Use of Harvest Aids in Louisiana Soybeans

 Over the last several weeks, we have received numerous calls about soybean harvest aid timing, products, and general recommendations. The use of harvest aids in Louisiana soybeans is a common practice, with timely applications improving seed quality and harvest efficiency while potentially resulting in a soybean harvest 10 to 14 days earlier when compared to non-treated beans.

Timing

If the goal of harvest aid use in soybeans is to promote early harvest and improved harvest efficiency, harvest aids must be applied as timely as possible. Once seed have separated from the white membrane inside the pod, they have reached physiological maturity and will no longer increase in size. Any use of a harvest aid prior to the majority of seed reaching physiological maturity will result in a loss in yield. Table 1 gives the paraquat label requirements for harvest aid application timing in soybean. Research conducted in Louisiana by Dr. Jim Griffin and Joey Boudreaux established that a harvest aid application could be made to soybean without yield penalty as long as soybeans are at reproductive growth stage R6.5 (physiological maturity). They provided a list of procedures to help determine when harvest aids can be safely applied to soybeans:

1. Begin to scout fields for harvest aid timing when leaves begin to yellow

2. Collect pods from the top four nodes of the plant at multiple, random locations within a field

3. Open soybeans from pod, they should shell easily, and look for soybean separation from the white membrane

4. If soybean separation from the white membrane has occurred for all pods collected, the seed has reached maximum dry weight and harvest aid application can be made without yield penalty

Plant appearance at growth stage R6.5 will vary by variety so close attention should be made to pods collected from the field and if seed have separated from the white membrane (Griffin and Boudreaux 2011 Louisiana Agriculture magazine Vol. 54, No. 2, Spring 2011). Table 1. Proper application timing of harvest aid in indeterminate and determinate soybean varieties.

Indeterminate Varieties

65% of pods have reached a mature brown color or seed moisture is less than 30%

Determinate Varieties

Plants are mature; beans are fully developed, 50% of leaves have dropped and remaining leaves are yellowing.

Products

Producers have several harvest aid options, though the typical harvest aid application consists of paraquat with an additional nonionic surfactant. With excessive morningglory pressure, growers might consider including carfentrazone (Aim) or saflufenacil (Sharpen) with paraquat to improve desiccation of vines and in situations with high grass pressure, a tank-mix of paraquat with sodium chlorate may be warranted to improve the desiccation of grassy weeds prior to harvest. Questions have also been received in regards to the use of sodium chlorate to aid in drift reduction of paraquat applications made by air. The LSU AgCenter has no data to support this claim and only recommends the use of these products together for improved desiccation of weeds and soybeans present in the field.

It is also imperative that producers consider the required preharvest interval (PHI) associated with each product label. When using multiple products, the longest PHI must be adhered to. Labeled rates and comments are presented below in the excerpt from the 2017 Louisiana Suggested Weed Management Guide.

Redbanded Stink Bug Considerations

Producers should also continue monitoring redbanded stink bug (RBSB) populations and should not rule out the inclusion of an insecticide with the application of a harvest aid. LSU AgCenter entomologists recommend the control of threshold populations of RBSB until the soybeans are out of the field. This means that many producers could, and should, include an insecticide for the control of RBSB with their harvest aid application (sodium chlorate cannot be tank-mixed with any insecticide). It is important to keep in mind the restrictions placed upon many of the products at this point in the season. These restrictions may include total active ingredient restrictions and PHIs. Acephate, a common recommendation for RBSB control, can only be applied up to 2 lb ai A-1 year-1 in Louisiana. Other insecticides also have increased PHI such as the pre-mix product Endigo, with a PHI of 30 days. It is important to read and adhere to the label of all labeled materials prior to use. When label restrictions prevent the inclusion of an insecticide with the harvest aid, producers should not delay the harvest of soybean so that the seed can be removed from the field as quick as the label