see below). Ideally samples should be sent the same day they’re collected, but if necessary they can be stored for a day or two in a refrigerator. Do not freeze the samples. Do not send samples on Friday or Saturday.

Select top few inches from the waterhemp  for testing

Select top few inches from the waterhemp for testing

Sample submission forms are available for download on our website: http://web.extension.illinois.edu/plantclinic/downloads/WaterhempForm.pdf Fill out a new form for each field. There is a $50 fee for the testing, which includes both the glyphosate and PPO-inhibitor resistance tests. Authors: Suzanne Bissonnette and Diane Plewa