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Frequent rain making Palmer amaranth management very difficultFrequent rain making Palmer amaranth management very difficult

Palmer amaranth is growing quickly and now is often 1 to 3 inches where a pre was used and 10 to 14 inches in fields where no pre was used.

Larry Steckel 2

May 25, 2018

2 Min Read

This recent weather pattern has Palmer amaranth management in a terrible fix for many fields in west Tennessee. The rain that has occurred on an almost daily basics 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 very little window to spray until the first week of June for numerous fields.

Palmer amaranth is growing quickly and now is often 1 to 3 inches where a pre was used and 10 to 14 inches in fields where no pre was used. This spraying delay has led to several weed management questions.

With respect to the questions about managing large Palmer in corn, there are some good options to use when the field will carry the sprayer. Those are discussed in an earlier blog (Managing large Palmer amaranth in large corn).

Options are not near 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 countryside. If you want to be able to use this technology in 2019, this cannot happen.

Xtend soybeans

A frequent question the last few days has been on aplan B Palmer amaranth management in Xtend soybean fields where it is not practical to spray Engenia or XtendiMax. The labels for both Engenia and XtendiMax state they cannot be sprayed if residences, bodies of water, sensitive crop plants are downwind.

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 and finding an hour when they could be sprayed and be on label is almost impossible.

Unfortunately, there is no really 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 are not PPO-resistant. Then when the wind is in favorable direction (hopefully 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 be destroyed. Consider then replanting back to a LibertyLink 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.

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