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Weed Control in Dry Beans (05/21/15)

The following is a question from a consultant in NE. The answer can apply to dry bean growers in ND.

Weed Control in Dry Beans

The following is a question from a consultant in NE. The answer can apply to dry bean growers in ND.

I am a crop consultant in Nebraska and was wondering if you have a weed control program that you would recommend for us to use in our dry edible fields this year. Our main problem weed is waterhemp. Our soils are light sandy and last year we applied 3 pts of Eptam + 1 pt of Dual PPI, followed by 2 pts of Prowl preemergence. About a month later we applied 4 oz of Raptor + 11 oz of Basagran + nonionic surfactant 0.25% v/v and 1.41 lbs AMS per 100 gallons. Four days later we applied 0.5 pts of Reflex with 0.25 % NIS and 1.41 lbs AMS per 100 gallons. This program was successful where we had a light water hemp infestation. However it was a great failure in the heavily infested fields. We did cultivate sometime after the Reflex application. If you don’t mind sharing with me what is the standard practice at your research station I would love to know what you use.  I am sure you are thinking why doesn’t this guy ask the Nebraska weed science people. We have talked to them before but they do not have waterhemp in the dry edible growing areas of Nebraska. Thank you for your help.

Answer: Below are some factors to consider with herbicides used:

1. Eptam has about 3 weeks effective weed control then is broken down rapidly.

2. Dual has about 4 weeks effective weed control then is broken down rapidly.

3. Prowl is mostly non-soluble in water and requires rain or irrigation to move into the soil when weed seeds germinate. Prowl has several weeks of activity after activation.

4. Most all waterhemp is ALS resistant so Raptor would be ineffective. You may know if it is susceptible but I would doubt it.

5. Rates of Basagran and Reflex used are too low.

6. Nonionic surfactant (NIS) is the least effective adjuvant with the herbicides used

7. The rate if AMS was too low.

8. All POST herbicides should be applied to waterhemp less than 2 inches tall for greatest control.

Consider these options:

PPI Eptam at 3.5 pt + Sonalan at 2 pt/A or the highest rate allowed for soil type.

Apply Spartan Elite PRE at rates labeled for your soil type. Spartan Elite contains sulfentrazone (Authority or Spartan) + Dual. I am not sure if Spartan Elite or Spartan Charge is labeled in NE because of crop injury but you can check. Spartan Elite has shown synergistic weed control in NDSU research. Sulfentrazone give 8-10 weeks residual control. PRE herbicides require incorporation with water.

If all herbicides are incorporated sufficiently this program should provide excellent weed control through canopy. If waterhemp emerges apply the following herbicides before waterhemp plants reach 1.5 inches tall:

Apply Basagran at 16 fl oz + Reflex at 4 fl oz/A + methylated seed oil (MSO adjuvant at 1 to 1.5 pt/A + AMS at 8.5 lbs/100 gal

If needed apply the same treatment again after 10 days. No more than 0.75 pt/A can be applied in a growing season in ND so you must check to see your total use limit and adjust rates accordingly and apply consistent with the label.

At NDSU we developed a program called the NDSU Dry bean tank-mix where 4 to 5 herbicides are applied together at reduced rates with MSO adjuvant. Some forms of it are used extensively. It was developed to control a wide range of weeds but in this case with your pivot weed being waterhemp we can adapt it for that weed. For example since waterhemp is resistant to ALS herbicides then Raptor can be eliminated unless you have other weeds that Raptor will help control. Refer to page 33 in the following file for the Dry bean tankmix listing:

http://www.ag.ndsu.edu/weeds/weed-control-guides/nd-weed-control-guide-1/wcg-files/5-Soy.pdf

Sequential POST applications are very important in dry bean weed control but must be done to SMALL weeds if it is to work. Refer to paragraph E3 and E4 on page 81 in the following file for information on Basagran and the effect of MSO adjuvant and on Reflex:

http://www.ag.ndsu.edu/weeds/weed-control-guides/nd-weed-control-guide-1/wcg-files/5-Soy.pdf

Also refer to paragraph F5 and F6 on page 83 in the same file listed above for more information on the NDSU Dry bean tank-mix.

MSO adjuvant is the most effective adjuvant for Basagran, Raptor, Reflex and many other herbicides. It high effectiveness may also cause some level of burn to dry beans leaves. Usually it temporary and the beans grow out of it. You will have to make the choice if you or your growers are willing to accept some potential crop injury from use of a very effective adjuvant. You can use an NIS with little or no crop injury but poor weed control or use an MSO with some potential dry bean injury but with the greatest weed control.

Rich Zollinger

Extension Weed Specialist

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