By Darren Hefty
If you had a chance to attend the Ag PhD Field Day on our farm back in July, chances are you saw the Brian vs. Darren plots of corn, soybeans and wheat. Brian and I independently put together our best plans to maximize yield in each of these crops. You can bet we’re pretty competitive and were both going to pull out all the stops to try to win. What was interesting to me was that we didn’t see the other’s plans until the day before the field day. When I saw Brian’s plan for his wheat I started laughing. Other than one minor detail (which fungicide product to use at heading), our plans were identical. I guess I’d better quit giving Brian such a hard time that he can’t keep up with me!
When it came to our wheat programs, both of us believe strongly in investing in a pre-emerge herbicide. While there are a number of products that can be used, there are really two excellent options that offer rotational flexibility and still have strong weed control characteristics.
Sharpen
When it comes to burndown and residual control of broadleaf weeds, it’s pretty hard to beat Sharpen. Sharpen is in the PPO family of chemicals and adds another mode of action to your wheat program that you otherwise wouldn’t normally see. Sharpen must be sprayed before the crop is up or you risk severe damage to your wheat, but it is very safe when sprayed pre-emerge. In terms of its burndown ability, Sharpen is one of the fastest-working products you’ll find. At the 2 ounce rate you can use in front of wheat, it also has a nice amount of soil residual control on weeds like kochia, lambsquarters, pigweeds, Russian thistle, marestail, wild mustard and more. We’d recommend mixing it with Roundup to also control grasses. Adjuvants help in the speed and effectiveness of the burndown. Use MSO (methylated seed oil) at 1 gallon per 100 gallons and AMS (ammonium sulfate) at 17 pounds per 100 gallons.
Pre-Pare
For pre-emerge grass control (or early post-emerge if you’re unable to get your pre done in time), Pre-Pare is a very good option. It does have some activity on broadleaves as well, but Pre-Pare is an ALS herbicide; and a number of the broadleaf weeds like kochia have developed resistance.
In terms of the weeds Pre-Pare controls, the main grasses are green foxtail, wild oats, cheat, and Japanese brome. It does provide suppression on downy brome, Persian darnel, Italian ryegrass, barnyardgrass and foxtail barley, as well. On the broadleaf side, you’ll get some residual control on a number of weeds including mustards, pigweed, pennycress, shepherdspurse, wild buckwheat, volunteer canola and more.
The tricky part with Pre-Pare is dialing up the right rate for each field. The labeled rate is up to 0.3 ounces per acre. However, the rate we often talk about is 0.2 ounces. In low pH, you’ll need higher rates to get good control. In high pH soils, you’ll get great weed control with lower rates and possibly see some crop response with high rates, especially where you have any overlaps. To avoid potential problems on your farm, we talk about the 0.2 ounce rate. Work with your agronomist to use the right rate for your fields.
The other thing to keep in mind with rates is this: no pre-emerge herbicide should ever be expected to control every weed in the field season-long. It’s just not going to happen. Whether it’s Sharpen, Pre-Pare or any other product, you should plan on coming back in with a post-emerge treatment to clean up any escape weeds. The good thing about following a pre-emerge herbicide is that the weed pressure should be significantly less, allowing the post-emerge herbicides a much better chance of nearly 100% weed control.
YOUR ASSIGNMENT: If you haven’t used a pre-emerge herbicide before, treat at least one field this fall or next spring. Leave a check strip or two in the field that you will evaluate for weed control and also for yield at harvest. We’re pretty confident that over a period of years you’ll see a nice return on investment using pre-emerge herbicides; but you will likely see other benefits like not having to rush to get your post treatments on, having peace of mind knowing many of your weeds are already wiped out, and having more time to do things because pre-emerge herbicides can be applied before planting or shortly afterwards when you aren’t as busy, etc.