Evaluation of Residual Herbicides for Interseeding in Corn

Posted: March 29, 2017

Trials conducted over three years show that several shorter-lived residual corn herbicides can be used successfully with interseeded cover crops; at the same time the use of longer-lived residual herbicides will likely preclude successful interseeding practices in corn.

We have examined interseeding cover crops in corn for the last several years.  The results have shown that annual ryegrass and red clover cover crops can successfully establish when interseeded at the V5 corn growth stage. However, this strategy may be limited by carryover injury to cover crops from residual herbicide programs.

We conducted field experiments from 2013 to 2015 in Pennsylvania, Maryland and New York (10 total site-years) to evaluate the effect of common residual corn herbicides on interseeded red clover and annual ryegrass. We tested 22 herbicide treatments in at least two-site years and collected cover crop biomass in late-fall to evaluate herbicide carryover injury. Cover crop establishment and response to herbicide treatments was variable across study locations.

High levels of red clover and annual ryegrass biomass reduction were observed across herbicide treatments at the MD location, whereas negligible to moderate levels of biomass reduction were observed at other locations. Among herbicides used for annual grass control, s-metolachlor (Dual Magnum), pyroxasulfone (Zidua), pendimethalin (Prowl) and dimethenamid-P (Outlook) resulted in significant annual ryegrass biomass reduction relative to the untreated check, whereas annual ryegrass biomass in acetochlor (Harness) treatments did not differ from the untreated check.

The relative order of observed annual ryegrass biomass reduction among chloroacetamide herbicides was Dual Magnum > Zidua > Outlook > Harness. Among herbicides used for broadleaf weed control, mesotrione (Callisto) resulted in significant red clover biomass reduction compared to the untreated check. Red clover biomass in saflufenacil (Sharpen), rimsulfuron (Resolve/Basis) and atrazine treatments did not differ from the untreated check. This research provides preliminary evidence that annual ryegrass and red clover can be interseeded following use of several shorter-lived residual corn herbicides and also demonstrates that use of longer-lived residual herbicides likely preclude interseeding practices in corn production systems. Finally, our research demonstrates that the potential for carryover injury to interseeded cover crops can vary significantly across different soil and environmental conditions.

The table below provides some guidelines for herbicide use in the mid-Atlantic region with interseeded cover crops.

Residual Corn Herbicides For Interseeding

Potential for Cover Crop Injury (% Fall Biomass Reduction)

<15% = LOW (L)    15-30% = MODERATE (M)     >30% = HIGH (H)

Herbicide Treatments Product Rate Label Rate App Timing Annual Ryegrass Red Clover Grass-Legume Mix
SUs (2)

Resolve 25 DF 0.5 oz ½X PRE L L L
Resolve 25 DF 1 oz 1X PRE L L L
Triazines (5)

Atrazine (4L) 1 pt ½X PRE L M M
Atrazine (4L) 2 pt 1X PRE M M M
Atrazine (4L) 3 pt 1 ½X PRE H H H
Metribuzin 75 WG 4 oz 1X PRE H L M
Chloroacetamides (15)

Dual II Mag 7.64 EC 1.67 pt 1X PRE H M H
Zidua 85 WG 2.5 oz 1X PRE H M H
Harness 7 EC 1 pt ½X PRE M L M
Harness 7 EC 2 pt 1X PRE M L M
Outlook 6 EC ½ pt ½X PRE L L L
Outlook 6 EC 1 pt 1X PRE M L M
Dinitroanilines (3)

Prowl H2O 3.8 CS 1.5 ½X PRE L L L
Prowl H2O 3.8 CS 3 pt 1X PRE H M H
PPOs (14)

Sharpen 2.85 SC 1.5 fl oz ½X PRE L L L
Sharpen 2.85 SC 3 fl oz 1X PRE M M M
HPPDs (27)

Balance Flex 2 SC 5.3 fl oz 1X PRE M M M
Callisto 4 SC 5.4 fl oz 1X PRE L H H
Impact 2.8 SC 0.75 fl oz 1X POST M H H

Keystone LA NXT 2 pt ½X PRE L L L
Prowl + Atrazine 1.5 pt+1 pt ½X PRE M M M
Harness + Resolve 1 pt+0.5 oz ½X PRE L L L
Verdict 5.57 EC 8 oz ½X PRE L L L
Lumax EZ 3.67 SE 1.35 qt ½X PRE H H H
Acuron 3.44SC 1.25 qt ½X PRE H H H

Potential for interseeded cover crop injury from residual corn herbicides (Pennsylvania Guidelines).

Contact Information

William S. Curran
  • Professor of Weed Science
Phone: 814-863-1014