By Brian Hefty
Over the past couple years I have had many farmers ask me this question: “Is it even worth it to use Roundup anymore?” I understand there are resistant weeds out there, but most weeds are still very susceptible to Roundup, and there are some things you can do to make Roundup work better on tough-to-control weeds. Here are eight simple steps you can take:
- Use flat fan nozzles instead of drift reduction nozzles whenever the wind is relatively calm and out of the right direction. Flat fan nozzles give you smaller spray droplets. That means better spray coverage, which leads to slightly better weed control with Roundup. Plus, with most tankmix partners – namely fungicides and most herbicides – they need flat fan nozzles because they aren’t nearly as systemic as Roundup.
- Spray when the weather is better. We have told you for years that unless the NIGHTTIME temperature within two days before or after spraying is above 50 degrees, Roundup will likely not work as quickly or as well. I know it seems a little counterintuitive to say that weeds must be healthier in order to get a better kill with Roundup, but it’s true. If the weed is lethargic due to cold temps, it doesn’t bring in as much herbicide, nor does it efficiently move that herbicide to the growing point(s) as quickly. The net result is that in cold weather, a lethal dose of Roundup often never arrives at the growing point(s) of your target weed. You then think the weed is resistant, but that’s not true. Most of these things are exactly the same if your weed is under severe drought stress or the temperature is well over 90. Once the weed gets some moisture or once the temperature cools down, the weed grows better and dies easier.
- Keep your water volume low. Don’t fall victim to one of the biggest myths in our industry. More water does not always equal better control. If you are spraying tiny weeds, they can’t hold much moisture on their leaves, right? Therefore, when spraying small weeds, you want less water, meaning each spray droplet is more concentrated. When spraying early, keep your water volume at 5 to 10 gallons per acre when spraying Roundup.
- Use the right rate. The maximum labeled Roundup rate in Roundup Ready 2 Yield soybeans is 44 ounces per acre in one application. I know we’re all trying to save money this year, but what does it cost to bump your Roundup from 22 ounces to 32 ounces? Not much. If that’s the difference between control and non-control, it’s well worth the extra couple of bucks.
- Spray weeds when they are small. I know that Roundup used to kill all your weeds when they were 2 to 4 feet tall, but like other herbicides, Roundup is best when your weeds are 2 to 4 INCHES tall.
- Use REAL ammonium sulfate (AMS). AMS ties up hard-water ions and provides a nitrogen boost, which really helps on nitrogen-sensitive weeds like waterhemp. AMS also slightly lowers water pH and provides fertilizer (N & S) to help your crop recover more quickly and help your weeds die more quickly. No AMS replacement we’ve found is as good as the real stuff.
- Always add non-ionic surfactant. I know that Roundup already has some cationic surfactant in it, but adding some non-ionic surfactant does help improve the spreading and sticking of Roundup to the leaves of weeds, and it slightly boosts control from what we have seen.
- Use the right tankmix herbicide partner. Everyone is trying to sell you something to go with Roundup, and there is a wide range of costs. Ask lots of questions before you settle on what you want to mix with Roundup, if anything. Then, if you want to improve your control and often save money, switch the tankmix partner field by field based on weed spectrum, the amount of weeds, and weed size.
I know you may be tempted to think that Roundup isn’t doing much anymore on your farm, but think long and hard before you kick Roundup to the curb. From what I’ve seen, it still kills lots of weeds and is still worth the small investment in almost all cases in Roundup Ready crops.