When the combine rolls through a field, we often are ready to be done for the year. Pigweed isn't.
Unfortunately, if you are fighting pigweeds you can't afford to stop.
I have already had calls from growers and consultants concerned about pigweeds coming up behind corn and milo. Pigweeds survive on rice levees and will come up when soybean harvest starts rolling.
Our summers are long, and pigweed only needs three to four weeks to make viable seed under the right conditions.
We have herbicide recommendations in the MP-44 that address post-harvest options behind corn and some other crops.
In general, the herbicides we are talking about are paraquat, Liberty, 2,4-D, Sharpen and Dual for residual. I am sure there are others. If I left yours out, let me know and we will add it.
Many companies are adding fall or post-harvest options to their labels for this purpose. Be aware of re-crop intervals before choosing a product.
Also, watch out for sensitive crops in the area. Your neighbor’s field might be at a sensitive stage for drift from some of these chemicals. Information on crop sensitivity is also in the MP44.
I have gotten several pictures from growers who have adopted windrow burning to eliminate seed in harvest trash. I think this will result in a significant change in the way we control weeds and reduce the weed soil seedbank in many fields.
Windrow burning results
My research counterpart, Jason Norsworthy, has done work looking at windrow burning and the results have been pretty amazing. By concentrating combine trash into a windrow and then burning he has significantly reduced pigweed populations the following year.
This can be accomplished by making chute that is attached to the back of your commercial combine. You must create a concentrated windrow in this way to get the fire hot enough and burn long enough to destroy seeds in the trash and on the ground below the windrow.
Fact sheet FSA 2180 discusses these options in detail.
I will be working with Jason on a wheat project looking at the effect of this type of burn on ryegrass in wheat starting with some test plots this fall. We started this work last year but the wheat was rained out.
Don’t walk away and let a clean field go to seed this fall, it can ruin an otherwise great opportunity to reduce weed populations and save some real dollars in 2016.
Our harvest weed seed control work is funded through the soybean and wheat promotion boards as well as some industry support and it is greatly appreciated.
There are photographs of windrow chutes on my twitter feed at @BobScottweedDr.