For producers managing corn, effective weed control is a non-negotiable component of a successful season. The corn herbicide list available to growers has expanded significantly, offering solutions for both pre-emergent and post-emergent challenges. Understanding the nuances of each product, from application timing to crop safety, is essential for protecting yield potential. This guide provides a detailed overview of the primary herbicides used in modern corn cultivation.
Pre-Emergent Herbicide Options
Pre-emergent applications form the first line of defense, creating a chemical barrier in the soil that prevents weed seeds from germinating. Timing is critical with these products, as they must be applied before weeds emerge but often after the corn has established sufficient root mass. Atrazine remains a popular choice due to its broad-spectrum control and relatively low cost, effectively managing grasses and broadleaf weeds. S-metolachlor, often found in products like Dual Magnum, provides excellent control of annual grasses when applied pre-emptively. Other common active ingredients include acetochlor, alachlor, and mesotrione, which are frequently mixed with other chemistries to enhance the spectrum of control and prevent resistance.
Key Soil-Applied Products
Atrazine: A triazine compound that offers residual control and is often used in tank mixes.
S-metolachlor: Controls a wide range of annual grasses and small-seeded broadleaf weeds.
Armespire: A newer chemistry that provides early-season grass control with flexibility in application timing.
SureStart II: A blend designed for consistent emergence control across varying soil conditions.
Post-Emergent Grass Control
When pre-emergent applications fail or weeds emerge after planting, post-emergent herbicides become necessary. These products are highly effective but require careful consideration of corn growth stage and weed size. Fusilade DX targets grasses through contact, making it ideal for controlling emerged foxtail and crabgrass before they establish deep roots. Select Max offers a similar mode of action but is often valued for its quick knock-down effect on stubborn grassy weeds. LibertyMax provides a non-selective option, though it requires precise application to avoid damaging the corn crop, particularly in heat-stressed conditions.
Contact and Translocation Herbicides
Fusilade DX: Targets photosystem I, providing rapid burn-down of emerged grasses.
Select Max: Controls hard-to-kill grasses with a robust dose of sethoxydim.
LibertyMax: A glufosinate-based option for burndown applications in LibertyLink corn.
Broadleaf Weed Management
Broadleaf weeds such as pigweed, waterhemp, and morning glory can compete aggressively with corn, stealing vital nutrients and light. For these targets, residual herbicides applied early in the season are highly effective. Callisto, which contains halauxifen, is frequently used because it controls a wide range of broadleaf weeds while allowing for replanting flexibility in the same season. Engenia and Resolve are other options that utilize similar chemistry to manage tough broadleaf species. These products are often applied in conjunction with grass control measures to simplify the application schedule and reduce overall chemical load.
Resistance Management and Application Tips
Over-reliance on a single mode of action has led to the rise of herbicide-resistant weeds, making strategic planning essential. To mitigate this risk, experts recommend rotating between different chemical families and incorporating mechanical cultivation when possible. Always adhere to the labeled rate and timing, as exceeding recommendations can lead to crop injury or environmental harm. Soil temperature and moisture also dictate product performance; cool, dry conditions can reduce activation of pre-emergent compounds. Utilizing physical markers, such as flagging treated areas, helps prevent accidental re-application and ensures compliance with rotational grazing restrictions if livestock are present.
