MSc Final Oral Examination: Christian Willemse


Interested Members of the University Community are invited to attend the Final Oral Examination for the Degree of Master of Science of Christian Willemse of the Department of Plant Agriculture 

Date:Thursday, February 11, 2021
Time: 2:00 PM 
Method: Via Zoom Video Conferencing -
Meeting ID: 949 9082 7879
Passcode: 320905

Thesis Title: Control and Distribution of Multiple-Herbicide-Resistant Waterhemp (Amaranthus tuberculatus (Moq.) J. D. Sauer) in Corn (Zea mays L.) in Ontario 

Advisory Committee 
Dr. Peter Sikkema, Advisor
Dr. Darren Robinson
Dr. David Hooker
Dr. Amit Jhala

Examination Committee
Dr, Istvan Rajcan, Chair
Dr. peter Sikkema
Dr. Darren Robinson
Dr. Francois Tardif                                                                    


Field surveys in 2019 and 2020 identified multiple-herbicide-resistant (MHR) waterhemp populations resistant to acetolactate synthase (ALS)-, photosystem II (PS II)-, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS)-, and protoporphyrinogen IX oxidase (PPO)-inhibitors in the additional counties of Bruce, Elgin, Haldimand, Huron, Norfolk, Northumberland, and Wentworth. Several preemergence (PRE), early postemergence (EPOST), postemergence (POST) and PRE followed by (fb) POST herbicide programs were evaluated for control of MHR waterhemp in corn. The PRE application of S-metolachlor/mesotrione/bicyclopyrone/atrazine and saflufenacil/dimethenamid-P controlled MHR waterhemp ≥ 95%. Several ePOST applications including glyphosate + S-metolachlor/mesotrione/bicyclopyrone/atrazine, glyphosate/2,4-D choline + rimsulfuron + mesotrione + atrazine, and glyphosate + S-metolachlor/atrazine/mesotrione controlled MHR waterhemp 90% to 100%. The POST application of atrazine + isoxaflutole, mesotrione, tembotrione, topramezone, or tolpyralate controlled MHR waterhemp 81% to 99%. A POST application of glufosinate following tolpyralate + atrazine PRE, and a POST application of mesotrione + atrazine following dicamba/atrazine or S-metolachlor/atrazine PRE, increased MHR waterhemp control 5% to 37%. These results provide useful information regarding the distribution of MHR waterhemp in Ontario and control in corn.