IMPROVED WINTER ANNUAL, BIENNIAL, AND PERENNIAL WEED CONTROL

If you’re in reduced tillage, these three weed categories listed above can be difficult to control, especially in-crop. Fall offers a great opportunity when the temperatures are warmer than in the early spring so you can get a better kill on these weeds. For control of perennials, Roundup is likely your best option because it gets down into the root system to completely take out the weed. I’d recommend spraying it alone, if possible, because adding 2,4-D or dicamba with it could reduce the control of perennials if you burn off the top growth faster than the Roundup can move down into the roots. The same goes for biennial control, in my experience. Just know that Roundup works best BEFORE your first killing frost!

As for winter annuals, if weeds like marestail, henbit, and chickweed are your big concerns, then you are going to love fall applications, as well. Here’s where you can use strong rates of things like Freelexx (the only 2,4-D to consider, in my opinion, due to its low volatility) and dicamba to knock out weeds that have emerged. Certainly Roundup, Liberty, or Gramoxone could, and likely should, be added to broaden the spectrum of weeds controlled. The other product category to add at this time is a residual herbicide.

EXCELLENT EARLY SPRING WEED CONTROL

Adding a residual herbicide in the fall is a great way to ensure the best weed control next spring. To begin with, residual herbicides need several inches of rain to work 100%. I realize there’s a lot of confusing information about ½ inch or 1 inch of rain to activate a herbicide. Yes, to get it started, that’s true enough; but to get it to really work, you need much more than that. By spraying late in the fall shortly before freeze-up, it’s almost a 100% lock to have snow or rain before you need that herbicide working at the maximum level.

I mentioned this wouldn’t necessarily add to your total crop protection costs for the year compared to what you’re doing now. The reason why is three-fold:

1. Late fall residuals will still have almost all of their window of control and maximum killing power left in the spring. In the north, the ground freezes, so almost no herbicide is used or broken down in the fall when you spray right before freeze-up.
2. By having exceptional early-season weed control, you will need fewer resprays in-season. The other important step is to plant crops early in those fields that received fall residual applications so you get to crop canopy earlier and before the residual runs out.
3. There are often cheap fall programs to help make higher rates much more affordable.

FOR FALL BURNDOWN: Freelexx or dicamba are great for knocking down broadleaf weeds. Either Roundup, Liberty, or Gramoxone are generally added to take out grasses and any weeds Freelexx or dicamba miss. Rates are normally significantly higher than in-crop applications where crop safety is a concern. Standard rates in the fall are 1 quart of dicamba or 2 quarts of Freelexx.

FOR FALL RESIDUAL: Valor has been the most popular product in front of soybeans. It has an attractive price point, adds to your burndown, has strong residual control on most broadleaf weeds, and has fairly short rotational restrictions to most crops. Valor is in the PPO family of herbicides. Authority/Spartan is another good option from the PPO family. Pair one of those PPOs up with a yellow (Prowl or Trifluralin) and you’ve got a nice 1-2 punch. You can use metribuzin, as well, to complete the 3 PRE program; but metribuzin can leach through the soil a lot more than the others, so know your soils and your weather, and use your head.

IN FRONT OF CORN. The most popular fall residuals are the Group 15s (Zidua, Dual, Harness, Outlook, etc.). Use the full rate for your soil type in the fall. I’ve always liked Harness a little better than the others due to better small-seeded broadleaf control, but in recent years Zidua has worked as good or even better. Zidua also holds on in the soil longer in higher rainfall environments. One other product to mention is atrazine, but I don’t like it in the fall due to its leachability, limited weed control spectrum, and the fact that it limits your crop choices next spring to corn or sorghum.

HOW CAN I GET THIS DONE ON MY FARM WITH EVERYTHING ELSE I HAVE GOING ON EACH FALL?

Every farm operation is different. Spraying will get done sometime. If fall has significant benefits, why wouldn’t weed control get prioritized then? You may have to just try it on a couple fields to see if it’s worth it to you. If you don’t have many weeds at all, then it may be no big deal. I’m guessing you have significant weed pressure from winter annuals, biennials, and perennials if you don’t do much tillage. In conventional tillage fields, I’ll bet you have kochia, waterhemp, palmer pigweed, or other tough annuals. This growing season, many of the cleanest fields we expect to yield the highest were sprayed in the fall. Spraying goes pretty fast when you get a few good days. Give fall application a try this year.