Waterhemp

As harvest nears, it’s time to evaluate this past season and look ahead to 2020. Reviewing the health and success of your fields is vital to developing an effective management plan. With most corn and soybean regions impacted by severe weather this spring, some fields saw higher weed pressure. During recent AgriTalk podcast episodes, Syngenta Agronomy Service Managers Mike Leetch and Leon Hunter shared insights on how to address weed pressure this fall to prepare for next season. Some key takeaways include:

• There are several Amaranthus species forming seed heads in unplanted fields.
• Some growers did put down a cover crop, which helped suppress weed pressure in unplanted fields.
• Some planted fields contain waterhemp and Palmer amaranth weeds as tall as 5’-8’.
• Next season, fields are going to be a weedy mess if no action is taken to fight these weeds.

Weeds like waterhemp and Palmer amaranth can produce hundreds of thousands of seeds per plant. One plant per square yard that produces only 50,000 seeds will drop 242 million seeds per acre. Other species that are less prolific seed producers are still problematic. One plant per square yard that only produces 100 seeds per plant will still drop nearly one half million seeds per acre.

Unfortunately, there is no easy way to stop weeds from going to seed. When you evaluate fields to plan harvest order, you should assess the weed pressure you are seeing, as you may need to approach management for each field differently. To stop weeds from going to seed, you may want to consider inter-row cultivation or hand weeding the most troublesome spots, or avoid harvesting in heavily infested areas altogether.

After harvest, consider a fall-applied burndown herbicide to control fall weed flushes. Planting a winter cover crop is another tool to help suppress weed growth.

When planning for next season, maintain your crop rotation plan and choose a strong corn and soybean herbicide portfolio to help fields start clean and stay clean.

• For corn, start with preemergence corn herbicides like Acuron®, Acuron Flexi, Lexar® EZ or Lumax® EZ at full labeled rates.
• In soybeans, use Boundary® 6.5 EC, BroadAxe® XC or Prefix® herbicides preemergence at full labeled rates. For dicamba-tolerant varsities, Tavium® Plus VaporGrip® Technology herbicide is the first dicamba herbicide premix and includes S-metolochlor to control both pre- and post-emergent weeds for up to 3 weeks longer than dicamba alone.

Timely application of these herbicides not only help fields start clean, but also can result in extended residual weed control. Discuss weed management plans with your retailer or Syngenta sales representative to find the product best suited for your farm and ensure strong weed control. Listen to more of what our agronomic service managers have to say about fall weed management.

Mike Leetch, agronomy service manager for the western Midwest.

Leon Hunter, agronomy service manager for the eastern Midwest.

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