David Moseley, James Villegas, Stephen Ippolito, LSU AgCenter Scientists

Best management decisions during the final weeks of the season can have a significant impact on yield and profitability. Two important considerations are irrigation management during seed fill (especially during these extremely hot and dry conditions) and the proper timing of harvest aid applications. Additionally, redbanded stink bugs (RBSB) remain a threat and should be managed until the crop is harvested.

Maintain Irrigation Until R6.5 to Maximize Seed Size

The current drought and high temperatures have increased concerns about seed fill in many soybean fields. Soybean seed continue to accumulate dry matter until physiological maturity, which occurs at approximately the R6.5 growth stage (Figure 1). During this period, adequate soil moisture is critical for maximizing seed size, final yield, and profitability.

Harvest Aid Timing Matters

As harvest approaches, many growers are now thinking about when to apply harvest aid applications to improve harvest efficiency and speed dry down of both weeds and soybean plants. Research conducted in Louisiana has indicated that harvest seed quality and yield were not affected by harvest aid applications if applied after most or all pods reached physiological maturity (R6.5) (Boudreaux and Griffin, 2011). At physiological maturity, seeds have separated from the white membrane inside the pod and seed margins are prominently defined (Figure 1). Careful scouting is necessary because soybean maturity can vary across a field. Please check the label for each individual harvest aid product as labels are very specific regarding when harvest aids may be legally applied to soybean.

Redbanded Stink Bugs Remain a Threat Until Harvest

LSU AgCenter entomologists recommend controlling threshold populations of RBSB until soybeans are harvested. Even fields approaching maturity can suffer seed quality losses when RBSB populations remain above threshold.

As a result, including an insecticide with a harvest aid application may be necessary in some situations. However, growers should be aware of label restrictions, including preharvest intervals (PHIs) and maximum seasonal use rates for insecticides. In addition, sodium chlorate cannot be tank mixed with any insecticide.

When label restrictions prevent the inclusion of an insecticide with a harvest aid application, growers should avoid delaying harvest and remove the crop from the field as soon as label requirements allow. Timely harvest remains one of the most effective ways to reduce additional losses from late-season stink bug infestations.

Figure 1. Pod and seed development from early pod set (R3) to maturity (R8).

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