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Unharvested Louisiana crop could cause more problems

As of Nov. 5, unharvested Louisiana soybean acreage was estimated at 310,000 acres — roughly 40 percent of the crop. Preliminary economic loss estimates are in excess of $40 million. These are not final numbers, but only estimates from economists, county agents, local FSA offices, and elevator and producer contacts.

The percentage of the crop left in the field varies considerably with geography and other factors such as planting date and maturity group.

In general, north of Alexandria, La., harvest was 65 to 80 percent complete when the monsoons began and south of Alexandria harvest was 25 to 75 percent complete. Between Avoylles, St. Landy and Point Coupee parishes, 16 percent of total acres remained unharvested.

We have finally received some drier weather, which has allowed some of the later-planted acreage to be harvested, but it will not have much bearing on the final outcome.

Damage reports have been high on the beans that were harvested after the most recent rain system. Damage assessment reports are 30 to 80 percent, on average, with moisture around 19 percent or higher. There have been isolated reports of producers cutting beans of higher quality.

With all of this acreage remaining in the field, with insurance adjusters finalizing claims, and with many fields too wet for fall tillage, what is the potential of volunteer Roundup Ready soybeans emerging in next year's crops (if this year's crop is not disked under or harvested)?

I hope (as sad as it is to say) that if seed quality is poor enough, remaining seeds will not be able to germinate. In some cases, however, they could.

According to Donnie Miller, a weed scientist at the Northeast Research Station in St. Joseph, La., “It all depends on the weather. The more winter rainfall we get, the more these beans are going to rot. Regarding burndown options in the spring, if a producer is having a problem with volunteer soybeans, Gramoxone and Aim is effective in addition to being economical.”

Professor Roy Vidrine at the Dean Lee Research Station in Alexandria said, “I believe that following a heavy frost, the majority of the existing soybeans will be eliminated. Excess moisture would lessen germination potential unless we are dealing with soybeans that have hard seed coats.

“There also is ample time between now and when crops will be planted in the spring to allow bean seeds to decay, especially during a mild winter.”

Jim Griffin, a weed scientist in Baton Rouge, La., said, “Some of these beans will come up regardless of cultural practices done in the fall. It might be better to leave them on the top of the ground rather than trying to disk them in and rutting up the fields. Weathering, birds and rodents will play a large role in eliminating viable seed over the winter.”

To sum all of this up, it might be better to leave the crop on the ground and let it overwinter rather than rut up fields. Most fields I have been in should not have a problem with volunteer soybean because the seed have already sprouted or rotted.

If, however, there are concerns about these volunteer soybeans, rotation into other crops such as corn, sorghum or cotton will allow different herbicide chemistries to be used for control. Also, burndown herbicides other than glyphosate are very effective against volunteer soybeans.

David Y. Lanclos is the soybean, corn and grain sorghum specialist at LSU AgCenter.

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