The recent Mid-South weather pattern has put Palmer amaranth management in a terrible fix for many fields in West Tennessee.
The rain that has occurred on an almost daily basis for over a week in many areas has delayed early POST herbicide applications. The forecast for rain into June looks to be a similar pattern. There will likely be a very small window to spray until the first week of June for numerous fields.
Palmer amaranth is growing quickly and now is often in the 1- 3” range where a PRE was used and 10-14” range in fields where no PRE was used. This spraying delay has led to several weed management questions.
With respect to the questions managing large Palmer in corn, there are some good options to use when the field will carry the sprayer.
Options are not nearly as easy or simple with respect to managing large Palmer amaranth in Xtend soybeans. The long delay in spraying will definitely tempt applicators to throw the stewardship book out the window and spray Engenia or XtendiMax as quickly as possible when a field will carry. This could lead to a lot of dicamba drift across the country side. If you want to be able to use this technology in 2019 this cannot happen.
A frequent question the last few days has been on a Plan B Palmer amaranth management plan in Xtend soybean fields where it is not practical to spray Engenia or XtendiMax. The label for both Engenia and XtendiMax states they cannot be sprayed if residences, bodies of water or sensitive crop plants are down wind. Fields planted to Xtend soybeans that are bordered at least on two sides by one of these can result in it being hard to find a day when the wind is in the correct direction to make an application. Add in the rain that has occurred frequently as of late, finding an hour when they could be sprayed and be on label is almost impossible.
Unfortunately, there is no real good direction to go for fields caught in these situations. That is why it was stressed in the dicamba training this winter that there were fields where Xtend soybeans should not be planted due to this very situation. The only option is to use a high rate of fomesafen and glyphosate and hope most Palmer present are not PPO resistant. Then, when the wind is in a favorable direction (hopefully sometime before Christmas), come back and spray Engenia or XtendiMax.
In some cases where the wind direction will not cooperate and the Palmer amaranth infestation is mostly PPO resistant, then the soybeans may need to be destroyed. Consider then replanting back to a Liberty Link variety and utilize Liberty for weed control.
With respect to cotton, there is the glufosinate option for fields near sensitive crops or home places. That option should be the first choice.