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)

Upcoming Events
2026 Northeast Extension Fruit Consortium Winter Webinar Series
February 4, 2026 : Management of Up and Coming Strawberry Diseases in the Northeastern United States
Session 1: Management of Up and Coming Strawberry Diseases in the Northeastern United States
February 11, 2026 : Kiwiberry Production in the Northeast
Session 2: Kiwiberry Production in the Northeast
February 18, 2026 : Heat Mitigation- Sunburn and Fruit Coloring
Session 3: Heat Mitigation- Sunburn and Fruit Coloring
February 25, 2026 : The Dating Game- Updates in Lepidopteran Mating Disruption
Session 4: The Dating Game- Updates in Lepidopteran Mating Disruption
March 4, 2026 : USEPA Endangered Species Act Strategies and Pesticide Use
Session 5: USEPA Endangered Species Act Strategies and Pesticide Use
March 11, 2026 : Practical Drought Management for Fruit Growers
Session 6: Practical Drought Management for Fruit Growers
Managing the Invasive Swede Midge Webinar
March 6, 2026 : Managing the Invasive Swede Midge Webinar
Swede midge is an invasive fly that causes serious economic losses to brassica crops. Due to its small size and hidden feeding habits, swede midge is often called an "invisible pest" and damage may be misdiagnosed. In this webinar, we will review the swede midge life cycle and crop damage symptoms, current management recommendations, new research findings, and highlights from on-farm case studies with a focus on organic management.
New Farm Manager Skills Day - Get the Tools You Need to Grow Your People (Hudson Valley)
March 10, 2026 : New Farm Manager Skills Day - Get the Tools You Need to Grow Your People
Millbrook, NY
Are you moving into a supervisory farm management role this season and want to get off to a good start? Are you an experienced manager who wants to connect with other "people" managers and work on your skills? This one-day workshop is for you!
