By Darren Hefty
All the northern U.S. readers will be thinking it’s way too early to talk about grass control in corn, but corn is already going in the ground in southern and coastal markets. However, you may need to switch products or timing in 2018 to achieve the results (as close to zero weeds as possible) you desire.
TRAITS
First, let’s talk about the trait shift going on. For this discussion it’s not important to discuss the insect control traits like SmartStax and moving to above ground only pest control traits. The simple fact is that those traits still contain the Roundup Ready trait. Let’s focus on the shift away from Roundup Ready corn to straight conventional corn as that is where the herbicide programs will take completely separate forks in the road.
CONVENTIONAL CORN (Or fields of any trait prone to late season grass escapes)
Your best escape grass control option in conventional corn is Accent Q that costs $15/acre by the time you add all the surfactants, etc. It’s not the best weed killer. It has to be sprayed fairly early in the season (by V5-V6) for crop safety reasons. Oh, and you have to spray grass weeds by the time they are 1 to maybe 2 inches tall if you want to kill them with Accent Q. Please don’t misunderstand, Accent was a game-changing product when it came out in the early 1990s since we had no other options that worked consistently. However, it’s nothing like we’ve gotten used to with Roundup. Roundup can control grass, short or tall, at almost any point during the season and is easy on the corn in most cases when applied according to the label.
THE ANSWER in conventional corn is that you make a big switch in the products you choose to use pre-emerge. If you haven’t been using a pre-emerge herbicide at all, in conventional corn you really don’t have a choice but to use one. Grass is the #1, #2, and #3 yield-robbing weed in conventional corn. To address it, you can’t use your combination grass and broadleaf killer you’ve been using in Roundup Ready corn. Products like SureStart, TripleFLEX, and Verdict have been great in Roundup Ready corn, but they don’t have enough residual control on grasses to completely take out the first flush and hang around to stop each flush of grass afterwards until your crop reaches canopy.
A full rate of Harness, Surpass, Dual, Zidua, or Outlook is your best choice. These options are cost effective and very good on annual grasses like foxtails. They also have SOME activity on small-seeded broadleaves, which is a nice bonus. Utilize any of these products in conventional or no-till systems. In areas with plentiful and timely rainfall they can be applied right before or even after planting and give you great effectiveness. Since they are all shoot inhibitors and do not have contact activity on weeds, they will need enough rainfall after application to move down into the soil profile and get into the target weeds. If you do tillage after application, keep it shallow. These herbicides are shoot inhibitors, so most of their weed-killing power comes from being concentrated in the top inch of soil.
If you’ve moved away from the Roundup Ready corn trait or would simply like to achieve better grass control in corn, use a full rate of Harness, Surpass, Outlook, Zidua, or Dual this year instead of a combination grass and broadleaf product. Odds are, you’ll be very happy you did.