Research Finds Multiple Herbicide-Resistant Marestail is Present in New York
Joshua Putman, Field Crops and Forage Specialist
Southwest New York Dairy, Livestock and Field Crops Program
Thirty populations of marestail (horseweed) were collected in the fall of 2020 and are being screened for resistance to commonly used herbicides. Of the 30 collected, 27 appear to be resistant to glyphosate (Roundup) and 28 populations appear to be resistant to cloransulam herbicide, an ALS-inhibitor. This indicates that we have multiple-resistance in NY. It is also suspected that 4 of these 30 samples may be resistant to paraquat (Gramoxone) herbicide. The screening efforts will continue to evaluate the effect of products like 2,4-D and dicamba, Liberty, and PPO-inhibiting herbicides like Reflex and Sharpen.
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Upcoming Events
Fecal Egg Count Mobile Workshop - East Aurora
October 21, 2025 : Fecal Egg Count Mobile Workshop - East Aurora
East Aurora, NY
This workshop will explain why regularly testing fecal egg counts can help you with understanding your animals' parasite loads and dewormer resistance. Attendees have the opportunity to prepare and evaluate fresh fecal samples under the microscope and practice interpretations.
Fecal Egg Count Mobile Workshop - Jamestown
October 30, 2025 : Fecal Egg Count Mobile Workshop - Jamestown
Jamestown, NY
This workshop will explain why regularly testing fecal egg counts can help you with understanding your animals' parasite loads and dewormer resistance. Attendees have the opportunity to prepare and evaluate fresh fecal samples under the microscope and practice interpretations.
2025 Annual Cornell Sheep and Goat Symposium Day 1
October 31, 2025 : 2025 Annual Cornell Sheep and Goat Symposium Day 1
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Announcements
Herbicide Resistance Screening
We are screening weed species for herbicide resistance.Species we are looking for include, but aren't limited to:
- Tall Waterhemp
- Palmer Amaranth
- Marestail
- Redroot Pigweed
- Foxtails
- Common Lambsquarters
- Common Ragweed
Reach out to Katelyn Miller at 716-640-2047 or km753@cornell.edu for more information.