There was about 100,000 acres of crop that the Mississippi claimed when it went out of its banks in July. About 50,000 acres of that is being replanted back to soybeans. Most of that 50,000 acres is being planted this week (8/5). Some questions have come in on how to approach weed control in these ultra-late planted soybean.
My first thought to that question is to realize that the Mississippi flood land is some of the worst with respect to Palmer amaranth infestation. Even if very little Palmer pigweed had been on those fields last year the Mississippi just deposited millions of new seeds.
Another thought is that some of this Palmer pigweed is likely resistant to PPO-herbicides. With that in mind a Liberty Link soybean makes sense here. However, I have been told that some of the replant seed being used locks one into replanting with Roundup Ready.
In Liberty links soybeans start clean with Gramoxone and a PRE applied herbicide that contains two herbicides effective on Palmer amaranth. Then plan to spray Liberty about 14 to 21 days after planting tankmixed with Dual Magnum or Zidua. Weed control should be done here if the Dual Magnum or Zidua gets activated. Remember we only have about 2 months of growing season left.
In Roundup Ready soybeans we will start out the same way with Gramoxone at burndown plus a PRE. Prior to PPO-resistant Palmer amaranth, I never had a major favorite for any particular herbicide PRE. That has changed as we must get the PRE to work on Palmer pigweed in these cases. I really think pyroxasulfone (Zidua, Anthem) needs to be in the PRE mix. Examples of some PREs that have the best chance to get these late soybeans off to a good start would be Verdict + Zidua, Envive + Zidua, Fierce, or even metribuzin plus Zidua/Anthem. Another choice here would be Boundary (Dual Mag + metribuzin). However I would definitely spike the rate of Dual Magnum up to 1.5 pts. Then just plan to come back 10 to 14 days after planting with a quart of Prefix. Go with Dual Magnum in place of Prefix if the field is going to corn or grain sorghum next year. Then consider another application of Dual Magnum or Warrant 10 days after that early POST. The idea is to never let the Palmer emerge at least to canopy closure.
Remember the fields that will not be planted will be a huge harbor for Palmer amaranth seed production if left to grow. Tillage, mowing or Gramoxone plus some residual need to be considered to keep the soil seed bank numbers down for next year.
Is the 100000 acres just in TN or all of the MS river floodplain? Been trying to find data on how many acres total were lost in MS floodplain but haven’t had any luck.
That is my best guess for TN after visiting with growers with bottom land in the Mississippi. Take it for what it is worth….
My goodness Larry, your putting an awful lot of weed control money into beans that may not make your seed back!!!!’
Mike
That is a good point. However we have had late July an early planed soybeans make 40 bu or better if we can avoid a Sept frost in past years. If you are going to take the gamble you should plan for a decent crop. If you manage for a poor crop you are guaranteed to get it. Moreover if it is not planted weeds should still be managed which will have cost with no potential upside this year and Letting the fields grow up in Palmer will be very costly next year.