Flexible Burndown Herbicide Programs for Corn or Soybean

For various reasons, you might need to make a "game-time decision" as to whether you are planting corn or soybeans this spring. In that case, it would be best to apply a flexible herbicide program that allows planting of either crop. A limited number of corn and soybean herbicides allow you to switch crops if necessary. Here is a list of herbicides that can be used Preplant or PRE in both corn and soybean. Be cautious of application rates and wait periods that may differ for each crop. Also, keep in mind that some of these products and active ingredients are available in generic alternatives.

Burndown

• 2,4-D LVE — When applied at 1 pint/acre, there is a 7-day waiting period for soybean. This is also the safest use in corn. If applying 1 quart, wait at least 15 days to plant soybean.
• Basis Blend — Apply at 0.825-2.5 oz/acre in burndown programs before corn emergence; corn injury may occur under cool, wet conditions, so 1.5 oz rate is a good compromise. In soybean, apply 0.825 oz at least 15 days before planting; tankmix to enhance control. It provides some weedy grass control and fair to good burndown activity on several key broadleaves.
• Elevore — Either corn or soybean can be planted 14 days after application when applied at 1 fl oz/acre. However, corn can be planted after 3 days if seed is planted at least 1.5 inches deep and completely covered. Provides control of glyphosate-resistant marestail.
• Glyphosate — This can be used in the burndown and POST in Roundup Ready crops. Increase the rate to 1.5 lb ae/acre for larger weeds.
• Gramoxone 3.0 SL/paraquat 3 lb/gal — Can increase the rate up to 2.7 pt/acre for larger weeds. Can tank-mix with metribuzin plus 2,4-D and still be able to plant corn or soybean. This mixture provides better burndown activity than paraquat alone.
• Harmony/Extra, Audit 1:1, and other thifensulfuron + tribenuron mixes  — Can be added to the 2,4-D and/or glyphosate burndown at 0.45 to 0.90 oz/acre for both corn and soybeans. You must wait 7 days to plant soybean and 14 days for corn. Without glyphosate, it provides average (70-80%) control on many key broadleaves and no grass control; with glyphosate, it improves control of curly/broadleaf dock, wild garlic, common groundsel, field pansy, and Canada thistle.
• Liberty 280 — labeled up to 43 fl oz/acre in the burndown application. Liberty is most effective on small, actively growing weeds under warm temperatures. Use sufficient carrier volume (minimum 15 GPA, 20 GPA is better) and spray tips to get thorough coverage of the weeds.
• Reviton — Can be used in a burndown program before field corn or soybean. Corn can be planted immediately after application; wait 7 days to plant soybean if using 2-3 fl oz (0 days at 1 fl oz). It has a low use rate (1 to 3 fl oz/A) and can be tankmixed with other herbicides, especially glyphosate. MSO or COC plus AMS must be added to the spray solution. Reviton is similar to Sharpen and is less active on marestail but has better activity on field pansy/violet, primrose, and some grasses compared to Sharpen.
• Sharpen — Labeled for both corn and soybean. Use only 1 oz/acre in soybean for burndown and add MSO as the adjuvant if planting soybean immediately. Higher rates can be used, but be aware of planting restrictions, especially for soybeans. Always add MSO and AMS as the adjuvants to the spray tank for optimal weed control.

Grass residual (primarily)

• Group 15 products (s-metolachlor/Dual, etc.; acetochlor/Enversa, Warrant, etc.; and Outlook) — Can be used in both corn and soybean for residual grass, yellow nutsedge, and some small-seeded broadleaf control.

Broadleaf residual

• Lorox— Can be used in both corn and soybean. It primarily provides control of annual broadleaves but can suppress certain annual grasses.
• Metribuzin — This product was labeled preemergence at up to 5.3 oz per acre on medium textured soils with greater than 2% organic matter as part of the burndown program in either crop.
• Python — Python is effective on a number of annual broadleaf weeds and can be used in both corn and soybean. The use rate range is 0.8 to 1.14 oz/acre (up to 1.33 oz in soybean).
• Valor — Can be used in both corn and soybean. Corn may be planted 7 days after application at the 2 oz/acre rate (requires a minimum of 25% surface residue and 0.25 inch of rainfall between application and planting). Do not tank-mix with common grass herbicides (Dual, Outlook, etc.) in soybean due to injury concerns.

Grass and broadleaf residual products

• Verdict — This is a mixture of the active ingredients found in Sharpen and Outlook. The most common application rate is 13 fl oz/acre for corn and 5 fl oz/acre for soybean.
• Zidua and Anthem Maxx/Flex – can be used in the burndown mix and either corn or soybean can be planted and will provide control of many annual weeds.
• Fierce – can be used in both soybean and no-till or minimum till corn to control many annual grasses and broadleaves. In corn, you must wait at least 7 days to plant corn after application.
• Combinations that include a grass product (Dual, Outlook, and Warrant/Enversa) plus Python would also provide residual grass and broadleaf control for both corn and soybean.
• In conclusion, knowing what weeds are causing problems and understanding that in some cases, multiple trips across the field for better weed control during the growing season might be more economical in the long run to ultimately protect and improve crop yields. However, one-pass burndown/residual herbicide programs may have a fit in certain situations.