By Blake Jackson
As barley and wheat harvest progress across Pennsylvania, many growers will soon begin planting double-crop soybeans. Although delayed planting generally reduces weed pressure, establishing a clean field remains essential for protecting yields, especially when dry weather limits crop growth.
According to Penn State Extension Weed Specialist Dwight Lingenfelter, glyphosate-resistant marestail (horseweed) continues to be one of the most troublesome weeds in double-crop soybean production.
Plants cut during grain harvest often recover, develop multiple branches, and become more difficult to eliminate.
Several herbicide programs can help manage these weeds before planting. Tank-mixing glyphosate with Sharpen or similar products can improve burndown of marestail, while adding metribuzin extends residual weed control.
When using Sharpen products, including MSO and AMS in the spray solution is important for optimum performance.
Applying 2,4-D LVE remains another option, but growers must delay planting for seven days unless using Enlist E3 soybeans, which allow immediate planting after Enlist herbicide applications.
Liberty Ultra or other glufosinate products also provide effective burndown of marestail and several troublesome broadleaf weeds, particularly when applied under warm, sunny, and humid conditions with proper spray coverage.
Gramoxone can suppress small marestail plants, while Elevore offers strong control but requires a 14-day waiting period before soybean planting.
Dicamba products are generally discouraged because of the increased risk of drift damage to nearby sensitive crops during summer conditions.
Selecting herbicide-tolerant soybean varieties such as LibertyLink, Enlist E3, or XtendFlex provides additional post-emergence weed management flexibility. Roundup Ready varieties remain suitable where resistant weeds are not a concern.
Residual herbicides are especially valuable in fields with Palmer amaranth or waterhemp. Their effectiveness depends on receiving adequate rainfall shortly after application to activate the products before weed emergence.
Choosing the right residual herbicide and ensuring timely activation can significantly improve season-long weed control in double-crop soybean production.
FAQs
- Why is weed control important in double-crop soybeans?
A weed-free start helps maximize soybean yield and reduce competition for moisture and nutrients.
- What is the biggest weed concern in double-crop soybeans?
Glyphosate-resistant marestail (horseweed) is one of the most challenging weeds to control.
- Why is Sharpen commonly used before planting?
It improves marestail burndown and can be combined with residual herbicides for extended control.
- Can dicamba be used as a burndown treatment?
Its use is generally discouraged because of the high risk of drift onto sensitive crops.
- What activates residual herbicides after application?
At least one-half inch of rainfall shortly after spraying is typically needed for effective activation.
Photo Credit: gettyimages-zoomtravels
Categories: Pennsylvania, Crops, Soybeans, Wheat, Harvesting