By Blake Jackson
Recent rainfall and favorable growing conditions have created new weed management challenges in Pennsylvania crops and pastures, according to Penn State Extension Weed Specialist Dwight Lingenfelter. Producers are encouraged to scout fields regularly and respond quickly to emerging problems.
In soybean fields, horseweed, also known as marestail, continues to be a concern due to widespread resistance to both glyphosate and ALS-inhibiting herbicides.
For LibertyLink, Enlist E3, and XtendFlex soybean systems, glufosinate products remain among the most effective post-emergence options, particularly when combined with Enlist herbicides where appropriate. Early treatment is important, as larger plants become increasingly difficult to suppress.
Palmer amaranth and waterhemp are also expanding their presence across the state. These aggressive pigweed species can grow rapidly following rainfall and become difficult to control once they exceed four inches in height.
Effective management often requires a combination of residual and post-emergence herbicides. Liberty-based programs continue to provide strong control, especially in herbicide-tolerant soybean varieties.
Extension specialists are also receiving reports of common ragweed surviving glyphosate applications. Where resistance is suspected, alternative herbicides such as glufosinate and certain PPO products may still provide satisfactory control when weeds are treated while small.
Volunteer corn is another issue appearing in soybean fields. Post-emergence grass herbicides remain the preferred management tool, but proper adjuvants are essential for optimal performance.
Growers should also be aware that some broadleaf herbicides can reduce grass herbicide effectiveness when applied together.
Pasture and forage producers are reminded that timing is critical for successful weed control. Buttercup and poison hemlock are highly visible at this time of year, but herbicide applications are generally less effective once these weeds reach maturity or begin flowering. Fall and early spring treatments typically provide better results.
Similarly, roughstalk bluegrass and many perennial weeds, including Canada thistle, milkweed, hemp dogbane, and poison ivy, are best managed later in the season.
Strategic mowing during summer followed by targeted fall herbicide applications often delivers the most effective long-term control and helps reduce weed pressure in future growing seasons.
Photo Credit: gettyimages-zoomtravels
Categories: Pennsylvania, Crops, Soybeans, Weather