Applying herbicides at just the right time is more critical than ever with the onset of resistant weeds and the plethora of new herbicides to control them.
Knowing the best time to apply herbicides used to be easy when only one product, Roundup® herbicide, dominated the market. As weeds have evolved resistance to glyphosate, among other herbicides, growers are relying on multiple products encompassing alternative sites of action, each with different timing restrictions, according to Nick Hustedde, technical service representative for FMC.
“There are as many as eight defined application timings in row crops,” Hustedde says. “There’s early preplant, preplant, preemergence, early post, mid post, late post, lay by or drop nozzle and even harvest aid applications.”
Here’s a closer look at each one to ensure the right herbicide is applied at just the right time
- Early preplant application. Applications made from 15 to 30 days before planting are referred to as “early preplant.” Herbicides applied at this time are typically non-selective burndown herbicides that target weeds that come up early, such as marestail, winter annuals, giant ragweed and lambsquarters. “Typically, soil-applied residual herbicides are mixed along with those herbicides to control grass species, waterhemp, cocklebur and morning glories,” Hustedde says. Two common tank mixes are foliar-applied Roundup/2,4-D or Gramoxone® herbicides along with a soil-applied, residual herbicide such as FMC Authority® brand herbicides.
- Preplant application. Preplant application is defined as 15 days prior to planting up until the actual planting date. Only certain herbicides can be used at this time due to plant-back restrictions. “In soybeans, for example, with Roundup herbicide and 1 pt. of 2,4-D, you have to wait seven days until you can plant to avoid crop injury,” Hustedde says. “Growers who don’t have that much time before planting might switch to Gramoxone herbicide or Liberty® herbicide, which wouldn’t have this restriction, and mix it with an Authority brand herbicide to add residual control.”
- Preemergence application. Preemergence applications are made after planting but prior to emergence. “We recommend using a soil-applied Authority or Anthem® herbicides for residual activity and then tank mixing it with Gramoxone or Liberty herbicide to take care of any established weeds at application.”
- Early-post application. In corn, early-post application runs from crop emergence up to the vegetative stage when there are three collars exposed on the plant, also referred to as V3. In soybeans, early-post application runs from emergence up until V3, which is when three fully expanded leaflets appear on the soybean plant. “A good herbicide to use at this time is Anthem® MAXX foliar-applied residual herbicide from FMC,” Hustedde says. “It offers residual control of a wide spectrum of grasses and broadleaves, including ALS-, triazine- and glyphosate-resistant weeds like waterhemp and Palmer pigweed.”
- Mid-post application. In corn, mid-post applications are made at the V3 to V5 vegetative stage when the plant has three to five leaf collars exposed. In soybeans, mid-post applications are made at V3 to V5 when there are three to five expanded trifoliates on the plant. Treatment options during this window include herbicides designed for crop trait systems in addition to labeled residual herbicides.
- Late-post In corn, late-post applications are made when the plant has five to eight leaves, V5 to V8, and reaches 12 – 20 in. in height. In soybeans, late-post applications are made from R1, a reproductive stage when the plant starts to bloom, up until R3, which is the beginning of pod formation. Target weed species are late-season broadleaf weeds such as morning glory, pigweed and velvetleaf. PPO foliar-applied herbicides such as Cadet® herbicide, Marvel™ herbicide or Cobra® herbicide in soybeans, or Cadet herbicide or Aim® EC herbicide in corn are very effective on these weeds.
- Drop nozzle application: Drop nozzle applications often occur later in the season to address unexpected weed flushes. As its name implies, a spray nozzle is dropped between the rows to get late-season weeds, typically morning glories, pigweed and velvetleaf. Herbicides that work well for this include foliar-applied Aim EC herbicide, Status®, Impact® or Buctril® herbicides in corn.
- Harvest aid application: Once the crop has matured, some herbicides can be applied to take out late-season grasses and broadleaves such as fall panicum, foxtails, morning glories, velvetleaf and pigweed, which can interfere with crop flow into combine heads. “Aim EC herbicide together with 2,4-D can be a good choice for this.”
Hustedde says knowing these time frames has never been more important, especially as the off-label use of dicamba has resulted in widespread crop damage. “With dicamba in particular, the later we apply it, the more likely we will have conditions for volatility, which can cause off-target movement.”
For more information on application timing, visit FMCcrop.com. To schedule an interview with Nick, contact Jodie Wehrspann at [email protected]. Nick Hustedde with FMC is the technical service representative for Illinois and Indiana.
Always read and follow label directions. Authority and Anthem brand herbicides, and Cadet, Marvel and Aim EC herbicides are not registered for sale or use in California. FMC, Authority, Anthem, Cadet, Marvel, and Aim are trademarks of FMC Corporation or an affiliate. Roundup is a trademark of Monsanto Technology LLC. Gramoxone is a trademark of Syngenta Group Company. Liberty and Buctril are trademarks of Bayer. Cobra is a trademark of Valent U.S.A. Corporation. Status is a trademark of BASF. Impact is a trademark of AMVAC Chemical Corporation. ©2017 FMC Corporation. All rights reserved. 17-FMC-1069 11/17