To Choose The Best Herbicides To Terminate Cover Crops

On April 27, 2019

To Choose The Best Herbicides To Terminate Cover Crops

Warmer temperatures are promoting cover crop growth and moving up targeted planting dates across the state. Selecting the right herbicide burndown program for cover crop termination will help you start clean this growing season. Extension Agronomists John Wallace and Dwight Lingenfelter offer these suggestions as you get into the field.

Glyphosate is the most effective burndown herbicide for grass cover crops. Actively growing cover crops and sunny warm days (> 55° F) generally increase the activity of glyphosate. Under these conditions, a 0.75 lb acid equivalent (ae) to 1.5 lb ae rate with appropriate adjuvants (surfactant + Ammonium sulfate (AMS)) should provide good control of most grass cover crops. A 0.75 lb ae rate is equivalent to 22 fl oz of Roundup or 32 fl oz of Credit, Rascal and other 3 lb ae formulated glyphosate products. Other tips for optimizing glyphosate activity on cover crops include: 1) reducing the carrier volume to 10 gallon/acre (gpa); and 2) avoiding use of 28 or 32% Urea-Ammonium Nitrate fertilizer compound (UAN) and high-rates (> 0.25 lb active ingredient (ai)) of clay-based herbicides like atrazine, simazine and metribuzin.


Paraquat (Gramoxone SL) can be used as an alternative to glyphosate for termination of grass cover crops but is generally less consistent. To optimize control with paraquat, use a high carrier volume (20 gpa) and flat fan nozzle tips to improve coverage. Inclusion of a non-ionic surfactant, a triazine herbicide (atrazine, metribuzin), and UAN as a partial carrier can each improve paraquat activity.


Inclusion of 2,4-D ester or dicamba in burndown programs is likely necessary to achieve adequate control of legume cover crops and can also broaden your weed control spectrum. Both of these herbicides are compatible tank-mix partners with glyphosate and can be used prior to corn or soybean. Apply dicamba or 2,4-D ester 7 to 14 days before planting corn and plant corn at least 1.5 inches deep to enhance crop safety. Be sure to read the herbicide label for pre-plant restrictions prior to soybean for the various 2,4-D and dicamba products now on the market.

Herbicide recommendations for termination of various cover crop species prior to corn and soybean can be found in the Penn State Agronomy Guide ( or the Mid-Atlantic Field Crop Weed Management Guide. Here are a few tips for common cover crop species:

Some research suggests that winter wheat is more difficult to control with glyphosate compared to cereal rye. Make sure to use higher glyphosate rates and follow other best management practices described above to optimize herbicide activity in wheat burndown programs. The Roundup Powermax label recommends 32 fluid ounce (fl oz) on up to 18-inch tall wheat. Applications targeting wheat prior to the boot stage are generally more effective.

Annual ryegrass control can be more challenging than winter cereal cover crops. Glyphosate has better activity on annual ryegrass than paraquat (Gramoxone), but several best management practices should be followed, including: 1) timing applications to sunny, warm days (> 55° F); 2) targeting actively growing plants prior to rapid growth stages (< 8-inch); and 3) use of higher glyphosate rates (1.25 to 1.5 lb ae/ac) with appropriate adjuvants.

In general, 2,4-D ester or dicamba should be tank mixed with glyphosate or paraquat to improve control of clover species and hairy vetch. A few differences among clover species have been observed in recent field trials conducted at Penn State. Crimson clover is comparatively less susceptible to 2,4-D ester or dicamba applied alone. A tank mix that included glyphosate or paraquat with 2,4-D ester or dicamba products is necessary to achieve adequate crimson clover control, whereas red clover and hairy vetch can be controlled with 2,4-D ester or dicamba applied alone.

To Get Your Spotted Lanternfly Permit

A Spotted Lanternfly permit is required for any business performing work within and/or moving goods within and out of a quarantine zone. This will include farm businesses such as nurseries, greenhouses, woodworking businesses, and others which sell materials that could contain eggs, young or adult SLF, thereby spreading the pest around.  The following counties are currently under quarantine: Berks, Bucks, Carbon, Chester, Dauphin, Delaware, Lancaster, Lebanon, Lehigh, Monroe, Montgomery, Northampton, Philadelphia, and Schuylkill.

An owner, supervisor, or manager designated from each business must complete the required training and take a twenty-question exam.  Each person who successfully completes the training and examination will receive a permit allowing for normal business operation. This person will be responsible for training employees on what to look for and how to safeguard against moving spotted lanternfly. The department encourages everyone, even those who do not need a permit, to take advantage of training.

There is one remaining training and testing session offered by Penn State Cooperative Extension and the PA Department of Agriculture. It will be held on April 30 at 9am at the East Drumore Twp Building, 925 Robert Fulton Hwy, Quarryville. To register, contact Yusur Aladhami, PA Dept. of Ag., at 717-772-5220.

Quote Of The Week: “Consult not your fears but your hopes and your dreams. Think not about your frustrations, but about your unfulfilled potential. Concern yourself not with what you tried and failed in, but with what it is still possible for you to do. Pope John XXIII