By Brian Hefty
Whether your broadleaves are Roundup-resistant or not, you can stop them easily with 5 simple rules:
- Improve your spray coverage. Pick your weediest fields and spray those on the calmest and best days with extended range flat fan nozzles. If you have triple nozzle bodies, it’s easy and quick to switch spray tips. Flat fan nozzles will provide significantly better coverage than Turbo TeeJet or air induction nozzles. This means slightly better weed control. Ask yourself – in your weediest fields, are you okay with 97% control or would you want 99%?
- Always include another herbicide with your Roundup. It only costs a little more to add the tankmix partner, but you will kill more weeds and leave residual with most products to extend your control. Status is the most broad-spectrum herbicide. Use 2.5 oz if you have no resistant weeds; use 5 oz if you’ve got them. I prefer to see you spray Status prior to 8” corn to minimize drift issues and maximize crop safety and control. Callisto, Impact, and Laudis are virtually the same thing. They’re not as good on buckwheat, marestail, and morningglory as Status, but they are great on most corn broadleaves, safe to the crop, and have no volatilization concerns. Buctril has no residual, but it is great on buckwheat and lambsquarters. For big velvetleaf, use Resource.
- Use a spray adjuvant. Non-ionic surfactant can help Roundup and most post-emerge herbicides to spread out (improve coverage) and stick better. This means slightly improved control. Some herbicides work even better when mixed with methylated seed oil (MSO) or crop oil concentrate (COC), as they help the herbicide penetrate the leaf surface of the weed. However, MSO and COC can add more leaf burn to your crop. If the weather has been cool and damp and you’re spraying early in the season, leaf cuticles will likely be thin. MSO and COC will give more burn to the crop and are needed less for weed control in this situation. When it has been hot and dry, especially late in the season, leaf cuticles will probably be thick, meaning MSO or COC could help improve weed control and not burn your crop excessively.
- Spray when the weather has been nice for at least a couple of days. Our standard Roundup rule is if the nighttime temp drops below 50 degrees within 2 days before or after spraying you need to up your Roundup rate by 50%. There’s no herbicide I can think of that works better in cold temps than warm. If you want the best possible weed control, spray when it’s warm – not excessively hot (90+), but warm.
- Spray weeds when they’re small. The bigger weeds get, the higher rate you need and the less chance you’ll have to get good control. Just as importantly, the longer you let weeds grow in your field, the more they lower your yield. As farmers, we’re always searching for some new thing to add yield and profitability, but don’t forget that having good weed control is still the most important thing you can do for your crop.