Herbicide Resistant Horseweed in New York and Possible Implications
Mike Basedow, Tree Fruit Specialist
Eastern New York Commercial Horticulture
Horseweed (also called marestail) is a frequently occurring species in New York. It can be found growing in a variety of habitats, including along roadsides, in field crop and vegetable operations, and in berries, grapes, and tree fruit. Often considered a winter annual, horseweed has a wide germination window and seedlings can emerge in the spring, summer, and fall. Herbicide resistance, particularly to glyphosate, is widespread in the US and has recently been identified in New York (see the 2022 summer issue of Fruit Quarterly https://nyshs.org/fruit-quarterly/). Many of these populations were collected from soybean systems where glyphosate is frequently used for managing unwanted vegetation. Two New York populations, collected from a vineyard and an apple orchard in the Finger Lakes Region, were found to be susceptible to glyphosate but resistant to labeled rates of paraquat. Paraquat resistance in horseweed has been formally confirmed previously in Belgium (nurseries), Canada (peaches), Japan (orchards, grapes, roadsides, railways), California (almonds), Delaware (soybeans) and Mississippi (soybeans) (https://weedscience.org/Home.a... ).
Herbicide Resistant Horseweed in New York and Possible Implications (pdf; 1849KB)
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Upcoming Events
Rulfs Orchard Vegetable and Berry Field Meeting
August 4, 2026
Peru, NY
Join CCE vegetable specialists Elisabeth Hodgdon and Chuck Bornt for a vegetable and berry field meeting at Rulfs Orchard, in Peru, NY. We'll tour the farm's fields and talk about integrated pest management of sweet corn and cucurbit crops. Then, we'll view a drone demonstration and discuss new technologies for pesticide application and spotted wing drosophila management in berries. Light refreshments will be provided. A rain date will be announced if adverse weather is predicted.
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August 6, 2026
Johnstown, NY
Visit organic seed production trials and tour the farm to see small-scale production systems at work, including tarping, cover cropping, and the use of assorted mulches and covers to modify the growing environment.
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August 11, 2026
Rexford, NY
Join the ENYCHP and Cornell scientists on August 11 for the Capital Region Orchard Twilight meeting in Saratoga! We will be touring Bowman Orchards and reviewing seasonal recommendations for pests and diseases for apples, plums, and berries, as well discussing crop insurance.
NYSDEC Pesticide Applicator Recertification Credits: 1.25 in categories 22, 1A, & 10. Refreshments will be provided.
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