The late spring is getting later for all but a teeming crop of weeds in the Northeast. The situation prompted Penn State Extension Weed Specialists Bill Curran and Dwight Lingenfelter to issue yesterday's advisory on common burndown herbicides for corn.
Remember, warm sunny days improve weed metabolic activity – and herbicide activity on them. So after a cold spell, wait for a few days of warm, sunny weather before applying herbicides.
Also remember that herbicides work slower under cool conditions. So increasing the rate of the burndown herbicide may be necessary if weeds are stressed by cold conditions or are larger in size. Scout fields prior to spraying to ensure you use the correct herbicide program for the problem. Consider the following common burndown products labeled for corn:
Broad-spectrum foundation products
Glyphosate – Use a higher labeled if tank-mixing with residual herbicides and nitrogen carriers. Do not use with suspension-type liquid fertilizers. Adding ammonium sulfate or a similar product improves performance. May be applied in clear liquid nitrogen fertilizer or clear liquid complete analysis fertilizers, but may be less effective on certain annual and perennial weeds.
Gramoxone SL (Syngenta) – Its paraquat active ingredient is main alternative to glyphosate for nonselective burndown. Since it is a contact herbicide, apply in at least 20 gallons of liquid carrier. Avoid using flood jet tips for best results. Include an appropriate nonionic surfactant. Add a triazine herbicide (atrazine, metribuzin, etc.) to increase burndown activity. Using UAN as a partial carrier increases activity.
Liberty (glufosinate) – It's labeled as a postemergent for Liberty Link corn and soybean, but is also labeled for burndown in conventional corn and soybean. Its strength is small annual weeds and it is not very effective on larger winter annuals, perennials, or burndown of cover crops.
It best fits soybeans, not corn. It has gained some traction in the Mid-Atlantic for burndown control of marestail in particular. Remember, Liberty is most effective on small actively growing weeds under warm temperatures, with bright sunlight, include AMS and use sufficient carrier volume and spray tips to get thorough coverage of the weeds.
Broadleaf only products
2,4-D ester - Use the ester formulations , instead of the amine. Esters are usually more effective under cool conditions, are less water soluble and better on perennial weeds. Also, esters usually penetrate the waxy leaf surface (cuticle) better than amines. 2,4-D will help control a number of emerged winter annuals, including marestail.
Dicamba (Clarity/Banvel) – It can be tank-mixed with 2,4-D, and like 2,4-D, direct contact with corn seeds must be avoided. Dicamba is often necessary for successful alfalfa and/or clover burndown.
Atrazine - Controls small emerged annual broadleaf weeds, suppresses annual grasses and provide residual control. Can be applied in UAN for improved burndown activity.
Balance Flexx and Corvus (Bayer Crop Science) – Both include a corn safener.The thiencarbazone component improves foliar and residual grass control. Tank mix with other herbicides including 2,4-D, Gramoxone, or glyphosate for broader spectrum activity.
Basis Blend (Dupont) – It can be applied preplant or preemergence to corn. Apply 7 or more days before planting for greater crop safely. Typically, it's tank-mixed with atrazine and/or 2,4-D LVE to increase the spectrum of activity. Resolve (rimsulfuron) and Resolve Q (rimsulfuron plus thifensulfuron plus safener) have similar use labels.
Clopyralid (Component of Hornet and Surestart – Dow AgroSciences or TripleFLEX - Monsanto) – It can provide burndown and residual control of selected annual broadleaves. It's particularly effective on ragweed, helps control clover and alfalfa, and will suppress emerged Canada thistle.
Harmony 50 SG (Dupont) – Apply preplant or at planting. It'll help control wild garlic and provide some suppression of certain winter annual weed species. Include an appropriate surfactant. Not as broad spectrum at Harmony Extra, it's typically tank-mixed with glyphosate and/or other herbicides.
Harmony Extra 50 SG (Dupont) - Allow at least 14 days between application and corn planting. It improves control of wild garlic and some winter annual weeds. Include a surfactant. Again, it's typically tank-mixed with glyphosate and/or other herbicides.
Panoflex 50 SG (Dupont) – It's labeled for spring burndown, and is active on winter annual broadleaves. Tank-mix with 2,4-D ester or glyphosate to broaden weed control spectrum.
Instigate (Dupont) – This product may be applied up to 14 days before to corn planting. Adding COC or MSO is recommended for burndown of labeled weeds 3 inches or less in height. For larger weeds, tankmix with paraquat, glyphosate or other burndowns.
Lumax/Lexar (Syngenta) –The atrazine and mesotrione components can provide substantial burndown and control of small annual broadleaf weeds. Mesotrione is quite effective for suppressing dandelion.
Metribuzin (formerly Sencor 75DF) – This product was labeled preemergence for medium textured soils with greater than 2% organic matter as part of the burndown program. A number of metribuzin products (Metribuzin, TriCor, Dimetric, Glory, etc.) have different labels, so check with your local supplier for details. It can be tank-mixed with glyphosate, Gramoxone, 2,4-D or other preemergence products.
Prequel 45 WG (Dupont) – It provides some control of small emerged annual weeds and can be tank-mixed with 2,4-D, atrazine and other herbicides to broaden weed control.
Sharpen 2.85 SC (BASF) - This is a contact herbicide that can be applied up to 14 days ahead of corn planting. Include MSO to maximize burndown activity on emerged broadleaf weeds including glyphosate-resistant marestail. At its higher rate, Sharpen provides residual control of annual broadleaf weeds.
Valor 51 WDG (Valent) – This product, not Valor XLT, is a contact herbicide and may be included to enhance the speed of burndown and provide residual control of annual broadleaves.For more details on application rates and timing, click on: Burndown herbicide options for corn.