By Scout Nelson
Dr. Debalin Sarangi, an Extension weed specialist from the University of Minnesota, and Joe Ikley, an Extension weed specialist from NDSU, collaborated with Ryan Miller, an Extension educator in crops, to discuss weed management during a challenging growing season in the June session of Field Notes.
The weather has significantly impacted planting dates and herbicide applications this season. Early small grains and corn are progressing well in the west-central and northwestern parts of the state, while soybeans and later crops like sunflowers and dry beans have been difficult to plant.
Corn and soybean planting is on track, but cool weather and frequent rains have slowed crops and weed growth. Soybeans in southern Minnesota are behind expected growth stages, while kochia and waterhemp weeds show slow growth.
When warm weather returns, weeds such as waterhemp can grow an inch per day. It's crucial to monitor fields closely, as these weeds can quickly exceed the recommended treatment height of 4 inches for most herbicides.
Adding a Group 15 residual herbicide to the mix can help manage weed emergence, especially for waterhemp, which can continue to sprout well into August.
Preemergence herbicides are generally effective, but early postemergence herbicides have been slow due to cool temperatures. Contact herbicides should yield results within days, while systemic herbicides require active weed growth, which has been delayed by the weather.
Regulatory changes have limited dicamba availability for soybeans, with existing stocks selling deadlines in May. Use restrictions persist, especially regarding temperature and application dates. The application window is closing in southern Minnesota, while more opportunities exist in the north.
Increased wind speeds have raised concerns about herbicide drift, which can damage crops at varying growth stages. It is essential to monitor weather conditions closely to minimize drift and ensure herbicide applications are effective and safe.
Warmer temperatures will accelerate corn growth, necessitating strict herbicide application guidelines. Some early crops in southern Minnesota are already beyond recommended sizes for certain herbicides. If preemergence herbicides aren't applied, soybean growers may need alternative chemistries.
Waterhemp and kochia pose significant challenges due to resistance to herbicides. Managing these weeds involves various herbicide actions, rotating crops, and non-chemical methods like cover crops and tillage. Applying herbicides when weeds are small ensures effectiveness.
Experts caution against relying on rescue treatments for large weeds, as these applications may not fully control them and can contribute to herbicide resistance. Effective weed management involves timely applications and using multiple strategies to ensure long-term control and crop health.
Photo Credit -istock-ligora
Categories: Minnesota, Crops