This little guy is an example of the most developed soybeans currently in the neighbourhood. A significant amount of angst and anxiety is being spent worrying about the possible frost for tonight and Saturday. If temperature predictions are correct and -1 degree is the actual low everyone can stop worrying. Soybean tissue can stand frost better than corn. Trust me. They will be fine.
Vlado Puskaric, the legendary Pioneer corn breeder of my generation never understood why, to use one example dicamba, was allowed to be registered on corn. He was like a mama bear protecting her cubs and anything that hurt the children was public enemy number one and this included many herbicides of the day. I remember not having any defense when he cornered me, other than to say weeds caused big problems too. He would then stomp off with smoke coming out his ears.
Fast forward to today. If we were still working with 30 year old herbicide technology, the risk of injury to emerged corn given the low temperatures of the next two nights would be substantial. Even older products like Dual are much more gentle to the crop now than they used to be and still provide excellent weed control.
Thanks to technology we can and probably should spray the corn crop shown above. The safest route, assuming it is glyposate tolerant corn is simply glyphosate. If you want to add a little bit of Calisto or Peak go ahead, but the more combinations you use the more the plant will have to work to break them down. A second application will be necessary and that is when a tank mix can be applied to help out with weed resistance management.
The risk to choosing not to spray is wet weather. If the next week turns wet and keeps the sprayers out of the field then there will be yield loss from the uncontrolled weeds. A wet week is hard to envision, however we need to ask what is the worst thing that could happen. At some point it will rain and then it might not stop. So get the weeds under control now. The risk of herbicide injury is much less than the risk of uncontrolled weeds. How times have changed.