Spring is here, and depending on your specific area, corn planting may range from not yet begun to 100% completed. While getting your crop in the ground is important, it’s also important to keep the fields weed-free to maintain the best potential for yield.
The critical weed-free period is the period of crop development where weed competition can reduce yields dramatically (up to 60% reduction or more). If the crop is kept weed-free during these stages of development, no yield reduction should occur.
For corn, the Critical Weed-Free Period lasts from emergence until the 8 leaf stage of development. Weeds emerging after this time won’t affect yield, although control may still be necessary to prevent additions to the weed seed bank, or prevent issues at harvest.
For this reason, it is important to have a herbicide program in place to prevent germinating weeds from emerging and causing yield losses. Using herbicides with residual activity, as well as multiple modes of effective action on target problem weeds, is a sure-fire way to maximize your crop’s potential.
Click here to see a chart showing you some of our most popular herbicide programs for your corn crop. Make sure that your desired program:
- Has effectiveness on the weeds in your individual field
- Has residual activity for targeted weeds
- Uses multiple modes of action for tough to get or resistant weeds like Canada Fleabane
- Rotates chemistry on that particular field
Always refer to pesticide labels and OMAFRA Pub 75 for official ratings, notes, and rates!
Don’t forget to check out the Corn Herbicide Program, here.
We are here to help – get in touch if you have any questions or need help with your corn crops!
| Corn Pre-Emerge Programs – 2 pass herbicide program | |||||
| Product | Rate | Cost/ac | Fleabane | Strengths | Weaknesses |
| Integrity | 0.3L/ac 0.45L/ac | $20.07 $30.10 | Emerged Residual | One of best for fleabane, good for velvetleaf, ragweed, slightly better proso millet than Primextra. No known resistance. | Weaker on nightshade than other products. Still weak on proso millet. |
| Primextra II Magnum | 1.2L/ac | $ 20.64 | No | Good nightshade control, wide-spectrum product. Most popular option. | Potential control issues if weeds are triazine resistant, weaker on fleabane, velvetleaf. |
| Converge XT | 30ac/Pack | $ 18.70 | No | Best annual grass control ratings, including proso millet. Very good annual broadleaf control as well. No known resistance. Can use higher rates for single pass. | Weaker on fleabane, no perennial weed control, less crop tolerance. |
| Acuron | 1.6L/ac 1.98L/ac | $28.16 $34.85 | Yes, high rate | Heavy up-front program, improved control of nutsedge, proso millet, fleabane over Halex GT. Longer residual. | Cannot incorporate. Eliminates Callisto as a post option. Add glyphosate if needed. No labelled recrop to dry beans. |
| Marksman | 1.5L/ac | $ 20.10 | Emerged Residual | Dicamba + Atrazine. Will have better activity on tough perennial weeds and fleabane. Provides residual activity. | No residual for grasses; tank-mix with Dual for added grass control. |
| Product | Rate | Cost/ac | Fleabane | Strengths | Weaknesses |
| Integrity | 0.3L/ac 0.45L/ac | $20.07 $30.10 | Emerged Residual | One of best for fleabane, good for velvetleaf, ragweed, slightly better proso millet than Primextra. No known resistance. | Weaker on nightshade than other products. Still weak on proso millet. |
| Primextra II Magnum | 1.2L/ac | $20.64 | No | Good nightshade control, wide-spectrum product. Most popular option. | Potential control issues if weeds are triazine resistant, weaker on fleabane, velvetleaf. |
| Converge XT | 30ac/Pack | $18.70 | No | Best annual grass control ratings, including proso millet. Very good annual broadleaf control as well. No known resistance. Can use higher rates for single pass. | Weaker on fleabane, no perennial weed control, less crop tolerance |
| Acuron | 1.6L/ac 1.98L/ac | $28.16 $34.85 | Yes, high rate | Heavy up-front program, improved control of nutsedge, proso millet, fleabane over Halex GT. Longer residual. | Cannot incorporate. Eliminates Callisto as a post option. Add glyphosate if needed. No labelled recrop to dry beans. |
| Marksman | 1.5L/ac | $20.10 | Emerged Residual | Dicamba + Atrazine. Will have better activity on tough perennial weeds and fleabane. Provides residual activity. | No residual for grasses; tank-mix with Dual for added grass control. |
| Product | Rate | Cost/ac | Fleabane | Strengths | Weaknesses |
| Halex GT + Atrazine | 1.7L/ac + 0.235L/ac | $29.59 | Emerged Residual | One-pass “kitchen sink” approach, good residual control. Dual + Callisto + glyphosate, add own atrazine. | Weeds that are already emerged ahead of application impact crop. Bulky product. Need surfactant. |
| Acuron + Glyphosate | 1.6L/ac
1.98L/ac |
$33.99
$40.68 |
Yes, high rate | Comparable to Halex GT; improved residual and better activity on tough weeds, grasses, fleabane. Up to 6 leaf. | Weeds that are already emerged ahead of application impact crop. Bulky product. |
| Destra IS/ Engarde + Glyphosate + Atrazine | 40ac/case
40ac/case |
$28.31
$30.78 |
Emerged Residual | Use Engarde up to 2 leaf, Destra 3-8 leaf. Excellent Proso Millet, velvetleaf control. Comparable broadleaf control to Halex. Changes up grass chemistry. | Slightly weaker on ragweed. No residual control of Group 2 resistant grasses. |
| Product | Rate | Cost/ac | Fleabane | Strengths | Weaknesses |
| Callisto GT | 0.9L/ac | $14.00 | Emerged Residual | Excellent broad-spectrum broadleaf control, residual control of nightshade, pigweed, velvetleaf, and ragweed suppression. | Glyphosate doing most of the work on perennial weeds and grasses. Add atrazine for improved waterhemp control. |
| Glyphosate + Peak | 1L/ac equiv. + 5.23g/ac | $14.30 | No | Good option for perennial weeds like sow thistle, alfalfa, clover. Very crop safe. | Weaker on annual broadleaf weeds, glyphosate doing the majority of work. |
| Glyphosate + Lontrel XC | 1L/ac equiv. + 68mL/ac | $16.96 | Emerged | Best option for perennial weeds like sow thistle, alfalfa, clover. Crop safe. Tank-mixable with other herbicides. | No residual, glyphosate will be doing the majority of the work on grasses. Apply close to canopy closure. |
**This is a summary of our most popular herbicide programs. Refer to OMAFRA Publication 75A for all weed control options, ratings and rates.