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Our Recent Weather is Perfect for Spring Horseweed/Marestail Germination and Establishment

Posted: May 10, 2017

Get out and scout those fields now before soybean planting begins.
Image 1. Horseweed seedlings.  Image by Heather Karsten taken at the Penn State Agronomy Research Farm, Centre County PA on 5/8/17.

Image 1. Horseweed seedlings. Image by Heather Karsten taken at the Penn State Agronomy Research Farm, Centre County PA on 5/8/17.

The last 10 days of cool wet weather is perfect for promoting spring germination of horseweed/marestail in those no-till fields that are about to be planted to soybean. This is very similar to what happened last year in May when we had about a two-week cool wet period which appeared to have triggered this winter/summer annual into a more prolonged germination and emergence period in the spring than in some other years (Image 1).

In 2016, we had horseweed/marestail emerging through the month of May and in many cases after spring burndown treatments had been applied.  Fields that did not receive a residual herbicide along with the burndown, had problems with lack of control and few options for postemergence management.

This year is following a similar pattern, so be sure to scout. If you are dealing with fields with a history of marestail, adjust those herbicide programs accordingly. For details on management considerations for marestail, refer to a recent article we posted a couple weeks ago entitled “Manage Horseweed/Marestail Before You Plant Soybeans.”

Contact Information

William S. Curran
  • Professor of Weed Science
Phone: 814-863-1014
Dwight Lingenfelter
  • Program Development Specialist
Email:
Phone: 814-865-2242