Every year there are challenges in growing soybeans. This year weed control will be one of these challenges. This is partly due to lack to product but also due to some challenging weather, that has allowed weeds to get pretty big.
When spraying Roundup Ready soys, recognize that if you can see the weeds from the road you are losing yield. You have to get that first weed flush out early. If there is a second flush, deal with it later.
Last year there were some lambs’ quarters that did not die when treated with a low rate of glyphosate. If you own some of these be sure to spray early at a high rate to control them. If you do not own them be concerned that you may soon get them. It is believed that these lambs’ quarters are a naturally occurring population that takes over when you kill the other populations. It is thought that these plants have a higher level of calcium in their leaves that tie up glyphosate. They can be controlled with normal rates if sprayed when small. Once they get bigger you have to increase the glyphosate rate.
If you are spraying IP beans post emergent remember it is better to spray too early than too late. I have seldom gotten into trouble by spraying too early. I have seen trouble lots of times when growers delay spraying their soybeans. Once weeds get to a certain height they become harder to kill. Then the program you are using only partially kills them. Then they start to regrow slowly. These slow-growing weeds are extra hard to kill. Some of them are impossible to kill. If you delay spraying there is a good chance you will see some of these weeds at harvest.
Some post emergent products can only be applied when the soybeans are at a certain stage, so keep an eye on the staging of your soys.
Watch what you tank mix. In some cases when you mix a broadleaf herbicide with a grass herbicide one or the other loses some effectiveness. In these cases it is more economical to make the two trips. BF